MEPS 481:53-67 (2013)  -  DOI: https://doi.org/10.3354/meps10245

Among-year variation in growth of Antarctic krill Euphausia superba based on length-frequency data

Andrew Olaf Shelton1,2,*, Douglas Kinzey3, Christian Reiss3, Stephan Munch4, George Watters3, Marc Mangel2,5,6

1Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, 2725 Montlake Blvd E, Seattle, Washington 98112, USA
2Center for Stock Assessment Research, University of California, Santa Cruz, 110 Shaffer Road, Santa Cruz, California 95060, USA
3Antarctic Ecosystem Research Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, 8901 La Jolla Shores Drive, La Jolla, California 92037, USA
4Fisheries Ecology Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanographic and Atmospheric Administration, 110 Shaffer Road, Santa Cruz, California 95060, USA
5Department of Applied Mathematics and Statistics, Jack Baskin School of Engineering, University of California, Santa Cruz, Mail Stop SOE2, Santa Cruz, California 95064, USA
6Department of Biology, University of Bergen, 5020 Bergen, Norway

ABSTRACT: Understanding the temporal variability in vital rates (e.g. growth and survivorship) of wild populations is practically and statistically difficult but crucial for connecting such variation to mechanistic drivers and their population consequences. For somatic growth, empirical estimates of variation are rare because they often require expensive long-term tag-recapture programs. In marine pelagic ecosystems, where many species are difficult to sample and not amenable to tagging studies, researchers have relied on estimating growth from length-frequency distributions. We developed a general approach for estimating growth from observed length-frequency samples by combining kernel density estimates of the length-frequency distribution and the von Bertalanffy growth function. Our approach is conceptually straightforward and easy to implement. We applied the methods to Antarctic krill Euphausia superba collected from the Southern Ocean over a span of 19 yr to document among-year variation in krill growth during the austral summer. Our estimates of growth align closely with existing estimates of growth, but we provide the first estimates of among-year variation in krill growth. We estimate very high among-year variation in growth (annual estimates for a 30 mm krill in the Elephant Island region ranged from 0.00 to 0.17 mm d-1; mean = 0.073, among-year coefficient of variation ≈ 0.8). We correlated growth rate variation to estimates of ocean chlorophyll but not to other oceanographic indices, contrasting with results from previous studies. The large amount of variation in growth unexplained by environmental covariates has substantial implications for ecosystem management in the Southern Ocean ecosystem.


KEY WORDS: von Bertalanffy · Krill · Growth · Temporal variation · Southern Ocean · Kernel density estimator · Antarctic Peninsula


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Cite this article as: Shelton AO, Kinzey D, Reiss C, Munch S, Watters G, Mangel M (2013) Among-year variation in growth of Antarctic krill Euphausia superba based on length-frequency data. Mar Ecol Prog Ser 481:53-67. https://doi.org/10.3354/meps10245

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