MEPS

Marine Ecology Progress Series

MEPS is a leading hybrid research journal on all aspects of marine, coastal and estuarine ecology. Priority is given to outstanding research that advances our ecological understanding.

Online: ISSN 1616-1599

Print: ISSN 0171-8630

DOI: https://doi.org/10.3354/meps

Impact Factor2.1 (JCR 2025 release)

Article Acceptance Rate52.2% (2024)

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Volume contents
Mar Ecol Prog Ser 571:233-243 (2017)

Association of foraging Steller sea lions with persistent prey hot spots in southeast Alaska

ABSTRACT: Understanding how air-breathing marine vertebrates find and utilize prey provides insight into their foraging mechanisms and ultimately their population productivity and trends. Utilization depends on their ability to locate areas where productive foraging conditions exist. We quantified the abundance of forage fish in southeast Alaska during acoustic surveys between October and April to improve our understanding of Steller sea lion Eumetopias jubatus foraging behavior. Energy densities (millions kJ km-2) of forage fish were orders of magnitude greater between November and February due to the presence of large schools of Pacific herring Clupea pallasi. Herring schools were highly aggregated, although the location of these aggregations shifted southward from November to April. Thus, a productive foraging area in one month did not necessarily equate to a productive area in the next month. However, by surveying on successive days and weeks, we found that herring aggregations persisted at shorter time scales. When the study area was partitioned into 1 × 1 km blocks, the day-to-day abundance of prey within a block was highly correlated with prey abundance the following day (correlation coefficient, r = 0.75, p < 0.001) and with prey abundance for the following week (r = 0.55, p < 0.001). More importantly, the persistence of these prey hot spots was an important characteristic in determining whether foraging sea lions utilized them. The odds of observing a foraging sea lion were about 1 in 3 for locations where prey hot spots were persistent. The persistence of these hot spots allowed predators to predict their locations and concentrate search efforts accordingly.

KEYWORDS

Michael F. Sigler (Corresponding Author)

  • National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 17109 Point Lena Loop Road, Juneau, Alaska 99801, USA
mike.sigler@noaa.gov

Scott M. Gende (Co-author)

  • National Park Service, Glacier Bay Field Station, 3100 National Park Road, Juneau, Alaska 99801, USA

David J. Csepp (Co-author)

  • National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Alaska Fisheries Science Center, 17109 Point Lena Loop Road, Juneau, Alaska 99801, USA