Curiously, of the ones that died, it seems that in nearly every case, of the fish that were killed, all the fish of that species were killed, and we find very few fossils of species of fish that still survive today.
Do you have any documentation on that? I have the opposite impression. And there is a bias against assigning fossils to currently living species since it emphasizes the lack of change observed in many cases. Instead I've noticed that paleontologists say a given fossil is "very similar" to a modern species. Yet they refuse to just assign it to the same species and be done with it.
If evolution were true than only a tiny percentage of fossils found should be of current species, yet the numbers I've seen in general are that there is a very high degree of overlap between living species and the fossil record, and that most differences between fossils and living species are very minor. Certainly it fits better with a polyphyletic model on a young earth than old-earth models.