he could use the original animations or idk

A bit late, but I don't think it's possible to port the animations to Source or for use. Instead right now I'm trying to analyse their animations in game (which is a real pain since they're pretty erratic and I've gotta stand still and watch their animations before they come to kill me) and replicate them to look near identical.

Makes you wish you can spectate Salmon runs in Splatoon 2, but just be sure to record game footage, replay and slow down the footage in order to analyze it better. Youtube has a video speed setting so you could look some salmon runs on there and hope to get good views of the salmonids running amok and try to recreate them by head. Wish porting animations were a bit easier indeed.