By Rodney Hsu

The human race is a group of incredibly organized beings. We always have the urge to make sure everything is categorized, sorted and differentiated. Each of us has an unique name and we recognize our individuality by special physical characteristics that stand out from others. The purpose of naming everything that exists is to simplify our conversations by making easy references. A similar kind of system has also been used in the field of biology. We categorize organisms into groups. Different levels of grouping are used based on the amount of differences that exists between organisms. For example, all organisms are divided into five kingdoms: Animals, plants, fungi, bacteria and protists. From these kingdoms, we further divide them into families, classes, and eventually into species. Such a taxonomic system is not very old, it has only existed for a bit more than a couple of centuries. Most of us probably believe that for those organisms that we already know, their species status has already been established without uncertainties long ago. That is not the case. Like every other system in life, it is always questioned. To this day, the definition of species is constantly debated. It is seemingly one of the most simplest concept in biology, yet it still raises many controversies. This is especially true in fish as scientists are still unsure about the species status of many fish out there.

The term species has been defined in many ways. Charles Darwin first recognized species by sorting living beings into groups based on physical characteristics that he saw. Since his work, many species have been reviewed and changed. The most commonly used definition today is the biological species concept, which recognizes a species as a group of living beings that share the same characteristics and do not interbreed with other populations that do not have similar physical attributes. For example, lions and tigers are two distinct species as they share different characteristics in fur colour, body size, paw size, etc. Lions and tigers inhabit in different regions of the world, therefore there are no chance that the two would meet. Even if the two meet, it is unlikely they would mate naturally and produce offsprings. This also applies to fish. In the same pool of a river, it is unlikely that a chum salmon would mate with any other salmon species as they do not share similar physical characteristics such as different sexual dimorphism.

There are exceptions to this theory. In fact, there are many flaws that suggest other species concepts may be needed to define what a true fish species is. Pink salmon has a two year life span. In Southern British Columbia, a strong run of pink salmon can be seen during odd years while a relative small number of fish return to spawn during even years. The two populations never meet and therefore never interbreed as they are separated by time, yet we consider them as one species. Bull trout and dolly varden have been determined as two distinct species, yet the two look alike and share the same habitat. It has also been found interbreeding occurs between the two. A steelhead and a rainbow trout have completely different lifecycle and body size, yet they both share the same species name Oncorhynchus mykiss? What about Kokanee and sockeye salmon?

The irregularities that I addressed above suggest that other criteria beside observations are needed to determine the status of a species. It also suggests that the status of a species is not static, each species is continuously evolving and it will always be reviewed and questioned. Today, over 50,000 fish species have been identified, but those are only a portion of those slippery critters that exist on this planet. Fish identification is important to a biologist, an angler and everyone who is concerned about our aquatic resources. Without it, we may easily lose many unknown yet significant fish species forever by negligence.