(26-02-10) Marine scientists are opening a window into the mysterious world of the top predator in the Canadian Arctic about which almost nothing is known: the Greenland shark.
Scientists recognized that Greenland sharks are underknowed creatures, as said Steve Campana, of the Bedford Institute of Oceanography: “These are very, very strange sharks. Its meat is poison. Its mouth is far under its body. It has almost no spine. It's so lethargic that it doesn't even snap at the scientists who hook it and attach a radio to it. And it may live 200 years.”
Two years ago, Mr. Campana and Aaron Fisk of the University of Windsor took their team to the sea ice 300 kilometres north of Iqaluit, camping out in a frigid plywood shed to tag and release Greenland sharks.
Only one other big shark in the world is almost unknown, the extremely rare deep-ocean "megamouth." Why study the Greenland shark? In the eastern Arctic "this is the apex (top) predator, the king of the food web, along with the polar bear. There's a sister species in the western Arctic. And as with any ecosystem, if you don't know anything about the apex predator, you're in a lot of trouble figuring out what's going on."
“Everything about this fish is odd”, Mr. Campana says. "They are really the antithesis to the fast-swimming great white and mako (sharks)." The cold water might make them slow, but even in warmer water they just cruise along the bottom, slurping up fish, and occasionally seals. The seals may be dead when the sharks eat them. No one really knows.
Researchers are hoping that samples of bone may hint at a fish's age; the team will look for radioactive elements released during atmospheric tests of nuclear weapons, to show which fish were alive in the 1960s.
The Greenland shark can grow to eight metres and has hundreds of sharp teeth. "Just running your hand lightly along them you can slice yourself wide open," says Mr. Campana. "When we found a dead shark we would open up its stomach. Every single one was jam-packed with food. A lot of it was large fish," but there were some baby seals”.
It's possible the shark scavenged dead seals, but seals are also known to be curious, and some young ones may have wanted too close a look at the shark. The sharks are incredibly abundant, says Mr. Campana, "and yet we don't have a clue how fast they grow, how old they get, where they give birth, how many they give birth to..."
The team used radio tags, which don't hurt the sharks, to record information about their living conditions (water temperature and light) and location. The tags are programmed to release months later and then "pop up" to the surface and radio their findings to a satellite.
Inuit fishermen often catch them by accident, hooking a turbot that a shark then bites on the hook. The meat is poison if cooked like normal fish, so full of urea that it takes boiling and re-boiling to make it safe.
GREENLAND SHARK 8 METERS LENGHT
The Greenland shark is the second biggest shark in the North Atlantic. Unlike most sharks it stays in polar waters years round. It can be 7 meters long, weighing over a ton. It is most common on depths between 200 and 600 meters. In the Denmark Strait (between Greenland and Iceland) it’s claimed that it’s been caught sharks with a length of 8 meters.
The skin is grey or brown, about 1 cm. thick and feels like sandpaper when you touch it. It’s jaws is covered with about 100 sharp teeth. This shark eats everything, even things that is not classified as food is found in its stomach (like boxes, rubber and brushes).
Maybe this is a result of its bad sight? Most Greenland sharks have one parasite in each eye. In spite of this it’s proved that this shark can hunt, probably mainly by use of other senses. The hunt gives results, and it may therefore not be as slow a swimmer as previous thought. As for most sharks the Greenland shark reproduces slowly.
A couple of hundred years ago scientists and fishermen claimed that all Greenland shark were female and the porbeagle was its mate. Thereby the Norwegian names "håkjerring" (meaning: "shark + wife") and "håbrann" (shark + a former Norwegian expression for husband).
Fishing for Greenland sharks is probably the oldest known shark fishery in northern Europe. It’s not known when it started, but a report from Troms in Norway in 1650 says: "During the long nights before Christmas, in the deep fjords, they catch a fish called "Håkjerring" (Greenland Shark). In the summer, when this fish is caught using fishhook, the fisherman remove the liver and then uses a pipe to blow air into it’s stomach."
The fishermen did this to prevent the carcass from sinking. They didn’t want other fish to feed on rotten shark flesh. In 1840 two Greenland shark companies were established in Hammerfest (north in Norway). Their vessels hunted from June till September. The record for one vessel was 1780 Greenland sharks in one season.
That catch represented 200 buckets of liver. There are many such examples of Greenland shark fisheries in Norway, and they all used fishhooks to catch the sharks. The fish line was provided with an iron chain near the hook in order to prevent the shark from cutting the line with its sharp teeth. Only the liver was taken and the oil produced from the liver was valuable merchandise.
VESSEL- FACTORY TO PRODUCE OIL ON BOARD
In 1908 a specialized fishery for Greenland shark had been established far from the Norwegian fjords and coast. Vessels with steam engines fished in waters east of Greenland. Some vessels combined this fishery with the traditional hunt for seal. The fishery was such a success that some of the vessels specialized on the Greenland shark fishery. Some of the larger vessels with steam engine, had their own factory for producing fish oil on board. In the 1930`s the catches were reduced year by year, and in 1940 only two specialized shark vessels participated in this fishery off the coast of Greenland.
After the Second World War the high price of the fish oil gave new life to the Greenland shark fishery. The vessels operated in a huge area from the coast of Norway, areas near Shetland and The Faro Island, off the coast of Iceland, in the Denmark Strait, and in the Barents Sea. Different types of vessels participated, and they all used bottom lines. This fishery reached it peak in 1948.
In 1949 there was a dramatic drop in the price for fish oil, naturally followed by a drop in the number of vessels taking part in this fishery. In the following years only a few vessels were fishing Greenland shark along the Norwegian coast, doing this in between other fisheries.
The bait used for the bottom lines was often a combination of several types of fish, flesh and blubber. Blubber from seal and whales were common baits, and so was flesh from the Greenland shark (yes, this shark is a cannibal).
In the 1970`s a couple of vessels were hired by the Norwegian Directorate of Fishery. Their mission was to catch as much Greenland shark as possible in some limited areas. This was done after several reports from fishermen who had experienced that Greenland shark ate the fish hanging on regular long lines.
History had shown that it would not take much effort to reduce the population of Greenland sharks in a certain area, and this proved once again to be true. The shark liver was still taken, but that alone could not pay the fishermen’s expenses. The local fishermen were satisfied, but this was the last time there was a specialized fishery for Greenland shark in Norway. Some anglers occasionally fish for this shark in deep Norwegian fjords, but that is just for the battle these large sharks can give an angler.
Text: Tom Spears / MWN
