Hatch timing, incubation period, and reproductive cycle for captive primiparous and multiparous red king crab, Paralithodes camtschaticus

Adolescent and mature female red king crab Paralithodes camtschaticus were captured by scuba divers and held in seawater tanks at the Kodiak Fisheries Research Center at ambient temperatures. Over three separate years, we monitored dates of embryo extrusion, timing and length of the hatching period, duration of embryological developmental, total degree-days, and volume and number of larvae released on a daily basis. Primiparous females extruded their embryos on a mean date of 3 February, two months prior to extrusion by multiparous crab. Mean hatching date for primiparous females occurred 16 days prior to that of multiparous females in 2001, and 12 days earlier ill 2003. Primiparous females required a mean of 365 days and 2601 degree-days for complete embryonic development, whereas multiparous females required significantly less time, with a mean of 328 d, and 2482 degree-days. Although multiparous females were significantly larger than primiparous females, there was no significant difference between reproductive types in the time required for complete hatching (mean 32 days), total volume (mean 308 mL) or number of larvae released (mean 106, 884). Multiparous female crabs held in filtered or unfiltered (raw) seawater showed no differences in hatch timing, hatching days, or volume released. Virtually all larvae (91-95%) were released in the 4 hour period between 1800 and 2200 hours, and 50% were released in the first half-hour of darkness. Extended hatching exhibited by red king crabs is not synchronous with the occurrence of planktonic food sources, but may be an adaptation to the uncertainty of food availability. Shorter development times for multiparous embryos are necessary to complete the reproductive cycle prior to obligatory molting before extruding the next batch of eggs. This information was incorporated into a conceptual model of the first 3 years of reproduction for red king crab.