The effects of predation by the blue crab, Callinectes sapidus on a macrobenthic infaunal community in Galveston Bay, Texas.




Fort, E.A.

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Texas A&M University.


The importance of macrobenthic predation in regulating distribution and abundance of an infaunal sand community was examined by conducting a series of manipulative field experiments. The effect of the blue crab Callinectes sapidus, was examined by using predator inclusion and exclusion cages. Response to various predation pressures by the infaunal community was seasonal. From July to January the infauna in the noncrab treatment generally responded with a large initial increase in density, primarily due to the opportunistic polychaete, Streblospio benedicti, and a subsequent decrease in diversity. From February to June larval recruitment was responsible for a high species diversity. The effect of crab predation was intermediate between the non-predation treatment and the ambient levels of predation from spring through late fall. Decreasing water temperature sharply curtailed the poikilothermic crab's predatory behavior from late fall to early winter. It is postulated that the relatively smaller sized larvae comprising the majority of the infaunal community from winter through spring rendered other prey items more attractive to omnivorous adult crabs. The infaunal responses to various predation rates suggests that this community is not resource limited and therefore not regulated by competitive interactions for food or space. Severe predation pressures exhibited in part by C. sapidus, from late spring through late fall, as well as other species, combined with abiotic influences appear to regulate community dynamics.


128 p., Thesis


blue crab, Callinectes sapidus, predation, polychaetes, Streblospio benedicti, cages, aquatic communities, feeding behavior, environmental effects