Movement rates of morphometrically mature male snow crabs, Chionoecetes opilio (O. Fabricius, 1788), in the eastern Bering Sea, Alaska (Brachyura: Oregoniidae)

Abstract

Movement rates of morphometrically mature male snow crabs, Chionoecetes opilio, in the eastern Bering Sea, Alaska were estimated for 33 individuals at liberty between 280 and 467 days. Using depth measurements from data storage tags attached to individual crabs, daily acrossshelf movement rates were estimated as the daily change in crab depth divided by the slope (i.e., depth/horizontal distance) of the seafloor on which each crab resided each day. Rates and distances were analyzed at different time scales (day, month, year) and general additive models were used to test the significance of factors that could potentially influence the daily rate of movements. Individual crab rates averaged between 0.1 and 1.1 km/day over their time at liberty, with one individual attaining a maximum rate of 8 km/day. Rates varied significantly (P < 0.05) with the bottom depth, season (day of year), and the release area. Although overall rates did not vary with crab size, maximum rates were highest among the smallest individuals, two of which (100-102 mm carapace width) traveled approximately 250 km in ten months. Movement rates were highest during spring when travel was directed mostly inshore, and slower during fall and winter when offshore movements occurred. In contrast to other studies that demonstrated decreased snow crab movement rates in cold water (e.g., < 1 °C), no temperature effect was found for these males in the eastern Bering Sea. Further research is necessary to determine if factors that act at shorter time scales (< 24 hours), such as tidal currents and light intensity, influence snow crab movements.