This is a Blender(3.5.1) file of 3D model and animations of a Black rockfish.

I stuck with the structure and animation around the mouth and gill.
The size is about 52CM in the unit system of the blender.
Includes two types of models with different vertex counts.
BlackLockFishLowPoly:1091verts
BlackLockFishMiddlePoly:4873verts
How to import to the game engine

https://www.youtube.com/watch?v=7-dr0OBGK4E