Seasonal waterbird distribution patterns vary in response to current shellfish aquaculture and areas suitable for future development in Rhode Island USA

Abstract

Marine aquaculture is globally widespread and supplies most of the world's shellfish. In the United States, shellfish aquaculture spans all coastlines, with states like Rhode Island experiencing recent substantial increases in aquaculture. Rhode Island’s marine ecosystem supports numerous migratory waterbird species, and the expansion of shellfish aquaculture has the potential to directly impact the distribution of these species. We used land-based survey data to assess whether and how distance to shellfish aquaculture affects seasonal waterbird distribution patterns and identify species most and least likely to be impacted by future aquaculture development. We conducted a total of 3698 surveys across 54 study sites from 2020─2023 and fit monthly generalized additive mixed models to predict waterbird distributions for 29 species. For most waterbird species, distance to aquaculture explained little to no spatial variation in their monthly distribution patterns; indicating other resource layers were more informative. Dabbling ducks often favored closer proximity to aquaculture, while sea ducks, mergansers, gulls, and terns showed species-specific preferences, and herons and egrets consistently favored shallower waters. Using model-derived distributions, we found that ∼28 % of species preferred areas better suited for future aquaculture development, while ∼10 % favored areas poorly suited. Our research provides valuable insights into the factors driving waterbird distributions, particularly in relation to their proximity to current shellfish aquaculture. Our findings suggest that although current aquaculture operations are not having substantial impacts on species distribution patterns, future development will likely conflict with species favoring shallow waters, as these areas are also most suitable for aquaculture expansion.