Bering Sea | Fishes and Fish Habitats
Dietary and spatial overlap among jellyfish and small pelagic fish in the eastern Bering Sea during warm ocean conditions Presenter: Mary Beth Decker , marybeth.decker@yale.edu, Yale University Richard Brodeur , ricbrodeur1@gmail.com, Oregon State University Emily Fergusson , emily.fergusson@noaa.gov, NOAA Alaska Fisheries Science Center Wesley Strasburger , University of Alaska Fairbanks Kristin Cieciel , kristin.cieciel@noaa.gov, NOAA Alaska Fisheries Science Center Populations of scyphozoan jellyfish in the eastern Bering Sea (EBS) can grow rapidly within a single season and have fluctuated widely over recent decades. Understanding the role of jellyfish in the EBS ecosystem is required for fishery and ecosystem management, however we lack direct measurements of the impact that changes in jellyfish abundance have had upon this ecosystem and its fish populations. We examined the role of jellyfish as competitors of juvenile forage fishes (herring and gadids) and juvenile salmonids by (1) examining the diets of the dominant scyphozoan jellyfish in the region, Chrysaora melanaster, and (2) estimating the dietary and spatial overlaps among jellyfish and major planktivorous pelagic fish taxa. Ocean sampling for diet analyses occurred in two contrasting years: 2014 (high jellyfish biomass but cooler temperatures) and 2016 (low jellyfish biomass but warmer temperatures). Jellyfish diets were very diverse and contained primarily small copepods and pteropods but showed mostly low overlaps with small pelagic fishes, which consumed mainly euphausiids and small fishes. Fishery research data were used to examine the spatial overlap of small pelagic fish and jellyfish within the EBS during the summers of 2014 and 2016. Generally, jellyfish and the small pelagic fishes showed low spatial overlap, but there were some high spatial overlaps among the small pelagic fish and salmonids. Spatial overlap and trophic relations are not uniform throughout the EBS nor across years, however, regions of high overlap do occur, which could result in resource competition in low productivity years or areas.
Alaska Marine Science Symposium 2023 206
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