Marine mammals are an excellent medium through which to study top-down ecology. By researching the distribution and abundance of cetaceans (whales and dolphins) you can also form the basis for management of their prey and the whole ecosystem below them. In a largely unknown area such as the southern Red Sea, where anecdotal evidence suggests there are strong cetacean populations, surveys such as those carried out by the Hurghada Environmental Protection and Conservation Association (HEPCA) provide invaluable information to help guide management and protection.
The HEPCA vessel Red Sea Defender recently made a three-week scientific exploration from Marsa Alam down to a point 50km north of the Sudanese border. The main aim of the trip was to collect data on the species of cetacean present and their approximate numbers. This was achieved using line-transects, which involve sailing on set routes through an area with three observers on watch at all times. Whenever cetaceans were sighted photographs were taken to identify the species and even the individual animals. Seabirds, turtles, fish and sharks were also noted to give an overall impression of the megafauna in the area.
Field research is all about establishing what is really going on in the world and often our findings genuinely surprise us. On previous surveys north of Shalatin HEPCA had logged many sightings of spinner dolphins (Stenella longirostris), pan-tropical spotted dolphins (Stenella attenuata) and bottlenose dolphins (Tursiops truncatus) and the same was expected to the south. To our amazement, as soon as we entered this new area we began seeing many groups of Risso’s dolphin (Grampus griseus); large, black cetaceans with bulbous foreheads and tall dorsal fins.
Almost every day spent on transect we saw at least two groups of these impressive animals, often swimming in to ride the sub-surface bow-wave of the boat. Although they are born black, Risso’s accumulate extensive white scarring throughout their lives from their social interactions and this can used to indentify individuals within a sighting. However, their patterns of scarring are added to by the day, so it is limited as a tool to identify an individual over multiple sightings. Instead we use the nicks and notches on the dorsal fin, which still change over time, but are easier to track as identifying features.
Although a great deal of analysis has to be done before the findings from this survey can be used to guide management and conservation, if there is indeed distinct areas down the west coast of the Red Sea that favor different species of cetacean then that is highly important information. It implies that environmental conditions and the resulting ecosystems are markedly different and further investigation is required to understand how best to manage the varying habitats.
As a cetacean biologist it was fascinating to observe the contrast in the Red Sea, not just in terms of cetacean distribution, but as an entire biosphere. It is an area so rich in biodiversity and life, and yet so fragile and so desperately in need of protection. The research that HEPCA carries out on the cetaceans of the Red Sea establishes the status of these air-breathing mammals by observing them at the surface, but it also provides us with so much knowledge about what is going on beneath and helps protect it for the future.
Ian Paynter (HEPCA intern)