I noticed this in the last snapshot as well but the salmon make these incredibly loud noises when there becomes a lot in one place. I kill them off and the noise goes away but once a lot more spawn in it comes back and I cant get rid of it except for either turning game noise completely off or killing them in mass quantities. I tried to record a video of it but this wont let me upload it.
Also interesting to note, the specific ones that are too loud can be identified by seeing which Salmon appear to be stuck in the water block they spawned in