PREDATORY DEMAND AND IMPACT OF STRIPED BASS, BLUEFISH, AND WEAKFISH IN THE CHESAPEAKE-BAY - APPLICATIONS OF BIOENERGETICS MODELS

We applied bioenergetics models for dominant Chesapeake Bay piscivores , striped bass (Morone saxatilis), bluefish (Pomatomus saltatrix), and weakfish (Cynoscion regalis), along with site-specific data on diets, growth, and energy density, to examine trophic linkages and the relat ionship of predatory demand to prey supply. Atlantic menhaden (Brevoor tia tyrannus), bay anchovy (Anchoa mitchilli), and spot (Leiostomus xa nthurus) accounted for 65-99% of the annual biomass of piscivore diets (excluding age-0 striped bass that ate mostly invertebrates). The die ts of young piscivores were dominated by anchovy, but menhaden and spo t became increasingly important to older fish. Young (age < 2) striped bass ate mostly benthic prey. Older striped bass fed increasingly on pelagic sources, primarily menhaden, but bluefish and weakfish increas ed benthic resource use from 10% at age 0 to 50% by age 2. Comparison of consumption (supply) to demand (potential consumption) measured the suitability of Chesapeake Bay for predator production. Bluefish came closest to achieving their demand for prey, suggesting that they are m ore successful predators than either striped bass or weakfish. Results suggest that Chesapeake Bay may be a better nursery than production a rea for older fish, and prey supply (not temperature) may account for the movements and use of the estuary by older piscivores.