Gear associated with off-bottom oyster aquaculture adds artificial structure to areas otherwise devoid of structural complexity and heterogeneity. As the commercial development of aquaculture grows, assessing the influence of culture gear on local marine communities becomes imperative. Similarly, shellfish-based living shorelines and oyster reef restoration projects require monitoring to assess the added habitat value of these landscape modifications. Camera-based approaches have been used to monitor and assess these habitats previously in other areas. But low visibility, like what is observed in Delaware Bay, poses a significant challenge to estimating species assemblages in estuarine environments. In this study, we developed an effective means of monitoring fish assemblages in low-visibility locations: comparing the biodiversity, including species composition, and abundance, as well as behavioral responses of organisms found near oyster rack-and-bag systems to those in natural oyster reefs.
We deployed stationary cameras to record video at a natural reef site, a rack-and-bag oyster cage, and a flat, sandy bottom in Lewes, DE from June to August 2024 for 1.5 hours (n=20). Animals were identified to the lowest possible taxonomic classification. The time the animal entered and exited the view was noted along with any behavioral responses. Preliminary results suggest that oyster structures enhance local abundance (p = 0.045, n = 8, Kruskal-Wallis test, Fig. 1). The type of oyster-derived structure may minimally influence abundance (p = 0.070, n = 8, Dunn test) while not affecting species richness (p = 0.143, n = 8, Kruskal-Wallis test); however, each structure supported communities that forage in different zones within the water column.