Date of Award

12-2022

Document Type

Thesis

Degree Name

M.S.

Department

Marine Sciences

Committee Chair

Delbert L Smee, Ph.D.

Abstract

An oyster’s realized niche is constrained by different stressors based on tidal elevation, such as desiccation or benthic predators. These factors constrain survival and set the boundary for their realized niche. Eastern oysters (Crassostrea virginica) also harden their shells in response to predation risk which reduces their mortality. We performed an empirical study to investigate if this defense mechanism could be manipulated to expand their realized niche. We raised oysters in the presence of blue crab predators (Callinectes sapidus) or in controls sans predators, then monitored their survival at different tidal elevations. Oyster survival was significantly higher in the highest tidal elevations tested. Exposure to predators before deployment also significantly increased shell hardness and survival, with intertidal oysters experiencing the greatest improvement. Thus, predator induction expanded the realized niche into higher tidal elevations. Intertidal placement had larger effects on survival than predator exposure, but predator exposure increased oyster survival at all tidal elevations, suggesting that predator induction could help oysters both deter predators and resist abiotic stressors like desiccation. We recommend intertidal placement as well as predator induction when performing spat-on-shell restoration, to take advantage of this natural predation refuge.

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