Bioaccumulation and potential sources of DDTs in Trachinotus ovatus during typical cage cultured periods

In the 12th Stockholm Convention, DDTs is one of the nine organic chlorine pesticides, which were proposed to be controlled as persistent organic pollutants (POPs), because of its harmful effects to the environment and the ecosystem. In China, a large amounts of DDTs have been used in the past few years, and it still can be generally detected in the environment although it was banned for using in agriculture in 1983. Many studies showed that fish consumption is a significant route for human exposure to POPs in the world. China is the largest fishery producer in the world with nearly 60 million metric tons in 2015, accounting for 70.0% of the total global fishery production. Recent study showed that residues of the DDTs have been widely identified and reported in some aquaculture fishes in China, especially in Trachinotus ovatus. To determine the bioaccumulation and the potential input sources of DDTs to cage farmed T. ovatus, samples of seed,feeds, adult fish, seawater and the sediments were collected at the beginning, medium and the end of aquaculture practice. DDTs were detected in all samples analyzed, with mean concentrations (± standard deviations) at (3.15±0.42) μg/kg wet weight in seed, (4.49±0.39) μg/kg wet weight in adult fish, (3.95±0.33) μg/kg dry weight in fish feeds, (3.76±0.43) ng/L in cage water and (4.34±1.18) μg/kg dry weight in sediment. The concentration of DDTs in the fish increased during the culture period and significantly higher when harvesting compared to the beginning and the medium, but well below the 0.5 mg/kg wet weight of national standards for food safety level. In addition, only ο,ρ’-DDT, ρ,ρ’-DDD and ρ,ρ’-DDT were detected in the sediments, but those three and ρ,ρ’-DDE were detected in the seeds, fish feeds and seawater. ο,ρ’-DDT and ρ,ρ’-DDT were the major constituents in all samples, with respectively average percentage at 42.09% and 37.07% in fish, 44.85% and 34.62% in fish feeds, 40.91% and 37.99% in cage water, 33.03% and 51.34% in sediment. Finally, statistical analyses suggested that fish feed, as well as pond water at a lesser degree, may have been the major source of DDTs in cage farmed fish of T. ovatus. In order to ensure the quality and safety of T. ovatus, we should focus on strengthening the control and management of toxic and harmful substances in the feed.