Beasts of Bermuda has an aquatic fish system, created alongside the implementation of piscivorous creatures for the purpose of feeding them. Fish in Beasts of Bermuda typically roam the Ocean, but can occasionally show up inside freshwater bodies of water. They provide double food value towards piscivores, but are edible by any carnivorous creature. When consumed by creatures that lack the piscivorous trait, fish will gradually accumulate as negative comfort bias. For every four food value gained by consumption of fish by a non piscivore, they will lose one comfort bias.
Consuming fish grants a small amount of water or air when consumed, mostly to offset the Elasmosaurus' air consumption when actively hunting fish. Actually they are broken and will reworke in the future.
There is a way to become a fish in Beasts of Bermuda, but the secret is highly guarded.
Will there be different fish?
Currently, this is not the biggest preocupation of devs and AI are difficult to program. But maybe in the future the devs will focus more on the fish species that will more or less feed the piscivores creatures.