Optælling af narhvaler i Qaanaaq Kommune, august 2001. Technical Report No. 50

Four aerial surveys of narwhals were conducted in Inglefield Bay, Qaanaaq, in August 2001. The surveys utilized a digital
photographic technique where images were
obtained from two digital cameras that
stored the image-files on two laptop computers. A scheduled survey of narwhals in the
Melville Bay was cancelled due to inclement
weather conditions that delayed the surveys
by two weeks. A total of approx. 12,000 images were obtained during the four surveys.
Almost all the whales were located in the
eastern stratum of Inglefield Bay. In this
area most whales were either found in Academy Bay or in the northeastern corner. As
expected the distribution of whales was
highly clumped but the observations of
most whales in the eastern part of the bay
indicates that no major exodus from the bay
had occurred prior to the survey. The average
group size was 1,76 narwhals per group
(SD = 2.12). Of 139 whales that could be
classified to age groups 103 were adults, 15
immature and 22 were calves from the same
year. Thus the percentage of calves was 16%
(22/139). Of the 103 adults 31 had tusks.

Two observers examined all images and a
third determined the images with ‘questionable observations’. There was reasonably
good agreement between the observers and
about 90% of the images had ‘unquestionable whales’ and it was therefore decided
to use the information from one of the observers after the third observer decided upon
the questionable observations.
Each survey covered between 174 and 244
km2 of the total area that was estimated at
2,516 km2
. Thus a total of 853 km2 or 34%
of the total area was covered. A total of 361
narwhals were observed on 24 of the 65
transects that was covered. The number of
narwhals at the surface was calculated as
an average of all the counts. The number of narwhals at the surface was 1,549 (95% confidence interval: 683 - 2,415). 

To correct for the fraction of whales that
were submerged it was tested to which
depths submerged silhouettes of narwhals
could be seen on aerial photos. One large
and three mid-size whales could easily be
detected down-to depths of 3 m, whereas 3
small whales could only be detected at 1 m
depth. None of the whales could be seen at
depths exceeding 3 m. This implies that the
detection depth is probably less than 3 m
and if small whales should be included a
detection depth of 2 m is probably more
reliable. Information on the time spent at
the surface or down-to 2 m depth was obtained from two studies in northern Canada and from the Melville Bay and a preliminary figure from these studies was 38% of
the time between the surface and a depth of
2 m. If this number is used to correct for
whales submerged below 2 m depth (SD =
0.09) a total of 4,076 (95%CI: 938 - 7,215) in
Inglefield Bay in August 2001 is obtained.

The surveys can be compared to a survey in
1985 and 1986 that was not corrected for
submerged whales. The number of whales
at the surface was lower in 2001 than in
1986 but not compared to 1985. There are
however reasons to believe that both the
surveys in 1985 and 1986 are underestimates. It is recommended to conduct another
survey in Inglefield Bay before it can be
concluded if the trend reflects annual variations in the number of narwhals that utilizies Inglefield Bay or if there is an actual
decline in abundance.