Shark survey results surprise and reassure

By Tina Comeau

SOU’WESTER

The results of the first ever shark survey conducted in Canadian waters last spring has brought forth both surprises and reassurances when it comes to the health, stock and recovery of the porbeagle shark.

Steven Campana, a scientist with the Canadian Shark Research Laboratory at the Bedford Institute of Oceanography, says one of the surprises resulted from the number of sharks caught and released.

“I think the number was 865 that were caught in this survey and that was somewhat larger than they were expecting,” he says.

The reassurances resulted from the information that was gathered. As their population model had predicted, the survey found more middle-size porbeagles and slightly fewer of the very young and very old.

“I think it’s reassured the shark fishing community, to a certain extent, that they’re not doing immediate harm to the population with their small directed fishing quota,” Campana says. “At the same time I think it’s provided some reassurances to DFO managers that the directed fishing is not doing immediate damage to the population.”

Certainly, Campana says, if they had seen a big decline in catch rates it would have sounded an alarm bell and would have, he suspects, led to some fairly serious changes in fishing management.

“But we didn’t see that and therefore, for the time being anyway, it looks like we’re on the road to recovery,” he says.

The objective of the survey carried out last June – which was jointly funded by DFO and the Atlantic Shark Association – was to provide a basis for monitoring the health, abundance and future recovery of shark species found off Atlantic Canada, particularly the porbeagle shark.

The government and the fishing industry are both intent in allowing this population to grow in size and recover. Porbeagle sharks, which have been commercially fished for years, saw their stocks depleted due to over-fishing in the 1960s.

The survey was conducted in a 200,000-square-kilometre area that covered waters from Georges Bank up to central Newfoundland, and also included the Gulf of St. Lawrence and the Gulf of Maine.

“The big question was to see how the survey catch rates would compare with commercial catch rates in the same areas in recent years,” Campana explains. “The bottom line is they’re very comparable.”

And aside from the one already referred to, there were other surprises in the survey.

“For instance some of the key areas that we expected to catch large numbers of porbeagle we did, but there were also a few areas that are not traditionally fished where we were catching porbeagles, in particular large females,” Campana says.

One of these areas was near Georges Bank, where enough shark were caught to lead scientists to think that this is a mating area.

The biggest shark caught in the survey weighed 120 kilograms (265 pounds) and was just over 2.4 metres (eight feet) in length.

During the survey satellite tags were placed on many of the mature females that were caught and released.

“We’re definitely starting to see some very interesting behavior there,” Campana says. “A couple of these sharks have left the continental shelf and swum out towards to centre of the Atlantic, which surprised us.”

This survey will be followed up by another one in a couple of years. Campana says the follow-up survey will give researchers an even better perspective on the health, status and recovery of the stock.