Species Composition Varies Among Artificial and Natural Benthic Substrates Within Estuarine Environments

ABSTRACT As the commercial development of aquaculture grows, assessing the impact of culture gear on local marine communities becomes increasingly imperative. Gear associated with off‐bottom oyster aquaculture introduces artificial structure to areas that would otherwise be devoid of structural complexity and heterogeneity. In this study, we compared the abundance, diversity and composition of fish assemblages near oyster rack‐and‐bag cages and natural systems. In lower Delaware Bay, USA from June to August 2024, we deployed stationary video cameras to survey the abundance, diversity and composition of fish and macroinvertebrates on a natural oyster reef, a rack‐and‐bag oyster cage, and bare sediment (acting as a ‘control’). Total counts were greatest at the natural reef compared to the rack, followed by the control. MaxN, sightings and species richness differed between reef and control settings, and Shannon diversity did not significantly differ. Further, substrate alone affected fish abundance and composition, not water temperature or tidal position. All three sites had unique community compositions, primarily driven by the presence of Sciaenids on reefs and macroinvertebrates on rack‐and‐bag cages. While assessing abundance and diversity metrics alone suggests similar habitat provisioning between natural reefs and rack‐and‐bag systems, the observed changes in the broader community composition suggest that each structure provides different ecological functions. This relationship is often conserved in similar studies that offer multiple metrics for assessing the habitat function of oyster aquaculture gear. However, there has been a lack of emphasis on the differences in composition and how that may influence habitat value among altered benthic substrates versus natural habitats. Our research provides evidence of variable functional impact associated with altered benthic landscapes, providing insight into more refined ecological effects associated with subaqueous land use.