Behavioral Ecology of Podding Red King Crab, Paralithodes camtschatica

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Diel activity cycles and foraging dynamics for two pods of 500–800 juvenile red king crab, Paralithodes camtschatica, were monitored for 196 d. (Nov. 1987–June 1988) and 148 d. (Oct. 1988–Feb. 1989) in Womans Bay, Kodiak, Alaska, using SCUBA. Nocturnal foraging and homing behavior of podding red king crab were documented for the first time. Variation in time of pod dispersal into a nightly foraging aggregation was explained (R2 = 0.72) by changes in water temperature, crab weight, and time of sunset. A trend of increased foraging time and movement to deeper, cooler water was apparent after mid-April, as water temperatures reached 4 °C and began a sustained summer increase. Molting occurred only at night, and seasonal variations in molting rate were estimated using molting probability models based on length-frequency distributions. Average pod movement was counter to the direction of strongest water currents, and homing behavior suggested some affinity for a low-light environment in man-made niches. Items most frequently eaten were sea stars (Evasterias troschelii) and macrophytes (Laminaria sp. and Ulva sp.). I discuss the inception of podding as a discontinuity in behavior, perhaps reflecting a break in the fractal continuum of niche availability within red king crab habitat.