An international team of researchers, led by scientists based at the University of Bristol, UK, developed a method to measure the impact of humans on wildlife mortality. When applied to fishing, this method shows that keeping the same levels of accidental dolphin capture is not sustainable in the long term. The study was published in the journal Conservation Biology.
Commercial fishing often results in the death of non-targeted wildlife and threatens protected species, including dolphins, seals, turtles, sharks, and rays. “Bycatch and discarding of marine wildlife in commercial fisheries are major challenges for biodiversity conservation and fisheries management the world over,” said Dr. Simon Allen, one of the researchers involved in the study from the University of Bristol.
For this reason, the team designed a way to calculate how many animals are captured, including those reported in skippers’ logbooks and those identified by independent observers. “Unfortunately, our results show clearly that even the lowest reported annual dolphin capture rates are not sustainable,” Dr. Allen said.
“We introduced a novel approach to assessing human-caused mortality to wildlife that can be applied to fisheries bycatch, hunting, lethal control measures, or wind turbine collisions. And when we incorporate stochastic factors, random events, we show that previous methods of assessing wildlife mortality were not conservative enough,” added Dr. Oliver Manlik, Assistant Professor at the United Arab Emirates University and who was also involved in the study. “This raises concerns for the dolphin population and highlights a problem with other assessments that do not account for random events, like heatwaves because these environmental fluctuations are becoming more frequent and intense with climate change.”
Dr. Allen points out that, at the moment, the UK and EU are failing to address this problem. In most cases, there’s only voluntary monitoring and no conservation objectives to aim for. The authors call for great transparency and more rigorous methods to allow this industry to understand the impact of fisheries on non-target species, including whales, dolphins, seals, and seabirds.
The team includes a member from the Species Conservation Toolkit Initiative and is aiming to make the new method to assess human impact — called ‘Sustainable Anthropogenic Mortality in Stochastic Environments’ or ‘SAMSE’ — more easily accessible to researchers and wildlife managers across the world.
Manlik O, Lacy RC, Sherwin WB, Finn H, Loneragan NR, Allen SJ. A stochastic model for estimating sustainable limits to wildlife mortality in a changing world. Conserv Biol. 2022 Feb 4:e13897. doi: 10.1111/cobi.13897.