FISHES: INFERRING ECOLOGY FROM MORPHOLOGY You can learn much about the ecology of a fish just by looking at it and using a bit of deductive logic. This exercise takes a group of fish from Putah Creek and asks you to look at them closely and then infer their basic ecology. Is the fish in front of you a slow or fast swimmer? Is it a predator on large prey or small prey relative to its body size? Tail shape. A rounded tail implies a slow swimmer while a deeply forked tail implies a very fast swimmer. There is a gradient of tail shapes. Mouth size. The bigger the mouth, the larger the prey size. Large fish with large mouths tend to eat other fish, ducks, dogs, etc. Small fish with large mouths each large invertebrates,while those with small mouths tend to eat small invertebrates and algae. Mouth position . A terminal mouth (end of head) indicates ,usually, a predator or a fish that can pick individual prey from the bottom or plants. A subterminal (inferior) mouth (below end of head) indicates a bottom feeding fish. A superior mouth (top of head)
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pelvic fins, putah creek, flat pectoral fins, fast swimmer