Final answer:
Allopatric speciation is the correct answer as it refers to the evolution of new species through geographic separation, which in the case of fish populations in different ponds prevents them from interbreeding.
Step-by-step explanation:
Fish populations that do not interbreed because they are in different ponds may evolve into separate species due to allopatric speciation. Allopatric speciation involves geographic separation of populations from a parent species and subsequent evolution. This type of speciation occurs when a population becomes geographically discontinuous, which prevents the free flow of alleles between them, leading to genetic diversity over time influenced by natural selection, mutation, and environmental conditions. In contrast, sympatric speciation occurs without geographic separation, as a result of genetic differentiation within the same geographic location, often through mechanisms such as polyploidy or adaptation to different ecological niches within the same environment.