Ecomorphological relations between Cottus species and their environment in northeastern Utah

Authors: Christopher W. Hoagstrom, Nathan Holmes

Year: 2008 (xl)

Abstract

Factors inducing phenotypic plasticity of fishes are poorly understood. A recent study in middle North America revealed a relation between sculpin (Cottus) morphology and stream bottom velocity. We investigated this relation in 16 streams of northeastern Utah, but included 16 additional environmental variables, representing three spatial scales (mesohabitat, stream reach, watershed). We took 21 morphometric and two meristic measurements on all sculpin over 71 mm standard length, measuring a total of 373 individuals from 12 streams and 36 mesohabitats. Fifty-eight of these were mottled sculpin (Cottus bairdii) and 315 were Paiute sculpin (Cottus beldingii). Sculpin morphology varied substantially. One principle component (PC; explaining 29% of variation) revealed disparity in robustness, mouth size, and number of prickles among individuals and between species. Mottled sculpin were more robust with a larger mouth and more prickles. Another PC (explaining 11% of variation) revealed disparity in fin length, fin height, and head width among individuals but not between species. Environmental variables significantly explained morphological variation suggesting substantial phenotypic plasticity. Variation associated with the first PC was partly explained (r² = 0.64) by brown trout (Salmo trutta) abundance, fish species richness, mottled sculpin abundance, and stream bottom velocity. Variation associated with the second PC was partly explained (r² = 0.41) by Paiute sculpin abundance, mottled sculpin abundance, watershed area, brown trout abundance, water depth, stream bottom velocity, and substrate type. Overall, our results support the earlier study because stream bottom velocity influenced morphology. However, inclusion of additional variables substantially improved the explanatory model. In particular, biotic interactions (competition, predation) were important. Notably, nonnative brown trout were a substantial influence on sculpin morphology.