Seasonal variation in planktivory risk in a Southern New England coastal habitat

Planktivory is believed to be a major selective force in marine systems, but little is known about how the intensity of planktivory risk varies spatially or temporally. We assessed seasonal daytime planktivory patterns over fifteen months (Apr 2003 to Jun 2004) at a temperate site in eastern Long Island Sound, CT. Planktivory was measured using modified Plankton Tethering Units (PTUs) deployed from floating docks and baited with live brine shrimp. Planktivory risk varied throughout the year. The highest levels of risk occurred in Aug, Sept and Oct (85%, 75% and 42.5% of brine shrimp consumed, respectively), the lowest levels of risk occurred from Dec to Apr. Mean monthly consumption of brine shrimp strongly correlated with the presence of planktivorous fish. Many species of benthic invertebrates exhibited high levels of recruitment during times of the year when planktivory risk was high, although some species recruited when planktivory risk was low. These seasonal planktivory patterns (highest risk occurring during the late summer and early fall) may be typical for many temperate near-shore habitats, especially those associated with man-made structures (e.g., floating docks, pilings).