Distribution, Prevalence and Intensity of Gill Lice Salmincola Californiensis in Colorado

Gill Lice are parasitic copepods that attach externally to fish, limiting oxygen exchange through the gill filaments on which they are attached.  Gill lice negatively affect fish behavior, immune system function, growth, warm water tolerance, sexual maturation, fecundity, and survival.  To date only one species of gill lice, Salmincola californiensis has been confirmed in Colorado.  We inspected multiple fish species and populations throughout Colorado and have created a map that shows the distribution of gill lice in Colorado.  S. californiensis infections have been observed on multiple salmonid species of the genus Oncorhynchus throughout the state.  These species include Rainbow Trout, Cutthroat Trout hybridized with Rainbow Trout and Kokanee Salmon.  Other salmonid species such as Brown Trout, Brook Trout and Native Mountain Whitefish are not susceptible to S. californiensis infection and no gill lice have been observed and confirmed on these fish species in Colorado.  Relatively little information is known about gill lice, and a better understanding of their distribution and  life history traits will help managers determine which fish populations may be most at risk of experiencing detrimental effects due to gill lice infestation, as well as mitigate the negative consequences due to these infections.