I don't know if this will help or answer your question or maybe you already know this checkout this site: http://www.howstuffworks.com/us-customs-service3.htm
Here's an exerpt from it:
Fish, wildlife and products made from them -- These are subject to state laws, import and export restrictions, prohibitions, permits or certificates as well as quarantine requirements. For details, contact the U.S. Fish and Wildlife Service before you leave if you plan to bring back any wild birds, land or marine mammals, reptiles, fish, shellfish, mollusks or invertebrates or parts of these (such as feathers, bones or fur) or products made from these parts (such as ivory combs or tortoiseshell boxes). We must be aware of endangered species and products made from these species and must obtain permits from Fish and Wildlife to import them.
Hope this helps.