Estimation of Nekton Density and Production Enhancement from Seagrass Nursery Habitats Along Regions of the U.S. Atlantic Coast

Seagrass beds are designated as essential fish habitat by the National Oceanic and Atmospheric Administration (NOAA) and the regional fishery management councils due to their critical role as nurseries for nekton. Yet, they face significant threats globally and have suffered substantial declines in extent and habitat quality. Quantitative estimates of the degree to which seagrasses enhance nekton productivity can help inform conservation and management measures and assist in communicating the critical role of these threatened coastal habitats. In this study, juvenile fish and mobile macroinvertebrate (nekton) density data were compiled from seagrass and nearby unstructured habitats for both the Atlantic coast of South Florida and the Mid-Atlantic regions of the USA. Based on these field data, species that were consistently enhanced in seagrass habitats were identified. The annual production resulting from the identified juvenile enhancement by seagrasses was then estimated using an existing methodology based on established growth and mortality relationships for each species. Seagrasses enhanced nekton production by an additional 218.0 [SD 48.0] g m⁻² year⁻¹ (17 enhanced species) and 126.8 [SD 34.8] g m⁻² year⁻¹ (nine enhanced species) in the Atlantic coast of South Florida and the Mid-Atlantic regions, respectively. Data limitations resulted in only 54% and 44% of recorded species being assessed in the two regions, respectively, indicating that the current estimates are likely a substantial underestimate of the true nekton production enhancement. These estimates nevertheless provide a first quantitative assessment of seagrass enhancement of nekton production on the U.S. Atlantic coast, which can be built on as more data become available.