I am also Croatian, born and live in Dubrovnik, seaman all my life, but have never seen this grill style neither at home nor aboard any vessel I've been so far.
And I ate a lot of fish in my life.
We have among others Koi carp here that grow huge. They are classed as noxious pests and while great sport bow-fishing the only one I ate tasted like mud,(like all freshwater fish to me with the exception of Eel),Trout make great Snapper bait though.
Will cooking them like this make them palatable?
The carp of me is caught and released by sport fish. The largest are heavy to 35kg. These fried biscuits are made for food. Carp has a smell of sludge and is heavily fatty fish and good marinade and this way of baking from bad fish makes very good food.