u/Interesting-Law685

I just bought the 3 dlcs for dredge and is wondering how I get one of the fish for the scientists on the rig. I got the sea cucumber, the fish with the long nose and the fish that’s takes up 3 slots, how do you get that last bigger costal fish?
I’ve been to all of the oil spills and not one has shown up, is it a night time fish? I can’t seem to find it in the book either. Maybe I didn’t look in the right spots tho