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Plenty of Fish in the Sea Worksheet 1. Did you know that there are 28,000 species of fish? Who knew there were so many fish? All fish share certain characteristics, traits that are common to all fish. So, what makes a fish a fish? All fish live and breed in water. All fish have gills. Other traits are shared by most fish, but not all. Most fish have scales, but some fish have lost their scales. Most fish are cold blooded, but some species have become warm blooded. Let’s explore the world of ichthyology! As you progress through this activity, write down two observations about each fish on your Ichthyologist for a Day Worksheet. 2. All fish living today fall into 1 of 3 groups: agnathans, chondrichthyans, and teleosts. Agnathans are fish that do not have jaws. Their name, “a + gnatha,” means “without jaw.” Instead of jaws, they have either fleshy mouths or sucker mouths. The lack of jaws makes it difficult for them to catch prey or feed on tough foods. The jawless fish alive today are either deep ocean scavengers that eat soft, rotting dead matter or parasites that feed on the blood of other fish. They are the hagfish and lamprey. Besides lacking jaws, what is another reason these fish eat the diets that they do?

3. Chondrichthyans are fish that have cartilage skeletons. These include sharks and rays. They have very strong, hard teeth, but the rest of their skeleton is made of cartilage. Their name, “chondro + icthyan,” means “cartilage fish.” Teleosts include most fish, such as the goldfish and tuna. They have skeletons made of bone. Categorize these fish by their groups and take a photo.

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4. Fish can be divided into two categories: freshwater fish and saltwater, or marine, fish. Based on their observable traits, place each of these fish in the appropriate category and take a photo. Explain why you grouped the fish the way you did.

5. Freshwater fish tend to be brown or green. Freshwater environments tend to scatter light, so colors cannot be seen well underwater. It tends to be darker, so the fish are not as brightly colored so they can camouflage into their surroundings. Saltwater, or marine, fish tend to have more striking colors and a white belly. 6. Did you know that koi and goldfish are the only domesticated fish? Humans domesticated carp fish, which led to the koi fish and goldfish. In the wild, carp are brown, bottom-feeding omnivores that live in lakes and ponds. Koi fish were domesticated in Japan from the crucian carp and goldfish were domesticated in China from the Prussian carp. In ancient times, people found it easy to raise carp for food. Why do you think carp were easy to raise? Draw the koi, goldfish, crucian carp, and Prussian carp on your Ichthyologist for a Day Worksheet.

7. Other species of fish are carnivores. These fish were more challenging to raise because they were hard to feed. When it came time to harvest the carp, people ate the normal-colored, or brown, fish. Any fish with new, interesting , or pretty colors were kept alive because of their unique color patterns. After many generations, a brown survivor fish with a few red scales was bred into a completely red fish, and became an ornamental fish. While bright colors and patterns were an advantageous trait for the carp in the sense that they increased its chances of survival when it was raised by people, what disadvantages might come with this trait?

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8. Because they are so visible, koi and goldfish must be constantly protected from predators. This gave rise to ornamental ponds with their many miniature bridges, lotus plants, and decorative rocks that give the fish more places to hide. If koi or goldfish are released into the wild, they will revert to their natural brown coloration within a few generations. Why do you think this is?

9. Compare the northern pike and the great white shark. The great white shark lives in the ocean and is a chondrichthyan, or cartilaginous fish. The northern pike lives in rivers and lakes and is a teleost, or bony fish. Both fish are apex predators, which means they are at the top of the food chain. Based on their anatomy, what can you tell about their hunting styles? Draw the northern pike and great white shark on your Ichthyologist for a Day Worksheet.

10. The pike is heavily camouflaged. It is an ambush predator. It sits patiently in vegetation, waiting for small fish to pass by. Its fins are positioned towards the back of its body, giving the tail section a larger surface area. Why would this tail be beneficial to the pike?

11. The pike’s large tail allows it to dart forward quickly to grab prey. The great white shark is only countershaded, and has no patterns, as it does not hide in plants. It lives in the open ocean and roves around looking for seals and sea lions, attacking them from below. It is a powerful swimmer and can drag struggling seals underwater. Why do you think sharks cannot be ambush predators? Hint: Look at the shark’s gills.

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12. The shark’s gills are very different from the pike’s. The pike is a bony fish and has gills that actively pump water so it can breathe. This active pumping structure is a special feature of bony fish. Chondrichthyans, or cartilaginous fish, do not not have moving gills, so water is not actively pumped through their bodies. In order to move water through their gills they must keep swimming forward so that the water is forced through their gills by the forward motion. The great white shark has to keep swimming or it can suffocate. This is why it can’t be an ambush predator like the pike. Even though the pike and great white shark are both apex predators, why is the shark so much larger?

13. Oceans have more biomass and biodiversity than rivers or lakes and have the largest animals. There are a lot more resources for food and a lot more competition. It pays to be large because that means no other organism can prey on you! In a lake, apex predators are limited to a certain size because there is limited food, and a predator that is too large will have a hard time consuming enough food. 14. Here are the black bullhead, the carp, the pike, the trout, and the largemouth bass. Make a prediction about their positions in the food chain by placing them accordingly in this scene. Take a photo. Explain your reasoning based on their observable features. Draw the black bullhead, trout, and largemouth bass on your Ichthyologist for a Day Worksheet.

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15. The black bullhead are scavengers, eat dead and decaying matter, and live in deep water. They have small eyes and feelers to feel objects in the darkness. Trout are midwater predators and feed on small fish and insects near the top of the water. They have forward-facing mouths to grab prey in front of them. Carp are bottom-feeding omnivores and have downward-facing mouths. Pike and largemouth bass are predators and have large mouths and large heads. Congratulations! You are on your way to becoming an ichthyologist! In this activity you learned about the physical and behavioral adaptations of fish. Create an argument using specific evidence from this activity about how their physical and behavioral adaptations can affect their survival rate.

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