I always kill these fish when they grow huge. Idk why, it just makes me feel like defeating an alpha (Which I never have), and also for the prime fish meat. Not much to say here but... They have a bleed effect, and they all swarm you like megapirahnas when one is attacked. If no other sabertooth salmons are there, it will flee (According to dossier I think).
If you go to a certain spot on ragnorok (i forgot what its called) but its next to the canyon the spinos spawn in. You can see these them jump out of the water and try to swim up the waterfall i just think thats a cool detail its the onl time they can get out of the water without instantly dying