Abundance estimation of floating marine debris in the North Pacific using 2010-2016 IWC-POWER data
Tomoki Yasuhara, Koji Matsuoka and Toshihide Kitakado
Marine debris is an element of concern in the marine ecosystem. During IWC-POWER cruises, floating marine debris has also been sighted in order to observe the type and the extent of the marine debris in the North Pacific Ocean. Here, a statistical analysis was conducted to estimate the density and distribution of floating marine debris there. Line transect methods were used for estimating detection function and abundance for several types of marine debris (â€œfishing gear netâ€, â€œlong lineâ€, â€œsingle fishing floatâ€, â€œcluster fishing floatâ€, â€œwoodâ€, â€œunidentified styrofoamâ€, â€œstyrofoam othersâ€, â€œunidentified plasticâ€, â€œplastic smallâ€, â€œplastic medium and largeâ€, â€œgarbageâ€ and â€œothersâ€). A multiple-covariate distance sampling (MCDS) analysis was applied to take environmental factors into consideration. In addition to the â€œdesign-basedâ€ method, a â€œmodel-basedâ€ approach was also employed to estimate spatial distribution of marine debris. As a result, the MCDS analysis showed that environmental covariates such as sea state and weather condition can affect detectability of debris. Abundance of â€œplastic smallâ€ and â€œsingle fishing floatâ€ were especially high in the study area. It is suggested that some of those debris might be attributed to the 2011 tsunami occurred in Japan. A model-based method showed that densities of debris were high in between 20Â°N-40Â°N and concentrated in around 145Â°W.