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Study to serve as baseline for long-term research on cetaceans

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Humpback whale (Megaptera novaeangliae) breaching in Algoa Bay (Photo: Dr Stephanie Plön)
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A southern right whale (Eubalaena australis) surfaces against the backdrop of coastal developments at Algoa Bay (Photo: Brigitte Melly)
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Long-beaked common dolphin (Delphinus capensis) in Algoa Bay (Photo: Dr Stephanie Plön)
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Indian Ocean bottlenose dolphin (Tursiops aduncus) with calf (Photo: Dr Stephanie Plön)
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Dolphins in front of the Alexandria Dune Field, Algoa Bay – conservation icons serving as an indicator species for the environment they occupy (Photo: Brigitte Melly)
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Two Indian Ocean bottlenose dolphins (Tursiops aduncus) frolicking in the bay (Photo: Brigitte Melly)
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Dr Stephanie Plön, a Marine Mammal Scientist jointly appointed by SAIAB, SAEON and Bayworld.
- Dr Stephanie Plön, Marine Mammal Scientist: SAIAB, Bayworld and SAEON

 

Whales and dolphins are often considered icons for conservation as they can be used as indicator species for the environment they occupy.

Although the Eastern Cape waters are known for their high diversity in marine mammals, no research on whales and dolphins had been carried out in Algoa Bay since 1998. Thus the start of a three-year project in 2008 to determine the seasonal and geographical distribution of cetaceans in Algoa Bay in itself represented a highlight as until then only anecdotal evidence was available on the distribution of these animals in the bay.

This study is being led by Dr Stephanie Plön, a Marine Mammal Scientist jointly appointed by the South African Institute for Aquatic Biodiversity (SAIAB) and Bayworld, in collaboration with SAEON. In addition, SANParks is also a collaborator in this particular project. The main aims of her research are to determine which species of whales and dolphins are found in the bay, to look at their seasonal distribution, and to determine whether there are certain areas in the bay that are more important to the animals than others.

Encroaching developments in Bay

This is of particular interest in view of the numerous developments that have been and continue to occur in Algoa Bay, such as the new deep-water port of Coega, potential associated increase in shipping traffic, increased recreational and commercial fishing activity, the allocation of a whale watch permit,and the proposed development of an oil refinery and wind farms.

On the other hand the establishment of a large marine protected area (MPA) has been proposed for Algoa Bay. Although this project commences somewhat late as some of these developments are already well underway, it is intended as a baseline upon which future projects can be based. In addition, it will serve as a reference point for long-term research on cetaceans in the bay.

Monthly surveys are carried out along predetermined transects focused on the coastal areas of Algoa Bay, extending from Cape Receife on the west to Woody Cape on the east. On these surveys, data are collected on the following information for all animals sighted: species, GPS position, sea surface temperature, bottom depth, group size, group composition, and behaviour. The latter is often difficult to determine with animals that spend the most part of their lives submerged, but six different, predetermined behavioural categories are used, such as travelling, foraging, resting, playing and mating.

Photographs are also being taken to identify individuals at a later date. A geographic information system (GIS) analysis will determine whether there is a correlation between animal distribution and various environmental parameters and whether certain areas can be considered “hotspots” or not.

The project is now well into its second year and a few preliminary results and trends are visible. By January 2011, 99 boat-based surveys comprising 479 hours of search effort had been conducted since June 2008. A total of 479 sightings were recorded, with the following six species being observed: southern right whale (Eubalaena australis), humpback whale (Megaptera novaengliae), Bryde's whale (Balenoptera edeni), humpback dolphin (Sousa chinensis), bottlenose dolphin (Tursiops aduncus), and common dolphin (Delphinus capensis).

Preliminary analysis of the data indicates that there are definite differences in habitat preference between the different species, as was to be expected. Preferences for certain areas in the bay by the individual species have also been identified, as well as some seasonal patterns.

Nursing area

Probably the most exciting result to date is the observation of numerous cow-calf pairs of both humpback and southern right whales in the bay. This appears to indicate that the bay can be considered again as a nursery area for these animals; potentially also a calving ground.

This is a recent development as prior to 2000 whales were only rarely seen in the bay, possibly due to their low population numbers post whaling. However, as the populations increase the animals appear to “spread out” and use areas where they have not been observed in recent decades. These data combined will aid in the design of protected areas as well as inform decision makers about the potential impacts of future developments in the bay.

The research is being funded by Oceans and Coasts (former Marine and Coastal Management) and SANParks, while SAEON is providing logistical support for the research. The research vessel Honkenii, one of the vessels owned by the SAEON Elwandle Node, has played a vital role in this project and without SAEON’s contribution this project would not have come off the ground.

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