Ten top crustacea handling tips

  Handling live crustacea Fact Sheet   May 2010 Ten top crustacea handling tips Seafish has produced Good Manufacturing Practice (GMP) guidelines ...
Author: Rosa Fox
0 downloads 2 Views 249KB Size
 

Handling live crustacea Fact Sheet

 

May 2010

Ten top crustacea handling tips Seafish has produced Good Manufacturing Practice (GMP) guidelines for commercial operatives engaged in handling and storing live crustacea from capture to the point of dispatch. The guidelines aim to help businesses achieve high standards by encouraging practices that ensure product safety, product quality and the efficient use of resources, as well as help meet legal obligations. This fact sheet summarises ten of the key requisites when handling and storing live crustacea.

Crabs being stored in bins covered with carpet soaked in seawater

-

1. Keep animals in the dark Crustacea live in an environment with low levels of light. They typically inhabit shelters, burrows, under boulders or overhangs of rock, and they are active mostly at night. When exposed to bright light, the animals become stressed and try to move away quickly into shade, depleting their energy reserves and increasing their oxygen consumption; however, overcrowding in shady areas can further increase levels of stress. -

Keep the animals in the dark, or at least in the shade.

-

Use dim electric lighting directly over the storage tanks, and any extra lighting should be switched on gradually.

-

Avoid sudden increases in light levels and try to maintain natural light cycles.

-

Animals stored out of water should be covered with a blanket or carpet soaked in good quality seawater.

Provide as much shade as possible in a storage tank so that animals can avoid light without overcrowding.

2. Cool animals and keep them cool Crustacea are cold-blooded animals that take on the same body temperature as their surroundings. They cannot control their internal temperature and they need to be protected from rapid changes in temperature. Cool animals use less oxygen and energy, and are less likely to fight and molt. -

Cool the animals from the temperature of the ambient seawater to the storage temperature slowly. Avoid rapid temperature drops as that will stress the animals.

-

Once cooled, maintain a cool temperature throughout the handling chain – aim for 4-8°C.

-

Using low temperatures during dry storage will reduce evaporation that can dry out the gills. Do not place ice directly onto the animals – it will cause a thermal shock and may kill them.

2

FS52 0510 – May 2010 Ten top tips for handling live crustacea

-

Use indirect icing: ice packs/chilled gel packs will cool the air within dry transport containers and can be used to cool temporary storage systems. To cool water in a vivier tank, enclose ice in a sealed container or plastic bag - do not put freshwater ice into seawater - it will reduce the salinity, which will stress the animals.

-

Be aware that aerating the water on a warm summer’s day, or air from a compressor (this equipment heats up compressed air) will have a considerable warming effect on seawater. Consider immersing the compressed air line in a chilled water bath to cool it.

-

Handle the animals as little as possible as this can warm and stress crustacean.

3. Immerse in fresh, good quality seawater Crustacea live in the sea and, ideally, should be kept immersed in seawater. This environment allows the animals to absorb oxygen and remove waste products using their gills, and also remove silt from their gill chamber. They breathe using their gills which must be kept wet; gills will be damaged irreparably if allowed to dry out. -

The salinity of seawater used to store animals should be between 30-35 parts per thousand (psu or grams of salt per litre of water). Oxygen levels should be about 95% saturation (lobsters require around 8 mg/l of dissolved oxygen), and saturation should not be allowed to drop below 6 mg/l as animals become weak, wounds heal slowly and survival during onward transport is reduced.

Aerate and immerse in seawater

4. Keep seawater aerated Aeration of seawater is important, particularly when returning animals to water after a period out of water. These animals will have a greatly increased oxygen demand for a few hours and they need to remove accumulated metabolic wastes from the bloodstream. Aeration should be at the optimum level, but excessive aeration is not recommended. -

The aeration of a storage container should be at a depth of at least one metre or on the base of the tank if shallower. Use a good quality diffuser that generates small bubbles and surface turbulence to aid transfer of oxygen to the seawater. Cool seawater contains more dissolved oxygen than warm seawater

-

In the absence of water treatment equipment, seawater should be exchanged regularly to maintain oxygen levels and remove toxic waste products. If water cannot be exchanged, suitable aeration equipment must be used to replace oxygen consumed by animals.

-

Aeration also promotes the exchange of carbon dioxide from the water, and

3

FS52 0510 – May 2010 Ten top tips for handling live crustacea

helps with the breakdown and removal of other soluble waste products, such as ammonia/ammonium.

-

5. Keep animals dark, cool and damp Animals that are not kept in seawater should be maintained in a dark, cool and damp environment, protected from drying out, and stored the ‘right way up’ so that the water is retained in the gill chamber. Animals should not be stored for a long time out of water as they cannot remove toxic metabolic waste substances that accumulate in their blood. These can be removed only when animals are subsequently immersed in good quality seawater. -

Keep crustacea in fish boxes covered with a carpet or sacking drenched regularly with full salinity, clean seawater. Nephrops can be stored in a tube matrix and lobster very effectively in lemonade bottles,

-

Animals can also be maintained in a sprinkle tank whereby a small amount of water is sprinkled over crustacea stored in perforated boxes.

