Canadian sharks

You can recognize blue sharks by their slim, graceful bodies, long pectoral fins and their distinctive colouring: deep blue on top, lighter on the sides, with a white underside. The blue shark’s colouring helps it blend in with the water no matter what side you see it from. Blue sharks are highly migratory and have been tracked crossing the entire Atlantic Ocean.

Even though blue sharks are probably the most common species in Canadian waters, Hector and the other blue sharks are still in trouble. The main threat to the blue shark is being caught as bycatch in fisheries targeting other species. Canada’s pelagic longline fishery catches almost 100,000 sharks each year. About 35% of blue sharks will die after being ‘unintentionally’ caught as bycatch and thrown back.

Many fisheries management bodies think that the blue shark is so common that it doesn’t need strict protection however the science that we have on this species is based on very uncertain and incomplete data.

What we do know is that blue sharks are considered ‘Near Threatened’ by the International Union for the Conservation of Nature and were listed as ‘Special Concern’ by the Committee on the Status of Wildlife in Canada. These listings should be taken as warnings. Should we have to wait until a species becomes endangered before we take any action to help it? Wouldn’t an ounce of prevention be better than generations of negotiating ‘rebuilding plans’ for yet another species? We certainly think so.

Some small steps were taken to protect blue sharks last year at the International Commission for the Conservation of Atlantic Tunas (ICCAT) meeting. The final agreement triggers further discussion by ICCAT, but not necessarily catch limits, if North Atlantic Blue Shark landings exceed recent levels (~39,000 metric tons). We would have liked to see firm catch limits put in place to make sure that a fishery would be shut down if it were putting blue shark populations in jeopardy.  There is still work to do!

They are also total show-offs, often making spectacular leaps from the water. Unfortunately, this means that these acrobats are often targeted for sport fishing as they can put up quite the fight on the end of a fishing line. Shortfin makos are known as a cold-tolerant pelagic shark species. This is because, along with the porbeagle shark, makos are one of several shark species that can maintain a body temperature that’s warmer than the water surrounding it, thanks to a specially designed circulatory system. In fact, makos have their warmer internal body temperatures to thank, in part, for their active lifestyles, including their high speed swimming abilities and acrobatic leaps.

Canadian fisheries management could certainly do a better job protecting the shortfin mako. This species is ‘managed’ domestically under a non-restrictive catch guideline of 100 tonnes. Not only is this guideline not enforced, but it is not based on any scientific justification. It also does not account for discard mortality – the number of sharks that are killed at sea and thrown back are not factored into this number.

A new study showed that the fishing mortality of shortfin mako in the Northwest Atlantic is higher than previously estimated. This could mean that more are being fished that we thought and that the population may be in worse shape than we thought. The newest stock assessment for shortfin mako, which was released in August 2017, found that contrary to what was previously thought, the shark’s population has severely declined and it is currently being overfished. The science assessment indicates that catches of North Atlantic shortfin mako would need to be reduced by 72-79% just to keep the population from decreasing further. Catches need to be cut to zero to have even a 50% chance of rebuilding the population within twenty years.

Instead of setting meaningful restrictions on the number of makos that can be fished, the Canadian Department of Fisheries and Oceans has set a ‘guideline’ that is too high to actually limit anything. Is this a reasonable way to manage a vulnerable shark population? Not in our opinion.

This year, at the annual meeting of the International Commission for the Conservation of Atlantic Tunas (ICCAT) in November, countries will decide on additional international management measures for these sharks based on the new science advice. Considering the grim picture painted by the latest stock assessment, we think that the best way to limit the harm to this species is by requiring that any shortfin mako caught in a fishery must be thrown back, and we’ll be looking to ICCAT members to support this management measure.

Porbeagles eat mostly fish and squid, though like many other sharks, they are often found with bits of garbage in their stomach as well. The porbeagle may live up to 45 years and reach a maximum length of up to 3.5 metres.

Unfortunately, Canada’s treatment of its resident shark is hardly stellar. Porbeagle sharks are caught as bycatch in several of Canada’s fisheries, include swordfish pelagic longline and groundfish bottom longline fisheries. Similar to the shortfin mako, porbeagle is ‘managed’ under a non-restrictive catch guideline of 185 tonnes, which is far above current catch levels. Porbeagle were assessed as “Endangered” by the Committee on the Status of Endangered Wildlife in Canada in 2014, and have been waiting for formal listing for protection under Canadian law in the years since. Under the current plan, porbeagle populations will be recovered in just over 100 years. And no, that’s not a typo.

There is slightly more hope for the porbeagle shark at the international level. In 2014, the International Commission for the Conservation of Atlantic Tunas (ICCAT) passed a measure that requires that all sharks that are caught alive be released back into the ocean. The measure also mandates the Commission to consider additional measures for porbeagles if more than 40 tonnes are caught in the ICCAT area during one year.

While their name might suggest they’re an Arctic species, Greenland sharks have been confirmed as far south as New York, and they are most certainly found in Canadian waters. Since they are so long-lived, late to mature and slow to reproduced, fishing even a few of these sharks could have serious implications for the entire population. There are no scientific estimates of the size or health Greenland shark populations yet, and there’s a lot more we don’t know about these ancient sharks.

In Canada, Greenland sharks are among the most common species caught as bycatch in Canadian gillnet and trawl fisheries for Greenland halibut, though, at the moment, we have no estimate of how seriously we’re impacting them. In order to protect these species, we need to improve our knowledge of their biology and population size, health and dynamics. We also need to better monitor our fisheries so we can understand the impact we’re having and then implement bycatch measures which will minimize the harm our fisheries cause to the Greenland shark population or allows it to rebuild.

At the international level, the Northwest Atlantic Fisheries Organization (NAFO) requested that its Scientific Committee review the life history, population status, current fishing mortality and longevity of Greenland sharks, and develop advice for management, in line with the precautionary approach, for consideration by the Fisheries Commission by 2018.