New Subspecies of Redband Trout formally described - McCloud River Redband

The Redband Trout of the McCloud River upstream of the falls in populations such as Sheephaven Creek have been recognized as distinct for sometime, but have been classified as Oncorhynchus mykiss stonei with the other Redband Trout of the Sacramento basin. However, a new study on the genetics of these trout has shown that they are distinct enough from other populations of Redbands in the basin to warrant subspecies status under the scientific name Oncorhynchus mykiss calisulat. This subspecies status includes the Sheephaven Creek population, as well as fish in other nearby isolated tributaries such as Edson, Tate and Moosehead creeks among others, which are found to constitute a single genetic unit.

The McCloud River Redband Trout - now recognized as Oncorhynchus mykiss calisulat

Those familiar with McCloud River Redband might be slightly confused as the type specimens for O. mykiss stonei were collected from the McCloud River, however these type specimens were from the population found below the falls. Based on the results of this study, the type specimens from the lower McCloud River are more closely related to the fish found in the Pit River and Goose Lake basin than they are to the fish in the upper McCloud River. Additionally, while the upper McCloud River Redband Trout represent a single ancient lineage of Redband Trout isolated above the falls in the basin, the fish in the Pit River and lower McCloud River appear to have genetics of several lineages, including more than on strain of Redband Trout and Coastal Rainbow Trout.  

Interestingly, the Sacramento Redband Trout found in the the Pit River and North Fork Yuba River appear to be more closely related to Redbands found in the Warner Valley and Surprise Valley than they are to Goose Lake Redband Trout. The study also showed the uniqueness of the Golden Trout of the Kern River and support their recognition as a unique species of trout. As genetic methods continue to evolve more isolated populations of O. mykiss are sampled it is possible the additional subspecies will be formally recognized in the coming years. For example, there is some evidence of a unique population of Redband/ Rainbow Trout in the Upper Skagit drainage that may warrant subspecies status in the future, not to mention unique populations such as those in the White River or Fort Rock basins in Oregon.

A link to the study can be found here.

Campbell, M.A., E. Habibi, G. Aubringer, M. Stephens, J. Rodzen, K.W. Conway, A.J. Finger. 2023. Molecular systematics of redband trout from genome-wide DNA sequencing substantiates the description of a new taxon (Salmonidae: Oncorhynchus mykiss calisulat) from the McCloud River. Zootaxa 5254 (1): 000-029. https://doi.org/10.11646/zootaxa.5254.1.1