Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Migrations of humpback whales past Cape Vidal, South Africa, and an estimate of the population increase rate (1988–2002)

Migrations of humpback whales past Cape Vidal, South Africa, and an estimate of the population... Shore-based surveys of migrating humpback whales Megaptera novaeangliae were undertaken from Cape Vidal, northern KwaZulu-Natal, South Africa, each year between 1988 and 1991, and in 2002. Daily observations of migrating whale groups were carried out from an approx. 60 m-high platform during all surveys. Whale groups were tracked by position-fixing on surfacing bouts using survey theodolites, to determine swimming speeds and headings and distance offshore, while group size estimation was carried out at each theodolite measurement. Numbers of whales observed or projected (at tracked speeds) to cross the midline of the survey area within the observation period each day were tallied in each of three distance bins. These counts were adjusted to account for daily sighting effort and for proportions that were likely to have been missed on account of their distance offshore or poor sighting conditions to produce daily sighting rates. Such daily tallies were summed over the survey period to estimate the number of whales passing Cape Vidal each year, with counts from days of <2.5 h of observation effort (due to weather or sighting condition restraints) replaced by the mean of the previous and following days. The numbers passing to the north of Cape Vidal during coincident periods of 17 days over the 1988–2002 surveys (6–22 July) and 25 days over the 1990, 1991 and 2002 surveys (6–30 July) provide statistically significant increase rates of 11.5% (SE 2.8) and 9.0% (SE 2.7) per annum respectively. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png African Journal of Marine Science Taylor & Francis

Migrations of humpback whales past Cape Vidal, South Africa, and an estimate of the population increase rate (1988–2002)

Findlay, KP; Best, PB; Meÿer, MA
African Journal of Marine Science , Volume 33 (3): 18 – Nov 1, 2011
Download PDF

Migrations of humpback whales past Cape Vidal, South Africa, and an estimate of the population increase rate (1988–2002)

Abstract

Shore-based surveys of migrating humpback whales Megaptera novaeangliae were undertaken from Cape Vidal, northern KwaZulu-Natal, South Africa, each year between 1988 and 1991, and in 2002. Daily observations of migrating whale groups were carried out from an approx. 60 m-high platform during all surveys. Whale groups were tracked by position-fixing on surfacing bouts using survey theodolites, to determine swimming speeds and headings and distance offshore, while group size estimation was...
Loading next page...
 
/lp/taylor-francis/migrations-of-humpback-whales-past-cape-vidal-south-africa-and-an-R0pWYs00Cj
Publisher
Taylor & Francis
Copyright
Copyright Taylor & Francis Group, LLC
ISSN
1814-2338
eISSN
1814-232X
DOI
10.2989/1814232X.2011.637345
Publisher site
See Article on Publisher Site

Abstract

Shore-based surveys of migrating humpback whales Megaptera novaeangliae were undertaken from Cape Vidal, northern KwaZulu-Natal, South Africa, each year between 1988 and 1991, and in 2002. Daily observations of migrating whale groups were carried out from an approx. 60 m-high platform during all surveys. Whale groups were tracked by position-fixing on surfacing bouts using survey theodolites, to determine swimming speeds and headings and distance offshore, while group size estimation was carried out at each theodolite measurement. Numbers of whales observed or projected (at tracked speeds) to cross the midline of the survey area within the observation period each day were tallied in each of three distance bins. These counts were adjusted to account for daily sighting effort and for proportions that were likely to have been missed on account of their distance offshore or poor sighting conditions to produce daily sighting rates. Such daily tallies were summed over the survey period to estimate the number of whales passing Cape Vidal each year, with counts from days of <2.5 h of observation effort (due to weather or sighting condition restraints) replaced by the mean of the previous and following days. The numbers passing to the north of Cape Vidal during coincident periods of 17 days over the 1988–2002 surveys (6–22 July) and 25 days over the 1990, 1991 and 2002 surveys (6–30 July) provide statistically significant increase rates of 11.5% (SE 2.8) and 9.0% (SE 2.7) per annum respectively.

Journal

African Journal of Marine Science – Taylor & Francis

Published: Nov 1, 2011

Keywords: Megaptera novaeangliae; migration; shore-based monitoring; western Indian Ocean

There are no references for this article.