Invertebrate Drift in Neighboring Perennial and Seasonal Tributaries of the Sacramento River

ABSTRACT INVERTEBRATE DRIFT IN NEIGHBORING PERENNIAL AND SEASONAL TRIBUTARIES OF THE SACRAMENTO RIVER by Gina Marie Benigno Master of Science in Biological Sciences California State University, Chico Summer 2011 While seasonal floodplains are known to provide abundant food and important rearing habitat for native and anadromous fish in California, the value of other types of seasonally aquatic habitats is less well understood. The use of seasonally flowing tributaries of the Sacramento River as non-natal rearing habitat for salmonids and as spawning areas for native fish has been previously documented. In order to evaluate food availability in Sacramento River tributaries, I compared invertebrate drift in a seasonal tributary with a neighboring perennial tributary through the duration of seasonal tributary flow, from November 2005 through June 2006. I compared drift density, taxonomic diversity, and community composition between the two tributary types. Overall drift abundance was greater in seasonal tributary samples. Taxonomic richness in the seasonal tributary was comparable to the perennial tributary, although community composition was different between the two tributary types. Specifically, chironomid larvae and small crustaceans were abundant in seasonal tributary drift, while terrestrial invertebrates were the primary component of perennial tributary drift. The results illustrate that seasonally flowing tributaries can provide greater prey availability to fish that use these habitats compared with perennial tributaries.