Photo-identification of North
Atlantic Killer Whales
Paul R.
Fisher &
Edward G. Brown
Introduction
During 1986
and 1987, a group of scientists from nine nations co-operated in `The
North Atlantic Killer Whale Project' to review information available on
killer whales of their respective regions. This culminated in a collection
of papers on `North Atlantic Killer Whales' which was published in a
special issue of Rit Fiskideildar, Journal of the Marine Research
Institute, Reykjavik, Volume XI, in 1988. Since then, a great deal of
research on the movements and distribution of killer whale Orcinus orca
pods in the North Atlantic has been carried out by dedicated surveys that
have managed to photograph a significant number of killer whale pods. This
has resulted in the formation of `photo-identification' catalogues of
killer whales in Norwegian and Icelandic waters.
As the number of sightings has
increased in Shetland waters during the last few years the Shetland Sea
Mammal Group has decided to co-ordinate a photo-identification programme
of killer whales in Shetland waters to learn more about their movements
and behaviour, and to contribute to a shared photo-identification
catalogue of North Atlantic killer whales. There has been no evidence to
date from comparison of photo-identification catalogues that any
intermixing occurs between Norwegian and Icelandic killer whales (T.
Simila pers comm.), allowing the photo-identification catalogue to be used
for following individual animals throughout the North Atlantic.
The movement and aggregation
of killer whale pods has been found to be associated with the seasonal
movements and spawning of shoaling fish (Christensen 1988). Pods move
inshore to coincide with the peak in spawning herring which migrate along
the Norwegian coast (Simila et al. 1988). Shetland fisherman have reported
aggregations of hundreds of killer whales close to the continental shelf
during summer months. Although killer whales feed primarily on fish
(herring off Norway and Iceland, halibut off Norway, and mackerel off
Faroe and Shetland), they are also known to take a wide range of other
prey species, often using co-operative feeding. These include grey seal,
harbour porpoise, eider, kittiwake, guillemot and puffn (Bloch and Lockyer
1988). Killer whales have also been studied feeding on the discards from
Dutch mackerel freezer trawlers working northeast of Shetland (Couperus
1994). Little is known about offshore killer whales but they are likely to
feed almost exclusively on fish.
Killer Whales in Shetland
Waters
In the last eight years
there have been over 240 recorded sightings of killer whales in Shetland
coastal waters. Almost 65% of these records are from the last three years
which reflect an increase in the numbers of whales visiting our coastal
waters. Killer whales visit Shetland throughout the year, with a seasonal
increase in sightings from May to September. Based on these observations
and surveys of the north east Atlantic and northern North Sea (Evans 1988)
it is likely that a number of killer whale pods are transient, ranging
between Iceland, Faroe, Norway and North East Scotland.
The main areas where killer
whales are regularly seen in Shetland waters are Yell, Bluemull and
Colgrave Sounds, Whalsay, Papa Stour and along the southeast coast from
Lerwick to Sumburgh Head. Pods invariably move north to south, following
the east coast and either continue south into the Fair Isle Channel or
pass round Sumburgh Head and head north again passing Papa Stour.
Preliminary observations of killer whale feeding behaviour suggest that
common seals and grey seals are frequently preyed upon in Shetland coastal
waters close to haul out sites, and seals may also be taken while foraging
offshore.
Photo Identification
Close-up photographs of the
killer whale dorsal fin and the pale saddle patch can be used to identify
individuals within pods. The saddle patch shape is not symmetrical and
therefore only photographs of the left side of killer whales showing the
saddle patch and dorsal fin are used in established photo-identification
catalogues. Black and white film of a high ASA (speed) is usually
preferred, for sharp focus and contrast, although good quality colour
photographs are equally useful as the images can be manipulated digitally
on a computer.
Anyone who has existing
photographs of killer whales in Shetland or who may be able to take
photographs in the future is invited to participate with the
photo-identification programme of killer whales in Shetland waters. The
aims of the programme are as follows:
-
To
initiate a pilot study to collate existing photographs and sightings
information for killer whales
-
To
establish an identification catalogue of killer whales sighted around
Shetland and to compare with other North Atlantic killer whale photo
identification catalogues
-
To
disseminate this information by producing an observers identification
chart of individuals using high quality colour ID photographs/slides of
killer whales
-
To record
and catalogue vocalisations of killer whale pods which visit Shetland
and compare these recordings with other studies
To date we have received
over 70 negatives, slides and prints of killer whales of which 28 images
have been selected and scanned to a digital format to archive, and
observer guides to cetacea and recording forms have been distributed to
inter-island ferries and interested fishing crews. One pelagic fishing
boat has already provided video film of killer whales feeding round their
purse-seine nets. A portable hydrophone and Sony Professional Walkman have
been purchased with a grant from The Shetland Wildlife Fund, to record
vocalisations from individuals and the `dialect' of pods.
Photographs and video film of
killer whale groups are useful to identify individuals and study
associations between individuals within pods. All photographic material
will be returned, and a project update will appear in future issues of the
Shetland Sea Mammal Group Newsletter and Annual Report.
Thanks to Dr Tiu Simila Dr
Dorete Bloch, Dr Peter Evans, Brain Couperus and committee members of the
Shetland Sea Mammal Group for their advice and encouragement, and records
and photographs from various individuals to date. This project is
supported by the Shetland Wildlife Fund, Shetland Enterprise, Shetland
Islands Tourism and the RSPB.
References
-
Bloch, D.
and Lockyer, C. (1988). Killer whales Orcinus orca, in Faroese
waters. Rit Fiskideildar, 11: 55‑64.
-
Christensen, 1. (1988). Distribution, movements and abundance of killer
whales Orcinus orca, in Norwegian coastal waters, 1982‑1987,
based on questionnaire survey. Rit. Fiskideildar, 11: 79‑88.
-
Couperus,
A.S. (1994). Killer whales Orcinus orca, scavenging on discards
of freezer trawlers north east of the Shetland Islands. Aquat. Mamm.,
20: 47‑51.
-
Evans,
P.G.H. (1988). Killer whales Orcinus orca, in British and Irish
waters. Rit. Fiskideildar, 11: 42‑54.
-
Simila,
T., Hoist, J.C. and Christensen, 1. (1988). Occurrence and diet of
killer whales in northern Norway: seasonal patterns and abundance of
Norwegian spring‑spawning herring. C. J. Fish. Aquat. Sci., 53:
769779.
If you can help with
this project please contact
Paul
Fisher or
Ed Brown
with details.
Nature in Shetland
