Seals and Cod
Harp Seals and Grey Seals Have Been Blamed for Causing the Collapse of the Cod Fishery and for Preventing its Recovery
What is the truth about the harp seal-cod relationship and the grey seal-cod relationship?
Simplified food web of the Northwest Atlantic, including harp seals (David Lavigne, 1996) (a). Some of the metabolic pathways on which such food webs are based (from www.genome.ad.jp/kegg/). Printed in Ch. 1 Biosimplicity via stoichiometry: the evolution of food-web structure and processes, James J. Elser and Dag O. Hessen, published in Aquatic Food Webs, Oxford Univ. Press 2005.
In fact, the marine ecosystem of which harp seals and grey seals are a part is complex. It includes a complex food web, changing climate and weather effects, and interactions not fully understood.
To the left, is a simplified pictorial of the Northwest Atlantic food web, which includes harp seals and grey seals.
But what is known is that cod is only a small fraction of the harp seals' diet and that harp seals also prey on species that in turn, prey on cod. Thus a larger cod population may accompany a larger seal population.
In recent years, the Canadian Department of Fisheries and Oceans (DFO) has shifted the blame for the failure of the North Atlantic cod to recover to grey seals. The grey seal population has increased in parts of the Gulf of St. Lawrence. Since grey seals eat cod as part of their diet, the DFO has begun to focus on this seal species as the newest scapegoat.
Grey seals consume different amounts of cod in different parts of the year. Recent work suggests that, during the winter, cod may provide 60% of the grey seals' sustenance. Nevertheless, this is only one small part of the vast web of life in which the grey seals play a role in the Northwest Atlantic, and more specifically in the Gulf of St. Lawrence and the Scotian Shelf.
Here are links to other resources:
Marine Fish Population Collapses: Consequences for Recovery and Extinction Risk, Jeffrey A. Hutchings and John D. Reynolds, BioScience, Vol. 54 No. 4, April 2004.
On the potential impact of harbour seal predation on the cod population in the eastern North Sea, B. Johan L. Hansen, Karin C. Harding, Department of Marine Ecology, Göteborg University, Box 461, S-405 30 Göteborg, Sweden, Journal of Sea Research 56 (2006) pp. 329–337
World Fisheries: The Current Crisis, Alan Nixon, Canadian Library of Parliament, Parliamentary Research and Information Service, January 1997
Seals to the slaughter
16 March 1996
From New Scientist Print Edition. Subscribe and get 4 free issues.
Beater harp seal pup (c) IFAW
"HARBOUR Grace is a pretty place, and so is Peeley's Island," goes an old Newfoundland song. "Daddy's going to buy me a brand new dress when the boys gets home from swilin'." Swilin' - the spring hunt for young seals on the sea ice - used to be one of the few ways Newfoundland fishermen could earn the extra cash for a daughter's dress.
This year, it is the only way many of them will earn any money at all. In 1992, the Grand Banks fishery, the region's main employer, closed after the cod stocks were destroyed by overfishing ("The cod that disappeared", 16 September 1995, p 24). In a desperate attempt to find jobs for Newfoundlanders, Canada is subsidising and enlarging the seal hunt. About now, the seals will be congregating on ice floes to give birth. In two weeks, when the pups have moulted, they are fair game. Fishermen are getting their clubs ready for the biggest legal slaughter of wildlife in the world, apart from fishing itself.
No one would bother if it weren't for the subsidies. Markets for seal products have collapsed, wrecked by public outrage over pictures of bloodied baby seals spread around the world by animal rights campaigners. But the subsidies aren't just intended to create a few thousand poorly paid jobs. The Canadian government insists that killing seals is the only way to bring back the cod fishery. Government scientists say seals eat vast amounts of cod and are hampering their recovery. Scientists outside the government call that nonsense. They say killing seals is just as likely to deplete cod stocks still further. And they charge that the government's seal science has been distorted for political reasons, while any government scientist who refuses to toe the official line is gagged.
