DIVERSITY, MOVEMENT AND SURVIVAL OF JUVENILE FISHES AROUND AQUACULTURE GEAR IN NEARSHORE ENVIRONMENTS OF DELAWARE BAY, USA
Date
2025-05
Authors
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Publisher
University of Delaware
Abstract
As aquaculture continues to expand in coastal systems worldwide, evaluating
ecological impacts on wild fish communities is essential for sustainable marine
resource management. This study examined the influence of rack-and-bag (RB) oyster
aquaculture structures on the diversity, movement, and apparent survival of juvenile
fishes in nearshore environments of Delaware Bay, USA. Using a mark-recapture
framework, Passive Integrated Transponder (PIT) tagging, and environmental
monitoring, we investigated the habitat use of two focal species—American Eel
(Anguilla rostrata) and Black Sea Bass (Centropristis striata)—across two
ecologically distinct sites: Port Mahon and Lewes.
Over a 12-week sampling period, eel traps were deployed at fixed distances (0,
3.5, 7, and 14 meters) from aquaculture gear to detect spatial gradients in fish
distribution. Biodiversity metrics revealed higher species richness and abundance at
Port Mahon, while Lewes exhibited greater species evenness. A pronounced halo
effect was observed at both sites, characterized by elevated capture rates and species
richness nearest to RB structures, suggesting that aquaculture installations enhance
localized habitat complexity and biological activity. Cormack-Jolly-Seber models
estimated an apparent survival rate (Φ) of 64.6% for American Eels, with a detection
probability (p) of 15% at Port Mahon. In Lewes, Black Sea Bass exhibited a higher
survival estimate under a time-variant detection model (Φ = 90.6%), though with wide
uncertainty. For comparison, a time-invariant model for Black Sea Bass yielded a
lower survival estimate (Φ = 43.88%; 95% CI: 19.98–70.99%) and a detection
probability of 13.42% (95% CI: 3.52–39.68%). These results reflect the episodic use
of aquaculture gear by American Eel and Black Sea Bass. My findings indicate that
RB oyster aquaculture provides valuable refuge and foraging habitat for juvenile
fishes and may function as a habitat enhancement tool in estuarine systems. The
spatial patterns observed underscore the ecological role of aquaculture gear in shaping
fish community structure and movement, with implications for the design and
management of sustainable aquaculture operations.