[MARMAM] New Article: A simple photogrammetric technique to measure sperm whales at sea

nathalie Jaquet jaquetn at gmail.com
Sat Oct 21 06:14:06 PDT 2006


Dear all,

The following has now been published in Marine Mammal Science:

Jaquet, N. (2006). A simple photogrammetric technique to measure sperm
whales at sea. Marine Mammal Science 22 (4): 862-879.

ABSTRACT:
Knowledge of whale length is important to ecological studies. However,
photographic techniques to measure sperm whales traditionally require
high vantage points or a complicated stereo system. Furthermore, these
traditional techniques require an alongside approach that often
prevents individual identification. For simple and fast size
measurements at sea, I used a laser range finder alongside a digital
camera to obtain distance to the fluke at the same time as
photo-identification. The camera/lens and laser range finder were
calibrated on objects of known lengths. The coefficient of variation
(CV) for test objects was low (CV=0.21%). Forty-seven individually
identified sperm whales were measured repetitively on up to 12
different occasions, and the CV was lower (CV=1.3%) than for other
photogrammetric techniques (CV=4.4 to 5.1%). A regression of log fluke
span to log total length from whaling and stranding data yielded an r2
of 0.87 (CV of residuals =6.7%). Thirty-eight female/immature sperm
whales were measured in the Gulf of Mexico (median=9.3m,
range=7.1-12.3m), 167 in the Gulf of California (median=10.7m,
range=8.4-13.1m) and 13 bachelor males off Kaikoura, New Zealand
(median=14,2, range=11.7-15.8m). The results were within known sperm
whale size and suggested that the population in the Gulf of Mexico was
made up of smaller animals than that of the Gulf of California. This
technique is easy to implement and allows the measurements of
identified individuals.

pdf reprints are available upon request at : jaquetn at coastalstudies.org

Nathalie
===================
Nathalie Jaquet, PhD
Senior Scientist
Center for Coastal Studies
5 Holway Street,
Provincetown, MA, 02657

Phone Office: 508 - 487 3623 ext 111
FAX:     508 - 487 4695
Email: jaquetn at coastalstudies.org



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