Robin W. Baird, Sascha K. Hooker, Hal Whitehead, and Roger Etcheberry
Paper SC/49/SM4 presented to the IWC Scientific Committee, September 1997.
Abstract
We review all known published and unpublished records of striped
dolphins (Stenella coeruleoalba) in Canadian waters. Sixty
records (representing 42-43 occurrences) from the Atlantic coast and
13 records (representing 12-13 occurrences) from the Pacific coast
are presented. The 11 records from eastern Canada prior to 1989 include
five strandings (four single and one mass), three sightings, and two
to three kills in fishing operations. Atlantic records since 1989 are
primarily sightings in one area, occurring every summer that substantial
research effort has been expended. This area, termed the Gully, is
a deep-water canyon which bisects the continental slope, and appears to
be part of the regular range of this species. An analysis of sightings in
relation to effort in that area showed that striped dolphins were
concentrated in deep water areas, at times with particularly high sea
surface temperature. On average, group sizes are small (mean = 16)
compared to elsewhere in their range, and associations with other species
of cetaceans appear to occur more frequently in this area (40% of
sightings). Stranding records from eastern Canada have primarily occurred
in late-fall and winter. The presence of two near-term fetuses in animals
which stranded in November suggest that calving in the western North
Atlantic may occur in early-winter. Most records from the Pacific coast
are strandings of single individuals occurring in winter/spring. Considering
the difference between seasonality of strandings (winter) and sightings
(summer) off eastern Canada, and the bias of research towards shallow,
inshore waters, it is unclear whether striped dolphins should be
considered extra-limital off the Pacific coast. Considering their
deep water habits, this species is likely more common in Canadian waters
than records indicate. Only a few records of mortality in fishing
operations exist, and none in recent (since 1988) years.