Marine debris in the food web: L inking environmental availability of microplastics to ingestion by predatory fishes

Anthropogenic stressors including overharvest, climate change, and pollution have been implicated in shifting ecology of nearshore and offshore marine ecosystems. In particular, the identification of regional ocean “garbage patches” has resulted in increased awareness of the impact of marine debris (i.e., plastics) on the ocean environment while emphasizing the need to quantify biological consequences of plastic pollution. Ingestion of plastic by seabirds, marine mammals, and fishes, for example, are documented to result in asphyxiation, a false sense of fullness and subsequent starvation, and the bioaccumulation of pollutants. Data on the ingestion of marine debris by highly migratory pelagic fishes of economic and ecological importance to the western North Atlantic Ocean (e.g., tunas, dolphinfish, and wahoo), though, is lacking. The objectives of the current study are to quantify and categorize plastic debris in the Exuma Sound, The Bahamas, as well as document plastic ingestion by pelagic sport fishes in The Bahamas. To accomplish this, towed trawl transects were conducted in the northern Exuma Sound to collect and enumerate surface plastics, and stomach content analyses were performed on fish carcasses collected from local anglers. Findings indicate that plastic ingestion by pelagic fishes harvested in The Bahamas is prevalent, with 21% - 30% of each species (dolphinfish, wahoo, yellowfin and blackfin tunas) containing plastic in their stomach. Plastic densities in the Exuma Sound are comparable to those measured in the North Atlantic “Plastic” Gyre, but demonstrate greater temporal and spatial variability. In addition, trawls conducted immediately following Hurricane Joaquin allowed for the first quantifiable observation of the redistribution of marine debris following a large storm event. The results here indicate that highly sought-after fishes of importance to commercial and recreational fisheries are contaminated by plastic, highlighting the need for further research into adverse effects on fish and human health.