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Comparing Temperature Effects on Molting And Growth of Newly Settled Red And Blue King Crabs

In summer 2012 NOAA Newport Laboratory researchers studied blue king crab juvenile molting, growth, and lipid storage at several temperatures. The Alutiiq Pride Shellfish Hatchery supplied the juveniles from larvae reared there in spring 2012. Juvenile blue king crabs were cultured in low-density populations (150 per cubic meter) and individually at four temperatures: 1.5, 4.5, 8, and 12°C.

After 60 days, crabs cultured in populations and individually showed no difference in growth rates, and mortality was low (2–6%) in all temperature treatments. In identical experiments conducted in 2010, red king crabs grew faster in populations and had substantially higher mortality (23–40%) likely from cannibalism. A comparison of growth in the blue and red king crab experiments showed that red king crabs molt more often than blue king crabs and grow larger with each molt. Therefore, at any temperature red king crabs will achieve larger size than blue king crabs in a given time. While red king crabs grew more in warmer temperatures, the maximum growth of blue king crabs occurred at 8°C suggesting that the warmest experimental temperature (12°C) may be too high for blue king crabs.

These results indicate that blue king crabs will require more time in culture than red king crabs to reach comparable size, but this can be offset by higher survival. Also, blue king crabs will grow best where temperatures do not exceed 8°C, perhaps in deeper or in more northern waters. Blue king crabs also may be more vulnerable to the long-term rise in ocean temperature in Alaska.

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