Could we get a brief description of the new indigenus species? I pieced together some of the informations, but i am not sure i got everything right.
Sure, though this won't be a comprehensive list or full description.
Cube crabs: A family of various types of crabs, which when they draw their limbs up to their bodies, form a roughly cube shape. Hard carapace, strong claws, carnivore/scavenger. Red cube crabs are about 3x3, while blue ones are 7x7.
Kelp Snake: A venomous snake, about 3x10. Camouflages itself as a kelp frond and waits for prey to come close. Carnivorous and venomous.
Glow slug: About 1x1, if not smaller, glowing slug with venomous stingers across its entire body.
Sword Gar: A very large predatory fish which primarily lives in fresh or brackish waters, ventures out into the ocean to hunt.
Puffer whale: A very large predatory fish which lives in the depths, ventures into the shallows to hunt.
Thundershell: A large clam, about 30x20 at adulthood, but grows very slowly. Most commonly 10x10. Thick shell, able to deal an electric shock.
Giant urchin: A family of large urchins, ranging from 5x5 to 40x40. Purple urchins are 5x5, grey are 15x15, and white are 40x40.
Sea ants: Colonies of 1x1 aquatic insects which form large nests of saliva hardened sand and debris. Mildly territorial.
Kelp grouper: A moderately sized fish, which is fairly territorial. Lives exclusively in the kelp forest.
Tangle star: A bristle starfish-like creature which grows and additional tentacle about every month, can become quite large.
That's what I remember off the top of my head, I'm sure there are more that I can't remember, so if there's any specific species you need additional info on, let me know.
Can we get more information on the areas that are getting the most overgrazing? Kelp Forest, the seaweed place, etc. Also could we evolve to increase our brain power and like migrate to the freshwater river canals, so that we have an entrance point to the island (maybe would need to adapt freshwater survivability then...)
The sea grass prairies and the kelp forest do have more leafy vegetation and do get considerably more grazing than the coral reefs. Though, urchins do eat some of the soft corals, they're most often partial to green vegetation.
As for increasing your brain power, yes you can do all of that. Any time you give your species a new behavior, it increases their Mind stat. This does contribute to your growth limit coefficient, so be wary of stacking lots of behaviors without evolutions to increase their effectiveness at gathering food/reproduction.