Why do the scientific names of fishes sometimes change? There are four primary reasons that systematists changenames of organisms: (i) “splitting” what was considered to be a single species into two (or more); (ii) “lumping” two species that were considered distinct into one; (iii) changes in classification (e.g., a species is hypothesized to belong in a different genus); and (iv) an earlier name is discovered and becomes the valid name by the Principle of Priority. Frequently, name changes involve more than one of these reasons, as shown in the following examples.
An example of “splitting” concerns the Spanish Mackerel of the western Atlantic (Scomberomorus maculatus),which was considered to extend from Cape Cod, Massachusetts, south to Brazil. However, populations referred to this species from Central and South America have 47–49vertebrae, whereas S. maculatus from the Atlantic and Gulf of Mexico coasts of North America have 50–53 vertebrae. This difference, along with other morphometric and anatomical characters, formed the basis for recognizing the southern populations as a separate species, S. brasiliensis(Collette et al. 1978).
An example of “lumping” concerns tunas of the genus Thunnus. Many researchers believed that the species of tunas occurring off their coasts must be different from species in other parts of the world. Throughout the years,10 generic and 37 specific names were applied to the seven species of Thunnus recognized by Gibbs and Collette(1967). Fishery workers in Japan and Hawaii recorded information on their Yellowfin Tuna as Neothunnus macropterus,those in the western Atlantic as Thunnus albacares,and those in the eastern Atlantic as Neothunnus albacora.Large, long-finned individuals, the so-called Allison Tuna,were known as Thunnus or Neothunnus allisoni. Based ona lack of morphological differences among the nominalspecies, Gibbs and Collette postulated that the YellowfinTuna is a single worldwide species. Gene exchange amongthe Yellowfin Tuna populations was subsequently confirmed using molecular techniques (Scoles & Graves 1993),further justifying lumping the different nominal species. Following the Principle of Priority, the correct name is the senior synonym, the earliest species name for a Yellowfin Tuna, which is albacares Bonnaterre 1788. Other, later names are junior synonyms.
Tunas also illustrate the other two kinds of namechanges. Some researchers placed the bluefin tunas in thegenus Thunnus, the Albacore in Germo, the Bigeye in Parathunnus, the Yellowfin Tuna in Neothunnus, and the Longtail in Kishinoella, almost a genus for each species. Gibbs and Collette (1967) showed that the differences are really among species rather than among genera, so all seven species should be grouped together in one genus. But which genus? Under the Principle of Priority, Thunnus South1845 is the senior synonym, and the other, later names are junior synonyms – Germo Jordan 1888, Parathunnus Kishinouye 1923, Neothunnus Kishinouye 1923, and Kishinoella Jordan and Hubbs 1925.
The name of the Rainbow Trout was changed from Salmo gairdnerii to Oncorhynchus mykiss in 1988 (Smith & Stearley 1989), affecting many fishery biologists and experimental biologists as well as ichthyologists. As with the tunas, this change involved anew generic classification as well as the lumping of species previously considered distinct.