Under those particular circumstances, it seems to me to be somewhat unwise to kill even more fish.
From what I gather:
The critters that can't migrate to areas with sufficient oxygen will die first. These are the critters that make up what amount to our reefs (tunicates, sponges, bivalves, and even a hard coral or two). At the same time, the oil and dispersants will kill and poison the fish eggs, larvae, and planktonic stew that floats near the surface. This effectively removes the bottom two links of the food chain.
Some finfish will be able to successfully migrate to clean areas, but will those new areas remain clear enough to sustain life? That question no one can't answer, but I can say this: Because of the robust artificial reef program, the Mobile/Pensacola areas have more red snapper
habitat than anywhere else within 250 miles... in any direction. If every single red snapper made it out of the oil, where would they live? what would they eat? what structure would they orient to for protection from predation? The answer is that many, many fish will die on the trip, and any fish that finds habitat will have to take it over from whatever fish were there originally.
In other words, the few fish the oil kills outright will pale in comparison to the holocaust that will result from oxygen depletion and food chain collapse. Even if our boat took 10,000 red snapper, it's still less than a drop in the bucket. The only difference between the fish that we shot, and the fish that we didn't is that at least the fish that we shot were dispatched quickly, and not poisoned or suffocated slowly, where they would have dropped to the seafloor and rotted in what will amount to a desert.