The feeding ecology of Morone americana larvae in the Chesapeake Bay estuarine turbidity maximum: The influence of physical conditions and prey concentrations

Abstract

Feeding ecology of white perch Morone americana larvae, a major component of the ichthyoplankton community in the estuarine turbidity maximum (ETM) region of upper Chesapeake Bay, was evaluated in years of contrasting physical conditions. In 1998, high river flow led to an ETM with high turbidity and pronounced salinity stratification. In 1999, under low river flow conditions, turbidities in the ETM region were lower and the salt front was located 15 km up-stream of its location in 1998. Copepodites and adults of Eurytemora affinis were the predominant prey in guts of all length classes of larvae (3.2-9.8 mm standard length, LS) that were examined. Repeated-measures, multiple regression analyses were conducted to evaluate the influence of several factors on feeding success by determining if physical conditions (temperature, current velocity, salinity, turbidity and light) and prey concentrations explained variability in mean gut fullness (gut contents mass per body mass) of small (<5 mm LS) and large (>5 mm LS) white perch larvae. Eurytemora affinis concentrations were significant in the statistical models for both small and large larvae. High concentrations of E. affinis, which enhanced encounter rates of white perch larvae with prey, may have been the most important factor determining feeding success in the ETM region. Larval feeding incidence (percentage of guts with food) was higher in 1998, suggesting that annual variability in river flow influenced larval feeding success by controlling physical and biological conditions in the ETM region. © 2005 The Fisheries Society of the British Isles.