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Photo ID catalogue - more information

Field and matching techniques

Photographs are taken of the dorsal fin and back of individual dolphins in the field. These photographs are then examined and individual animals are identified by examining the pictures for unique markings. Most common markings include nicks in the dorsal fin, rake marks (tooth rakes) and white patches. For most dolphins marks on the dorsal fin are the most identifying feature.

In the field it is not always possible to know whether both sides of a dolphins dorsal fin has been photographed or whether the two sides (left and right) are from the same dolphin. Often once more photographs are collected it is realised that what was thought as two dolphins from a left and right fin, is in fact the same dolphin and so the images are combined and the dolphin given the same catalogue number.

Images are best collected on 35mm slide format or digitally. Prints restrict some matching techniques such as projecting the image onto a screen in order to trace the outline of the fin, however negatives from prints have been successfully mounted and projected to aid matching.

Factors to remember when interpreting photographs

When interpreting the dolphins presented in this catalogue it should be remembered that dorsal fin nicks probably last for life, except that addition of marks near or over a previous mark can obscure the ability to re-identify them. The permanence of these markings varies greatly.

a. Nicks in the dorsal fin have in some studies been used for identification for 12-18 years.
b. Tooth rakes may disappear within 6 months.
c. White patches often fade within 5-20 months.

This makes recognition of individual dolphins from year to year difficult if there are no permanent markings on the fin.

Scope of images presented

This photo ID catalogue includes individuals identified by the Shannon Dolphin and Wildlife Foundation (SDWF). This is the second issue and includes 108 recognisable dolphins, photographed from May 1993 to October 2002.

This catalogue is a dynamic document and it will be regularly updated. Please make sure that you have the most recent catalogue when matching images.

Further information and associated data

Only the images used to identify individual dolphins are presented here. For data on date, location, associations etc please contact the data holder directly.

Dr Simon Berrow,
Project Manager
Shannon Dolphin and Wildlife Foundation
Merchants Quay
County Clare
Tel: 065 9052326
Mobile: 086 8545450
Email: SDWF@oceanfree.netSend an e-mail to

Compilation of this catalogue was funded by the National Parks and Wildlife Service, November 2002.


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