Foraging ecology of swordfish in the California Current Large Marine Ecosystem during an ecosystem regime shift

Details

• Journal Title:
  ICES Journal of Marine Science
• Personal Author:
  Preti, Antonella ; Muhling, Barbara A ; DiNardo, Gerard T ; Pierce, Graham J ; Lyons, Kady ; Stohs, Stephen M
• NOAA Program & Office:
  NMFS (National Marine Fisheries Service) ; SWFSC (Southwest Fisheries Science Center)
• Description:
  Marine heatwaves are periods of anomalously warm ocean temperatures that can substantially impact marine ecosystems. These events can lead to changes in trophic interactions, food webs, and ecosystem structure, even after they have subsided. In this study, we described changes in swordfish (Xiphias gladius) foraging ecology in the California Current Large Marine Ecosystem (CCLME) over a period of rapid oceanographic and ecosystem change. We used 17 years of data (2007–23) to examine how swordfish diet composition varied through time in the CCLME before, during, and after the severe marine heatwave of 2014–16. Stomachs were collected by fishery observers aboard commercial vessels using drift gillnet and deep-set buoy gear. Prey were identified to the lowest taxonomic level possible and diet composition was analysed using univariate and multivariate methods. Our results showed a shift in diets occurred from cephalopods to epipelagic teleosts in 2014–16. While jumbo squid (Dosidicus gigas) was the most important prey during the early years of the study, Pacific hake (Merluccius productus) and northern anchovy (Engraulis mordax) dominated the diets in more recent years. The diet shifted towards teleosts in 2014–16 coincided with warm sea surface temperature anomalies, stronger stratification and shallower isothermal layer depths, negative North Pacific Gyre Oscillation, and higher anchovy biomass in the study region. Overall, swordfish diets appeared to integrate prey availability, environmental forcing, and spatiotemporal patterns in the CCLME. Our results showed that swordfish are generalist and opportunistic predators that have many characteristics of useful ‘ecosystem sentinels’ such as conspicuousness, sensitivity to ecosystem processes, and timely response to ecosystem shifts. Our findings can inform ongoing ecosystem monitoring efforts in the CCLME, as well as the development of ecosystem models. We also provide a unique perspective on how marine heatwaves may impact trophic connections and marine ecosystems.
• Source:
  ICES Journal of Marine Science, 82(8)
• DOI:
  https://doi.org/10.1093/icesjms/fsaf139
• ISSN:
  1054-3139 ; 1095-9289
• Format:
  pdf
• Publisher:
  Oxford University Press (OUP)
• Document Type:
  Journal Article
• License:
  https://creativecommons.org/publicdomain/zero/1.0/
• Rights Information:
  CC0 Public Domain
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:abac82a599190bc20514c4ab4528b243fe2951a05c92d7b0727b5b86a2eddf5f9832990e747f6751355b6f8cdd403dd1837420e4628c6cb6589328117385c49e
• Download URL:
  https://repository.library.noaa.gov/view/noaa/71397/noaa_71397_DS1.pdf
• File Type:
  [PDF - 1.44 MB ]