T
he commercial culturing of marine species in California is limited primarily to the production of shellsh such as oysters, mussels, and abalone. While the culturing of nsh for enhancement purposes is well established in California, commercial culturing has been limited in scale and remains focused on solving technical questions through research. The commercial production of most cultured shellsh has declined from recent peaks. Oyster production is down from a peak in 1994; abalone production is down from a peak in 1996; and mussel production is down from a recent peak in 1997. In several instances, demand exceeded production and the declines reected several ongoing challenges faced by these industries in their efforts to maintain production. More information on production levels can be found in the specic sections that follow. Developing and maintaining production of cultured marine species is still inuenced by technical problems, in some cases in spite of a well-established production history. Fledgling industries, such as those engaged in scallop and nsh production, face technical challenges in developing breeding and rearing techniques. The well-established industries, such as oyster and abalone culture, face technical challenges in maintaining production when faced with environmental change or disease impact. Humancaused changes in water quality, for example, present signicant challenges to culture facilities that are sited in bays and estuaries. In order to address product safety concerns in these areas, the production of mussels, oysters, and clams are often subject to closures or depuration requirements. The presence of a shellsh aquaculture facility in an area can, as a consequence, provide a contamination early-warning system for sport-harvest of shellsh and an assessment of the biological conditions in the general area. With the exception of concerns related to the accumulation of biotoxins, changes in water quality do not present signicant technical challenges in the culturing of scallops because of the tendency in that industry to site in offshore areas. Natural changes in water quality have also hampered shellsh production. Much of the recent decline in production can be attributed to El Niñorelated impacts, particularly in the culturing of mussels and abalone. A broader discussion of these technical challenges can be found in the specic sections that follow this overview.
by a signicant summer-time mortality of unknown cause. Abalone production has been inuenced by mortality from withering syndrome and hampered by regulatory requirements intended to prevent the spread of an exotic parasitic worm. Large numbers of juvenile white seabass have been destroyed to address disease concerns. In each instance, the industry made positive contributions to cooperative efforts among resource agency diseasemanagement researchers. Taken as a whole, the industry has ardent entrepreneurial support, has great economic potential, and has been a source of signicant positive societal benet. If not conducted in a resource-sensitive manner, aquaculture can also cause negative environmental impacts, by introducing exotic species, by introducing or contributing to the spread of disease, or by altering the natural systems within which production facilities are located. The key to achieving the positive aspects of aquaculture while minimizing negative ones rests in how effectively the industry, the research community, and regulatory agencies can work together. Industry leaders are now focusing on developing best management practices to ensure that shellsh culture does not impact the health of ecosystems upon which they depend. A common goal will be to ensure that the industry achieves its successes in resource sensitive ways without having to do so under an undue regulatory burden. Our ability to achieve that goal may hinge on developing trust through effective communication.
Aquaculture: Overview
Aquaculture: Overview
Fred Wendell California Department of Fish and Game
Development of a technical response to disease, and conforming to regulatory requirements related to disease control have both inuenced production in the oyster and abalone industry and have inuenced the success of white sea bass enhancement efforts. Oyster production in Tomales Bay, for example, continues to be inuenced
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Culture of Abalone History
P
ioneering efforts to mass cultivate abalone in California began about 35 years ago. Three abalone species, the red (Haliotis rufescens), the green (H. fulgens), and the pink (H. corrugata) have been farmed, and research into cultivation techniques has been conducted on the black (H. cracherodii) and white abalone (H. sorenseni). The red abalone, however, is the mainstay of the industry and comprises more than 95 percent of total production. Abalone are grown in either land-based tanks or in cages suspended in the water column. The cages are typically tethered from a raft but have also been suspended beneath a wharf. Aquaculturists that operate these inwater systems typically obtain small seed abalone from land-based hatcheries for grow-out. In a typical hatchery operation, ripe brood stock abalone are induced to spawn using hydrogen peroxide or ultraviolet light treated seawater. Fertilized eggs that successfully develop to the veliger swimming stage are transferred to through-owing larval rearing tanks. In about six days at 59° F, larvae are ready to settle from the planktonic to the benthic stage. They are transferred to nursery tanks, and commence to feed on diatoms. After six months of growth, half-inch abalone are then transferred to plastic mesh baskets suspended in larger tanks. At this point, the abalone begin feeding on macroalgae. An additional six to eight months are required before they reach the size where they are transferred to grow-out tanks or in-water systems. After growing in these tanks or in-water systems for 20 months or longer, they attain the typical three- to four-inch shell length preferred by the market. The number of participants in this industry and their total production have increased through time, peaking in 1996. In 1991, 15 registered abalone aquaculturists in California produced an estimated 175,000 pounds of abalone in the shell. By 1996, 27 registered abalone aquaculturists produced over 292,000 pounds of product. Participation and
production then declined slightly through 1998 when 22 aquaculturists produced 162,000 pounds of product valued at $2.4 million. Only 13 of the 22 abalone aquaculturists registered in 1998 were actively producing abalone and most of the production came from four or ve growers. The decline in participation and production since 1996 is attributable, at least in part, to disease impacts exacerbated to some extent by a signicant El Niño event. Until recently, cultivated abalone had been considered relatively disease-free. The bacterium Vibrio sp. infected larval cultures, but it was typically suppressed by using ltered, ultraviolet treated seawater. That perspective changed with the introduction of a parasitic sabellid polychaete worm from South Africa. By the mid-1990s, the parasite had spread to virtually every abalone aquaculture facility in the state. The worm induces the infested abalone to form a tube for it out of nacreous material. With heavy infestations, the abalone shell is brittle and very deformed and abalone growth is stunted. Impacts to the industry included loss from voluntary stock destruction and reduced income from marketing deformed product. Cooperative efforts by the industry, the Department of Fish and Game (DFG), and Sea Grant sponsored university researchers have almost completely eradicated the worm from California. Unfortunately, the industry also started experiencing elevated losses of cultured product from withering syndrome (WS) during this same time frame. This disease, caused by a rickettsia-like prokaryote, is characterized by a drastic shrinkage of the abalones’ foot and is always fatal. However, red abalone can be infected by the bacterium without showing clinical signs of disease. Research suggests that a stress trigger is necessary to induce clinical signs of the disease in this specie. The only recognized stress trigger is elevated water temperature. With the El Niño event, many facilities experienced elevated water temperatures that triggered WS, resulting in elevated mortality in their cultured stock. The dedicated entrepreneurs at the core of this industry have achieved their successes despite these challenges and interest in abalone aquaculture remains high, prompted in part by the closure of the commercial abalone shery in 1997. Presently, abalone are available to meet market demands only through importation or the purchase of cultured abalone. Consequently, there is a high market demand and a good price to growers for the farmed product.
Red abalone being grown out on plastic substrate.
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A more recent positive development in abalone aquaculture is the production of cultured abalone pearls. The product is produced by inserting a nucleus into the abalone. Given time, nacre is laid over the nucleus to form a semi-spherical pearl that has all the lustrous hues of the shell interior. Once extracted, these pearls are set in
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Status of Biological Knowledge
References Ebert, E.E. and J.L. Houk. 1984. Elements and innovations in the cultivation of red abalone Haliotis rufescens . Aquaculture 39:375-392.
considerable amount of research on abalone aquaculture has been accomplished by the private sector, particularly with respect to systems design and overall technology. University and DFG scientists have also made major contributions. Sea Grant-funded research has greatly increased our understanding of abalone developmental biology. Spawning induction procedures, larval settlement inducers, and larval rearing systems were developed by researchers funded through this program. Sea Grant-funded research has also contributed signicantly to our understanding of abalone diseases.
Ebert, E.E. 1992. Abalone aquaculture: a North Amercial regional review. In, Abalone of the World: Biology, Fishereis, and Culture. S.A. Shepherd, M.J. Tegner, and S.A. Guzman del Proo (eds.) Pp. 571-582. Fishing News Books, Oxford, United Kingdom.
The DFG began abalone culture investigations in 1971 at its Granite Canyon Laboratory near Monterey. That effort led to the development of a through-owing larval rearing system and the development of a ush-ll tank system that have been adopted by the industry. The DFG subsequently developed a pilot production hatchery at Granite Canyon that provided training opportunities and resulted in the production of seed abalone for enhancement research.
McBride, Susan C. 1998. Current status of abalone aquaculture in the Californias. Jour. Of Shellsh Research, Vol. 17, No. 3, 593-600.
A
Hahn, K.O. (Editor). 1989. Handbook of culture of abalone and other marine gastropods. CRC press, Inc., Boca Raton, FL.
Culture of Abalone
jewelry and the meat is processed for sale to restaurant trade as either a fresh or frozen product.
Leighton, D.L. 1989. Abalone (genus Haliotis) mariculture on the North American Pacic coast. Fish. Bull., U.S. 87:689-702.
