Gulf of St. Lawrence Krill Decline 70 Percent in 10 Years

By André Noël

MONTREAL, Quebec, Canada, June 8, 2004 (ENS) - Krill populations, the basis of the marine food chain, are in free fall in the Estuary and Gulf of St. Lawrence, according to new research by scientists with the Maurice Lamontagne Institute, a marine science center associated with the federal agency Fisheries and Oceans Canada.

A probable cause, the scientists say, is global warming, and the risk is a reduction in the number of whales and fishes in these waters. Since 2000, half the usual number of humpback, fin, sei and blue whales come to feed on krill each summer in front of Tadoussac, a town on the Saguenay Fjord that has become famous for its whale watching opportunities.

"The biomass of macrozooplankton [the krill] in these two areas [the Gulf and the Estuary] has dropped from 32 metric tons per square kilometer (km²) in 1994 to 10 tons per km² in 2003, which represents a reduction of 70 percent in 10 years," researchers Michel Harvey and Michel Starr write, in a recent publication of the Maurice Lamontagne Institute.

"The phenomenon is worrying, said Harvey in an interview.

Canada's Saguenay–St. Lawrence Marine Park is located nearly 600 miles from the Atlantic coast, at the confluence of two major water bodies - the St. Lawrence Estuary and the Saguenay Fjord, one of the longest fjords in the world.

Whale watchers enjoy the presence of a whale in Saguenay Fjord. (Photo by Nelson Boisvert courtesy NOAA)

Scientists do not know what consequences will result from the drop in krill levels. Some researchers already have noted changes in the dispersion and the concentration of whales.

"There remains much that is unknown," said Harvey. "Reduction in the krill is perhaps due to warming of the climate. If the air is heated, the Arctic ice melts and cooler water enters the Gulf and Estuary."

The word krill is of Norwegian origin and means "food of whale." A blue whale, the largest whale species, eats from two to four tons of krill per day.

The krill is a tiny shellfish, resembling a small shrimp, which feeds on vegetable plankton. It lives in cold water, but water that is too cold can harm its food supply or interfere with its reproduction.

The Gulf and Estuary of the St. Lawrence are characterized by three layers of water. On the surface, the water is relatively warm. In the intermediate layer, the depth of which varies from 25 to 150 meters (80 to 490 feet), temperatures fluctuate between one and two degrees Celsius. The deep layer is warmer.

Since 1948, researchers have identified three warm periods and three cold periods that the krill have survived. One particularly cold period since 1987 had temperatures lower than those measured during the previous 40 years.

The town of Tadoussac has been a destination for whale watchers. (Photo courtesy Environment Quebec)

The fall in krill levels was also measured along the coast of Nova Scotia and the east coast of Newfoundland after examination of the stomach contents of capelin, a species of fish. That suggests that the decline in krill is not a phenomenon unique to the St. Lawrence, the scientists said.

When the proportion of krill decreases, one finds an invasion of another order of crustaceans known as amphipods. While krill eat phytoplankton, amphipods are carnivorous. They eat fish larvae, as well as copepoda, another group of small crustaceans, which are an important source of protein for fish larvae and other marine life.

The invasion of the amphipods, to the detriment of the krill, may risk accelerating the decline of fish stocks, but, says Harvey, scientists do not know for sure.

Scientists in the Group of Research on Marine Mammals (GREMM) have noticed changes in the composition of herds of whales passing by Tadoussac and wonder whether these changes are related to the reduction in krill.

Each summer, from 30 to 40 whales follow benches of krill in the Laurentian Channel, a cold water current which starts along the coast of Newfoundland and ends in Saguenay Fjord.

But last summer, the researchers identified only 15 whales.

Whale in the Gulf of St. Lawrence (Photo courtesy Mingan Island Cetacean Study)

On the other hand, other species have made their appearance, said GREMM's Robert Michaud. Pods of toothed whales which feed on fish and not on krill, were seen twice last year.

Six humpback whales were also identified. These give very good shows for the tourists - displaying their tails and leaping out of the water.

Scientists say the number of blue whales going up the Laurentian Channel does not seem to have changed. They also offer a good spectacle as they weigh about 100 tons, larger than any land animal.

A tourist, Mr. Michaud, is not concerned about Tadoussac's tourist industry. Still, he wonders whether we are not already seeing the effects of climate change on marine life.

"Who knows if, in the future, the blue whales will not be affected by the fall of krill," he says. "They are already a vanishing species."

One cannot avoid anxiety in the face of the unforeseeable effects of climatic upheavals.