Date Thesis Awarded

5-2022

Access Type

Honors Thesis -- Open Access

Degree Name

Bachelors of Science (BS)

Department

Biology

Advisor

Mark Brush

Committee Members

James Skelton

Jessica Jenkins

Abstract

Aquaculture is a growing industry internationally. In the United States, aquaculture of bivalves occurs throughout the Chesapeake Bay. Cherrystone Inlet, a tidal inlet on the Virginia Eastern Shore, is the location of intensive hard clam culture, and recently oyster aquaculture has become common there as well. Given the intensive culture in Cherrystone and similar systems in the Chesapeake, it is important to understand the carrying capacity of the respective bivalves and how they can be grown together. Carrying capacity is defined here as the largest population of individuals that can be supported that allows individuals to reach a harvestable size within three years, the industry standard. We adapted a previously developed model of Cherrystone to confirm the carrying capacity of clams, estimate the carrying capacity of oysters, assess competitive interactions and carrying capacity when both species are grown together, and analyze differences in growth rates due to spatial variations, environmental conditions, and climate change. Sensitivity analyses showed oysters generally have higher clearance rates than clams, but both species can sustain positive rates of net production in this system. Runs were conducted with clams and oysters grown separately and together in Cherrystone, spanning populations of 25M to 500M. From these runs, individual growth rate, days to harvest, harvestable biomass, and phytoplankton biomass were calculated and used to estimate carrying capacity. The carrying capacity of hard clams was estimated to be 100M-200M, while the carrying capacity for oysters was estimated at 25M to 75M, both limited by food availability. When both species were grown together, growth rates decreased, and days to harvest increased, but the harvestable biomass can be maximized by growing 150M clams and 32.25M oysters. Spatial differences in growth rates suggested harvest could be maximized by separation of clam and oyster culture. Growth of both species of bivalves, particularly oysters, was predicted to decline by 2100 due to increases in sea level, salinity and temperature. If aquaculture in Cherrystone and the lower Chesapeake Bay continue 2100, results suggest yields will decline.

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