The DFG’s Marine Region shellsh pathology laboratory in Bodega Bay has expanded our knowledge of the biology of the parasitic sabellid worm that has contributed signicantly to the success that has been achieved in the cooperative eradication efforts. That laboratory also identied the causative agent for WS and has conducted extensive research into questions related to transmission and control of this pathogen. Two principle areas for research, nutrition and genetics, may provide signicant benets to the industry in the future. Prepared diets have been developed and are being used widely for juvenile stages. However, most prepared feeds are expensive and not readily accepted by adult abalone in comparison to giant kelp. Less progress has been made in genetics research. Most growers use a selection process where brood stock is selected based on growth rates. Wild broodstock is also used to maintain genetic diversity in cultured stocks. Some research has been done with triploidy as a means of enhancing abalone growth rates. While encouraging, the results have not been applied broadly within the industry. Earl Ebert US Abalone
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Culture of Mussels History
M
ussels of the genus Mytilus have uctuated in importance in California’s commercial and sport shellsh sheries for food and bait since the early 1900s. Experiments in culturing wild seed stock and in developing hatchery and grow-out methods in the 1980s have increased the economic potential of mussels, particularly Mytilus galloprovincialis (the Mediterranean mussel), which occurs primarily in southern and southcentral California. A related species, Mytilus trossulus (the “foolish mussel”) is sport-harvested in northern California and hybrids of M. trossulus and galloprovinciallis are commonly found between Cape Mendocino and Monterey Bay. The sea mussel, Mytilus californianus, is of minor economic importance in California at present, though it is taken by sport harvesters and it is periodically sold by a southern California harvester to restaurants. It is primarily used as bait along the West Coast, but in the 1980s, wild harvested sea mussels, highly esteemed by gourmet chefs in Oregon, were sold to ne restaurants in Portland and still may have a future in California. Between 1916 and 1927, a total of over 470,000 pounds of mussels, ranging from 9,000 to 69,000 pounds per year, were landed in California. After 1927, most areas were closed to harvest by the California Department of Health Services due to a major outbreak that year of paralytic shellsh poisoning. Mussel landings declined to 1,610 pounds in 1928 and stayed depressed until 1972, when a record 111,000 pounds were landed, primarily for bait. Bait sales continued to be the most signicant commercial activity for California mussels until improved methods of harvesting wild stocks were developed, new culture methods were adopted, and West Coast markets began developing for this tasty shellsh in the early 1980s. Research on harvesting wild-set Mediterranean mussels from offshore oil-production platforms for food was initiated in the Santa Barbara Channel in 1979. Divers routinely removed fouling organisms from the submerged support structures of offshore platforms at considerable expense to oil companies. An ecological consulting rm, hired to suggest ways to control the biofouling, found that various stages of the succession of organisms included settlement and growth of edible mussels, both M. galloprovincialis and M. californianus. Recognizing the potential for food production and increasing market demand for high quality shellsh, the owners of the rm contracted with various offshore oil companies to test the feasibility of harvesting and marketing the mussels. Experimental mussel, oyster, and clam culture also began in 1983 in Aqua Hedionda Lagoon near Carlsbad. Taking advantage of excellent natural mussel spatfalls in the
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lagoon and relatively fast growth of juveniles, the shellsh rm began to culture mussels in 1985. It obtained a ve-acre lease for use of the lagoon and began a commercial operation following modied Italian longline techniques. Mussel seed was placed in a tubular net “stocking” designed specically for mussel growing. The stocking or “reste” was originally imported from Italy, but is now available to growers from U.S. suppliers. The stockings were suspended from longlines fty yards long and supported by small buoys to keep the stockings off the bottom. Mussel production at the Carlsbad farm peaked in 1989, second only to the offshore platform harvest in the Santa Barbara Channel. However, the following year the State Department of Health decertied the shellsh growing area due to rising coliform counts in the lagoon. Production ceased in 1990 and remained static until a certied depuration system, required by the state, was put into operation in 1992. In 1985, approximately 104,000 pounds of mussels were harvested, primarily from offshore platforms, but by this time a farm in Tomales Bay also had begun to utilize European longline methods to grow mussels. Over the next seven years, three to ve other Tomales Bay oyster growers diversied into mussel production. These growers utilized wild-caught and hatchery reared seed, with the latter being relied upon more in the late 1980s, as natural recruitment during this period was often erratic and unreliable. After a brief period of expansion, several Tomales Bay growers ceased all but minimal production in the mid1990s to concentrate on oyster culture. By the fall of 2000, only one company was producing commercial quantities of mussels. These are sold exclusively to local restaurants around Tomales Bay. At least three other growers have the capability to produce commercial quantities and may scale up their operations again if market conditions improve. On the north coast, an oyster grower operating in Mad River Slough, Humboldt County, began farming mussels in 1992 using the oating raft culture method. Seed mussels, attached to a line inside exible plastic mesh netting, are suspended from the raft during grow-out. Cultured mussels from Humboldt Bay were initially used, but since the mid-1990s, wild juvenile mussels collected from the bay have been the primary source of seed. The mature mussels are sold locally at farmers’ markets and restaurants. One other Humboldt Bay operation began experimenting with mussel grow-out in 2001, using wild seed stock and following the raft culture method used in Mad River Slough. The total state mussel production tripled in 1986, reaching more than 334,000 pounds, with over 90 percent harvested from platforms in the Santa Barbara Channel and the remainder from Tomales Bay. Statewide produc-
CALIFORNIA DEPARTMENT OF FISH AND GAME December 2001
a cooperative effort was initiated by a Humboldt County shellsh nurseryman to produce the rst commercial quantities of hatchery-reared mussel seed on the West Coast. Growers utilized a variety of substrates and set the spat at different densities. A wide range of results, from zero survival to excellent survival and growth were reported. The methods of growing out seed evolved and matured in Tomales Bay and in the Puget Sound area of Washington state but were not proven on a commercial scale in south-central and southern California as growers continued to utilize natural seed.
Mussels harvested during the ve years between 1986 and 1990 provided a return of $1.17 million to California growers. Steady expansion of production during the following ve years between 1991 to 1995 increased statewide returns to $2.06 million. Return to growers dipped in 1996 and 1997 to about $500 thousand per year with a critical drop in 1998 to $280 thousand.
Southern California mussel companies also face stiff competition from imports, and also must cope with water quality uctuations, especially in nearshore areas or embayments. One south-coast aquaculturist has built a depuration system for bivalve shellsh, one of the rst in California. The grower has been able to use a protected lagoon to grow mussels, which are relayed to the onshore depuration system prior to sale. By utilizing seawater treated with ultraviolet violet light to eliminate harmful bacteria, he can produce wholesome, high quality mussels.
The wholesale price has not changed signicantly over the past 15 years still ranging from $1.10 to $1.25 per pound. Retail/restaurant prices have increased slightly from $2.00 in 1990 to $2.25 in 2000. Direct sale prices to the public at farmers markets and retail shellsh farms has increased, varying between $2.50 per pound in southern California and $4 per pound in the Tomales and San Francisco Bay area. The retail/restaurant price in Humboldt County is slightly higher at $2.50 per pound and direct sales at farmers’ markets are intermediate at $3.00 per pound. California growers continue to face stiff competition from mussels imported from eastern Canada, New Zealand, Maine, and Washington due to the advent of low cost air transport of fresh shellsh and individual ash freezing methods. Competing on the world market is a challenge to California producers, because of massive production of mussels in China, Korea, New Zealand, Australia, and other Pacic Rim countries. Expansion of the industry is dependent on the maintenance of clean growing areas, a supportive regulatory environment, aggressive marketing, and dependable sources of seed. Climatic and oceanographic events have also had signicant impacts on the economic health of this industry.
Culture of Mussels
tion dropped slightly in 1987 to approximately 286,000 pounds and decreased further in 1988 to 151,000 pounds, due to major winter storms, which dislodged market-ready mussels from platform structures. Production jumped to over 300,000 pounds in 1989 but dropped to 130,000 pounds in 1990 when the Carlsbad rm ceased production, continuing a slide in 1991 to a low of only 47,000 pounds. During the next six years (1992 through 1997), with the Carlsbad rm back in production, increasing harvest from offshore platforms in the Santa Barbara Channel, and steady production in Tomales Bay, the statewide total rose from 187,000 pounds to 471,000 pounds. Strong winter storms following warm El Niño seawater conditions in the fall of 1997 caused havoc to mussel production throughout the state the following year. An economically devastating drop in production of nearly 50 percent, to 256,000 pounds, occurred in 1998. One of the large southern California growers stated that spawning and recruitment were both affected by these events. A colder water regime in 1999 - 2000 improved the recruitment situation and has been encouraging to growers.
The ve participating growers in Tomales Bay purchased larger (0.5-1.0 inch) seed, which could be grown to market size in six to nine months. Excessive predation on maturing mussels by scoter ducks and on small natural-set seed by schools of perch over time proved burdensome to most of the shellsh growers who were concentrating on oysters as their primary product. All but one company in Tomales Bay ceased or minimized their mussel operations, citing competition from low-cost imported mussels as the reason.
Status of Biological Knowledge
G
enetic studies utilizing protein electrophoresis in the late 1980s showed that there were two distinct forms of edulis-like mussels on the West Coast that are morphometrically similar. One of these forms is electrophoretically indistinguishable from M. galloprovincialis, the Mediterranean mussel, which is known to have recently colonized many disparate shores around the world. The other form is also distinct from the Atlantic M. edulis and was designated M. trossulus, the Pacic Northwest mussel. It was found from Alaska to central California. The two forms occur together and are reported to hybridize with one another. Several genetic studies in the late 1990s have conrmed that M. galloprovincialis is found principally south of the Monterey Peninsula and M. trossulus is found primarily north of Cape Mendocino. A zone of hybridization has been documented between these two distinct coastal features.
Until 1986, all mussels grown commercially in California were set or collected as wild or natural seed. In 1985,
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Culture of Mussels
The hybridization and geographic range issues regarding M. trossulus in central and northern California confound the interpretation of earlier life history studies of mussels taxonomically classied as M. edulis, but, regardless of the taxonomic issue, all mussels share many common biological traits as they are all members of the bivalve class Pelecypoda (hatchet feet). Mussels have separate sexes, though some hermaphrodism occurs. There is evidence that changes in water temperatures, physical stimulation (such as disturbance by winter storms), variation in light levels, or phytoplankton blooms may stimulate spawning. Spawning in M. californianus occurs throughout the year at a very low level, with peaks in July and December. The spawning and recruitment of M. galloprovincialis also occurs year round, although it is heaviest in February, March, and April and again in September and October in southern California. Mussels reaching 1.6 inches are found to have gonads in various stages of development and are able to spawn. When spawning occurs in the natural environment, eggs and sperm are discharged through the excurrent chamber and fertilization takes place in the open ocean or estuary. Within 24 hours, the embryo develops into free-swimming trochophore larva that grows into a more advanced veliger stage, again, within 24 hours. The development of the ciliated velum (approximately 48 hours after fertilization) gives the larvae more control in swimming and in gathering food. The veliger is also known as the “straight-hinge” stage, denoting the appearance of the rst shell. In two to three weeks, veligers begin metamorphosis, a stage preceded by the development of an eyespot (a photosensitive organ) and a foot. This is the pediveliger stage, during which the veliger changes from a swimming larva to a bottom dwelling juvenile mussel or spat (seed). Newly settled mussels attach to substrates with proteinaceous threads (byssus or byssal threads) that are secreted by the postlarvae. Young mussels have the unique ability to detach their byssus, crawl to a different location, or drift away in a current to seek a more favorable substrate, and reattach. This trait is considered to be a signicant problem for growers, as postlarvae have disappeared from various substrates soon after placement in open water.
considered to be the main food item providing energy for rapid growth. Competition for space is an important factor inuencing growth and survival of mussels, both in wild and cultured populations. Mytilids of the same and different species compete for limited space in the rocky intertidal and subtidal growing areas. Cultured mussels on articial substrates also can become overcrowded if seed stocking densities are too high. Crowding causes instability of mussel masses and, when coupled with high current speeds, turbulence, and drifting materials, losses frequently occur. Barnacles and sea anemones also compete for space with mussels. Predators of California mussel species are abundant. They include two sea stars, ve species of muricid gastropods, and three crabs. Scoter ducks, the black oyster- catcher, shiner perch, and the sea otter are also important predators in coastal waters. An invasive species of algae, Caulerpa taxifolia, recently found in a southern California lagoon is another concern of both mussel growers and resource managers. Known for its progressive smothering of the Mediterranean seaoor, the alga is the focus of an intensive effort by state and federal regulators to eradicate the species before it spreads. Mussels are used in California and other parts of the world as sentinel species in “mussel watch” programs to monitor various organic and inorganic pollutants. As lter feeders, mussels also ingest and concentrate toxin-producing species of phytoplankton that periodically bloom along the Pacic coast. The California Department of Health Services utilizes mussels as bio-toxin indicators in a statewide monitoring program staffed by volunteers. A quarantine on sport harvest is imposed between May 1 and October 1 when the probability of toxic phytoplankton uptake in mussels is high. However, commercially grown mussels may continue to be harvested during this period as long as constant testing assures that only a safe, wholesome, and non-toxic product is available to the consumer.
Growth rates of both M. galloprovincialis and M. californianus have been reported to be at least 0.25 inch per month and as high as 0.5 inch per month in the Santa Barbara Channel. Growth rate is inuenced primarily by the quantity and quality of food, rather than temperature, and mussels achieved a two-inch shell length in six to eight months. Food consumed by mussels includes dinoagellates, organic particles, small diatoms, zoospores, protozoa, unicellular algae, bacteria, and detritus. Phytoplankton is
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CALIFORNIA DEPARTMENT OF FISH AND GAME December 2001
Cultured Mussels thousands of pounds harvested
400 300 200 100 0
1986
1990
1999
Commercial Harvest 1986-1999, Cultured Mussels Annual pounds of cultivated mussels landed by State aquaculture producers. Harvest data for 1997-1999 include only mussels cultivated in Tomales Bay and Drakes Estero. Data Source: California State Tax records (royalties reports) and DFG Aquaculture Harvest Survey Database.
Management Considerations
References
See the Management Considerations Appendix for further information.
