Describing the Diet of Juvenile White Sturgeon in the Lower Columbia River Canada Using Lethal and Non-Lethal Methods

Annual growth in the wild for endangered juvenile white sturgeon in the lower Columbia River is influenced by site fidelity, which is hypothesized to be a function of food availability or composition. We described i) food availability and the diet of juveniles, and ii) the reliability of non-lethal gastric lavage in describing the diet. Fish were angled in October of 2012 and 2013. A non-lethal gastric lavage (GL; n=108) sample was collected, the individual was euthanized, and stomach contents (SC; n=48) were collected. Benthic samples (BS; n=57) were collected from areas of juvenile capture to describe food availability. Prey diversity was influenced by habitat selected, not by fish size, age, or food availability, with fish in deeper slower water having the highest number of prey taxa (mean=4.6). Prey in GL, SC, and BG explained 52, 59, and 70% of the total prey taxa identified (n=27), respectively. GL was 74% efficient in describing total prey taxa (n=19) in the diet and a minimum of 50 samples were required to describe the diet to this level. Results improve knowledge of juvenile sturgeon feeding ecology and suggest that non-lethal GL can be used to assess diets when fish cannot be sacrificed.