The majority of our planet is made up of water, in fact almost 71% of it is, however the amount which remains untouched by plastic pollution is tiny. Plastic pollution comes in many forms, from discarded fishing nets to single-use plastic bags, drinks bottles to crisp packets. This pollution is categorised according to its size; macro debris is large, much of it floats and it is highly visible; microplastics in comparison are very small, only a few millimetres in length- these are either from cleaning and cosmetic products, like face scrubs or from larger pieces of plastic which have broken down in the ocean. All these forms of plastic pollution have an impact on marine wildlife, we’ve seen sea birds with stomachs full of plastic debris, seals with rope around their necks and turtles with plastic rings round their middles, but what effect is plastic pollution having on our cetaceans?
This is a summary of the current level of understanding we have of the threat plastic debris poses to cetaceans around the world, however much research is needed in this area for us to fully comprehend the effects.
It is largely unknown as to why plastic debris is appearing in the stomachs of cetaceans, as their echolocation skills would prevent them from directly ingesting it and plastic debris does not resemble their food sources, unlike turtles mistaking plastic bags for jellyfish. It is thought that cetaceans ingest plastic debris indirectly via their food source or it occurs incidentally when feeding. It has also been suggested that this may be a part of the stranding process; the UK Cetacean Strandings Investigation Programme (CSIP) examined 695 stranded cetaceans between 2005-2010 and found that of the 16 that had ingested plastic debris at least 7 of those had live stranded and may have ingested the plastic debris at the tideline.
In this instance we are referring to the entanglement of cetaceans in abandoned or lost fishing nets- otherwise known as ghost fishing. Nets can be lost or are often cut off if they become caught on an object on the seafloor rather than recovered; this leaves the nets floating free to catch marine life for years to come. During a post-mortem it is difficult to determine whether a cetacean is a victim of entanglement or not, as the same marks are caused by death from by catch- where a cetacean is unintentionally caught in active fishing nets.
What can I do to help?
- Participate in local beach clean-ups or set up your own.
- Always have a re-usable bag to hand instead of using plastic ones.
- Report any marine mammal stranding you find to the UK strandings network, CSIP.
For more information on the threats to cetaceans click here.