Coan, E.V., P.V. Scott, and F.R. Bernard. 2000. Bivalve seashells of the western North America: marine bivalve mollusks from Arctic Alaska to Baja California. Santa Barbara Museum of Natural History Monographs No 2; Studies in Biodiversity No. 2 Santa Barbara, CA. 746 p.
John B. Richards University of California, Santa Barbara George A. Trevelyan Abalone Farms, Inc.
McDonald, J.H. and R.K. Koehn. 1988. The mussels Mytilus galloprovincialis and M. trossulus on the Pacic coast of North America. Mar. Biol. 79: 117-176.
Revised by: John B. Richards University of California, Santa Barbara
Price, R.J. 1989. Paralytic shellsh poisoning and red tides. California Sea Grant Extension Program 89-1, University of California, Davis. 2 pp.
Culture of Mussels
500
Rawson, P.D., V. Agrawal, T.J. Hilbish. 1999. Hybridization between Mytilus galloprovincialis and M. trossulus along the Pacic coast: evidence for limited introgression. Mar. Biol. 134(1):201-211. Suchanek, T.H.; J.B. Geller, B.R. Kreiser, and J.B. Mitton. 1997. Zoogeographic distributions of the sibling species Mytilus galloprovincialis and M. trossulus (Bivalvia: Mytilidae) and their hybrids in the North Pacic. Biol. Bull. 193(2): 187-194. Trevelyan, G.A. 1991. Aquacultural ecology of hatcheryproduced juvenile mussels, Mytilus edulis L. Ph.D. Dissertation, University of California, Davis.
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Culture of Oysters History
C
alifornia’s oyster shery and oyster aquaculture industry have had a rich and colorful tradition. American Indians harvested the oyster resource for thousands of years before Spanish, Tsarist Russian, and European settlers occupied the West Coast. A substantial commercial oyster shery began in the 1850s, when settlers from the East Coast attracted to California by the prospect of gold and new opportunities created larger markets for oysters. The increased population and market pressure for oysters had an immediate impact on the state’s shellsh resources. The only available oyster was the Native oyster (Ostreola conchaphila; previously O. lurida; also called Olympia oyster in the Pacic Northwest), which was intensively shed, causing a rapid decline in the natural population. In response, Native oysters were transported from Shoalwater Bay, Washington (Willapa Bay), and later from other bays in the Pacic Northwest and Mexico, representing the initial attempts at oyster culture on the West Coast. Oysters were transplanted into San Francisco Bay, where they were maintained on oyster beds and then marketed throughout central California. The Shoalwater Bay trade of Olympia oysters dominated the California market from 1850 through 1869. Market demand for a larger, half-shell product stimulated experiments in transporting the Eastern oyster (Crassostrea virginica) from the Atlantic states to the West Coast. Several failed attempts were made to establish transport of the Eastern oyster to
Growing Oysters in Tomales Bay Credit: Fred Conte
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California by sailing ships. Successful transport of oysters was achieved only after the completion of the transcontinental railroad in 1869. Shipments of juvenile and market-sized oysters were transported by rail in barrels of sawdust and ice and transplanted into San Francisco Bay. Cool summer water temperatures, however, prevented successful natural reproduction of the Eastern oyster. Transcontinental trade for Eastern oyster seed was fully established by 1875. Small, one-inch seed was transplanted in San Francisco Bay for further growth. The Shoalwater Bay trade for Olympia oysters was gradually terminated, and from 1872 until the early 1900s California’s San Francisco Bay Eastern oyster industry was the largest oyster industry on the West Coast. Maximum production was reached in 1899 with an estimated 2.5 million pounds of oyster meat. With California’s population and industrial growth came a degradation of water quality in San Francisco Bay. By 1908, Eastern oyster production had fallen by 50 percent. By 1921, oyster meat quality declined to the extent that shipments of seed from the East Coast were terminated, and by 1939 the last of the San Francisco Bay oysters were commercially harvested. Oysters were still transported and held in Tomales Bay until they could be marketed in San Francisco, but the industry based on the Eastern oyster did not recover. The industry and state began reexamining earlier experimental plantings using the Pacic oyster (Crassostrea gigas), which originated in Japan. The California Department of Fish and Game (DFG) and commercial growers conducted experimental plantings of Pacic oysters in Tomales Bay and Elkhorn Slough in 1929. Experimental plantings continued in a number of bays, including Drakes Estero, Bodega Lagoon, and Morro, Newport, and San Francisco bays, throughout the 1930s. Humboldt Bay was excluded from plantings while the DFG tried to re-establish natural populations of Native oysters. Several Pacic oyster plantings proved successful, demonstrating that imported Pacic oyster seed could be grown commercially in California. Shipments of seed from Japan were made through the 1930s, suspended from 1940 through 1946, and increased signicantly in 1947. The imported seed was inspected in Japan by both DFG personnel and commercial producers prior to shipment. DFG personnel examined the shell for organisms considered harmful if introduced into state waters. Boxes containing oyster shell with attached young oysters (spat) were transported by ship in wooden crates kept moist with seawater. With the inux of seed oysters, the industry began its recovery in California and on the West Coast. The DFG lifted its restriction on Pacic oyster seed in Humboldt Bay in 1953, and in the next 30 years, the California industry showed rapid growth with production
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Cultured Oysters millions of pounds harvested
1.75 1.50 1.25 1.00 0.75 0.50 0.25 0.00
1960
1970
1980
centered in Humboldt Bay, Drakes Estero, Tomales Bay, Elkhorn Slough, and Morro Bay. The West Coast oyster industry initiated other signicant changes in the early 1980s, which have had a signicant impact on the industry nationally. These changes include the development of U.S. based shellsh hatcheries for the domestic production of Pacic oyster seed, and the ability to ship advanced hatchery-produced oyster larvae (swimming stage) to growout sites where the larvae are placed in tanks containing cleaned shell and heated seawater for spat production. In this process called remote setting, the larvae settle on clean oyster or scallop shell, called mother shell or cultch, attach and metamorphose into the more familiar at young oyster called spat. Spatted cultch ultimately results in about nine to 13 market-sized oysters clustered on remnants of the old mother shell. Another hatchery product is cultchless oyster seed that are grown out as individual oysters exclusively for the half shell market. Cultchless seed are produced by setting the larvae on sand or nely crushed oyster shell, resulting in unattached, individual oysters. Many California growers purchase cultchless seed from California-based advanced seed producers. These producers receive 3.0 to 5.0 mm cultchless seed from a hatchery, then use oating upweller systems (FUS) to hold the seed in ow-through containers receiving bay water containing algae. The oyster seed increases in size and is more easily handled in mesh bags used by the end producer. Individual growers are also adopting and expanding their own land-based FUS and downwellers to cut the cost of seed and assume the responsibility of early seed growth. All oysters grown in California currently are produced from hatcheries located in Washington, Oregon and Hawaii. The hatchery systems primarily produce two species of Pacic oysters; the Pacic oyster (C. gigas) and the Kumamoto oyster (C. sikamea) which also originated in Japan and does not reproduce in California’s cooler summertime
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Commercial Harvest* 1960-1999, Cultured Oysters Annual pounds of cultivated oysters harvested by State aquaculture producers. Data Source: California State Tax records (royalties reports) and DFG Aquaculture Harvest Survey Database. * Packed weight is estimated to be 15.5 percent of live weight for C. gigas and 10.9 percent for C. virginica. Shucked gallons are calculated as 8.6 pounds/gallon 1990 1999 for C. gigas and 8.5 pounds/gallon for C. virginica. Cultchless oysters, C. sikamea and a large portion of C. gigas are sold as shellstock.
Culture of Oysters
2.00
water. Other less prominent species produced by hatcheries have included the European oyster (O. edulis) and some Eastern oyster (C. virginica). The ability to ship oyster larvae long distances and set the spat at the growout areas has signicantly reduced the cost of seed. The last shipment of Japanese seed to California was in 1989. The level of oyster production within the various bays has uctuated throughout the years, primarily because of water quality, the bay’s ability to produce good standing crops of algae on which oysters feed, the adequacy of selected sites, and the nancial viability of the various oyster operations. All growing areas are classied and certied by the California Department of Health Services (CDHS) based on health-related water quality standards established and regulated by the Interstate Shellsh Sanitation Conference (ISSC) and the National Shellsh Sanitation Program (NSSP). Water-bottom and offshore growout areas are leased from the state through the Fish and Game Commission, harbor and recreation districts, or belong to private corporations. The industry uses a variety of oyster culture methods depending on the targeted market, the physical characteristics of the production bay and the need to protect the younger oysters from predators such as bat rays, rock crabs, and drills (snails). Culture methods are also inuenced by factors such as substrate type, current velocity, tidal range, and phytoplankton productivity. California oysters are grown from spat to market size in about 13 to 18 months, depending on the bay and the culture method used. California oyster production is currently centered in four areas, Arcata Bay located in the North Humboldt Bay complex, Drakes Estero, Tomales Bay and Morro Bay. Morro Bay oyster production has declined in recent years, but techniques have included bottom, rack-and-bag, and stake culture. Shellsh producers in the Santa Barbara Channel
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have used a system of longlines with attached bags of European oysters suspended from offshore rafts in the deep waters, but have discontinued production in recent years. Shellsh producers also cultured cultchless oysters in Agua Hedionda Lagoon, located north of San Diego, but have switched to mussel production which was considered more suitable to the area.
to an anchored line which suspends the bags vertically in the water or secures the bags on a stable, hard bottom, intertidal area. Bags can also be maintained horizontally at the surface using oats. To maintain the prime oyster shape for the half shell market, the bags must be moved frequently to prevent the individual oysters from growing together and resulting in an irregular shape.
Humboldt Bay growers use a variety of oyster culture methods, but the predominate method has been bottom culture of Pacic oysters. In bottom culture, cultch with attached spat is spread over leased areas in the bay, the oysters are grown to about four inches and are then harvested by hand picking and hydraulic dredge. Most of California’s shucked oyster product is from bottom culture in Humboldt Bay. Because of environmental concerns and the impact of hydraulic dredging on eelgrass, growers are currently changing about 85 percent of their bottom culture production over a period of about three years to off-bottom, longline culture of the Kumamoto oyster. The Kumamoto oyster derives a higher market price as non-shucked shellstock, and the remaining bottom culture will be targeted for the peak shucked-oyster market in November and December. Environmental and economical studies are being conducted to determine the impacts of these changes on both the health of the bay and the economic health of the industry.
Total annual oyster production for California has uctuated throughout the industry’s history, reecting cyclic shellsh mortalities (“Summer Mortality Syndrome”, SMS), availability of seed oysters, economic conditions, and the nancial stability of individual companies. With the advent of hatchery technology and remote setting of oyster seed, the industry demonstrated signicant growth from the mid-1980s to a second post-1960s peak in the mid-1990s. Reduced production after 1994 directly reects several industry setbacks, which include nancial restructuring after the 1990s recession, extended bay harvest closures due to sanitary degradation and oil spills, and recurrence of cyclic SMS. Several of these factors have been resolved, and production increases are expected. The data represents a conversion of all oyster products to a common denominator of shucked pounds of oysters expressed as packed weight. Total production in recent years is primarily Pacic and Kumamoto oysters. Annual Eastern oyster production has been 20 pounds or less for the past three years.
