Growth physiology of juvenile red king crab, Paralithodes camtschaticus, in Alaska

Abstract

Lack of recovery, following collapse of the Alaskan red king crab, Paralithodes camtschaticus, fishery, has prompted research directed towards rehabilitating the species. To better inform rehabilitation efforts aimed at increasing survival and growth of P. camtschaticus in their first year of life, I compared individual growth of hatchery-raised and wild-caught juvenile crabs in the laboratory and then compared both sets of laboratory individuals with cohorts from the field. To understand molt cycles, hemolymph was collected from age-0 and age-3 crabs to quantify circulating molting hormones (ecdysteroids) and the duration of premolt. Size, growth increment, molt interval, and cumulative molt interval did not differ significantly between hatchery-raised and wild-caught crabs. No consistent differences existed in CL between hatchery, wild-laboratory and field-surveyed juveniles for most months, although spine lengths of hatchery-raised and wild-caught crabs were significantly longer than field-surveyed crabs most months. Patterns of circulating ecdysteroids resembled published profiles for other crustacean species. Peak ecdysteroid levels occurred regularly (approximately 17 d) prior to ecdysis despite varying molt intervals. Age-0 and age-3 juveniles spent approximately 39 % and 32 % of the molt cycle in premolt, respectively. Overall, hatchery-raised and wild P. camtschaticus were markedly similar with respect to growth.