Bering Sea | Fishes and Fish Habitats
Temperature-dependent survival and growth of early juvenile Bering Sea snow crab ( Chionoecetes opilio ) and Tanner crab ( Chionoecetes bairdi ): Implications for optimal crab thermal habitat in a rapidly warming Alaska Arctic Presenter: Louise Copeman , louise.copeman@noaa.gov, Alaska Fisheries Science Center Long-term laboratory studies on temperature-dependent (-1.5 to 16 °C) growth and survival in early juvenile Alaska snow crab ( Chionoecetes opilio ) and Tanner crab ( Chionoecetes bairdi ) were conducted. A priori we assumed that snow crab would have a stenothermal response adapted to cold conditions (< 3 ℃ ) whereas Tanner crab would have a more eurythermal response. However, survival was generally similar between the two species and decreased at temperatures above 7 °C and below 0 °C. Intervals between molting events (inter-molt period) and the proportional change in size at each molt (molt increment) were temperature and species dependent. Tanner crab had both shorter inter-molt durations and larger molt increments at temperature > 2 °C, compared to snow crab. Largest molt increments for both species were measured at temperatures between 0 °C and 5 °C, indicating efficient growth at lower temperatures. Above 2 °C, absolute growth rates (mm.day-1) were higher in Tanner crabs compared to snow crabs. Temperature- dependent survival and growth functions were coupled to an ensemble of CMIP6 Earth System Models statistically downscaled bottom temperature data (1/12th degree resolution) to examine historical and future projections of thermal habitat for Chionoecetes crab in the Eastern Bering and Chukchi Seas (1993-2100). By the end of the century, average summer bottom temperatures are projected to approach 7.5 °C across much of the eastern Bering Sea shelf, a level beyond the optimal thermal limit for long-term survival of Chionoecetes spp (<80% survival over 200 days). Optimal summer thermal habitat (< 5 °C) will move offshore and northward and be limited to the northwest Bering Sea Shelf and the central Chukchi Seas by 2100. Different temperature-growth responses may result in juvenile Tanner crab having a future growth advantage over snow crab across the full latitudinal extend of the Bering and Central Chukchi Seas.
Alaska Marine Science Symposium 2023 43
Made with FlippingBook flipbook maker