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Drifting marine debris has been shown to host associated biological communities and facilitate their dispersal. Little is known about how biota engage with, and are transported by, this debris. This study characterizes debris-associated communities and explores the role of plastics in transferring fishes to new geographic regions. ~ 1500 underwater photographs were reviewed from five cruises during 2018–2020: one between Japan and Hawaii encompassing the Western and Eastern Pacific Ocean (Group I), and four passing through the North Pacific Garbage Patch in the Eastern Pacific Ocean (Group II). Debris properties were recorded and 13 associated fish species from 43 debris items were identified. Fish communities around marine debris have low diversity, individual debris items have highly dissimilar species compositions, and species composition is affected by horizontal debris item size. Debris items in Group I have significantly higher fish species diversity and differ in community composition from Group II. Four taxa (Abudefduf vaigiensis, Histrio histrio, Oplegnathus punctatus, and Petroscirtes spp.) were observed surviving east of the Hawaiian Islands, where they have not been previously reported. Marine debris is found to be a mobile natural habitat substitute that can facilitate long-distance species dispersal. While natural flotsam has long been a potential vector, long-lived and increasingly abundant plastic debris may set the stage for altering fish biogeography. [ABSTRACT FROM AUTHOR]

Marine debris from the Great Tsunami of 2011 represents a unique transport vector for Japanese species to reach Pacific North America and Hawaii. Here we characterize the invasion risk of invertebrate species associated with tsunami debris using a screening-level risk assessment tool – the Canadian Marine Invasive Screening Tool (CMIST). Higher-risk invertebrate invaders were identified for each of five different ecoregions. Some of these are well-known global invaders, such as the mussel Mytilus galloprovincialis and the ascidian Didemnum vexillum which already have invasion histories in some of the assessed ecoregions, while others like the sea star Asterias amurensis and the shore crab Hemigrapsus sanguineus have yet to invade large portions of the assessed ecoregions but also are recognized global invaders. In general, the probability of invasion was lower for the Gulf of Alaska and Hawaii, in part due to lower climate matches and the availability of other invasion vectors. [ABSTRACT FROM AUTHOR]