Influence of plankton on distribution patterns of the filter-feeder Brevoortia tyrannus (Pisces: Clupeidae)

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Abstract
Abundance of juvenile Atlantic menhaden Brevoortia tyrannus, plankton abundance, and physical data were collected concurrently along longitudinal transects in 2 estuarine creeks in North Carolina and 2 estuarine creeks in Virginia, USA, from March to August 1983. Menhaden abundance was positively correlated with abundance of microflagellates, diatoms, chlorophyll a, and to a limited extent dinoflagellates and cyanobacteria. Menhaden showed a distributional preference for larger (generally > 3 .mu.m in length) phytoplankton cells independent of phytoplankton taxa. Dinoflagellate blooms, which were usually composed of large cells (> 16 .mu.m in length) and had some of the highest chlorophyll a concentrations observed, were not always positively correlated with menhaden abundance. Some dinoflagellata taxa appeared to repel menhaden, whereas blooms of Prorocentrum sp. were always positively correlated with the distribution of the fish. Menhaden distribution appeared to respond to gradients of phytoplankton cells of sufficient size to be filtered by the fish, suggesting a chemosensory preference for plant rather than detrital particles and a foraging strategy patterned by the efficiency of their gill raker feeding structure.