The Newfoundland seal hunt killed 250 000 seals a year early this century, then 300 000 after 1945. Seal numbers fell, including harp seals, the most common species and the one that produces the white-coated pups. In 1983 Canada set a yearly hunting limit on harp seals of 186 000. But that same year, under pressure from anti-culling campaigns, the European Community banned the import of products made from seals under a year old. Fur markets died. In 1987 Canada evicted the Norwegian factory boats which had been taking most of the seals, and banned the killing of white-coated pups in an effort to salvage the hunt's image. But the price of a pelt fell from C$40 (£20) to C$9 and the cull reached a low of 27 000 animals in 1993.
Then the collapse of the fishery threw 30 000 Newfoundlanders out of work. The province called "The Rock" has few other jobs to offer - and a government relief package worth C$1.9 billion will run out in a few years. What to do?
In 1994 Canadian fisheries minister Brian Tobin decided to boost the sealing industry. The Canadian and Newfoundland governments started paying a subsidy of C$0.66 per kilogram of seal meat. Last spring only a late freeze that kept boats in port limited the catch to 61 000 seals. The Canadian Sealers' Association, an industry lobby group supported in part by the Canadian fisheries ministry, the Department of Fisheries and Oceans (DFO), redoubled its efforts to drum up markets.
This was a popular move with fishermen. It was good for their pockets - they could earn a bit of money, though profits were still very low. And it was also good for their morale - the hunt suited the widespread belief that killing seals would rid the fishing industry of a ravenous competitor. "No one blames seals for the collapse of the fish stocks," says Tina Fagan of the Canadian Sealers' Association. "That was overfishing. But seals eat fish. The cod won't recover unless more seals are taken out of the system." Last December, Tobin raised the harp seal quota to 250 000, saying there was one major reason the cod weren't recovering: "His first name is harp, and his last name is seal."
Sealer ready to club seal. (c) IFAW
The DFO provided the scientific rationale. Garry Stenson of the DFO Science Branch in St John's, Newfoundland, calculates that the harp seal population in the northwest Atlantic grew from 2 million in 1980, to 4.8 million in 1994. Their total prey consumption grew from 3.6 to 6.9 million tonnes and would increase since the herd was growing at 5 per cent per year.
The stomach contents of killed harp seals show that cod only makes up three to five per cent of their diet, Stenson says. But this would still account for up to 142 000 tonnes of cod in waters near Newfoundland in 1994, about the size of the last commercial cod quota. Moreover, says Stenson, seals eat cod too small for commercial fishing. So they take more fish per tonne than fishermen. The conclusion for the DFO is obvious. "Harp seals are one of the factors impeding groundfish stocks rebuilding," it says in its home page on the World Wide Web.
But there are three things wrong with that conclusion, say scientists outside the DFO. One is the accuracy of the DFO's estimates both of the size of the seal herd, and of how much cod it eats. The second, more telling problem is that seals are just a tiny part of a complex marine ecosystem so, no matter how much fish they eat, there is no guarantee that culling seals will increase cod stocks. The third is direct evidence, from the DFO itself, that seals are not affecting the recovery of the cod.
Peter Meisenheimer, a fisheries biologist working for the International Marine Mammal Association, a conservation group based in Ontario, says "The harp seal population has probably increased, because hunting has fallen. But the DFO cannot say with certainty by how much." The DFO's methodology for counting seals, a notoriously difficult task at best, has differed from year to year, says David Lavigne, a seal biologist at the University of Guelph, Ontario. He says this makes it impossible to compare counts from different years, and find trends. "They simply haven't spent the money required to do a proper job," says Meisenheimer.
IN FROM THE COLD
To make matters worse unusually cold offshore waters have driven more seals inshore in recent years. Such changes in distribution make it trickier to extrapolate from samples to total populations. It also fuels popular perceptions among fishermen that "there are an awful lot of seals out there", says Fagan. But there is no proof that the seal population is growing at 5 per cent per year, says Meisenheimer. "The DFO uses this number without mentioning that it is the highest of a range of estimates based on old information, not an empirical measure of the present situation." Harp seals are having fewer young and later pregnancies, and are thin, says Lavigne - all signs that the herd is not growing rapidly, "but reaching its carrying capacity and stabilising".
