Distribution of Endemic Slender Sculpin in Upper Klamath Lake, Oregon Relative to Habitat Variables

Slender sculpin are endemic to the Upper Klamath Basin and a species of concern to the state of Oregon, but very little is known about their status, distribution, and habitat use. We used a multistate occupancy approach that accounted for imperfect detection to model the effects of water depth, marshes, and springs on relative abundance classes of slender sculpin in Upper Klamath Lake. Both the presence of marshes and the distance from marshes were modeled to examine their effects on slender sculpin site occupancy and abundance state. There was a weak correlation between depth and distance from marsh. A total of 49 models were fit to the data and ranked using AICc. The five most parsimonious models accounted for essentially all of the model weight and all indicated effects of distance from marsh and depth on both the presence and state of abundance of slender sculpin. Abundance of slender sculpin varied among years, but the effect of springs on sculpin distribution and abundance was negligible. Sites less than 5.0 m deep had a 50% or greater chance of being occupied by at least one slender sculpin. For every one meter increase in depth the probability that a site was occupied by 1-10 slender sculpin declined by 25% and the probability it was occupied by more than 10 slender sculpin declined by 37%. Nearly all sites in the lake had a high probability of occupancy by a low abundance of slender sculpin, but sites located further than 800 m from a marsh had a probability of less than 0.001 of being occupied by more than 10 slender sculpin. Our results indicate the importance of shallow marsh habitats for slender sculpin and highlight the relevance of continued marsh restoration around Upper Klamath Lake.