SPATIALLY EXPLICIT MODELS OF STRIPED BASS GROWTH-POTENTIAL IN CHESAPEAKE BAY

Fish growth rate potential is defined as the expected growth rate of a predator if placed in a particular volume of water having known physi cal and biological characteristics. We used the concept of fish growth rate potential to evaluate the seasonal and spatial growth patterns o f striped bass Morone saxatilis across a midsection of the Chesapeake Bay. The growth rate potential of a 4-year-old (1.9-kg) striped bass w as assessed by integrating spatially explicit field data on prey sizes , prey densities, and water temperature with a foraging model and a sp ecies-specific bioenergetics model of fish growth rate. Prey sizes and densities were measured bimonthly at a high spatial resolution along a west-east transect of the bay with a 120-kHz dual-beam acoustic syst em. Along the transect, the water column was divided by columns and ro ws into a grid of cells 30 m long and 0.5 m deep. Growth and foraging models were implemented in each cell to calculate expected striped bas s growth rate. Two-dimensional (horizontal, vertical) spatial maps of striped bass growth potential showed strong seasonal differences, even though overall prey biomass was similar from month to month. Striped bass growth rates were highest during October and nil during August. M ean growth rate potentials across the bay derived from the spatially e xplicit model were lower in all months than estimates generated with c ross-bay, spatial averages of prey density. We argue that such spatial ly explicit modeling is necessary for directly linking biological func tion to physical and biological structure and for predicting how spati al patterning and absolute scaling of the habitat affect fish growth r ates and production.