Effects of Prey Importance and Migration Patterns on the Sustainability of Linked Predator-Prey Fisheries

Understanding predator-prey dynamics is important for ecosystem-based fishery management.  We developed a spatial age and size-based model to explore connectivity consequences for predator-prey relationships and spatial pattern of fishing.  The model is parameterized to represent Striped Bass Morone saxatilis and Atlantic Menhaden Brevoortia tyrannus dynamics.  The model had two areas to represent the estuary and coastal waters, four seasons to allow for seasonal migration, one primary predator species, one primary prey species, and a secondary prey pool. The model includes a type II functional response to calculate consumption of each age of menhaden by each age of striped bass. We ran the model for six scenarios of prey importance and stock mixing.  Average prey biomass varied among the six scenarios, but was highest under the low importance scenario and lowest under the high importance scenario.  Migration pattern had a substantial effect on prey biomass with the fully mixing scenario having lower biomass on average than the migration scenario with less overlap between predators and prey.  Similar to biomass, the fully mixing scenario had consistently lower average catch than the migration scenario.  Average catch of the predator was significantly lower under the mixing scenario than the migration scenario.