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The pingers and the porpoise – preventing deaths in fishing nets in Cornwall

When a porpoise or dolphin swims into a fishing net, rope or line, they can quickly become entangled. Like us, they breathe air, and so a race-against-time begins. If they can’t surface quickly enough, they suffocate. Hundreds of thousands of dolphins, porpoises and whales die this way every year - it's the single biggest threat they face.

At Whale and Dolphin Conservation, we're committed to finding ways to prevent these tragic deaths and we've collaborated for many years with the innovators at Fishtek Marine whose mission it is to develop practical technical devices to stop these entanglements. One of these devices is the Banana Pinger and in her guest blog, Fishtek's Melanie Parker tells you the story of this little yellow life-saver.

Breaching porpoise

What’s the problem?

The beautiful waters off the Cornish coast are full of life and have supported a healthy inshore fishing industry for centuries. It’s easy to understand why generation after generation of fishers have boarded their boats to see what they can catch by net, line or pot. But the fishers aren’t the only ones hunting for fish in these waters; several dolphin, porpoise and whale species also thrive in the seas around Cornwall, including harbour porpoises and common and bottlenose dolphins.

Sadly, because both humans and whales and dolphins are fishing in the same area, accidental entanglement of marine life (or 'bycatch’) is a recognised problem around Cornwall. Entanglement in fishing gear can kill or seriously injure the whale or dolphin involved and may impact on the survival of local populations. It is a problem for the fishers too, as it is upsetting for them to deal with and can result in expensive repairs to their gear. It can also lead to increased risk for fishers and reduce their target catch rates.

The number of dolphins and porpoises washed up on Cornish shores has been increasing over the last 20 years, and about a third of the stranded individuals last year had injuries consistent with bycatch or entanglement in fishing gear.

Porpoise in net
This poor porpoise died in a net © Cornwall Wildlife Trust

A simple solution

One group of Cornish fishers decided to solve their bycatch problem by attaching Banana pingers to their fishing gear. Pingers are small battery-powered acoustic alarms which are attached at intervals along a fishing net. They emit a repeated audible signal which alerts individual harbour porpoises to the presence and location of the nets, significantly reducing the likelihood of them becoming entangled.

Pingers emit a warning sound
Pingers emit a warning sound

Pingers are the most widely adopted bycatch mitigation tool for dolphins and porpoises. They are low cost compared with other approaches and require little or no change in fishing gear or practices. They have been shown to be effective in reducing the accidental capture of several dolphin, porpoise and whale species.

The fishers were very happy with their solution and found that they weren’t accidentally catching any harbour porpoises or dolphins when using pingers.

A fisher holds a pinger
A fisher holds a pinger

Problem solved! Until…

The fishers were informed that under the Marine and Coastal Access Act 2009, they would need a Marine Licence in order to legally fish with pingers. The Cornwall Wildlife Trust helped them apply for the licence from the Marine Management Organisation (MMO) in March 2018. Despite considered support from Natural England, the Statutory Nature Conservation Body, the MMO rejected the application on the basis of other technical advice they received.

It transpires that a number of concerns were raised about the use of pingers in the Cornish inshore net fishery including that, over time, the dolphins and porpoises would get used to the noise of the pingers and start to ignore it. Pingers would then get less effective as time goes on. This is known as ‘habituation’. Another concern was that the sound emitted by the pingers would add to the underwater noise in an area and, in the end, this might mean that dolphins and porpoises stop using that area, even when the pingers aren’t in use. This could mean that important feeding or sheltering habitats are no longer available to the dolphins and porpoises. The term for this is ‘ensonification’.

The implications of this licence decision are clearly disastrous for the welfare of entangled individuals and a concern for local populations of dolphins and porpoises if unfounded. The decision also sets a worrying precedent for future pinger applications in English waters.

WDC’s call to action

When Whale and Dolphin Conservation heard about this situation, they were quick to act, funding frontline science by Cornwall Wildlife Trust, Fishtek Marine and the University of Exeter, to analyse the data from a fascinating experiment conducted in Cornwall in the hope of mitigating the concerns marine managers raised. A fresh look at the evidence available, both for the specific fishery involved and in pinger science and trials around the world was undertaken.

In order to address the concerns about habituation and ensonification, scientists from the University of Exeter analysed data from a study that was conducted in waters off the coast of Cornwall, between July 2012 and April 2013. A Banana Pinger and two C-POD devices (which sit underwater passively recording any ‘clicks’ made by dolphins and porpoises in the area to give an idea of their presence) were deployed for about nine months.

What did we find?

Preliminary results look promising and suggest that the pingers are acting as an effective bycatch mitigation device. More details will be available once the results have been published. These findings are consistent with what fishers have told us they’ve seen of porpoise and dolphin behaviour when using pingers and studies worldwide, including a recent drone study from Denmark.

Applying science to make a difference

So, the work that WDC has supported has provided new insights and updated the evidence base available to the MMO and its advisers about the effectiveness of pingers at reducing the number of porpoises getting trapped in nets in UK fisheries. The detailed findings of this work are due to be published in the scientific literature early next year.

All involved hope these findings will be used when assessing future licence requests to use pingers in UK waters, and that many dolphin and porpoise lives will be saved.

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The views and opinions expressed by our guest bloggers are those of the author and do not necessarily represent those of WDC.

About Julia Pix

Communications manager - Public Engagement

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