Aerial line-transect surveys of cetaceans were flown in the Gulf of St. Law
rence in late August and early September of 1995 and in late July and early
August of 1996. Systematic north-south transects were spaced 15' of longit
ude apart. In 1995, the study area comprised the entire Gulf, divided into
three strata for analysis; 69% was flown. In 1996, a single stratum covered
only the north shore shelf; 75% of the design was flown. The survey platfo
rm was a light high-winged aircraft with bubble windows flown at 213 m (700
ft). Ten species were seen. Minke whales (Balaenoptera acutorostrata), Atl
antic white-sided dolphins (Lagenorhynchus acutus), and harbour porpoises (
Phocoena phocoena) yielded enough sightings to support good estimates, whil
e fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangli
ae), white-beaked dolphins (Lagenorhynchus albirostris), and long-finned pi
lot whales (Globicephala melas) yielded few sightings and unreliable estima
tes. Blue whales (Balaenoptera musculus) and belugas (Delphinapterus leucas
) were seen too rarely to support any analysis. The tenth species was a sma
ll delphinid, not positively identified. Minke whales were ubiquitous, but
more common in the northern strata. We estimated about 1000 in the whole Gu
lf in 1995 and about 600 in the northernmost stratum in 1996 (these numbers
, and those following, are uncorrected for visibility bias). We estimated a
bout 12 000 Atlantic white-sided dolphins in the Gulf in 1995, but in 1996
saw hardly any, perhaps because we flew the survey earlier. Harbour porpois
es (12 000 in 1995 and 21 000 in 1996) were most numerous in the northern s
tratum, but were also widely distributed at lower densities in the central
and southern Gulf. White-beaked dolphins (2500 in 1995 and 2500 in 1996) oc
curred only in the Strait of Belie Isle and the extreme northeastern Gulf.
We estimated a few hundred fin whales in the northern and central strata an
d about 100 humpbacks, mostly in the northeast. Long-finned pilot whales we
re only seen in the southeastern Gulf, surveyed only in 1995 (about 1500).