Partially related to this, but my parents live in a village on the Lower Danube (the second largest river in Europe, after the Volga). I remember that when I was a kid (in the '80s) you had no problems catching enough fish during a day in order to feed a family of 3 or 4 if you wanted, and even sell something on the side for some extra cash (not much, but it mattered). I remember my uncle telling me that back when he was a kid (the '70s) the fish resources were even more plentiful, as in whenever the river was flooding the marshland-like areas he and his friends would go in there and catch the fish using their bare hands.
Nowadays you can barely catch a fish. Some former colleagues of mine spent an entire day trying to catch something in the Danube and at the end they hadn't catch anything (bare in mind, they were using more modern tools compared to what people were using back in the '70s and '80s). The struggle is real.