Fish detection and classification of its species from a movie

Hey!

I have 5 hours of fish monitoring and I want to develop a "simple" code in order to save some time for the future (it's very exhaustive to watch the entire tape and do the counting and classification by hand).

The quality of the image is good and it records in 30 fps.

Pretty much what the program should do is:

From the entire 5 hours of movie, identify the frames that contain a fish in it, count it and identify it.

The problem I'm thinking is that fishes don't "move in 30 fps", so I'll have the same fish in lots of frames.

Anyone can help?