Granted, this doesn't happen every time, but I'd say there's about a 50/50 chance of it happening. Basically, if you go fishing for the first time, and it happens to be in the ocean, I've noticed that the first fish is always either a sardine, nothing unusual there... or a sunfish, which is very much a freshwater fish. I've never had the opposite happen when I fish in the river first. There, the first fish is always a sunfish. And the tutorial is the only time that a sunfish can be caught in the ocean. As such, I get the feeling that catching a sunfish as your first fish from the ocean probably isn't supposed to happen. To recreate this, make sure that your first fish is caught in the ocean. If the fish is a sardine, restart the day and try again. Eventually, it should be a sunfish. On a side note, I've never tried fishing for the first time at the forest pond or mountain lake before. Can anyone who has confirm what the first fish always is at those places? If it's a sunfish, then that should probably be changed, since it isn't actually possible to catch one there. I'd suggest another easy-to-catch fish that can be found at these places, like a carp.