Rate of growth in Atlantic Canada's grey seal population is slowing, says DFO report

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A herd of grey seals on Hay island off the coast of Nova Scotia. (Paul Darrow/Reuters - image credit)
A herd of grey seals on Hay island off the coast of Nova Scotia. (Paul Darrow/Reuters - image credit)

The grey seal population in Atlantic Canada continues to grow and is now estimated at 366,000, according to the 2021 stock assessment released Thursday by the Department of Fisheries and Oceans.

But DFO says the population is growing at a much slower rate than in previous years and for the first time in 60 years it is believed pup production has decreased on Sable Island.

The huge Sable Island colony produces 80 per cent of Canadian grey seal pups.

"Based on the results of just one survey, it is difficult to interpret the change in the trajectory of pup production on Sable Island. A single low pup production estimate could also be the result of a year with a low birth rate," DFO said in its latest stock assessment.

It also estimated the Scotian Shelf population at 310,700 with the vast majority from the Sable Island colony.

DFO says 76,600 pups were born annually on Sable Island, or 78 per cent of the Scotian Shelf total. In the Gulf of St. Lawrence, pup production was estimated at 16,900.

New modelling method

Scientists used a new model to estimate the population in the latest report. It converted pup production numbers from aerial surveys to total population by combining reproductive and survival rates with the small number harvested by humans.

Applying the new modelling to its 2016 estimate produced a sharply lower result.

Department of Fisheries and Oceans
Department of Fisheries and Oceans

DFO's 2016 assessment said the population was 424,000, but that's been reduced to 339,000.

"This is the second assessment that has resulted in a significant downward revision in the previous estimate of grey seal abundance," DFO said in its report.

It attributes the changes to a slowing increase in pup production and its new method of counting.

Need for more frequent surveys

"The new model provides a significant downward revision in estimated juvenile survival and indicates that the dynamics of the grey seal population are changing relatively rapidly in a manner that is not well understood," the report says.

The population is currently surveyed every five years.

The assessment says more frequent surveys would help scientists better understand what is happening with grey seals.

Aerial reconnaissance surveys flown along the south and east coasts of Newfoundland and the Nova Scotia and New Brunswick coasts did not detect any new breeding colonies.

In the Gulf of St. Lawrence, new, small colonies were detected on the south shore of Anticosti Island and two small islets near the Magdalen Islands.

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