Survival, Feeding, and Growth of Juvenile Dungeness Crabs From Southeastern Alaska Reared at Different Temperatures

Survival, feeding rates, and growth of individual juvenile Dungeness crabs (Cancer magister) were measured over 150 days at 0, 5, 10, 15, and 20°C in a laboratory study. Survival was highest at 0°C (79%) and lowest at 20°C (30%), but the number of surviving crabs declined at all temperatures over time. A high number (75%) of crabs survived at 10 and 15°C, temperatures associated with the greatest increases in size. Feeding rates increased with temperature up to 15°C. Crabs at 0°C did not eat and crabs at 5°C had a low but fairly constant feeding rate. Feeding rates at 10, 15, and 20°C increased significantly early on and then decreased to beginning rates; increases in feeding rates occurred after a large percentage of the crabs molted. Growth, measured by the increase in carapace width and wet weight over time, increased with temperature up to 15°C and then declined. Maximum growth occurred at 15°C. However, no significant differences in carapace width or wet weights existed among crabs at 10, 15, and 20°C by the end of the study. Crabs at 0°C did not molt or increase in weight; crabs at 5°C had very long intermolt periods and increased in weight by only 55%. Temperature effects on the size of molt increments were minimal; at 5, 10, and 15°C there were no significant differences in the size of molt increments. At 20°C the molt increment decreased with crab size. The intermolt period was the growth component most affected by temperature. The warmer the water temperature, up to 15°C, the shorter the intermolt period. Our results are consistent with the belief that Dungeness crabs have longer intermolt periods progressively northward along the west coast of North America.