Assemblage and foraging behavior of demersal fishes and large invertebrates across eelgrass and sandflat habitat at False Bay, San Juan Island

Abstract

Understanding the species assemblage and foraging behavior of demersal fishes and large invertebrates occurring at False Bay was the primary objective of this study. This knowledge can provide valuable insight on future restoration and preservation efforts used for reintroducing critically endangered species, such as salmon. This study provides more information and data on what species are present, the behavior that they exhibit, duration of presence, and whether more predations occur in the eelgrass beds or the open sandflat. We hypotheses that more assemblage and predation will occur in the eelgrass than the sandflat because eelgrass beds provide more protection, habitat, and biodiversity of fauna that can be food resources for large predators. Species assemblage and predation was documented through the use of BRUVs, a baited remote underwater video system, that was placed out via snorkeling at eelgrass beds and sandflat towards the mouth of False Bay. Analyses was separated into two sections: one looking through the video footage and identifying categories of interests such as species and behavior. The second section was creating plots to compare the categories and finding statistical significance in R to determine which variables drove predation and assemblages. 40 occurrences of species assemblage from 7 species were evaluated. After all the statistical analyses, the data and result does not support my hypotheses. The behavior was the most significant variable to determine predation and assemblage. Dungeness crabs was the most abundant species with 19 occurrences with an average size of 12-27 cm in the sandflat and 15-20 cm in the eelgrass. Moreover, Dungeness crab has the most occurrences and largest total duration in both habitats.