Longline culture primarily consists of a series of notched PVC pipe set in the substrate with twisted line stretched over the apex of the poles. Spatted cultch is inserted at intervals between the strands of the line which hold the growing oysters above the substrate. The lines containing the clustered oysters are harvested on a ood tide, thereby reducing disturbance to the substrate or associated eelgrass. Other forms of culture are off-bottom techniques, including bags of cultchless oysters supported by low racks and oating oyster bags attached to longlines. Drakes Estero has one of the largest off-bottom, rack culture systems in the west. Like all off-bottom culture, the method is used primarily to avoid predators, use more of the water column, and avoid siltation that occurs when the oysters rest on the substrate. The rack culture system uses spatted mother shells strung on short lines with a tube spacer separating each mother shell. The short lines are hung in an inverted u-shape over the horizontal rails of wooden racks set in the bay. Tomales Bay growers also use a variety of off-bottom techniques including rack-and-bag, stick and bag, and bag and longline culture. Rack-and-bag culture uses cultchless seed that is rst grown in trays, upwellers and downwellers, or oating, rotating, mesh cylinders. After initial growth, the small oysters are transferred to a series of different sized mesh bags positioned on low racks in the bay. Bag and longline culture use cultchless seed in mesh bags attached
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Oyster products are marketed as shucked meat in gallons and 10-oz jars, and as shellstock for the half-shell and barbecue markets. The shucked product is marketed as small (200/gallon), medium (140/gallon), and large (100/gallon). Shellstock is marketed as small (2.5-3.5 inches), medium (3.5-4.5 inches), large (4.5+ inches) sold by the dozen, and clusters (attached, mixed). The demand for oyster products far exceeds the state’s production level, and the majority of shellsh products consumed in the state are imported from the Pacic Northwest and the Atlantic and Gulf states. California’s product is considered prime, and its production areas are among the best in the country. The CDHS has regulatory responsibility over shellsh product safety and periodically conducts sanitary surveys with the Federal Food and Drug Administration under worstcase scenarios such as heavy rain to determine growing area water quality and sanitation conditions. Two essential programs are the monitoring of the bays for indications of contamination, including human sewage, and for the occurrence of natural biotoxins such as paralytic shellsh poison produced by toxic phytoplankton. The programs are designed to provide a safe product for the consumer and an early warning system for people sport-harvesting shellsh in noncommercial areas. The water and meat quality monitoring programs conducted by the CDHS also provide an assessment of the biological condition of the
CALIFORNIA DEPARTMENT OF FISH AND GAME December 2001
blades and incubate for about 10 days before release. Once expelled, the advanced larvae swim freely and feed on phytoplankton before settlement and metamorphosis (Native, 14-18 days; European, 10-14 days).
Status of Biological Knowledge
The Pacic, Kumamoto and Eastern oysters are alternative hermaphrodites; sex change occurs, but its timing is erratic. They have a tendency for protandry in their rst year, but the tendency is not as strong as that of Native and European oysters. They are oviparous (broadcast spawners); the eggs are immediately released and fertilization takes place in the environment. Mature, eggcarrying females spawn at about 63-77˚ F, depending on the species, variety, and latitude. Water temperatures required to establish a natural population are higher than those consistently found in California. Since natural spawning and successful reproduction rarely take place in California, the oysters are spawned and reared in shellsh hatcheries at about 77˚ F. The eggs hatch into free-swimming trochophores, then become veliger larvae. Within three to ve days these larvae settle, attach to a substrate, and metamorphose to spat.
O
ysters are bivalve mollusks that exhibit a variety of sizes, shapes, shell textures and colors, and vary in their mode of reproduction and sexual expression. These biological and physical features inuence where they grow and how they reproduce, which in turn inuence commercial aspects such as culture practices and marketing strategy. The depth of the shell cup and the shape of the oyster inuence market price of shellstock. Individual oysters conform to the shape of the substrate to which they are attached and are therefore highly variable in shape. In addition, shell shape, texture, and color are all inuenced by the oyster’s genetics and physical environment such as salinity, attachment substrate, crowding by other oysters and food. They feed on phytoplankton and nutrient-bearing detritus by pumping water over their gills, ltering the food material and passing it into the mouth. All oysters have a typical molluscan trochophore larva that develops into a veliger larvae capable of ltering food, swimming, and selecting a suitable substrate for attachment. The microscopic veliger settles, cements its left valve to the substrate, and undergoes metamorphosis into an oyster spat. For the rest of its life the attached spat will compete for space and nutrients and, if it survives, will grow into the adult form. The ve oysters now found in California belong to the family Ostreidae. They represent two groups characterized by biological variations, including different modes of sexual expression, reproduction, and dispersal of young. The exact temperature at which the oysters will spawn and the rate of larval development and growth depend on a variety of factors, including species, genetics and latitude of the breeding population. Natural spawning is also inuenced by lunar periodicity and tides. The Native and European oysters are rhythmical consecutive hermaphrodites; they can change sex either annually or at closer intervals. In their rst year, they are strongly protandric; the rst expression of sex at maturity is male. They may become female in the same year or in the following year if environmental conditions are good and food is plentiful. They are also larviparous (brooders); fertilization of eggs is internal, and the larvae are held for a period of time before release. Mature, egg-carrying females spawn at about 59-63˚ F. The eggs are released into the female’s own mantle cavity and are fertilized as she takes in water containing the male’s sperm. When the eggs hatch, the veliger larvae are held by the gill-
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Culture of Oysters
bays, which is essential information used by all agencies to prevent a reoccurrence of events which led to the contamination of San Francisco Bay.
The Native oyster is California’s only indigenous oyster species and occurs along the Pacic coast from Sitka, Alaska to Cape San Lucas, Baja California. The largest concentrations occur in the Pacic Northwest along the coast of Washington’s Puget Sound and in Willapa Bay. Although still grown commercially in Washington in specially constructed beds, natural concentrations are not abundant enough to support commercial endeavors. Populations of the Native oyster are still relatively low in California. Some protection of existing populations is provided by sport shing regulations, which allow a daily harvest of 35 native oysters under the general invertebrate bag limit. The adult is about one to three inches in length and more often irregular in shape. Shell textures vary from smooth to rough with concentric growth lines, and the exterior has purple-brown to brown axial bands. The two shell valves are symmetrical; their interior is shades of olivegreen and can have a metallic sheen. The internal shell’s muscle scar in adults is usually centrally located and unpigmented. The Native oyster is found in many of California’s coastal inlets, especially mudats and gravel bars located near the mouth of small rivers and streams. It cannot withstand high temperatures or frost when exposed, and does not survive low salinity or turbid water. The natural beds are invariably located in the low intertidal and subtidal zone of bays, where the oyster is better protected from both prolonged hot summer surface water temperatures and extreme cold winter water conditions. The oysters are often found clinging to rocky outcroppings or other structures that offer protection from rays and other predatory sh.
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Adult European oysters are about three to four inches in length, with a poorly developed beak that gives the valves an oval to round shape. The left or attachment valve is larger and more deeply cupped than the right valve, with 20 to 30 ribs and irregular, concentric lamellae. The upper, smaller valve is at, with numerous concentric lamellae but no ribs. The hinge ligament consists of three parts: a middle, at part on the left valve and two projections on the right. The internal valves are white, and the muscle scar is eccentrically positioned and unpigmented. Adult Eastern oysters may vary in length from two to six inches. The shells are asymmetrical, highly variable in texture and shape, and greatly inuenced by environmental conditions. The external shell is usually a shade of gray, and the internal valves white with a variable-colored muscle scar, usually deep purple. The left valve is longer than the right, not deeply cupped, and the beak is usually elongated and strongly curved. The shell margins are usually straight or only slightly undulating, and the inner margins of the valves are smooth. The adult Pacic oyster ranges from about four to six inches in length. The shell is coarse, with widely spaced concentric lamella and ridges. The shell is thinner than that of Eastern oysters yet more deeply cupped. The Kumamoto oyster is smaller but is prized for its deeper cup. It spawns in the fall in nature and grows more slowly than the Pacic. The Miyagi is the principal variety of Pacic oyster grown on the West Coast. The Pacic oyster’s shape may be highly variable and greatly inuenced by environmental conditions. The upper, at, right valve is smaller than the left, and the inner surface of the valves is white with a faint purple hue over the muscle scar. Oyster disease and shellsh pests are a major concern to the state resource agencies and the oyster industry. Because the West Coast industry depends on the movement of animals across state lines, the industry is subject to regulations established through cooperative agreements between resource agencies. All oyster seed and shellstock not destined for a terminal market that cross state lines are examined for the presence of disease and exotic “hitchhikers” (pests) which could be harmful to natural resources and commercial interests. Seed and shellstock that do not pass certication are destroyed through cooperative agreements with the state and the industry. The various state natural resource agencies have a cooperative program which regulates the interstate movement of shellsh seed and seedstock. Oyster diseases on the West Coast most frequently occur in hatcheries, but a few signicant oyster diseases have been reported from the eld. Hatchery conditions are articial environments which can stress oysters and render them susceptible to an array of infections. Hatchery-asso-
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ciated oyster diseases are usually conned within the hatchery. When identied, the stocks are destroyed and systems disinfected. This is a protective measure for the natural resource and considered the most economically practical approach by the industry. Field-associated oyster diseases are not common, but they do occur. Two examples of the most signicant of these diseases for the West Coast are “Summer Mortality Syndrome” (SMS) of Pacic oysters, and “Bonamiasis” of European oysters. Summer mortality of Pacic oysters was rst reported in the 1960s with mortality levels as high as 65 percent of adult Pacic oysters. Oyster losses attributed to SMS have uctuated over the years, and studies have addressed the initiating agent as possible unknown pathogens, environmental factors and impacts, and stressors such as the combination of depleted energy reserves and attempted gonadal maturation. SMS was researched for decades without resolving the cause. In 1993 and 1994, summer mortalities of Pacic oyster seed in Tomales Bay reached 52 and 63 percent respectively, and were associated with elevated water temperatures above 20˚C and a dinoagellate bloom. Pathological examination and histology suggested that these mortalities were related to environmental causes and not an infectious agent. SMS appears to be cyclic, may be related to decadal cycles, and is the most signicant mortality-related event experienced on the West Coast of the United States. In addition, as the losses are a “syndrome” and are not caused by a specic pathogen, multiple etiologies may result in oyster deaths during the summer. The type of stress that results in losses may also uctuate over time, making diagnosis of the cause(s) and management of losses difcult. Growers are attempting to circumvent the problem by not planting Pacic oyster seed during the warmer months from May to October. However, seed availability during the cooler months has been a problem. Growers report that cooler bay water temperatures in 1999 appear to have moderated the mortality rate from that experienced previously. Bonamiasis of the European oyster, caused by a parasite, has impacted the oyster industry to the same extent as SMS, as it has contributed to the inability to establish European oyster culture in California. The parasite infects the oyster’s blood cells, destroys its immune system, and impacts other physiological processes. Of recent concern is the 1980s discovery in California of a haplosporidium similar to that which causes MSX or Delaware Bay Disease on the East Coast. West Coast producers have not experienced the cyclic, catastrophic haplosporidia diseases that have occurred on the East Coast, despite movement of Eastern oysters between the coasts. It has been conrmed that the organism is the causative agent of MSX of Eastern oysters. The organism is found among Pacic oysters in one bay in California
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Shellfish and the Environment
O
ne of the more signicant challenges to aquaculture in the next decade will be the industry’s ability to position itself within the environmental framework and philosophy of natural resource management. Environmental issues are a concern nationally and are paramount in California. Immediate environmental concerns relative to shellsh culture are the potential biological and physical impacts of culture technology on sensitive components of the marine ecosystem. These sensitive components include eelgrass as essential habitat for salmonid and other nsh, and the invertebrate assemblage present on and within the substrate that is essential to the food web of birds and other marine species. Also included are the impacts on the life habits of birds and marine mammals and on the physical structure of the bay. It will be essential that shellsh technology not have signicant impact upon the health of the ecosystem on which it also depends. Shellsh culture and our living marine resources depend upon excellent water quality and a healthy environment and, therefore, these concepts are not mutually exclusive. In response to these concerns, long-term federal and state supported regional research has been initiated to study shellsh culture impacts. This research is being conducted by university and state research agency personnel, focuses on the industry in California, Washington, and Oregon, and is monitored continuously to identify areas that may need immediate alteration. In addition, federal and state funding, coupled with industry resources, is being directed toward the development of industry best management practices to guide the industry in its present and future development.
