Most of the time I find 1 in the south in each bay. Sometimes they do that because theirs less fish in the bay. It happened when I started the game, sooo maybe find them their, but if there's remaining only a bit of fish then kill em, and dont throw away the raw fish meat it will be used when you manage to knockout a spino, and use 70-100 or more bio toxin! You'll get them in jellyfish!