Date of Award

5-2026

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Marine Biology and Coastal Sciences

Thesis Sponsor/Dissertation Chair/Project Chair

Paul A. X. Bologna

Committee Member

Colette Feehan

Committee Member

Lisa Hazard

Abstract

Bay scallops (Argopecten irradians) are commercially, ecologically, and recreationally important bivalves that have undergone major shifts in New Jersey over the past 25 years, including the extirpation of the southern subspecies from New Jersey in 2001 and its replacement by the northern subspecies from Long Island by 2004. This transition altered reproductive timing, reflected in changes to the Gonadal–Somatic Index (GSI) as well as the timing of visual gonadal conditions exhibited during specific months. Early post-reestablishment data showed peak GSI in June and July, consistent with Long Island populations, but recent observations indicate a shift toward August and September peaks, mirroring the timing of New Jersey scallops prior to their early-2000s decline. Juvenile recruitment has shifted similarly, with increasing detections in September and October. Visual inspection of gonadal condition has also changed over time, as individuals collected in recent years are exhibiting “undeveloped” and “ripening” conditions more frequently in June and July, while August and September contain significantly more “very ripe” individuals. These patterns suggest a phenological adjustment that enhances reproductive success under current environmental conditions, likely influenced by habitat features such as eelgrass (Zostera marina). Although populations appear to be recovering, the results highlight the importance of phenotypic plasticity in dynamic coastal ecosystems and underscore the need for continued long-term monitoring to inform management and restoration.

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