http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Diets and prey selection of pinfish and southern flounder in a Halodule wrightii seagrass meadow
Effects of prey species and densities on diet and selection by pinfish and southern flounder were investigated in a Halodule wrightii seagrass meadow. A drop sampler/rotenone collection procedure was used to quantitatively sample predator and prey densities during the spring and early summer. Densities of most infauna, epifauna and macrofauna prey peaked in April and May. Periods of low density were attributed to mortality from environmental extremes and predation. Overall, pinfish were much more abundant than southern flounder, and densities of pinfish declined over the sampling period. The plant component in the diet of pinfish increased as these fish grew through the spring and early summer. Rather than evidence for a switch in this animal's diet, however, this shift to a predominantly plant diet appeared to be due to low densities of preferred animal prey. Plant material may have been incidental in the diet of these fish. Among animal prey, a modified linear index (MLI) was used to detect selection of prey over random feeding. Pinfish positively selected amphipods as prey and avoided annelids. Shrimp prey had positive MLIs in late spring and early summer, but values were not significantly different from those of random feeding. Data from fish collected in the field indicated that pinfish consumed prey between 10 and 33% of their own total length. Both predators exhibited no strong selection among available sizes in laboratory experiments. When two species of shrimp of the same size were offered to pinfish and southern flounder, predator fish did not significantly select either prey. In field experiments where prey densities were manipulated, pinfish selected amphipods and brown shrimp when they were available at elevated densities. Grass shrimp were negatively selected by pinfish even in treatments with increased densities of these shrimp. Southern flounder selected brown shrimp as prey regardless of their densities, while avoiding grass shrimp and amphipods.