Junk science and questionable political motives are behind a new federal report that calls for an experimental cull of 70 per cent of the grey seals in the southern Gulf of St. Lawrence, a leading critic of Canada's annual seal hunt says.

Rebecca Aldworth, Canadian director of Humane Society International, was reacting Wednesday to the release of a science advisory report that says Ottawa should consider a five-year study that would start with the slaughter of 73,000 grey seals in an area stretching from eastern New Brunswick to Cape Breton, N.S.

The study, produced by the Canadian Science Advisory Secretariat, says the experiment would determine whether significantly reducing the grey seal population in the Gulf would help cod stocks recover from a drastic decline.

However, it also acknowledges there are such large gaps in research on the problem that a large-scale seal cull could just as easily lead to wiping out cod in the Gulf.

Calls to the federal Fisheries Department, which commissioned the study, were not returned Wednesday.

Denny Morrow, head of the Nova Scotia Fish Packers Association, said the study represents a step forward for science.

"There's data there that indicates that the recovery of codfish stocks in the Gulf of St. Lawrence and probably other areas is being held back by the amount of grey seal predators," he said in an interview.

Morrow acknowledged there were scientific gaps in the research, particularly about the grey seal diet. But he said the document included one peer-reviewed study showing that the amount of cod in the diet of male grey seals reached as high as 41 per cent in the winter months.

"Fishermen have known this for years," he said. "If you've got large concentrations of cod, and you see a lot of grey seals, it doesn't take too much science to understand what is going on."

Document designed for election: critic

Aldworth said the document was designed to do one thing: curry favour with the fishing industry in advance of a federal election.

"The report underscores how very little is known about seals and fisheries interactions, and it reveals the very clear agenda of the Harper government to exterminate seals for their short-term political gain," she said in an interview from Montreal.

Morrow called Aldworth's accusation an insult to the scientists and industry experts who contributed to the study.

"I have the greatest respect for the scientists who put their time and reputations on the line," he said. "They looked at information from Canada and around the world."

The report has been forwarded to Fisheries Minister Gail Shea, who will decide whether the experiment is a good idea — unless an election is called.

Fishermen in Nova Scotia have long complained that hungry grey seals have hindered the recovery of cod stocks, which collapsed in the early 1990s after decades of overfishing.

The study says there are between 330,000 and 410,000 grey seals living off the Atlantic coast — a 30-fold increase since the 1960s.

The population boom has been attributed to a decrease in hunting and an increase in births on the sea ice that gets jammed behind the Canso causeway, which links Cape Breton with the mainland.

Most of Canada's grey seals — at least 260,0000 — live part time on Sable Island, about 160 kilometres southeast of Nova Scotia. The study says very little about the island's population, except that a cull there of 50,000 animals over five years would have little impact on the cod.

Canadian seal hunt focuses on harp seals

Instead, the study focuses on the southern Gulf, where an estimated 104,000 grey seals forage, including 36,000 from Sable Island, 5,000 from Nova Scotia's eastern shore and 63,000 resident seals.

Seal hunters typically slaughter about 1,000 grey seals in the Gulf every year, even though the allowable catch is about 50,000.

The annual Canadian commercial seal hunt has long focused on the far more numerous harp seals, which are estimated to number about six million off the East Coast.

The study's authors conclude the grey seals' diet appears to be an important factor inhibiting recovery of the cod in the Gulf, and that slashing the population by 70 per cent "would pose minimal conservation risks."

Grey seals eat between 4,500 tonnes and 20,000 tonnes of cod per year in the southern Gulf, the study says.

While it's true that grey seals transmit a parasite called sealworm to cod, the study says the infection appears to have little impact on the condition of the fish.

The study's authors acknowledge that according to one set of scientific assumptions, grey seals eat so few cod that elimination of the entire grey seal population would do little to help the cod recovery. Another set of assumptions was used to justify an experimental cull.

As well, the report's risk analysis says a cull could halt the decline of Gulf cod, but it could also hasten their demise and "lead to unforeseen, unpredictable and unintended consequences for the ecosystem."

The study says the impact of seal culls have rarely been evaluated, but other predator control programs have often resulted in unintended consequences. That's why any intervention in the southern Gulf would require a carefully designed program that would include rigorous monitoring, the report says.