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Future Trends
O
yster hatchery and production seed technology has rapidly expanded in the past ten years. This has included application of remote setting of oyster seed as an industry standard, and the production and use of triploid (3n) oysters containing an extra set of chromosomes. The 3n condition prevents the onset of maturation and results in oysters characterized by year-round production of high quality meat. Although triploid production was a positive technical breakthrough, the sterile 3n oyster does not reproduce and therefore can not be improved through genetics. To overcome this, the industry now applies high pressure following fertilization to retard both polar bodies. The resultant tetraploids (4n) are then articially crossed with diploids (2n), thereby producing sterile triploids (3n) that are used as production oysters while maintaining a viable genetic line in the diploid broodstock. This technology, coupled with the more recent establishment of broodstock genetic programs, will be a major industry thrust.
Culture of Oysters
but is not associated with signicant mortalities. Morphologically similar haplosporidians have also been reported from Washington state. Recent studies suggest a common ancestry for the organism on both coasts and that the haplosporidian was not endemic to the East Coast but originated in Pacic oysters from Japan. Hypotheses for the introduction of the disease to Eastern oysters include importation of infected Pacic oysters to the East Coast, ballast water containing the infective agent, or introduction of an unknown intermediate host. In any event, the ultimate result has been catastrophic for the Eastern oyster and the East and Gulf coast industries. The result of these studies demonstrates the rst molecular conrmation of the introduction of an exotic marine pathogen and emphasizes the need to adhere to strict importation guidelines as established by the International Council for the Exploration of the Seas (ICES).
Oyster genomic research is an industry priority and a regional cooperative effort involving university and industry geneticists and oyster hatchery managers. The establishment of a national Molluscan Broodstock Program (MBP) and the Molluscan Broodstock Center on the West Coast mark the true beginning of an oyster genetics program which fosters cutting edge genetics research. Using a mix of regional and national grants, geneticists are utilizing cooperative regional research to develop genetically marked family lines that are tested and selected for high yield and survival. Scientists are exploring the alternative strategy of crossbreeding and have demonstrated at the larval and market sizes that hybrid Pacic oysters have dramatically higher yield and superior metabolic performance than their inbred parents. This striking hybrid vigor or heterosis suggests that crossbreeding, in addition to traditional selection as practiced by the MBP, could improve oyster yield dramatically and quickly. Technology is also being developed to measure and more readily dene “future performance” at the larval stage, thereby avoiding costly growout trials and stock maintenance. Current and future trends of the oyster industry are reected throughout the West Coast and the Pacic Rim because of the industry’s regional infrastructure and markets. Industry shellsh hatcheries which were concentrated in the Pacic Northwest have opened in Hawaii, thereby taking advantage of stable water quality and consistent solar radiance used in energy-efcient algal culture. The primary markets for seed are West Coast producers who will expand into more international markets. The industry is rapidly expanding Kumamoto oyster production because of its higher value and half-shell market
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demand, and greater market attention will be given to value-added shellsh products such as ash-frozen halfshell products for international Pacic Rim markets. The oyster industry will concentrate on developing more efcient methods of off-bottom culture and culture techniques that are less intrusive and result in fewer environmental impacts. The greater adaptation of off-bottom culture, coupled with the higher valued half-shell Kumamoto oyster, is a potential that may offset the loss of shucked product produced in bottom culture. The development and adaptation of more environmentally sound practices will remain an industry priority. Fred S. Conte University of California, Davis Tom Moore California Department of Fish and Game
References Barrett, E.M. 1963. The California Oyster Industry. Calif. Dept. Fish and Game Bull. No. 123, 103 pp. Bonnot, P. 1935. The California Oyster Industry. Calif. Dept. Fish and Game. 21(1):65-80. Burreson. E.M., N.A. Stokes and C.S. Friedman, 2000. Increased virulence in an introduced pathogen: Haplosporidium nelsoni (MSX) in the Eastern oyster Crassostrea virginica. J. Aquatic Animal Health12:1-8. Conte, F.S. and J.L. Dupuy. 1982. The California Oyster Industry. Proc. North American Oyster Workshop, World Mariculture Society, Special Publication No. 1: 43-63. Conte, F.S., S.C. Harbell and R.L. RaLonde. 1994. Oyster Culture: Fundamentals and Technologies of the West Coast Industry. WRAC Publication No. 94-101 Sectional: 1994 and 1996. Elston, R.A. 1990. Mollusc Diseases: Guide for the shellsh farmer. University of Washington Press. 73 pp.
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Culture of Salmon D
ifferent methods are used for aquaculture production of salmon. The three major techniques are salmon ranching, land-based tank operations, and net-pen rearing. At salmon ranch hatcheries, adult sh are spawned, the eggs are hatched, and the young are reared in tanks to increase their size and chances of survival in the wild. The salmon smolts are then released and grow to market size while at liberty in the ocean. After maturing at sea, the salmon return to the hatchery, where they are harvested. If at least three to ve percent of the released salmon return to be harvested, a private salmon ranch may be protable. However, it is not uncommon for 98 to 99 percent of the salmon to be lost to natural and shing mortality before they can return to the hatchery. Land-based tank operations maintain all of the sh at the facility until harvest. Fish are kept in tanks made of concrete, berglass, or other materials. Round tanks are often in the range of 30 to 40 feet in diameter. Water is pumped through the tanks to maintain good water quality, and growth comes from manufactured feed provided by the aquaculturist. Net pen facilities use young sh produced in hatcheries, which are then placed into pens where they are fed until grown to market size. The pens are made from exible netting material suspended from oats and are generally a few hundred square feet at the surface. Pens are often linked together to form large units of up to many acres. The net-pens are usually placed in sheltered salt-water areas where protection from ocean storms is provided and good water quality is maintained by natural currents. Salmon have been produced in California by both private and public hatcheries. While the history of private trout production in California is strong and dates back to the 1800s, private commercial production of salmon in California has been intermittent and never very substantial. The beginning of recent interest in commercial salmon production was the authorization by the California Legislature in 1968 for the rst (and only) private salmon ranching operation. In 1979, the legislature authorized the operation’s move to its current site on Davenport Landing Creek (Santa Cruz County), where the operation has been inactive for several years. In California, land-based tank operations were tried in the 1980s and 1990s, and accounted for some limited private aquaculture production of salmon. Most commercially produced salmon were from tank-rearing operations located in northern California, where cold water suitable for salmon culture is more readily found. Fish were grown to market size in tanks using either fresh or salt water. Steelhead trout (Oncorhynchus mykiss) were produced from domestic brood stock maintained by California aqua-
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culturists, whereas coho salmon (Oncorhynchus kisutch) and Atlantic salmon (Salmo salar) eggs or ngerings were imported from out of state to California farms. Salmon culture has not been a major component of the state’s private aquaculture sectors and never contributed as much as ve percent to the total value of the industry’s production. Conversely, public salmon hatchery operations play a key role in the management of California’s natural resources. Hatcheries are built and operated to supplement natural salmon resources or to mitigate for the loss of natural production that occurs when water and power generation projects eliminate salmon spawning habitat. Thus, hatcheries help provide for the multiple benecial use of the state’s water resources. Public hatcheries produce approximately 40 million sh each year and are critical to maintaining the state’s sport and commercial salmon sheries. Over ninety percent of California’s salmon harvest comes from south of Point Arena, where hatchery-produced sh generally make up over half of the catch.
Culture of Salmon
History
Public hatchery production of salmon in California dates back to 1872 with the establishment of Baird Hatchery on the McCloud River in the upper Sacramento River drainage. Several other salmon hatcheries and egg taking stations also began operations in the late 1800s and early 1900s. Baird originally operated as an independent hatchery, then as an egg collecting station for salmon and trout reared at Mount Shasta Hatchery (then called Sisson Hatchery). After the construction of Shasta Dam, Mount Shasta Hatchery and the upper Sacramento spawning grounds were separated from the lower Sacramento River and the Pacic Ocean. Coleman National Fish Hatchery was built in 1942 to mitigate for those losses. It replaced many of the early hatcheries, including most of the salmon operations at Mount Shasta. Coleman Hatchery is on Battle Creek, a tributary of the Sacramento River at Anderson (south of Redding). It is the only federally operated sh hatchery in California. Today there are seven California Department of Fish and Game-operated salmon mitigation hatcheries and two state-operated salmon restoration and enhancement hatcheries. All nine of these state-operated hatcheries have been built since 1955. The mitigation hatcheries are located on central valley and north coast rivers downstream from dams constructed for water or power development.
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Hatchery
Location
Iron Gate ...............................On the Klamath River below Copco Lake Trinity...................................On the Trinity River below Clair Engle Lake Feather River ..........................Below Lake Oroville Mokelumne River Fish Installation .Below Camanche Reservoir Nimbus..................................On the American River below Folsom Lake Van Arsdale Fisheries Station .......On the Eel River below Van Arsdale Reservoir Warm Springs ..........................On a tributary to the Russian River below Lake Sonoma The DFG’s two restoration and enhancement hatcheries are the Mad River Hatchery near Eureka and the Merced River Fish Installation below Lake McClure. There is also a non-prot salmon and steelhead enhancement hatchery in California on the Smith River. The Rowdy Creek Fish Hatchery is located in the town of Smith River and began in 1967 as a Kiwanis Club project. It operates under an individual category in the California Fish and Game Code. In addition, public or privately funded nonprot salmon restoration and enhancement projects use a variety of habitat improvement, articial spawning, and rearing techniques to improve runs of wild sh or to contribute additional sh to the shery. Most are located on coastal streams in northern and central California. Saltwater penrearing operations have been located at Tiburon, Port San Luis, and Ventura. In 1998-1999, a total of twelve projects planted an average of 30,000 sh per project.
