Richard Sobol/ZUMA/eyevine

The author of a paper critical of Canada's annual seal hunt has defended his work after it was attacked for being biased and flawed.

Andrew Butterworth, an animal-welfare researcher and veterinarian at the University of Bristol, UK, said his study, the conclusions of which were described as “incorrect or misleading” in a critique by Canadian scientists and officials, was based on quality evidence and that his use of video footage of seal clubbing was scientifically rigorous.

"There are different viewpoints — and mine is framed with an assertion that we should take considerable care with the welfare of these animals at the time of this commercial killing," he said. "This would be the expectation in any other commercial killing activity of this scale."

Each year, starting in November, hundreds of hunters armed with rifles, clubs and hook-like tools called hakapiks kill tens of thousands of seals in Canada’s arctic waters. The review published online last September1 supported the contention by animal-rights groups that the hunt is inhumane. But other researchers later responded with a critique of that study2, saying that its methods were flawed and its conclusions biased.

Butterworth, who has served as an observer of the hunt, was a co-author of the review, published in Marine Policy. It concluded that “generally accepted principles of humane slaughter cannot be carried out” in the seal hunt1.

Parsing the data

That paper cited evidence including studies and videos that suggested that shooting and clubbing do not always cause immediate death. As a result, some pups have to be clubbed more than once, and others lie injured for a period of time before finally being killed. Many seals shot are probably not immediately unconscious, the authors note, as they are often then clubbed by sealers. The reviewers concluded that there are “reliable data indicating that cruelty takes place on a large scale”.

But in their critique, Pierre-Yves Daoust, a veterinarian and pathologist at the University of Prince Edward Island in Charlottetown, Canada, and his colleagues say that the review's conclusions were “incorrect or misleading” and that it offered “a highly selective and unfair portrayal of the available data”2.

Daoust and his colleagues write that clubbing after shooting does not mean the shot did not cause immediate death, but “crushing the top of the skull” ensures that the requirements of the Canadian Marine Mammal Regulations are met. They also say that some references cited by Butterworth are for older practices that are no longer current. Their critique also takes aim at the video evidence, saying that it fails to meet “fundamental criteria of scientific rigor”, in part because it was collected by non-governmental organizations opposed to the hunt.

“We respect that people have alternate viewpoints on this issue, but believe that scientific articles should provide conclusions based upon a full review of the available data,” wrote Daoust’s co-authors Garry Stenson, a zoologist at the Canadian Department of Fisheries and Oceans (DFO) in St John’s, and Mike Hammill, at the DFO in Mont-Joli, in an e-mail to Nature. Although Butterworth has visited the hunt briefly, his co-author has not and "their experience is based primarily on video evidence collected by anti-hunt groups with the express purpose of showing poor hunting practice”, they write.

Freeze frame

Daoust says that any observations of the hunt are by necessity only snapshots and that it would be extremely difficult to design a scientifically robust study of the harvest, given the size of the area it takes place in and the harsh conditions that prevail during it. “However, I believe that my observations and those of my colleagues have allowed us to improve the quality of the hunt from an animal-welfare perspective,” he says.

In a statement, the DFO insisted that its seal harvest practices are “among the best in the world” and that the hunt is “clearly sustainable” at current levels, which saw around 90,000 harp seals taken in 2013.

The stakes in the argument have been raised in recent years, as the World Trade Organization (WTO) is considering the legality of a European Union ban on imports of seal products.

“This is a 'precedent case', as this is the first time that welfare and public-concern considerations have been influential in a WTO trade decision on animal products,” says Butterworth, whose response to the critique was also published in Marine Policy[3].