Plastics and other marine debris have been found in the gastrointestinal tracts of cetaceans, including instances where large quantities of material have been found that are likely to cause impairment to digestive processes and other examples, where other morbidity and even death have resulted. In some instances, debris may have been ingested as a result of the stranding process and, in others, it may have been ingested when feeding. Those species that are suction or “ram” feeders may be most at risk. There is also evidence of entanglement of cetaceans in marine debris. However, it is usually difficult to distinguish entanglement in active fishing gear from that in lost or discarded gear. The overall significance of the threat from ingested plastics and other debris remains unclear for any population or species of cetaceans, although there are concerns for some taxa, including at the population level, and marine debris in the oceans continues to grow. Further research including the compilation of unpublished material and the investigation of important habitat areas is strongly recommended. 1. Introduction and Background Marine litter has been characterized as an environmental, economic, human health and aesthetic problem, posing a complex and multidimensional challenge with significant implications for the marine environment and human activities all over the world [1]. Much has been written about this pervasive pollution problem in recent years, and there are various international initiatives now striving to address it, including the United Nations Environment Program (UNEP) Global Initiative on Marine Litter. Part of the problem derives from the accumulation and fragmentation of plastics, “one of the most ubiquitous and long-lasting recent changes to the surface of our planet” [2]. In the marine environment, typically 40–80% of the larger categories of marine debris items are plastic. Much of this is packaging, carrier bags, footwear, cigarette lighters and other domestic items and much originates from land, as a recent study in Central and South America showed [3]. Lost or discarded fishing gear can also be important, particularly along continental shelves and remote islands. Thirty-one species of marine mammals have previously been reported to have ingested marine debris [4], and it has been suggested that even small ingested quantities can have large effects [5]. In addition to interference with alimentary processes, another effect could be that the plastics lodged somewhere in the alimentary tract could facilitate the transfer of pollutants into
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