Status
C
urrently, there is no private for-prot aquaculture production of salmon in California. Nationally, and internationally, net pen rearing of salmon has proven to be the most successful method of private aquaculture production of salmon for the seafood market. The only net-pen rearing of salmon in California has been some small sport shing salmon enhancement projects. Commercial net-pen rearing is not prohibited, in part because no suitable sites have been identied or developed which do not conict with other established uses. Every private aquaculture operation in California is required to register with the Department of Fish and Game. Before approving an application for registration, the department must determine that each facility will
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not cause signicant negative impacts on adjacent native sh and wildlife. Private salmon culture may be permitted throughout California where negative impacts will not result, except that commercial salmon farming is prohibited from the Smith River watershed. The lone California commercial salmon ranching project (Davenport Landing) is required to operate under an annual permit from the Fish and Game Commission. Commission authority to issue the salmon ranching permit is granted by the California Legislature. The legislature reviews the authorization periodically and in 1995 extended authority to issue the permit to January 1, 2001. While the project does not have a current permit, it historically has been authorized to ranch chinook salmon, coho, and steelhead. State and federal hatcheries produce chinook and coho salmon and steelhead using the same production techniques as other salmon ranching operations. Returning adults are articially spawned and the offspring are reared to smolt or yearling size before they are released at the hatchery (or at other freshwater sites) to migrate to the ocean where they grow to adults. Chinook salmon return to be spawned, usually three or four years after release. Coho generally spend one year in freshwater and return from the ocean to spawn as three-year olds. Hatchery steelhead spend one or two seasons in fresh water and one to three seasons in the ocean and can repeat spawn after release. Public hatchery production remains relatively constant; therefore, years of low natural production result in harvests with a larger proportion of hatchery sh. Depending upon the success of each year’s natural production, Department of Fish and Game biologists estimate that hatchery-produced sh generally contribute from 50 to 60 percent of California’s sport and commercial salmon harvests. Most of the public hatchery production of salmon in California is intended to mitigate for the loss of habitat caused by construction of dams for water and power development. The concept of providing mitigation for losses to sh and wildlife caused by the building of a government project was originally established by the U.S. Congress when it enacted the Fish and Wildlife Coordination Act of 1934. The need to replace the natural shery resources eliminated by these projects continues to have high priority with the people of California. Bob Hulbrock California Department of Fish and Game
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Culture of Salmon
References California Advisory Committee on Salmon and Steelhead Trout. 1988. Restoring the balance: 1988 Annual Report. 84 pp. Leitritz, E. 1970. A history of California’s sh hatcheries 1870-1960. Calif. Dept. Fish and Game, Fish Bull. 150. 86 pp. Leitritz, E. and R.C. Lewis. 1976. Trout and salmon culture-hatchery methods. Calif. Dept. Fish and Game, Fish Bull.164. 197 pp. Thorpe, J.E. (Editor). 1980. Salmon Ranching. Academic Press, New York, New York. 441 pp.
Weighing and spawning of Chinook salmon at Rowdy Creek Hatchery, a community-run hatchery near Crescent City. Credit: CA Sea Grant Extention Program
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Culture of Marine Finfish History of Finfish Culture
T
he impetus to develop marine aquaculture in the U.S. is strong. In 1998, the U.S. imported $8.2 billion in edible shery products. During the past 15 years, production of food sh by capture sheries reached a plateau of 66 million tons per year. Similarly, FAO statistics report that 60 percent of marine sheries are fully or overexploited. Under these conditions, and with a growing human population, it is estimated that aquaculture production will have to increase by 140 percent from 1995 levels by the year 2025. Marine nsh farming in California and the United States is in its infancy. In California, with the exception of anadromous species, no marine nsh are being produced on a commercial scale. In the United States, specically Texas, only red drum are cultured in large numbers. However, the red drum ngerlings being produced are used primarily for stock enhancement and not grown out and marketed for direct human consumption. Like the Texas stocking program for red drum, California has been evaluating the efcacy of marine stock enhancement since the early 1980s. This research has been conducted largely under the auspices of the Ocean Resources Enhancement and Hatchery Program (OREHP). In recent years, the stock enhancement research has lead to projects designed to evaluate the feasibility of commercial growout in nearshore cages. The two primary species that have been investigated in California are the white seabass (Atractoscion nobilis) and the California halibut (Paralichthys californicus). Giant sea bass (Stereolepis gigas) have also been studied but to a much lesser extent.
History of the Ocean Resources Enhancement and Hatchery Program (OREHP)
T
he OREHP began in 1982 and has since been reauthorized with minor modications. This program funds research through the sale of recreational and commercial marine enhancement stamps for all saltwater anglers south of Point Arguello. The California Department of Fish and Game manages the OREHP with the assistance of an advisory panel that consists of academic and management agency scientists, representatives of both commercial and recreational shing groups, and the aquaculture industry. Since 1995, OREHP has supported operation of the Leon Raymond Hubbard, Jr. Marine Fish Hatchery in Carlsbad, California. This research facility is dedicated to improving our understanding of marine sh culture.
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The species described in this chapter are native to California and have historically represented important sheries to the region. Detailed descriptions of the natural history and sheries for each are provided elsewhere in this volume.
Culture, Facilities and Systems
I
n California, land-based research facilities (hatcheries) are used for broodstock holding and maturation, and for larval rearing of marine nsh. Juvenile culture has been conducted on a limited scale for white seabass in cages, pools and raceways, and with California halibut in raceways. Seawater is pumped into land-based facilities from nearshore areas, (typically lagoons, harbors, or embayments) where water quality may be highly variable. Broodstock maturation systems are typically recirculated so that water temperature can be controlled and used to induce spawning. Pool volumes range from 5,000 to 11,500 gallons. Egg hatching and early larval rearing systems require ne control over water quality parameters. Low ow requirements make ow-through systems practical, but recirculating systems are generally recommended. Pool volumes for egg hatching and early larval rearing range from 80 to 450 gallons. Juvenile growout has been conducted in ow-through systems (pools and raceways) up to 8,000 gallons in volume and nearshore cages up to 145,000 gallons. California’s OREHP maintains one of the largest breeding populations of a single species of marine nsh, white seabass, in the world. More than 250 adult sh are maintained in captivity either in breeding pools or support facilities. The need for this large number of individuals stems from the stock enhancement objectives of the program and the desire to ensure genetic diversity of released animals. However, the large broodstock population also results in a surplus of egg production that could help support a developing commercial culture industry. Spawning of marine nsh, including white seabass and California halibut is often allowed to occur naturally or is induced semi-naturally using photo-thermal manipulation. That is, seasonal cycles are either natural (ambient water temperature and photoperiod) or controlled to promote spawning out of season. Hormone-induced spawning has not been investigated thoroughly and the few attempts to induce spawning have been largely unsuccessful. The disposition and general hardiness of California halibut and giant sea bass makes them potentially better suited to the extra handling required for hormone injections, while white seabass are not. Female white seabass and California halibut are reported to mature in the wild at four to ve years. For white
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Growth of each of these species is highly dependent on water temperature. White seabass and California halibut are physiologically adapted to estuarine conditions as juveniles and therefore can tolerate (and may prefer) higher temperatures (71-81º F) associated with embayments. Furthermore, the southern range for these species near Magdelena Bay in Baja California, Mexico where water temperatures can be expected to be even warmer than those in California. White seabass have been cultured in raceways to a size of 3.3 pounds in two years at temperatures of 56-79º F. A similar growout period in cages yielded only a 1.75 pound white seabass, but water temperature was considerably lower (52-72º F). California halibut cultured in raceways exhibited slow growth, reaching a maximum of 0.9 pound in two years under conditions of 55-77º F. It should be noted that these data are preliminary and that growth will likely be improved as the nutritional requirements and the potential for selective breeding are investigated more fully. White seabass begin feeding at an age of four to ve days (post hatch). Their relatively large size allows them to feed successfully on newly hatched Artemia. California halibut and giant sea bass both require smaller prey items such as rotifers for the rst week of feeding, before transitioning to Artemia nauplii. Beginning at 20 days, dry feed is offered to the sh along with the Artemia. In order to help the sh wean from a live prey diet to dry feed, frozen zooplankton (adult Artemia, krill or mysids) is also fed to the sh. The amount of live food (Artemia nauplii) and frozen feed is slowly reduced as sh begin feeding on the dry feed. Once on dry feed, the feed size is increased as the sh grow. The feed type, characterized by the protein and fat content, may also be adjusted to reduce costs and improve llet quality. Among the more common infectious diseases affecting white seabass and California halibut are: 1) protozoans; 2) bacteria; and 3) invertebrate parasites. Among these pathogens, the bacterium Flexibacter maritimus is the most common and difcult to eradicate. Infections by this organism occur frequently after handling the sh and may result in lesions and n rot. Among the non-infectious diseases, gas bubble disease is often severe among white seabass cultured in shallow water systems that are not adequately degassed, including oating raceways in natural water bodies. Nutritional deciencies are also likely in cultured marine sh, although the effects are not well understood.
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Cannibalism can be a signicant problem among younger life stages of marine sh before grading is practical. Cannibalism can be reduced by optimizing feeding and nutrition and by grading the sh. In outdoor rearing pools, birds such as herons are known to prey on cultured sh. These predators can effectively be excluded using inexpensive netting. In cages, marine mammals such as California sea lions and harbor seals can be a problem if given the opportunity. Birds, both diving and non-diving, can also prey on caged sh. To prevent predation on caged sh, extra netting (i.e., in addition to the sh containment net) should be employed above and below the water.
Aquaculture Potential
Culture of Marine Finfish
seabass, this represents a size of 27 inches and for California halibut, 18.5 inches. Eggs from each of these species are pelagic. Females are batch-spawners, with each batch typically yielding hundreds of thousands to more than a million eggs.
T
he aquaculture potential for white seabass and California halibut should be excellent. The potential for giant sea bass culture appears to be less promising, although further research is warranted for this species. White seabass and California halibut are popular, high-value species. Wild white seabass are available seasonally and at a large size of more than six to seven pounds. Wild halibut are available year-round and there is a growing market for live sh. In other regions, species similar to white seabass and California halibut are being cultured successfully -- in some cases on a truly commercial scale. Among some of the croaker species (related to white seabass), red drum, and seatrout are being cultured in the United States. Totoaba, corvina, and maigre (all members of the croaker family) are being evaluated for culture in Mexico, Argentina, and the Mediterranean, respectively. Several species of atsh are also being cultured. On the East Coast of the United States, the summer ounder and southern ounder are being evaluated for culture. In Japan, a ounder has been cultured on a commercial scale for many years, and two species of ounders are being cultured in South America.
Conclusions
A
quaculture of marine nsh is in its infancy in the United States, and California has not contributed signicantly to its development. With 1,200 miles of coastline, opportunities to farm the ocean should be readily available. Unlike the agriculture industry in California, which consistently ranks number one in the nation (greater than $26 billion in 1997), mariculture opportunities in California are impeded by competing uses for coastal resources and a restrictive regulatory environment. In addition to the typical burdens associated with bureaucracies, California regulatory agencies often over-
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lap in authority, lack a clearly dened process, and are often poorly educated about the need for aquaculture and what is involved with mariculture activities. There is a clear need for aquaculture development worldwide and California has access to the coastal resources and high value marine species necessary to compete in the world seafood market. A proactive approach is required to make this a reality. Mark A. Drawbridge and Donald B. Kent Hubbs-SeaWorld Research Institute
References Bartley, D. M., D. B. Kent, et al. 1995. Conservation of genetic diversity in a white seabass hatchery enhancement program in southern California. Uses and effects of cultured shes in aquatic ecosystems, Bethesda, MD, American Fisheries Society. Drawbridge, M. A., D. B. Kent, et al. (in review). Commercialization of White Seabass (Atractoscion nobilis) Aquaculture in Southern California: Biological and Technical Feasibility of Cage Culture. Aquaculture. Kent, D. B., M. A. Drawbridge, et al. 1995. Accomplishments and roadblocks of a marine stock enhancement program for white seabass in California. Uses and effects of cultured shes in aquatic ecosystems, Bethesda, MD, American Fisheries Society. New, M. B. 1997. Aquaculture and the capture sheries balancing the scales. World Aquaculture: 11-30.
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CALIFORNIA DEPARTMENT OF FISH AND GAME December 2001
Invasive Species I
nvasive species are the number two threat to rare, threatened or endangered species nationwide, second only to habitat destruction. Commercial shermen nationwide are seeing signicant impacts on local sh populations from invasive marine life. Indeed, coastal systems, including tidal ats and salt marshes, have been particularly susceptible, possibly because they are typically highstress, species-poor environments. California water agencies have expressed alarm at the “potentially devastating” impacts that invasive species can have on California’s waters. Unlike threats posed by most chemical or other types of pollution, biological pollution by invasive species normally will have permanent impacts, as they are virtually impossible to eradicate once established. Specic environmental threats from invasive organisms include consumption of natives and their food sources, genetic dilution of native species through cross-breeding, alteration of the physical environment, introduction of non-native parasites and diseases, and poisoning of native species through bioaccumulation of toxics that are passed up the food chain. For example: •
In the former Soviet Union, a species of comb jelly was introduced into the Black and Azov Seas through ships’ ballast and played a signicant role in virtually destroying an entire shery. Since the introduction of this species, shing harvest in those seas dropped 200,000 tons in a ve-year period.
