you want killer salmon to attack on sight?
first of all, you need to create a salmon actor model (probably from scratch, since you cannot use the existing salmon, as is, for this purpose). the easiest way is to model them and rig them to the Slaughterfish skeleton.
once you have your fish model created, you need to create an actor in the CK and assign it to your fish model. from there they handle AI the same way as any other actor (proper packages, factions, navmesh, etc). you can probably get away with copying everything the same as a slaughterfish.
by default the critter fish (salmon, river betty etc) are not actors, they are moving activators. they have predefined and/or scripted movement, so they cannot be made to attack the player using AI. Slaughterfish are proper actors and can be given AI to attack the player and swim freely within a navmeshed area