Hatchery nursery experiments on juvenile red king crab

Juvenile red king crabs. Photo by James Swingle.

Large-scale nursery experiments are under way at the Alutiiq Pride Shellfish Hatchery in Seward to refine grow-out technology for juvenile red king crabs. In spring 2009, successful larval rearing yielded 100,000 first stage juveniles. Juvenile nursery experiments will build on 2008 results and explore diet effects on growth, survival, and color. Biologists are supplementing diets with calcium and astaxanthin, to decrease cannibalism and darken the shell. Generally, hatchery reared juvenile red king crabs are somewhat lighter in color than wild crabs. Astaxanthin, a carotenoid in algae, is commonly used in aquaculture to enhance color pigments. The assimilation of astaxanthin may give the crabs a darker red color similar to their wild counterparts. Manipulating color through diets may be a key component in producing ecologically fit crabs for future outplanting.

A second set of experiments will sort crabs by size, to reduce predation pressure by the same species and allow crabs to reach later stages with higher survival rates. As hatchery crabs grow, their molting becomes increasingly asynchronous resulting in a range of sizes. Researchers anticipate that decreasing size variability within a tank will provide higher yields.

Technician Janelle Christiansen of Old Harbor is assisting with nursery experiments at the hatchery, and testing alternate tank designs for mass rearing red king crab juveniles. Her work is supported through the Administration for Native Americans.

AKCRRAB is a research and enhancement project sponsored by the Alaska Sea Grant College Program, UAF School of Fisheries and Ocean Sciences, NOAA Fisheries, the Alutiiq Pride Shellfish Hatchery, community groups, and industry members. For more information go to http://seagrant.uaf.edu/research/projects/initiatives/king_crab/general.