An integrated modeling approach for elucidating the effects of different management strategies on Chesapeake Bay oyster metapopulation dynamics

Eastern oyster abundance is at an all-time low, yet this species is a key component of many estuarine systems because it contributes to ecosystem function by providing habitat, improving water quality, stabilizing benthic and intertidal habitat, increasing landscape diversity and producing more oysters. Given the breadth of environmental benefits oysters provide, as well as their commercial and cultural importance, sustainable oyster production has become a priority in several regions, including the Chesapeake Bay. Current strategies include treating restored reefs as permanent sanctuaries, which provide long-term environmental benefits yet removes them from the fishery, or harvesting reefs on a rotational basis, which provides economic value yet decreases environmental benefits. The long term dynamics of these strategies is unknown. Oysters have a complex, biphasic life cycle (i.e., sessile adult and motile larval stages) and their viability is intimately tied to a suite of environmental factors including, but not limited to, flow regime, total suspended solids, temperature, salinity, and dissolved oxygen. In order to determine how different oyster management strategies affect oyster dynamics, we developed a multi-model approach that integrates a 2-D hydrodynamic model, a larval transport model, and a spatially-explicit, agent-based population dynamics model to simulate long term oyster dynamics. We applied our model to a ten reef system in the Great Wicomico River in the Chesapeake Bay, and simulated six different combinations of sanctuary and/or harvest management scenarios over an 8-year period. We evaluated the environmental and commercial benefits of each strategy. Our results indicated that sanctuary reefs are beneficial, and that the spatial position of sanctuary reefs strongly affected source-sink dynamics and must be considered before implementing a harvest regime. Simulations that did not consider the source/sink dynamics of the reefs yielded larger numbers of oysters for harvest in the short-term, yet resulted in a complete fishery collapse in the long term. Selective, rotational harvest, resulted in lower annual yield, but the fishery persisted throughout the eight year simulation. This integrated modeling approach helped reduce uncertainty within the study system and can help natural resource managers understand ecosystem-level processes leading to more informed decision making across spatial and temporal scales.