Southern Right Whale population increasing

09/10/2006 14:38 - (SA)

Cape Town - The Southern Right Whale population off the Southern Cape coast is responding "optimally" to protection measures, researcher Pete Best said on Monday.

In a statement announcing the start on Tuesday of the latest of a series of annual aerial surveys of the migrant whales, he said this year's survey would be the 28th. "During this period, 900 individual adult females have been identified, and the birth of some 2 700 calves has been recorded, and estimates of survival rate, age at maturity and calving interval obtained. "It has also been possible to show that the population has been increasing steadily at seven percent a year throughout," he said.

This figure was based not only on direct census results but also on a population model independent of possible changes in the efficiency of the aerial survey. "It has been demonstrated that this rate of increase is the maximum possible biologically, indicating that the population is responding optimally to protection," he said.

Best is attached to the Mammal Research Institute of the University of Pretoria, which will carry out the survey. He said the survey covered a stretch of coast from Nature's Valley near Plettenberg Bay, to Cape Town. Scientists would use the survey to photograph all the cow-calf pairs seen.

"As Southern Right Whales are individually recognisable from the pattern of wart-like callosities on their head, the photographs taken enable scientists to follow the reproductive history and survival of individual whales over many years," he said.

He said that though there was doubt about exactly how many Right Whales there were in the late eighteenth century when exploitation started, the best available evidence suggested that current numbers were about one sixth of their initial level.

He said the whales started to arrive off the Southern Cape coast in mid-winter, and were normally gone by the end of each year.

Some headed to feeding grounds in the South Atlantic between 40 and 55 degrees of latitude, while others went up the West Coast. Best said it was possible some headed for the Indian Ocean.

Image: © CSI-EaGracie
Source: news24.com