Dataset: Stone crab: 052012-DietChoiceExp1

Data was gathered experimentally at the Baruch Institute for Marine & Coastal Sciences. Wet weight (blotted (g)) of the prey items were determined before and after the trial with an analytical balance.

A total of 36 stone crabs (22 females [mean] and 14 males; CW ± SD, 90.7 ± 10.6 mm) were collected for use in the first experiment. The larger, crusher claw was removed from 19 of these stone crabs within 24 h of their capture. The crabs (each of which survived in the laboratory for several weeks) were housed in individual 5-gal buckets, each provided with a separate flowthrough seawater source, allowing water temperature and salinity to fluctuate with ambient conditions. The experiment was conducted over 4 72-h trials (blocked by time) during a 2-wk period. A control, which consisted of a bucket without a crab and the same amount of each food item, was included in each experimental block to account for any consumptionindependent changes in biomass of the provided diet items.

Each crab was provided with 6 diet options simultaneously that are commonly found in oyster reefs within North Inlet estuary: eastern oysters (Crassostrea virginica), hard clams (Mercenaria mercenaria), ribbed mussels (Geukensia demissa), green algae (Ulva spp.), red algae (Gracilaria spp.), and sun sponge (Hymeniacidon heliophila). Because of large differences in the mass-to-volume ratio between these food items, the mass and volume of the different food types provided could not standardized simultaneously. The reasoning was that crabs are consumption limited by the volume of space in the stomach, and therefore an attempt was made to standardize the relative volume of consumable tissue across diet types. They determined the amount of food consumed as the difference between the initial and the final blotted wet weight of each food item throughout the 72-h experiment. Although using wet weights is less accurate than using dry weights, it was necessary because stone crabs were fed living organisms, and the initial dry weight could not be determined without sacrificing the provided organisms. The amount of each food type consumed was analyzed using a multivariate linear mixed effects model (LMER in R), using the logarithm of wet weight consumed for each diet item as response variables, number of claws, sex, and CW as predictor variables, and trial date as a random blocking factor. This was followed by individual linear mixed-effects models using the same variables to examine each diet item separately.