It looks very nice and fluid, just the obstracle avoidance itself makes it very realistic in terms of movement.
Myself and looks like some other people would really preffer if you can include original rigs from Maya or Max, exporting skeleton from UE4 into fbx removes all IKs and rig helpers, however i think that it might be good enough to re-rig it into another fish without animation quallity data loss. Not sure would have to try it out.