What is a Fish Species?

It may come as a surprise but there is no exact definition for what qualifies as a fish species. The problem is not unique to fishes but to all life and is known as the species problem. Frameworks to define what a species is are hotly debated and some believe that perhaps species don't even exist. (there are many viewpoints) Some of the proposed ways to differentiate between species include physical characteristics, genetics, or sexual reproduction.

Even if there is no satisfying universal concept of what makes a species, it is still a useful construct for taxonomic purposes. For example, binomial nomenclature using a name for the genus and for the species helps solve a lot of problems that arise from using common or everyday fish names only. As anglers, thinking of fish in terms of taxonomic ranks still provides value as it gives you insight into the characteristics of a fish, just don't get too hung up on the edge cases or inconsistencies.

Ichthyology