Fisherman quest - uncatchable fish or broken quest?

There is a fisherman in the big eastern/southeastern island, the place is crawling with Mafia. The fisherman is in the northern part of the island. This fisherman gives you a quest to catch several fish. Note that the quest log says he wants a few of various types of fish, while during the conversation he says he wants a dozen of one type of fish.

Anyway, I soon found out that one of the fish species can't be hit or collected. They can be killed with grenades, however. See the screenshot. I did try a brute force method, in other words, I caught about 15 of each type of fish I could find, but even then I can't complete the quest.

Is there perhaps a console command to complete or cancel this quest?