Relationship between ocean area and incidence of anthropogenic debris ingested by longnose lancetfish (Alepisaurus ferox)

Abstract

Marine debris is present between the sea surface and the sea floor, but few studies have investigated plastic in water column. Therefore, we chose longnose lancetfish (Alepisaurus ferox) as a sample, this study samples mesopelagic species that ingest marine debris in the water column. We conducted a survey of the stomach contents of longnose lancetfish caught by longline fishing in three areas (Sagami Bay, Northwestern Pacific Ocean about 190 km southeast of Kyushu, Indian Ocean about 1200 km southwest of Sumatra Island, Indonesia). A total of 164 longnose lancetfish were caught. Our results highlighted four marine debris patterns. First, longnose lancetfish caught near the coast had a higher frequency of ingested anthropogenic items (Sagami Bay: 69%) than longnose lancetfish caught in the open ocean area (Northwestern Pacific Ocean: 13%, Indian Ocean: 18%). Second, the size of the plastic present in the ocean in the sea area close to the coast ingested by longnose lancetfish tended to be smaller than in the open ocean area. Third, 93% of the anthropogenic items obtained from the stomach were plastic, of which ¿90% was either polypropylene (PP) or polyethylene (PE). And last, the sources of marine debris in the middle and deep regions of the open ocean are fishing activities carried out in that sea area and items that drift from the land without losing buoyancy. Our research makes new discoveries about characteristics of the marine debris in the ocean.