NMFS Kodiak Lab Researchers Study Red King Crab Rearing Conditions and Cannibalism
Rearing containers of different sizes used to hold juvenile red king crabs. Photo courtesy of NMFS.
One year old and recently settled red king crabs. Photo courtesy of NMFS.
In summer 2010, scientists at the National Marine Fisheries Service (NMFS) Kodiak Laboratory completed two projects on laboratory culturing of juvenile red king crabs. The goal of the first project was to determine the effect of container size on crab growth and survival. The results will help biologists determine the most appropriate container size to maximize production and use of hatchery space when culturing red king crab. Ninety crabs were reared in 1.9 cm, 3.8 cm, and 7.6 cm diameter containers for nine months. Crabs in the smallest containers had a total survival of 17% after nine months, while crabs in the medium and large containers had a total survival of 83%. Crabs growth was significantly slower in the small and medium containers than in the large containers. Therefore, there is a trade-off between survival and growth when determining the most effective container size for culturing red king crab juveniles.
A second project conducted in 2010 examined the effects of prey density, habitat type, and predator density on the cannibalism of newly settled juvenile red king crab by 1 year old red king crab. Because larger crabs live in the same habitat as recently settled juveniles, cannibalism may affect survival after juvenile crabs are released in the wild in an enhancement effort. This cannibalism may be impacted by the density of the smaller crabs (prey) or the density of the predators. Results of the project revealed that predation rates decreased in more complex habitat and also decreased with increasing prey density. Predator density, however, had little effect on the predation rate per-predator regardless of habitat type. These results suggest that outplanting will be more successful if juvenile crabs are released into complex habitats at high densities. Future work will examine the behavior of other juvenile red king crab predators, such as sculpins, and will assess the effect of alternative prey availability. Manuscripts for peer review publication of both projects are in preparation.
News Flash is edited by Ben Daly. AKCRRAB is a research and rehabilitation 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.