Historical management strategies often comprised supplemental stocking of specific habitats with strains of cutthroat trout perceived to be native to those habitats. Despite the general idea being sound - that strain integrity should be maintained by stocking like with like - unfortunately, the 'strain' classifications of cutthroat trout in Colorado has recently been shown to be flawed. The result has been massive geological redistribution, loss and alteration of cutthroat trout diversity.
A paper published in the journal Molecular Ecology has demonstrated using mitochondrial DNA analyses, that historical perceptions of the taxonomic relationships of cutthroat trout were in fact flawed, and as a result, human activity has completely rearranged the geographical distribution of cutthroat diversity within Colorado. Historically it was believed that cutthroat in Colorado comprised four major lineages (subspecies). They were known as; Colorado River cutthroat trout (O. c. pleuriticus), Greenback cutthroat (O.c. stomias), Yellowfin cutthroat (O.c. macdonaldi) and Rio Grande cutthroat (O.c. virginalis). The figure below represent the prevailing belief towards the end of the 19th century, regarding the distribution of these trout within Colorado.
So what implications did this inaccurate taxonomy have for cutthroat trout in the area as a result of supplemental stocking?
The most striking result is the apparent absence of 'a greenback cutthroat trout lineage' among contemporary trout in the South Platte River (its presumed native range), which resulted in the subspecies being previously declared extinct. Instead this research has revealed that the lineage, historically known as the greenback cutthroat now persists only in a four mile stretch of a small stream, Bear Creek, in the Arkansas River basin. Despite the veneer that this is a positive finding, namely that a one believed to be extinct subspecies has been rediscovered, we should remember that the greenback cutthroat trout most likely declined to what was effectively an extinction within its native range, as a result of ill-informed stocking practices.
In addition, at least two of the six historical lineages appear to be extinct in contemporary cutthroat trout in the Southern Rocky Mountains, namely the O.c. macdonaldi and the O.c. virginalis lineages.
Although this retrospective discovery of widespread, human mediated redistribution and disturbance of cutthroat diversity in Colorado comes too late to preserve historical evolutionary lineages, it should serve as a warning to policy makers, conservationists and fisheries managers alike, that sound genetic information is pivotal to the successful preservation of biodiversity.
Metcalf J.L., Love Stowell S., Kennedy C.M., Rogers K.B., McDonald D., Epp J., et al. (2012) Historical stocking data and 19th century DNA reveal human-induced changes to native diversity and distribution of cutthroat trout. Molecular Ecology, doi: 10.1111/mec.12028