Summary of Lecture 22, OCE 100 - SUNY Oswego Lecture 22. There are about 20,000 different species of fish. About 12,0000 are marine species. There are similarities between classes. For example, all fish are cold-blooded.
All fish have gills and fins.
All fish have tapered bodies. Fish in Agnatha lack jaws and have no appendages for locomotion. Their bodies are pierced by gill slits. Lampreys , a group of parasitic fish, are in this class. Sea lampreys are now found in all of the Great Lakes, and the Great Lakes Fishery Commission is taking pains to control the lamprey population.