Dropping fish from an airplane into a lake is not an example of Darwinism. The concept is survival of the fittest. This is an example of man intruding in order to restore balance. Although it is done to create an ecological balance, man's interference likely created the shortfall in the first place.
Utah authorities airdropping fish to stock lakes is not completely an example of Darwinism in terms of what Charles Darwin himself seemed to explain it. Initially Darwinism implied biological evolution through natural selection. In the context of the fishes it would mean natural selection among and between the different fish species in a given colony. However airdropping fish stock is an artificial means of propagating fish species since humans are selecting the fish species to be airdropped.
So what, are fish gonna evolve from getting dropped from airplanes? As long as the fish are placed into environments that are suitable to them and their species it shouldn't be too much of an issue in my opinion. However, if the environments aren't quite like what they're used to (minus minimal changes in setting) then I could see that happening and that very well could be the case but I just don't see that happening.
The use of airdrop missions to restock fish into deprived lakes is more a case of neccessity rather than Darwinism. Many factors have led to the depletion of fish from these lakes but the use of this novel method of restocking them does not seem to me to be an example of Darwinism.