The Welfare Impact on Pinnipeds of Marine Debris and Fisheries

Uncounted, and usually unobserved, numbers of the animals that live in the oceans find themselves snared, trapped or entangled in lost fishing gear, monofilament line, nets, rope, plastic packaging and packing bands from crates, or become hooked on discarded fishing gear, or ingest human marine debris. Seals, sea lions and walrus (the pinnipeds) seem particularly susceptible to entanglement in marine debris—their exploratory natures may make this more likely, or perhaps they come upon plastic waste and rope on the shoreline to a greater extent than the other fully aquatic mammals. Pinnipeds meeting with plastic, either in the sea or on the shoreline, may carry debris wrapped around themselves for long periods. They often die as a result, sometimes from major chronic wounds. Although a wide range of the global species of seals can be affected by marine debris, some species are much more significantly affected than others. The key seal species affected by entanglement are monk seals, fur seals and California sea lions. Seals which become entangled or who ingest marine debris may be subjected to distress, pain, trauma, infection, skin and muscle lesions and compromised ability to move, feed and carry out normal behaviour. For these reasons marine debris has the capacity to present a significant and global issue with respect to animal welfare, as well as to more immediately apparent concerns regarding habitats and the quality of the marine environment.