•
Microscopic neurotoxin-producing organisms called dinoagellates have been transported in the sediments carried with ballast water and discharged into new regions of the world, where they have produced toxic red tides, including red tides in southern Australia that probably originated in ballast water.
•
Scientists have warned that a non-native goby now found in the Great Lakes raises toxin levels in indigenous sh and could pose a serious health risk to humans who eat game sh.
•
Microbial studies conducted in Canada on ships arriving in winter from Europe found that more than 50 percent of the ships carrying ballast water violated water discharge standards with fecal coliform bacteria. The authors surmised that ships arriving in the summer, or from Asian ports, would be likely to have substantially higher rates of contamination.
Here in California, numerous studies indicate that San Francisco Bay is already severely impacted by harmful non-native species. These studies have identied at least 234 nonindigenous plant and animal species that now live in San Francisco Bay. Moreover, the rate at which aquatic invasive species are becoming established in San Francisco
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Bay has increased from an average of one every 55 weeks before 1960, to one every 14 weeks between 1961 and 1995. Invasive species that have been positively identied as permanent residents of the Bay include Asian clam, the European green crab, the New Zealand sea slug, the Chinese mitten crab, and several species of sponges, jellysh, sh, anemones, snails, mussels, clams, and barnacles. Indeed, San Francisco Bay is likely the most invaded estuary in the world. The discharge of ships’ ballast water from foreign ports is currently the single largest source of coastal, aquatic invasive species. A recent survey found that 53-88 percent of the aquatic invasive species introduced into San Francisco Bay in the last decade originated in ballast water discharges, and there is evidence that the number of ballast-related introductions of aquatic invasive species is steadily growing. According to estimates by the San Francisco Estuary Institute, between half a billion and a billion gallons of ballast water are discharged into the San Francisco Bay/Delta Estuary each year by ships arriving from foreign ports. Aquaculture, unintentional introductions via recreational vehicles, deliberate introductions (i.e., to establish a shery), and importation of live marine organisms for human consumption, bait, pets or research are other important vectors of aquatic invasive species.
Invasive Species
History
Examples of Significant Invasive Species
N
umerous invasive species threaten the health of marine life both directly and indirectly through alteration of coastal ecosystems and habitats. This section highlights three of the more signicant species, which are a particular problem in the San Francisco Bay and surrounding areas, and reviews the status of invasions elsewhere in the state.
The European Green Crab (Carcinus maenas) The green crab, native to the Atlantic coasts of Europe and northern Africa, occupies protected rocky shores, sandats and tidal marshes. In 1989-1990, it was discovered in San Francisco Bay, and has since spread as far north as Washington and southern British Columbia and south to Morro Bay. It may have entered California through the discharge of ballast water from trans-oceanic ships, although spread is also possible through discard of seaweed packing material used in shipping live shellsh and the interstate transport of shellsh aquaculture products and equipment. The green crab is a voracious predator that feeds on many types of organisms, particularly bivalve mollusks, polychaetes, and small crustaceans. The green crab is
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A single female can carry 250,000 to a million eggs. After hatching, larvae are planktonic for one to two months. The small juvenile crabs settle in salt or brackish water in late spring and migrate to freshwater. Young juvenile mitten crabs are found in tidal freshwater areas, and usually burrow in banks and levees between the high and low tide marks. In China and Europe, older juveniles have been reported several hundred miles from the sea. Maturing crabs move from shallow areas to the channels in late summer and early fall and migrate to salt water in late fall and early winter to complete the life-cycle.
European Green Crab, Carcinus maenas Credit: DFG
capable of learning and can improve its prey-handling skills while foraging. The crab is quicker, more dexterous and can open shells in more ways than other types of crabs. In its native range, the green crab feeds heavily on mussels. On the East Coast, the crab is believed to have played a role in the demise of Atlantic soft-shell clam sheries in the 1950s. In Bodega Harbor, California, records show a signicant reduction in clam and native shore crab population abundance since the arrival of green crabs in 1993. Furthermore, laboratory studies show that the green crab preys on Dungeness crab of equal or smaller size. Dungeness crab spend part of their juvenile life in the intertidal zone, and may therefore be at risk from green crab predation. Besides its threat as a predator, the green crab may carry a parasite, the acanthocephalan worm, which can infect local shore birds.
The Chinese Mitten Crab (Eriocheir sinensis)
Mitten crabs are adept walkers and readily move across banks or levees to bypass obstructions such as dams or weirs. They are omnivores, with juveniles eating mostly vegetation, but preying upon animals, especially small invertebrates, as they grow. Mitten crabs pose several possible threats. Their burrowing activity may accelerate the erosion of banks and levees, disturbing local habitat. In addition, the crab can disrupt needed water deliveries to estuarine habitats by clogging the pumps that deliver the water. The mitten crab also has become a nuisance for commercial bay shrimp trawlers in south bay, who have reported mitten crabs damaging nets and killing shrimp. The crab may also compete in the delta with an exotic craysh that is the basis for a small commercial shery. The mitten crab may also be the secondary intermediate host for the Oriental lung uke, with mammals, including humans, as the nal host. The ecological impact of a large mitten crab population is the least understood of all the potential impacts. It could reduce populations of native invertebrates through predation and change the structure of the estuary’s fresh and brackish water benthic invertebrate communities.
The Chinese mitten crab is native to the coastal rivers and estuaries of the Yellow Sea. It was rst collected in the San Francisco estuary in 1992 by commercial shrimp trawlers in South San Francisco Bay and has since spread rapidly throughout the estuary. Mitten crabs were rst collected in San Pablo Bay in fall 1994, Suisun Marsh in February 1996, and the delta in September 1996. The Chinese mitten crab now extends at least from north of Colusa in the Sacramento River drainage, east to eastern San Joaquin County near Calaveras County, and south in the San Joaquin River near the San Luis National Wildlife Refuge. The most probable mechanism of introduction to the estuary was either deliberate release to establish a shery or accidental release via ballast water. In Asia, the mitten crab is a delicacy and crabs have been imported live to markets in Los Angeles and San Francisco. The mitten crab is catadromous - adults reproduce in salt water and the offspring migrate to fresh water to grow.
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Chinese Mitten Crab, Eriocheir sinensis Credit: DFG
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Invasive Species
An Asian Clam (Potamocorbula amurensis) In October 1986, the rst Asian clams found in California were collected in San Francisco Bay by a community college biology class. Just nine months later, the Asian clam had become the most abundant clam in the northern part of the bay, averaging over 2000 clams per square meter. The clam is a highly efcient lter feeder, ingesting bacteria and small zooplankton as well as phytoplankton. At year 2000 densities in the bay, virtually the entire water column may pass through the ltering apparatus of these clams between once and twice a day. Since its arrival, the clam has eliminated annual phytoplankton blooms that had previously characterized this ecosystem, disrupted food webs, reduced the populations of native zooplankton species, and possibly increased the vulnerability of the ecosystem to invasions by exotic zooplankton, many of which have since occurred. This clam is also thought responsible for a reduction in particulate organic carbon. With less food available for larval and other benthic lter feeders, the relative populations of native species could shift. The clam may also be acting as an accumulator of contaminants, concentrating selenium in bottom-feeding sh and birds at levels that are high enough to cause reproductive defects. This magnication of selenium concentrations in the food chain could also affect sh- and shellsheating marine mammals such as harbor seals, sea lions, and the sea otters, which are returning to the bay.
A South African Sabellid Worm (Terebrasabella heterouncinata) The South African sabellid worm is a parasitic polychaete worm that infests mollusks. It was introduced into California waters in the mid-1980s with abalone imported into a California aquaculture facility. The worm spread rapidly among abalone facilities through the transfer of infested seed stock and proved difcult to control once established. The worm infests only the abalone’s shell, signicantly reducing the growth rates of cultured abalone. A heavy infestation can cause shell deformation, elevate mortality as the shell becomes brittle, and reduce reproductive capacity as more energy is channeled into shell production. Introduction in state waters is highly likely, given the species’ broad host specicity. Sabellids have been detected in a native gastropod mollusk, in the intertidal zone adjacent to the discharge pipe from an abalone facility in central California. Attempts to eradicate this invasive species at this site and at culture facilities are ongoing.
CALIFORNIA DEPARTMENT OF FISH AND GAME December, 2001
Asian Clam, Potamocorbula amurensis Credit: DFG
The California Department of Fish and Game (DFG) has established inspection requirements for abalone stock transfers, required detailed clean-up plans from all infested aquaculture facilities, prohibited out-planting, and added the sabellid to the Fish and Game Commission’s signicant disease list. Such controls appear to be having some effect, as most abalone culture facilities report some level of control and eradication of this worm. However, there have been reports of re-infestation by abalone shipments that had been inspected and certied by the DFG. The inspection protocols used have been mathematically demonstrated to be unlikely to detect a low level of infestation in transferred abalone, such as one to ve percent or lower. Moreover, the mesh on the screens of the discharge pipes of onshore culturing facilities are far too large to prevent the release of eggs or larvae, and the openings in offshore barrel and cage culture are even larger. Subtidal inspection of possible release sites for the sabellid worm has been very limited, and the locations of some of these possible release sites are simply unknown. Further work is needed to ensure that all infestations are removed and effective controls are in place to prevent reinfestation.
A Tropical Seaweed (Caulerpa taxifolia) An invasive green algae dubbed the “killer algae,” was discovered in the waters of southern California off Carlsbad in early 2000. Native to tropical waters, it became popular in the aquarium trade in the late 1970s and either escaped or was released into the Mediterranean Sea in the mid-1980s. It is now widespread throughout much of the northwestern Mediterranean. It appears that the algae found off southern California is a clone of the released Mediterranean plant, and can grow in deeper and colder waters than the tropical populations. Its impacts have been compared to unrolling a carpet of Astroturf across
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the sea bed. In areas where it has become well-established, it has caused economic and ecological devastation by overgrowing and eliminating native seaweeds, seagrass reefs, and other communities. In southern California, the algae poses a signicant threat to eelgrass meadows and other benthic environments that are essential to the survival of native invertebrates, sh and aquatic birds. If the algae spread from the coastal lagoons to the nearshore reefs, it could inhibit the establishment of juveniles of many species, including kelp and the biota associated with kelp beds. Efforts to destroy this patch of algae have involved tarping off the area and injecting chlorine under the tarp.
Other Invasives Invasive species are present not only in San Francisco Bay but are common as well in other harbors and bays in California and along the Pacic Coast. For example, recent compilations list about 25 invasive species in Morro Bay in central California, and about 80 invasive species in the bays and harbors of southern California. One such organism is an Australasian isopod that signicantly erodes the banks of salt marsh channels and marsh edges in San Diego Bay, resulting in reduction of already-limited coastal habitat. Once established in one area, exotic organisms may quickly spread to another through either natural or anthropogenic transport. Invasive species initially established in bays may subsequently invade the open coast. A predatory New Zealand sea slug that was collected in San Francisco Bay in 1992 may have spread north to Bodega Bay and south to near San Diego, though further taxonomic work is needed to identify which of the two to four species of invasive sea slugs are involved and the locations of their spread.
