JPR Advance Access published online on April 25, 2008
Journal of Plankton Research, doi:10.1093/plankt/fbn046
Growth and development of Pseudocalanus spp. in the northern Gulf of Alaska
Institute of Marine Science, University of Alaska Fairbanks, AK 99775-7220, USA
2 Corresponding author: hopcroft{at}ims.uaf.edu
Received on January 19, 2008; revised on April 4, 2008; accepted on April 10, 2008
| Abstract |
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Pseudocalanus are the numerically dominant calanoid species in coastal subarctic Pacific waters. We examined their juvenile growth rates, and explored their relationships to temperature, chlorophyll a and body size for Pseudocalanus spp. from 2002-2004 in the northern Gulf of Alaska. Generally, the monthly mean growth rates increased from 0.049±0.007(SE) day–1 in March to 0.095±0.016 day–1 in August, declining slightly to 0.074± 0.009 day–1 in October. Typically, growth rates at most stations were around 0.05 day–1, with no consist or significant pattern between stations. After standardization to 5 °C and 10 °C, the mean growth rates were 0.045±0.002 day–1 and 0.075±0.004 day–1 respectively, with growth rate decreasing with increasing development stage. Unlike other local calanoid copepod species, Pseudocalanus species tend to be more temperature-dependent than food-dependent, with composite statistical models describing at most 30% of the observed variability in growth rate. Interestingly, development time was comparable to other co-occurring calanoid copepods, however, growth rates of Pseudocalanus spp. were considerably lower. We demonstrate this with a new multi-species model that describes the growth rates of other egg-scattering copepods in this ecosystem, but to which Pseudocalanus does not fit. Thus, the egg-carrying Pseudocalanus species appear to employ a life history strategy optimized for slow growth at low chlorophyll, that keeps individuals relatively small, and may therefore reduce visual predation upon them.
Key Words: Growth development functional relationship Pseudocalanus Gulf of Alaska
1 Present address: Cooperative Institute for Marine Resources Studies, Oregon State University, 2030 SE Marine Science Drive, Newport, Oregon 97365, email: hui.liu{at}oregonstate.edu