Marine debris entanglement in fur seals and sea lions

Franco-Trecu, V., Drago, M., Katz, H., Machín, E., & Marín, Y. (2017). With the noose around the neck: Marine debris entangling otariid species. Environmental Pollution, 220, 985-989.

As many as 700 wildlife species are believed to be negatively affected by marine debris, through ingestion or entanglement. Entanglement of marine mammals in plastic debris risks drowning, suffocation, injures, infections and inhibition of natural behaviour (including foraging and reproduction).

It is therefore a contributing factor to the reduction of populations of some species.  The present study focussed on two marine mammal species, South American fur seals and sea lions, with the aim of recording the extent and nature of marine debris entanglement.  Entrapment of plastic around the neck, forming a ‘neck collar’, is particularly common amongst pinniped species such as those observed in this study. 

Based at the Isla de Lobos in Uruguay, where both study species have established breeding colonies, researchers observed the animals for six hours daily between November and March, over a seven-year period from 2007.  Data and photographs were recorded from all entangled individuals observed, totalling 26 fur seals and 22 sea lions.  Data included the nature of material, extent of injury, and demographic information about the animal (e.g. estimated sex and age). 

Debris from fishing gear was the greatest cause of entanglement in both species

Aside from one individual found to have ingested a fishing hook, all recorded cases involved neck entanglement, and the material was identified in 90% of cases.  For both species, the most prevalent source of entanglement debris was artisanal or sport fishing gear. This was responsible for 27% of fur seal and 55% of sea lion entanglement cases.  For fur seals, this was followed by industrial trawler nets (23%), artisanal nets (17%), and packaging bands (15%).  For sea lions, packaging bands affected 23% of individuals followed by artisanal nets (9%).     

Given the large proportion of entanglement materials originating from fishing activities, the authors advocate for implementation of activities to monitor and control redundant fishing equipment entering the oceans. Furthermore, they emphasise the importance of educational activities to raise awareness of the negative effects of marine debris, both from fishing and other plastics such as packaging, and the preferential use of biodegradable natural materials.  Addressing the issue of marine debris and associated impact upon marine mammals is an important step towards improving both the welfare and conservation of affected pinnipeds.       

World Animal Protection’s view

Marine debris entanglement is an important issue negatively affecting the welfare of a wide range of wildlife species. We feel that it is important to educate and raise awareness.  Sharing information about the impact of marine debris on the welfare of animals and its primary origins is one step towards developing solutions to tackle the problem.