Date: Tue, 21 Jan, 1997
The Condition of St Lawrence Belugas is Improving
A Canadian Department of Fisheries and Oceans release

QUIBEC - The condition of the St Lawrence beluga population is improving, according to the latest data published by Fisheries and Oceans Canada. The results of an aerial survey carried out in 1995 show that the population index estimate for belugas of the St Lawrence and the Saguenay is 705, compared with 525 in 1992, which confirms that the population is not decreasing.

Moreover, Fisheries and Oceans Canada scientists are now considering the possibility that the St Lawrence beluga population could be increasing: other information on the dynamics of the population, such as the high age at death of adults, the apparently normal birth rate, and the rarity of juvenile mortalities, are encouraging.

The 1995 survey, carried out under the programme -St Lawrence Vision 2000-, is the latest in a 15-year series of aerial surveys by which Fisheries and Oceans Canada has monitored the numbers and trend of the St Lawrence population of belugas. The next survey will be carried out in the summer of 1997.

For the 1995 survey, two aircraft equipped with mapping cameras flew at 4000 feet over the estuary between Nle aux Coudres and Nle du Bic, taking continuous bands of photography which covered 50% of the area. While these aircraft were shooting their 1092 frames, a visual observer surveyed the length of the Saguenay Fjord aboard another aircraft.

The report -Population Index Estimate for the Belugas of the St Lawrence in 1995- is available at Fisheries and Oceans Canada's Communications Branch in Quebec City (418-648-7747) and Mont-Joli (418-775-0526).

The abstract of the Technical Report on the survey is as follows:

Kingsley, M.C.S. 1996. Population index estimate for the belugas of the St Lawrence in 1995. Can. Tech. Rep. Fish. Aquat. Sci. 2117. vi + 38 p.

On 25 August 1995 a survey flight was carried out to estimate a population index for the St Lawrence population of belugas (Delphinapterus leucas). Two aircraft, each equipped with a metric mapping camera shooting 9" x 9" frames through a 6" lens, flew at 4000 feet over a systematic grid of transects, aligned from northwest to southeast, that stretched from Nle aux Coudres to Nle du Bic. The transects were spaced 2 nautical miles apart, giving a 50% coverage of the estuary. One thousand and ninety-two frames were shot on colour positive aerial survey film. At the same time, another aircraft surveyed the length of the Saguenay Fjord with a single visual observer.

The wind was light over the whole survey area and the sky was clear, so good- quality photography was obtained. The film was analysed on a light table using low-power microscopy. A total of 377 belugas were counted on 86 frames. Ninety-three were judged to be duplicates of belugas also seen on the adjacent frame, so the net count was 284. Fifty of 197 (25%) appeared from their small size to be juveniles. The resulting estimate of visible belugas was 568 (sampling S.E. 94.0). A 15% visibility correction gave an estimated index for the St Lawrence of 653.2 (S.E. 108.1). The counts were not corrected for sun glare reflected from the water surface and appearing on the photo frames. On the simultaneous visual survey of the Saguenay Fjord, 51 more belugas were seen at baie Ste-Marguerite and one further upstream; these counts were not corrected for visibility. The final total estimated population index, including the Saguenay, was 705.2.

This index estimate is 34% bigger than the value of 525 obtained on a windier day in 1992 using the same methods, and a 16% increase over the 1990 estimate.

Copies of the Technical Report are available.

M.C.S. Kingsley m_kingsley@qc.dfo.ca



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