Ecosystem-based modeling evaluation of stocked predator introductions on reservoir food webs

A common goal of resource management agencies is to increase recreational fishing opportunities.  Toward this end, hybrid striped bass (Morone chrysops x M. saxatilis) have been stocked into many reservoirs in the US, including a handful of Ohio Reservoirs beginning during the early 1980s.  The Ohio Division of Wildlife (DOW) is currently seeking to expand its hybrid striped bass reservoir stocking program, ideally to take advantage of offshore gizzard shad (Dorosoma cepedianum) populations that are not fully exploited by other top predators.  To assist with this effort, we have been developing Ecopath models for several Ohio reservoirs of varying productivity, and using Ecosim to explore how variation in nutrient additions and simulated hybrid striped bass stocking rates and harvest levels would influence 1) the capacity of Ohio reservoirs to support hybrid striped bass biomass and 2) the structure and function of the rest of the food web (including both prey and sportfishes).  Herein, we present findings from our research, ultimately discussing how a stocked top predator can affect food web composition, interactions, and dynamics under varying management (stocking, harvest, and land-use management) scenarios.