Habitat and predator-prey studies with juvenile red king crabs in Newport, Oregon

Experimental setup for predator and substrate experiments. Photos by Al Stoner.

Allan Stoner and colleagues at the Newport Laboratory of the NOAA Alaska Fisheries Science Center are completing first year experiments on juvenile red king crabs. In June 2008, 2,500 first stage juveniles cultured at the Alutiiq Pride Shellfish Hatchery in Seward, Alaska, were shipped to Newport to determine habitat requirements for superior juvenile survival and growth in the field. Experiments explored habitat preferences of crabs using natural and mimic materials. The youngest juvenile crabs prefer substrata with a high physical structure, but the importance of physical structure becomes less important as the crabs get larger. Fish predator interactions were also investigated using northern rock sole, Pacific halibut, and Pacific cod. Predation rates were strongly mediated by the presence, density, and complexity of physical structures provided as habitat for the juvenile crabs. Experiments with a new batch of juveniles from the hatchery in 2009 will continue with other common predators, such as longhorn sculpin, to understand the best types of habitat for reducing mortality of hatchery-reared red king crab when released in the field. For stock enhancement purposes it is critical to determine whether hatchery-reared crabs have any behavioral or physical deficiencies that could reduce survival when outplanted.

Upcoming experiments in Newport will aim at understanding how water temperature affects feeding and growth of early juvenile red king crabs. Preliminary tests are under way with 1-year-old crab at temperatures from 1 to 12°C. These experiments will be relevant to both nursery grow-out at the hatchery and impacts of climate change in Alaska waters.

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.