In addition, says Meisenheimer, the DFO's estimate of the amount of cod in the seals' diets is based mainly on data taken in years when there was a commercial fishery. The proportion is likely to be higher then than now, as seals eat discards from nets when they can get them. One study by the DFO found large amounts of cod in seals' stomachs when there were trawlers about, but none when the boats were gone. Seals are especially unlikely to be eating much cod since it has now almost disappeared. They are far more likely to switch to something that is easier to find, says Lavigne.
MEALS FOR SEALS
Stenson is aware of the limitations of his data. "Studies are currently being conducted to improve our knowledge of both the diet and distribution of harp seals," he wrote for the DFO last year. "Until they are completed, these estimates of consumption should be considered preliminary and used with caution."
But if the DFO's scientists see a need for caution, its policy-makers do not. Jean-Eudes Hache´, a senior DFO fisheries manager, defends the increased seal hunt. "It is established that harp seals eat large amounts of cod," he says. "How many of these young cod would survive to maturity if they were not eaten by harp seals?"
But that is precisely the question the DFO is not addressing, says Lavigne. Cod have other predators and some of these also make a good meal for seals. "What else are the seals eating," asks Lavigne, "and what impact does that have?" The DFO's sealing model, he complains, is of limited scientific value, as it can give only one answer: seals eat cod, so seals reduce cod stocks. "But seals also eat animals that eat cod," he says. "Which is more important? Canada hasn't even begun to do the type of multispecies assessment you need to predict the impact of killing seals."
South Africa did its homework in 1991, he says, when it wanted to kill Cape fur seals to boost commercial hake stocks off Namibia. "South Africa asked an international group of scientists to consider the issue," says Lavigne. "We decided we needed a minimally complex model - one that contains enough features of the ecosystem that it isn't obvious what the answer will be until you actually run it." The Namibian model included the seals' impact on commercial hake and on a non-commercial species of hake that preys on the commercial variety. Seals eat both. The scientists concluded that killing seals was more likely to harm than to help the fishery, because seals ate more of the predatory species. South Africa called off the hunt.
The same relationship may exist between harp seals and cod. Illex squid eat young cod. Seals eat squid. Meisenheimer says a simple calculation, based on the DFO's figures for the different animals' population sizes and feeding rates, shows that, for every seal killed, extra cod do survive. "But depending on the assumptions you make about seal feeding rates, squid death rates, and the like," he adds, "the seal can rescue even more cod by eating squid. Under some conditions, a live seal can cause a hundred times more cod to survive than a dead one."
Meisenheimer emphasises that this is not a firm scientific analysis, but an illustration of principle. "The DFO is using similar calculations to justify the seal hunt, except they haven't even considered the most basic complexities in the system, such as the impact of seals on predators. Including that can give you a completely different answer."
Lavigne says it is "extremely naive to think we can tinker with the complex food web in the oceans, tweak one thing - seals - and have the result we want". He points to failed efforts to boost certain populations on land by killing their predators. Spanish hunters kill the Iberian lynx in the hope of boosting the rabbit population. But scientists reported last year that there are five to ten times as many rabbits in areas they share with the lynx, than in lynx-free areas: lynx also eat mongoose, which eat rabbits.
But oversimplified predator-prey models are only one problem with Canada's case for killing seals. Equally damning is the DFO's own research which shows no evidence of seals hampering the recovery of cod stocks. Ransom Myers, of the DFO Science Branch in St John's, reviewed data on 128 fish stocks worldwide that had been fished to very low levels. He was looking for evidence that the recovery rate for these stocks might be slowed by a decreased survival rate of young fish, perhaps because of increased predation. But no such effect showed up in 125 of the stocks, including Atlantic cod, Baltic cod, and every other example of fish similar to cod.
Jeff Hutchings, a fisheries biologist at Dalhousie University in Nova Scotia, says that seal populations around Newfoundland have increased since 1980, but the DFO's own survey data show no parallel increase in cod deaths in the age group eaten by seals. "We have no idea what percentage of the young cod seals are killing," adds Hutchings. "If this is not significant compared with other causes of death, he says, then killing seals will have little effect on fish stocks.
