Feeding Ecology of Select Groundfish Species Captured in the Northwest Fisheries Science Center's West Coast Bottom Trawl Survey, Using Gut Contents and Stable Isotopes

We are examining the diets of multiple groundfish species as an ongoing component of the NOAA Fisheries West Coast Bottom Trawl Survey. Stomachs and tissue samples were collected at sea and preserved for gut content and stable isotope analyses. Yellowtail, darkblotched, canary, sharpchin and stripetail rockfishes are largely zooplanktivorous, with euphausiids composing 48.0 to 84.7% of total prey weight. Darkblotched and canary rockfishes also feed on shrimp, which were 34.2% and 39.5% by weight, respectively. Sablefish, yelloweye rockfish, chilipepper and bocaccio are piscivorous, with fish making up 50.7% to 91.4% of total prey weight. Greenstriped and rosethorn rockfishes show a strong preference for benthic prey; various shrimp species make up 80.8% of greenstriped diets by weight, while rosethorn consumed 52.1% shrimp and 20.3% galatheid crab species. Finally, widow rockfish and Pacific ocean perch exhibit a more omnivorous feeding strategy, eating a variety of zooplankton including euphausiids (14.3% and 30.9%), amphipods (4.3% and 3.4%), shrimp (0.87% and 5.3%) and gelatinous organisms (2.6% and 60.94%). These results demonstrate that groundfishes are significant consumers in both benthic and pelagic habitats feeding across multiple trophic levels. The results of stable isotope analysis will show whether the gut contents represent recent or long-term trends.