PREY PREFERENCES OF BLUE CRABS CALLINECTES-SAPIDUS FEEDING ON 3 BIVALVE SPECIES

Individual blue crabs Callinectes sapidus were allowed to forage on 3 bivalve species (soft clam Mya arenaria; Atlantic rangia clam Rangia c uneata; hooked mussel Ischadium recurvum), with 2 of the 3 species mad e available together at one time in 2201 aquaria. In 3 separate sets o f experiments, we examined the blue crab's consumption and preferences between 2 bivalve species of different profitabilities [(net energy i ntake)/(handling time); J s(-1)]: M. arenaria and R, cuneata, M. arena ria and I. recurvum, and R, cuneata and I. recurvum. These experiments also examined the effects of 3 additional factors on prey consumption and prey preference: prey location (near to or distant from point of introduction of crab), prey refuge availability (shallow or deep sand for the clams; detached or clustered for the hooked mussel), and prey density (high or low numbers). Profitability curves correctly predicte d that the blue crab preferred the highly profitable soft clam over th e less energetically profitable Atlantic rangia clam. When the differe nce between prey profitabilities was not as great (i.e. between the so ft clam and the hooked mussel, and between the Atlantic rangia clam an d the hooked mussel) profitability alone was not a clear predictor of blue crab preference. Prey refuge availability significantly affected prey preference; deep sand provided (1) a greater refuge for the soft clam than for the Atlantic rangia clam and (2) a greater refuge for th e soft clam than clustering provided for the hooked mussel. Prey locat ion and refuge availability interacted to affect prey preference, in t hat prey location significantly affected prey consumption in shallow s and (more near prey than distant prey were eaten), but not in deep san d. Prey density generally affected total prey consumption, but not pre y preference.