Timing and Duration of Larval Hatching for Blue King Crab Paralithodes Platypus Brandt, 1850 Held in the Laboratory
Abstract Female blue king crab, Paralithodes platypus, were captured from the Pribilof Islands, Alaska, in July and October 2003 and shipped to the Kodiak Fisheries Research Center. Crabs were held in chilled seawater at 2, 3.5, or 4°C until hatching, and final counts were 4, 6, and 10 crabs in each treatment, respectively. Mean size of all crabs was 123.9 mm CL and did not differ significantly between treatments. Individual crabs required an average of 29 days for complete hatching, regardless of holding temperature. Earliest hatching began on or before 20 February 2004. Crabs captured in July and held at 4°C hatched significantly earlier, with a mean hatch date of 13 March 2004, than crabs captured in October and held at 2°C or 3.5°C, both of which groups hatched on a mean date of 18 April 2004. Crabs released an average of 416 ml of larvae, and 110,033 first stage zoeae. Excluding two crabs for which complete volumes were not obtained, there were no differences in volume or number of larvae released by crabs held at different temperatures. The pattern, duration and timing of larval release exhibited by blue king crab is similar to that observed for other lithodid crabs including red king crab (P. camtschaticus), golden king crab (Lithodes aequispinus), and southern king crab (L. santolla). Extended hatching periods for king crabs may be an adaptation to environmental variability and the uncertainty of adequate food sources for larvae, and represent a reproductive strategy of diversified bet-hedging.