The McCloud River is an aquatic sanctuary in Northern California, whose roaring waterfalls, luscious fish and scenic views attract hordes of recreationists. A lesser known fact is that the McCloud holds a scientific significance which rivals its capabilities as an entertainer: it contains the endemic native species known as McCloud River Redband Trout. This suggests that other endemic species may thrive in the McCloud. Our attention was brought to three species of fish from family Cottidae, namely the Pit, Riffle and Prickly Sculpin. Individuals from said groups were sampled from select rivers in Central/Northern California including the McCloud, and their genomic information was used in a statistical procedure known as a principal component analysis (PCA). This analysis compiles and rearranges data points in a way that accentuates variation between and within loci. The first PCA affirmed that Prickly sculpin were far different from Pit and Riffle Sculpin and those samples collected at the mouth of the McCloud River grouped with Prickly Sculpin. It also suggested that an extra group existed in the McCloud River and Hot Springs Creek which had genetic characteristics intermediate between known Pit and Riffle Sculpin. A second PCA was conducted to investigate this newly emerged group, and the results showed that this new group was significantly different from both Pit and Riffle sculpin. Additionally within it were two distinct groups of fish, one in the McCloud and one in Hot Springs Creek. This indicates that either there was secondary contact between the Pit and Riffle sculpin which led to a now-independent hybrid species, or this new group diverged from the same ancestor as Riffle and Pit Sculpin. Either way, our results differentiate McCloud River Sculpin from currently known species and suggest a full investigation is needed to unearth additional endemic species in the McCloud
