There are new species of fish being discovered all the time. In the last year alone, the discovery of a new species of fish living at extreme depths in the South Pacific, nine new species of handfish (a group related to anglerfish) off the coast of Australia, and two new anglers in the Gulf of Mexico (now endangered by oil spills) have all made headlines in the popular press and environmental blogs. These are, of course, just the most amazing and most photogenic of the new species have been found; Larry Page of the University of Florida has been in charge of two National Science Foundation grants that have categorized approximately 1500 new species of freshwater fish in the last five years, few of which have been splashed across the blogosphere despite being important contributions to the understanding of biodiversity. While the discovery of new species of any animal is interesting, I thought it might be instructive at this point to talk about how scientists decide what to name them.All living things are given a two word name. For instance, an ocellaris clown is named Amphiprion ocellaris. That two word name serves to situate the fish within its taxonomy. Most scientists still use the system of classification developed in 1758 by Carolus Linnaeus where organisms are hierarchically classified into a Kingdom, Phylum, Class, Order, Family, Genus, and Species. So, if I go back to my clownfish example, all clownfish are in the kingdom Animalia, which contains all animals on earth (including humans!) and the phylum Chordata, which contains all animals with a spine (we’re in the phylum Chordata as well). Since they have fins that contain bony rays, they are in the class Actinopterygii along with almost all typical aquarium fish, swamp eels, sea horses, trout, and many other things. They are in the order Perciformes, which contains pretty much all of the fish that are likely to come into the aquarium trade. They are in the family Pomacentridae along with damselfish. Perhaps you’ve heard that “clownfish are just damsels” – that is because they belong to the same family of fish and they are in the same family because they have similar characteristics. Your clownfish maybe more photogenic than a blue damsel, but they are mean and hardy! – just like those other, not-so-attractive feeder fish. They are in the genus Amphirpion with all the other clownfish (except the Maroon clown) and species ocellaris. Each organism has a unique species name. Thus, the scientific name is simply the genus name and the species name put together into one binomal (or two-name) name. Okay, so now you know how fish are classified and how they are named. What happens if you were to find an undescribed species of fish? First, you’d need to figure out what it is related to. You’d want to list some of the characteristics of the fish, look and see how the different taxonomic levels (phylum, class, order, etc…) are defined and figure out where your fish fits in. Once you’ve figured that out, you get to name it pretty much whatever you want – so long as it complies with the rules of International Code of Zoological Nomenclature (governed by the ICZN). And, as far as the actual name, as long as it has more than two letters and those letters can be found in the roman alphabet, you’re pretty much set. Of course, if it is found that your fish is insufficiently different, then your name will be sunk into synonymy with the pre-existing name because, even if your name is cooler, the ICZN rules on a first come, first served basis. Oh, and most importantly, your fish cannot be mythical. While the Loch Ness Monster (Nessiteras rhombopteryx) and Bigfoot (Dinanthropoides nivalis) have been named, they have been declared invalid as the monsters have not been proven to exist.