-

Do not allow static water to accumulate at the bottom or corners of the tank as this can become depleted in oxygen and high in waste material that can become toxic to the animals.

-

Air freighted lobsters can be transported in a lightweight, reliable, single-use, dry transport system acceptable to aircraft operators. Lobsters should be held head uppermost, and each box should contain a sachet of gel that has been chilled to maintain cool, dark and damp conditions.

Lobsters can be stored for a few days in the bottom of a fridge provided they are covered with a damp newspaper to prevent drying out.

6. Handle gently, avoid damaging the shell Crustacea are not used to air-borne noise and high levels of vibration and can become stressed if handled incorrectly or subjected to unfamiliar noise etc. Their shells are hard but brittle, and can crack easily on impact if animals are dropped or thrown. -

Be gentle when handling animals (mortality increases with handling), and never pick a lobster up by its antennae, legs or claws.

-

Never throw or drop animals. Containers holding animals must be handled with care.

-

Never use force to stop a lobster or prawn from flicking its tail.

-

Storage facilities should be designed to minimise the transfer of noise and vibration from pumps, motors and compressors to the storage tanks.

7. Select and grade carefully Live crustacea will need to go through several selection and grading processes from capture to consumption. Selection involves choosing the strongest animals to maximize survival, and grading divides animals into sex, weight or size categories to reduce stress size and related competition, and to fulfill market requirements.

4

FS52 0510 – May 2010 Ten top tips for handling live crustacea

contamination seen most often are physical and/or chemical, see the examples below. Physical contamination can be caused by: •

Careful handling

-

Select animals into those that are to be kept or discarded. Remove weak and recently molted animals (recently molted animals are likely to be eaten by other hard-shelled animals), and remove those with a diseased shell.

-

Damaged limbs should be cast (removed) as slight damage to the tips of the walking legs or a claw can result in heavy blood loss and death.

Grading is crucial

Chemical contamination can be caused by: •

Cleaning chemicals, washing up liquid, bilge cleaner or bleach, bilge water that comes from a single pump used to clear the bilges and provide the deck wash, diesel fuel, oil (particularly WD40), engine oil and hydraulic oils.  



Contaminated air supply due to clogged or missing air filters, worn compressors leaking oil into the air supply, poorly sited air intakes and exhaust fumes drawn into engine driven compressors.



Pesticides from fly spray and midge repellent.



Hand lotions or other skin care products if you do not use gloved hands in the tank



Chlorine; use aeration (24hrs) to eliminate the chlorine from tap water being used to make artificial sea water or reduce salinity. Some chlorination chemicals are very persistent and can be poisonous.



Heavy metals such as cadmium, copper, and mercury. Avoid bronze, phosphor-bronze, brass, zinc anodes or copper plumbing materials.

8. Keep animals free from contamination Bad practices can risk animals being exposed to contamination throughout the supply chain, leading to a loss in value or rejected product. Contamination can enter an animal directly or though a contaminated water supply. The main categories of

Sticks, stones, plastics, seagull droppings, glass, discarded pieces of used bait, cigarette ends, seaweed, mud, litter, pieces of glove, and by catch species.

5

FS52 0510 May 2010 Ten top tips for handling live crustacea

 



Toxic construction materials. Protect live holding tanks from contamination with building materials such as cement or lime dust that can rapidly remove oxygen from seawater. Excessive dust can also block filters.

The general principles of good storage and handling practices are to mimic, where possible, the ‘natural conditions and environment’ that crustacea inhabit. It is crucial to: •

Provide a stable and cool environment where changes in temperature occur slowly.



Provide salinity levels of 30-35 parts per thousand (grams of salt per litre of water), and oxygen levels at about 95% saturation (always above 6 mg/l).



Protect from vibration and shock, shade from bright light and ensure soluble waste products are removed from the water.

9. Prepare animals for onward transport Onward transportation can involve several stressful handling operations. To minimise stress during such operations: -

Chill animals to between 4-8°C.

-

Do not feed animals.

-

Handle gently at each stage.

10. Avoid the domino effect The survival of live crustacea can be reduced by the ‘domino effect’. One death in a packed container will affect the survival rate of the whole container. The death of one weak individual can reduce water quality rapidly creating a stress issue for the whole consignment, especially if crustacea are packed tightly in a holding tank.

For more detailed information A Seafish report: The Good Practice Guide to Handling and Storing Live Crustacea goes into a lot more detail and can be downloaded at: http://www.seafish.org/pdf.pl?file=seafish/Doc uments/Crustacea_web_final.pdf

For further information contact: Marcus Jacklin T: 01472 252340 E: [email protected]

Origin Way, Europarc, Grimsby DN37 9TZ t: 01472 252300 f: 01472 268792 e: [email protected] w: www.seafish.org SIN: http://sin.seafish.org supporting the seafood industry for a sustainable, profitable future