Master of Science

Abstract

This study described the distribution and feeding of juvenile salmon (<italic>Oncorhynchus</italic> spp.) and Pacific herring (<italic>Clupea pallasi</italic>) in Puget Sound to explore the potential for resource competition among these species. We used surface townets, midwater trawls, and acoustics surveys to assess distributions of fish in surface waters, among bathymetric zones, and depth strata in the water column. Seasonal and spatial variability was evident in epipelagic biomass. Occurrence of biomass generally increased progressively during the summer and shifted to deeper depths. Despite considerable variability, spatial, temporal, and dietary overlap was observed among herring and juvenile salmon, especially for Chinook and coho salmon. Crab larvae and amphipods were important prey for most salmon species and herring. Herring were present in higher abundances than salmon and had high population-level consumption demand. If food resources are limiting, there is potential for competitive interactions among salmon and herring.