Gut Content Analysis of California Gulls Foraging in the Columbia River
October 2009 - February 2010
- Corps of Engineers
Objectives Provide lowest-taxon data on the gut contents of California Gulls foraging in the Columbia River. Identify all salmonids in the gut contents to species. Methods Diet analysis on 128 California gull stomachs will be performed. Gut contents have already been removed from carcasses, and are currently stored frozen in Whirlpacks. Initial soft tissue identifications have been completed, but will need to be verified. We will produce three things: 1) Hard tissue ID including salmonids to species and other fish to genus or the level that would allow us to separate them from other fish in the Columbia River system near John Day Dam. It is hoped that using otoliths will provide a clear distinction between sub-yearling and yearling Chinook. 2) Verification of completed soft tissue ID including determination to species. 3) Prey items by number, mass and percent biomass. Non-fish items may be lumped into groups (e.g., aquatic insects). All methods used in this project will follow those described in Wiese et al. (2008) and Parrish et al. 2006a), and will use a key specifically designed to identify otoliths and fish cranial bones in the gut contents of piscivorous birds (Parrish et al. 2006b).