A Feeding‐Ecology‐Based Approach to Evaluating Nursery Potential of Estuaries for Black Rockfish

Abstract

AbstractPrevious work suggests that Oregon estuaries function as nursery habitat and may play an important role in settlement of Black Rockfish Sebastes melanops. No research, however, has been conducted on juvenile Black Rockfish feeding ecology in estuarine habitats, which is necessary to evaluate habitat use and quality. We examined stomach contents and carbon and nitrogen stable isotope ratios for juvenile Black Rockfish collected from May to September in 2016 and 2017 at both anthropogenic (dock) and natural (eelgrass Zostera marina) habitats in Yaquina Bay, a marine‐dominated estuary on the central Oregon coast. We found consumption of 94 different prey items, the majority of which are estuary derived, and benthic prey were most frequently consumed. In general, it appears that fish are feeding in the habitat in which they are caught, with marine‐fouling prey being consumed in greater abundances at the dock habitat, whereas algae‐ or eelgrass‐associated species were consumed in greater abundances at the eelgrass habitat. The increase in both δ15N and δ13C values in muscle tissue seasonally and the positive correlation with upwelling in 2016 suggests that upwelled, oceanic waters were the primary source of nutrients to Yaquina Bay in 2016. The high variability in δ15N and general increase in δ13C seasonally in 2017 suggests that oceanic waters were still present but may not have been the dominant nutrient source. Yaquina Bay appears to be an important foraging ground for juvenile Black Rockfish during summer months, providing a diversity of prey items, with special importance of benthic and eelgrass‐associated prey. Our results support the hypothesis that estuaries can function as a nursery habitat for Black Rockfish, although additional data is needed to provide an absolute designation. Changes in benthic communities or available habitat may have negative effects on foraging ability, and thus nursery function, and should be considered during management decisions.