Friday, 13 November 2009: 10:25 AM
Crustacean populations have evolved a variety of reproductive strategies as adaptations to predictable and unpredictable aspects of their environments. Climate change will create historically unusual situations, and the resiliency of different species will depend on the plasticity of their behavior. Hatch timing is one mechanism through which climate variability may affect population recruitment. King crab larvae hatch over long periods of time (30-50 days per female), from February to May; a "bet-hedging" adaptation to uncertain food supplies. Warmer temperatures cause earlier spawning, shorter embryonic development, and earlier hatching. Abundance of female red king crabs was significantly correlated (r=0.452, P<0.005, n=39) with the first principal component of a suite of environmental indicators, suggesting a strong association of recruitment with environment. Cold years produce strong, early phytoplankton blooms in synchrony with crab hatching, whereas warm years produce weak, late blooms that are out of synch with crab hatching. This match/mismatch between hatching and food supplies may be one cause of population fluctuations. In contrast, Tanner crab hatching occurs in high density aggregations over a brief period of 6-7 days per female, and coincides with the largest spring tide change. This may enhance the ability of larvae to reach nursery grounds, and suggests that the member-vagrant model is more appropriate for recruitment of this species. As a consequence, increasing water temperatures may have long-term detrimental effects for king crabs, but less impact on Tanner crab reproduction, whereas predation probably plays a larger role for Tanner crabs.
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