Subject: Beluga:St Lawrence beluga population: index of present size (fwd)

Mike Williamson (
Mon, 2 Feb 1998 15:10:17 -0500 (EST)


---------- Forwarded message ----------
Date: Mon, 2 Feb 1998 09:59:20 -0500
From: "Kingsley, Michael" <>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: St Lawrence beluga population: index of present size

Population index estimate for the belugas of the St Lawrence

                As of December 1997, the current estimate of the
population index for the St. Lawrence belugas is 700, with a standard
error of 46 and a 90% confidence interval of 606 to 829.  This estimate
is based on a straight-line smoothing of the most recent five surveys.
It should be considered temporary and to be revised when the next survey
is carried out.
                The latest survey was carried out on 26 August 1997,
using the same methods as in 1992 and 1995.  Two aircraft overflew the
St. Lawrence estuary at an altitude of 4000 feet on a pattern of 49
transects at a spacing of 2 nautical miles.  They photographed
continuous strips that were 6000 feet wide, giving a sampling rate of
nearly 50%.  At the same time, a third aircraft carried out a visual
survey of the Saguenay fjord.
                832 photographic frames were taken on colour positive
aerial survey film.  There were beluga images on 88 of them.  356 images
were counted, of which 72 were deemed to be repetitions of images that
also occurred on the preceding frame, leaving a net count of 284.  This
count was multiplied by 2.025 to account for the sampling rate, and
again by 1.15 as a partial correction for animals presumed out  of sight
under water.  The  resulting index estimate for the estuary was 661, and
20 more belugas were counted in the Saguenay for a total index of 681.
                 The result of the previous survey, flown in 1995, was
705, and the corresponding 1995 value of the smoothed index was 653.

Michael C.S. Kingsley