by Dr. Stephanie Plön
(Dr. Plön, a marine mammal scientist with the South African Institute for Aquatic Biodiversity (SAIAB) in Grahamstown, who is based at the PE Museum, recently gave a talk on her research on whales and dolphins of Algoa Bay.)
Industrial developments in the bay in the last few years, such as Coega harbour, as well as a heightened interest by the tourism industry have prompted Marine and Coastal Management (MCM) to fund a three year study investigating the distribution of these animals. To date there has never been a survey of whales and dolphins (collectively known as cetaceans) in the bay and the last dedicated study on dolphins in Algoa Bay was completed in 1994, indicating a dire lack of data.
Since June 2008 27 survey trips have been conducted by Stephanie and her team and 90 sightings (often of multiple animals) have been recorded of the following seven species: Humpback Dolphin (Sousa chinensis), Bottlenose Dolphin (Tursiops aduncus), Humpback Whale (Megaptera novaengliae), Southern Right Whale (Eubalaena australis), Minke Whale (Balaenoptera acutorostrata), Bryde's Whale (Balenoptera edeni), and common dolphin (Delphinus delphis). Any additional species are expected to be temporary visitors to the bay, such as the killer whale (Orcinus orca).
The survey design used is a random search effort, which is conducted at a speed of 6 knots until animals are encountered. Once animals are seen data on the species, number of animals, behavioural state, GPS location, sea surface temperature and bottom depth are collected. Photographs for identification of individuals are also taken where possible.
The last eight months of surveys have indicated that there are areas in Algoa Bay that appear to be preferred by certain species. For example, Brydes’ whales (Balaenoptera edeni) and humpback dolphins (Sousa chinensis) always appear to be encountered in the same general area. In addition, seasonal changes have also been observed, markedly the arrival and departure of the migrating whales such as the Southern Right Whale (Eubalaena australis) and the Humpback Whale (Megaptera novaeangliae). However, a full year of surveys needs to be completed to analyse seasonal changes in depth. In addition, it is planned to analyse the distribution data in relation to physical parameters, such as bottom topography, bottom depth, sea surface temperature etc.
Stephanie invites the participation of interested PEDSAC members. Small A5 datasheets will be available for members to fill in on their fishing trips and there will be a box on the notice board to hand in completed forms.
For more information please contact Stephanie on 076-3791067.