Existing Regulatory Regime and Regulatory Gaps National Invasive Species Act of 1996 Existing regulation of the major vector of invasive species introduction - ballast water discharges - is generally limited in its reach. The primary federal law regulating ballast water discharges, the National Invasive Species Act (NISA), calls primarily for voluntary ballast water exchange by vessels entering the U.S. after operating outside of the EEZ (mandatory ballast water exchange requirements exist only in the Great Lakes). Some of the limitations of NISA are that while it states that the voluntary program could become mandatory after several
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years, there are currently no criteria in the statute or accompanying regulations to guide that decision. Moreover, it addresses only vessels entering the U.S. from outside the EEZ, and ignores, for example, coastwise trafc from areas contaminated with problematic invasive species (such as the San Francisco Bay area). NISA requires annual reporting to assess the ongoing effectiveness of the program. The rst interim report by the National Ballast Information Clearinghouse, issued in October 2000, found that over the rst 12 months (July 1999-2000) that the rule was in effect, only 20.8 percent of the vessels that entered U. S. waters from outside the EEZ led the mandatory reports required under NISA and pursuant to U.S. Coast Guard regulations. For the entire U.S., compliance with reporting improved only slightly over the 12-month period, remaining between 23 percent and 29 percent from October 1999 through June 2000. Only for the West Coast of the contiguous U.S. did compliance with the reporting requirement increase markedly over time, primarily from an increase in California, which receives the most ship arrivals. This increase coincided with implementation of a 1999 California state law that requires submission of copies of the federal ballast water management reports to the State Lands Commission, authorizes monetary and criminal penalties for noncompliance, and utilizes an active boarding program that targets 20-30 percent of arrivals. As a result, compliance with reporting in California increased over the past 12 months to approximately 75 percent. The report concluded that due to the poor nationwide reporting rate (20.8 percent), it is difcult to estimate reliably (a) the patterns of ballast water delivery and (b) the compliance with NISA’s voluntary guidelines for ballast water management. Based on the information that was submitted, the report found that nationwide, approximately 42 percent (10.2 million metric tons) of the foreign water reported discharged into the U. S. had not been exchanged completely as requested in the voluntary guidelines. The report also noted that although it is clear that many vessels that discharge ballast water in the U.S. are not in compliance with voluntary guidelines, based upon their reports, the extent of non-compliance with these guidelines simply cannot be estimated accurately due to the very low rate of reporting.
Clean Water Act The Clean Water Act prohibits the discharge of “any pollutant by any person” into waters of the United States, unless done in compliance with specied sections of the Act, including the permit requirements in Section 402. National Pollution Discharge Elimination System (NPDES) permits issued to discharges into the territorial sea also must comply with “ocean discharge criteria” specically
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Currently, an EPA regulation adopted in the 1970s specically exempts ballast water from the NPDES permit program. In January 1999, a petition was made to the EPA by the Pacic Environmental Advocacy Center, on behalf of conservation groups, commercial and recreational shing interests, American Indian tribes and California water agencies, to regulate ballast water discharges under the NPDES permit program in Section 402, arguing that the regulatory exemption adopted by EPA exceeded their authority and violated the mandates of the Clean Water Act. Moreover, the assumption that ballast discharges are harmless is clearly no longer the view of the EPA or other federal agencies. After two years of waiting, the petitioners led suit against EPA in January 2001 to respond to the 1999 petition. If a pollutant is threatening or impairing use of a water body, the water body violates water quality standards and must be listed under Section 303(d) of the Clean Water Act as “water quality limited” for that pollutant. EPA or the state then must establish the “total maximum daily load” (TMDL) of the offending pollutant that can be released into the water body and still ensure that the water meets water quality standards, within a “margin of safety.” A water body whose use is impaired by aquatic invasive species could be “listed” under Section 303(d); if so, EPA or the state must identify the maximum load of problem aquatic invasive species that can be safely discharged into that water body. Given the signicant and ongoing impacts associated with numerous aquatic invasive species, it may be difcult for the applicable agency to set a TMDL for aquatic invasive species other than zero and still meet Section 303(d)’s “margin of safety” requirement. Currently, many reaches of the San Francisco Bay are listed as impaired by invasive species under Section 303(d).
National Environmental Policy Act The National Environmental Policy Act (NEPA) requires that federal agencies prepare an Environmental Impact Statement (EIS) for “major federal actions signicantly affecting the quality of the human environment.” NEPA may be used to require further examination of federal projects that may result in increased discharges of ballast water containing invasive species. At least one circuit court has recognized that NEPA requires federal agencies to evaluate a project’s indirect impacts on the spread and introduction of aquatic invasive species.
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Endangered Species Act Under Section 7 of the federal Endangered Species Act (ESA), federal agencies must ensure that their actions are “not likely to jeopardize the continued existence of any endangered species or threatened species or result in the destruction or adverse modication of habitat of such species…” In addition, federal agencies must consult with the Secretary of the Interior and/or Commerce, as appropriate, “on any agency action which is likely to jeopardize the continued existence of any species proposed to be listed…or result in the destruction or adverse modication of critical habitat proposed to be designated for such species.”
Invasive Species
designed to prevent the degradation of those waters, pursuant to Clean Water Act Section 403.
Section 7 of the ESA should be used to examine the impacts of a federal project that may result in increased discharges of ballast containing invasive species, where such discharges may affect endangered or threatened species.
Presidential Executive Order 13112 On Feb. 3, 1999, President Clinton issued an Invasive Species Executive Order creating a Cabinet-level National Invasive Species Council. The Council was charged with creating a National Invasive Species Management Plan that would address all types and sources of invasive species, including aquatic invasive species in ballast water. An Invasive Species Advisory Committee made up of a range of stakeholders has been working with the Council on a draft management plan. The draft management plan was released for review in October 2000 and was nalized in early 2001.
California Environmental Quality Act The California Environmental Quality Act (CEQA) requires appropriate mitigation of projects that contain signicant environmental impacts. A “signicant” impact is a “substantial, or potentially substantial, adverse change in any of the physical conditions within the area affected by the Project including land, air, water, minerals, ora, [and] fauna…” The documented adverse impacts associated with invasive species appear to t this broad denition. In addition to meeting the general denition of “signicant effect,” the impacts associated with increased discharges of invasive species may require a mandatory nding of signicance under CEQA, thus mandating feasible mitigation of those impacts or an alternative project.
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California Porter-Cologne Water Quality Control Act Under California’s Porter-Cologne Water Quality Control Act “any person discharging waste, or proposing to discharge waste, within any region that could affect the quality of the waters of the state” must le with the appropriate Regional Water Quality Control Board a report of the discharge. Pursuant to the act, the regional board then prescribes “waste discharge requirements” related to control of the discharge. The act denes “waste” broadly and the term has been applied to a diverse array of materials. The San Francisco Bay Regional Water Quality Control Board has determined that “ballast water and hull fouling discharges cause pollution as dened under the Porter-Cologne Water Quality Control Act,” raising the possibility that the act may be actively used to regulate such discharges.
California Fish and Game Code State sh and wildlife laws contain provisions that relate to the control of aquatic invasive species from a variety of vectors. Some examples in the California Fish and Game Code include the following:
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Section 2271. “No live aquatic plant or animal may be imported into this state without the prior written approval of the department.”
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Section 6603. “All sh, amphibia, or aquatic plants which the department determines are merely deleterious to sh, amphibia, aquatic plants or aquatic animal life, shall be destroyed by the department, unless the owner or the person in charge . . . ships them out of the state . . . .”
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Section 6400. “It is unlawful to place, plant, or cause to be placed or planted, in any waters of this state, any live sh, any fresh or salt water animal, or any aquatic plant, whether taken without or within the state, without rst submitting it for inspection to, and securing the written permission of, the department.”
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Section 15200. “The commission may regulate the placing of aquatic plants and animals in waters of the state.”
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Section 15600. “No live aquatic plant or animal may be imported into this state by a registered aquaculturist without the prior written approval of the department pursuant to the regulations adopted by the commission.”
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Public Resources Code In 1999, California became the rst state in the nation to enact legislation mandating exchange of ships’ ballast water in an effort to control the introduction of invasive species. The Public Resources Code requires vessels carrying foreign ballast to exchange that ballast in open seas. It also requires specied state agencies to analyze the status of invasions, the effectiveness of the ballast exchange program, and alternatives for ballast treatment; sets penalties for noncompliance; and levies fees on regulated vessels to pay for the program. Washington state passed a mandatory ballast water exchange law modeled on California’s law in 2000. California’s mandatory law, clear penalties, and an active ship boarding program has resulted in its taking the lead in the nation on the control of ballast water, as the Clearinghouse report conclusively found. Controlling the introduction of invasive species is well within the traditional police powers of the states. As long as the proposed legislation does not dictate the specic type of ballast water treatment techniques that vessels must use and does not favor “local” shipping over “foreign,” then state ballast water management laws do not appear to be preempted by constitutional law or by NISA.
Local Application of State and Federal Laws Place-based management of invasive species introductions can occur where agencies implement state and federal laws on a local level. For example, in response to a petition from conservation groups, the San Francisco Bay Regional Water Quality Control Board identied invasive species as “pollutant stressors” subject to Clean Water Act Section 303(d) in lower, south and central San Francisco Bay, Richardson Bay, Suisun Bay, San Pablo Bay, Carquinez Strait and the delta. The regional board ranked invasive species as a high priority for action in all affected water bodies. The listing was approved by the State Water Resources Control Board and U.S. EPA (see above discussion of TMDL requirements). The regional board approved a resolution to transmit to U.S. EPA an Exotic Species TMDL Report on impairment of the San Francisco Bay estuary by invasive species. Among other things, the regional board asserts in its report that a water quality-based endpoint to achieve the estuary’s water quality standards is no exotic species introductions. In other words, an acceptable TMDL of exotic species or organisms is zero.
CALIFORNIA DEPARTMENT OF FISH AND GAME December, 2001
Invasive Species
Conclusions The legal frameworks that apply, and may apply, to control of aquatic invasive species introductions are broad and varied. Many of these legal tools are just beginning to be utilized. As the costs associated with aquatic invasive species continue to mount, it appears likely that additional research and regulatory actions will be taken to reduce such discharges. To maximize the effectiveness of regulatory regimes, stakeholder input - from the conservation, shipping, port, shing, utility and other communities - should be encouraged and carefully considered. In spite of the signicance of the impacts of invasive species, relatively little research has been done to date on the status of current invasions (particularly outside of San Francisco Bay). Research is also needed on the potential for new invasions and on methods for preventing and addressing invasions. California’s 1999 ballast water exchange law requires the state to complete, by 2002, research and reports on existing coastal aquatic invasions, the effectiveness of ballast water exchange in controlling invasions, and the potential for other methods to control the discharge of invasives in ballast water. The San Francisco estuary Institute, under an array of federal and state grants, is taking a lead on needed research. They have received funding to investigate and report on invasions in southern California marine waters and to sample ballast water coming into the San Francisco estuary for invasive species. They are examining ballast water treatment through two projects: one with the city and county of San Francisco and the University of California, Berkeley Department of Civil and Environmental Engineering to research treatment of ballast water in municipal wastewater systems, and one to analyze more generally the potential for onshore treatment of ballast water in municipal and industrial treatment plants and ballast-specic treatment plants. Linda Sheenan The Ocean Conservancy Francis Henry California Department of Fish and Game
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CALIFORNIA DEPARTMENT OF FISH AND GAME December, 2001