In December, the International Society for Marine Mammalogists stated that "All scientific efforts to find an effect of seal predation on Canadian groundfish stocks have failed to show any impact ... the evidence indicates that stocks will recover, and killing seals will not speed that process."
Some DFO scientists agree with that statement off the record. But they fear losing their jobs if they say so openly. They are told not to talk to the public about cod, or seals. Do it once and, they are reprimanded - do it again and they can be sacked. This year DFO scientists pleaded, secretly, with their bosses not to say the seal hunt was based on science. They were ignored. "The tragedy is that science is being used as a tool to justify a political decision. And scientists who disagree are muzzled," says Hutchings.
JOBS FOR THE BOYS
But in Newfoundland, the only tragedy that matters is the economic future. It is bleak. Before, fishing employed too many fishermen to chase too few fish - so even if it recovers, it should provide a third as many jobs as before. What will everyone else do? Some people think the government could create more jobs by investing in something other than dead seals. Boosting the seal hunt is at best a partial solution, as no one thinks the market will expand that much. But it has provided work for one Newfoundlander. Last month Tobin resigned as Canadian fisheries minister and became premier of Newfoundland virtually without opposition. One big reason for his popularity is the seal hunt.
Newfoundland is not the only place where sealing is popular. The hunt for grey seals in Scotland stopped in 1979, but fishermen are clamouring to start again. They say the seal herd eats large amounts of commercial fish. The Sea Mammal Research Unit in Cambridge disagrees. Fishermen admitted killing seals illegally in Orkney in October.
Norway never stopped killing harp and hooded seals, though the hunt dwindled to a mere three boats last year as markets died. In an effort to revive it, Norway will end a seven-year ban on killing pups this year. It told the European Parliament in January that it kills seals because they "compete with us for fish".
But nowhere is the seal hunt as massive as the one now planned in Newfoundland. The tragedy for Newfoundlanders is that it could further unbalance an already impoverished marine ecosystem. And once again, the culprit will be, not seals, but political mismanagement in the name of science.
Flipper pie, anyone?
The size of Canada's seal hunt depends on whether sealers can sell what they catch. That used to depend on the number of pelts the Carino Company of Dildo, Newfoundland - a subsidiary of the Norwegian firm Rieber - would buy. This year it says the market, largely in Asia, has grown to 230 000 pelts. Now new markets are appearing, says Tina Fagan of the Canadian Sealers' Association.
The oil rendered from seal blubber is rich in omega-3 fatty acids, a popular health food supplement. Newfoundland sells seal oil capsules in China and Japan, and is applying to sell them in Canada. But Vernon Thomas of the University of Guelph in Ontario has doubts about the market. He says fish are a more economic source of omega-3 fatty acids, and less contaminated with pollutants such as PCBs, while the World Trade Organisation may take a dim view of a product that will have to be developed with the help of extensive government subsidies.
Seal meat is already subsidised by Canada. At the Canadian Food and Beverage Show in Toronto in February, the Sealers' Association displayed seal salami, pepperoni, sausages, vacuum-packed prime cuts, stew, canned meat, and even an old Newfoundland delicacy - flipper pie. The rest of the seal ends up as pet food, says Fagan.
Animal rights' activists maintain that the only seal product profitable enough to make the hunt worthwhile is their penises, an aphrodisiac according to the Chinese. A dried, beribboned seal penis fetches upwards of $100 in Far Eastern markets, and in Canada's fast-growing communities of Hong Kong Chinese.
Fagan denies promoting penises. But the harvest of adults, as opposed to immature seals, jumped from 20 to 65 per cent of the catch between 1993 and 1994. Male carcasses fetch higher prices than female ones. Exporting seal penises is illegal in Canada. But the International Fund for Animal Welfare believes that dealers "get around that by selling them with the seal still attached."
From issue 2021 of New Scientist magazine, 16 March 1996, page Page 34