Wednesday, May 23, 2012

Diet Supplementation Boosts Blue King Crab Survival Rate

Researchers at the Alutiiq Pride Shellfish Hatchery in Seward, Alaska, are reporting great success culturing blue king crab this spring. They credit their progress with investigation of effects of microalgae diet supplementation on survival and larval health.

Researchers found that a diet of live Thalassiosira weissflogii microalgae and enriched Artemia resulted in survival rates of 80 percent from matching to the glaucothoe stage and 53 percent from matching to the first juvenile stage.

These survival rates are the highest to date for either red or blue king crab since the project began, they said.

Before this year, large-scale culture of blue king crab was less successful than for red king crab. High rates of mortality were attributed to suboptimal hatchery rearing conditions. While the life histories of red and blue king crab are similar, different culturing protocols may be required to achieve similar production success, they said. 

The project is one of several underway through the Alaska King Crab Research, Rehabilitation and Biology program, also known as AKCRRAB, sponsored by industry members, community groups, the Alutiiq Pride Shellfish Hatchery, NOAA Fisheries, the University of Alaska Fairbanks School of Fisheries and Ocean Sciences, and the Alaska Sea Grant College Program.

While high survival of red king crab has been achieved without microalgae in the diet, microalgae may be essential for blue king crab larvae. However, use of microalgae in large-scale, flow-through systems poses logistical challenges because of their small cell size, which allows algae to be quickly flushed out of the tanks. To solve this problem, AKCRRAB biologists Jim Swingle and Den Daly developed a semi-static rearing technique where microalgae is retained in tanks to optimize larval exposure, they said.

Juvenile blue crab cultured at the Seward hatchery will be used in experiments to better understand the biology of early juvenile king crab at NOAA Alaska Fisheries Science Center Behavioral Ecology Lab in Newport, Ore., the NOAA Kodiak Fisheries Research Center, and the University of Alaska Fairbanks, Juneau Center.

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