© 2004 by ICES/CIEM International Council for the Exploration of the Sea/Conseil International pour l'Exploration de la Mer
Interannual abundance patterns of copepods during an ENSO event in Icy Strait, southeastern Alaska
a Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks 11120 Glacier Highway, Juneau, AK 99801, USA
b Alaska Fisheries Science Center, Auke Bay Lab, National Marine Fisheries Service, NOAA 11305 Glacier Highway, Juneau, AK 99801-8626, USA
*Correspondence to W. Park: tel: +1 907 465 6449; fax: +1 907 465 6447. e-mail: w.park{at}uaf.edu.
Interannual copepod abundance (number m–3) and sea surface temperatures (SST, 2-m depth) were examined from four stations in Icy Strait, southeastern Alaska, monthly from May to September, 1997–2002. SST was generally lowest in May (
7°C), increased rapidly to a summer peak (12°C), and declined again by September. SST was relatively high in the El Niño year, 1998, and was low during a regional cold event, 2002, compared to other years. Overall, copepods constituted 18.8% of the total biomass and 88.2% of zooplankton abundance, and included >34 species. The common copepod species were grouped into two size classes by total length (TL), those >2.5 mm (11.4% biomass, 24.2% abundance) and those <2.5 mm (7.4% biomass, 64.0% abundance). In order of dominance, large species included Metridia ochotensis, Calanus marshallae, M. pacificus, and Neocalanus spp. and small species included Pseudocalanus spp., Acartia longiremis, and Centropages abdominalis. Overall, the small species were more abundant than the large species. Densities of large copepods were relatively low compared to those of small copepods during El Niño (1998) and a cold year (2002), suggesting that large copepods with long lifespans are more sensitive to ocean climate fluctuation.
Keywords: a regional cold event, El Niño, ENSO, interannual density variation, large copepods, small copepods