Meeting Abstract
P2.30 Saturday, Jan. 5 Effect of food availability on thermal tolerance of juvenile Dungeness crabs in the San Francisco Estuary MCLEAN, K.M.*; TODGHAM, A.E.; San Francisco State University; San Francisco State University kmclean@mail.sfsu.edu
Understanding the consequences of anthropogenic environmental change to Dungeness crabs, Metacarcinus magister, is crucial for the successful management of this species. By 2100 the San Francisco Estuary (SFE) will experience a 1.5-4.5°C increase in average temperature as well as more frequent extreme thermal events. Within the estuary, 0+ age group juvenile crabs prefer eelgrass beds and oyster beds because they provide refuge from predators and elevated nutrient availability. Little is known about whether this increased nutrient availability enables juvenile Dungeness crabs to better tolerate extreme thermal events by providing them with more energy to grow and allocate to other physiological processes like stress tolerance. We investigated the effect of different food rations on the upper thermal tolerance of juvenile Dungeness crabs. 0+ Dungeness crabs (15-25mm) were collected from the SFE and were held in outdoor tanks for four weeks under two feeding levels: high (300mg squid tissue/48hrs) and low (50mg squid tissue/week). Crabs in the low food group weighed significantly less and had significantly smaller carapace widths than crabs in the high food group. When crabs were separated by whether they recently molted, the weight differences between feeding groups were apparent in both molted and non-molted crabs. Heart rate was then monitored in crabs as temperatures were increased from 12°C (current bay temperature) to 36°C (representing a thermal extreme) over a 4h period. Upper thermal tolerance was determined by a break in heart function. To assess the metabolic response to elevated temperature, crabs were placed in respirometers held at constant temperature (15, 20, 25 and 30°C) and oxygen consumption was measured until oxygen levels decreased to 80% air saturation.
