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Assessing the Carrying Capacity and Sustainability of Bivalve Aquaculture in a Shallow Estuarine Embayment using Mass-Balance Modeling
Kenny, Ian
Kenny, Ian
Abstract
Extensive aquaculture of both the hard clam (Mercenaria mercenaria) and the Eastern oyster (Crassostrea virginica) has been rapidly expanding over the past several decades on the east coast of the United States. Within the Chesapeake Bay, the industry has grown to a scale where many ecosystems in the bay containing large-scale aquaculture operations are now considered agro-ecosystems. High densities of cultured bivalves and the corresponding gear such as protective mesh netting and oyster cages are associated with a variety of ecosystem impacts, including changes to food availability, water quality, nutrient dynamics, and bottom habitat structure. These characteristics of agro-ecosystems are commonly associated with changes to the structure of the resident planktonic, benthic and nektonic communities. Cherrystone Inlet, a shallow tidal inlet on the western coast of Virginia’s Eastern Shore, supports an extensive hard clam aquaculture industry and a growing oyster aquaculture industry. As cultured bivalve populations in the system have grown, questions have emerged about their carrying capacity and potential impacts on the estuarine food web. To assess the ecological impacts and carrying capacity of cultured bivalves in Cherrystone Inlet, an ecosystem mass-balance model was adapted to the system parameterized with data from the literature and a series of field surveys. Model outputs suggest that increased cultured bivalve biomass negatively impacts phytoplankton, crustacean and gelatinous zooplankton, filter-feeding fishes, and certain piscivores through both indirect competitive and bottom-up trophic interactions. Results indicate that cultured bivalve biomass could be increased between 1.24 and 2.97 times current values until their ecological carrying capacity is reached, which first occurs when microzooplankton are grazed out of the system. Similarly, cultured bivalve biomass could be increased between 6.04 and 7.75 times current values until their production carrying capacity is reached, which occurs when phytoplankton have been grazed out of the system and cultured bivalves become food limited. Use of ecological carrying capacities quantified here would maintain the ecological integrity and sustainability of the aquaculture industry in this system and ensure the food web and other human uses remain undisturbed.
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2025-04-01
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Biology