Which change in a gene pool is occurring in the image below? mc022-1.jpg gene mutation gene flow genetic drift genetic resistance mark this and return

The image was missing from the question.
The correct answer is genetic drift.

As you can see, the image presents a large amount of fish being caught by a fishing net. The genetic drift is one of the four mechanisms of evolution and it changes the frequencies of alleles in the population randomly.
In our case, the fishes caught by the fishing net are not going to reproduce and pass on their genetic material, therefore changing the genetic structure of the next generation. This event is solely random ( there is no mechanism of selection which individual fish is going to be caught).