Namib-Skeleton Coast National ParkJuly 13, 2012
!Nara – A desert melon woven into cultureJuly 13, 2012
By Dr Simon Elwen, Mammal Research Institute, University of Pretoria
The ocean off Namibia has been severely affected by overfishing in the last few decades. As a result, marine research has focused mainly on commercially important fish species and those factors thought to impact on them. The cetacean fauna has been largely overlooked.
There are three dolphin species commonly found in Namibian coastal waters, namely Heaviside’s, dusky and bottlenose dolphins. In addition to prey depletion from overfishing, potential threats to the dolphin populations include by-catch in fishing nets, pollution, uncontrolled ecotourism and coastal development changing the nature of their environment. Currently there is very little data available on the ecology of these species. To be able to assess their conservation status, baseline data on the abundance, movements and habitat choice of all the coastal delphinid species of Namibia are urgently needed. Of principal concern is Heaviside’s dolphin, which is endemic to the Benguela Current region.
The Namibian Dolphin Project is a study of the ecology of the three dolphin species and is being run by the author and Ruth Leeney (Provincetown Center for Coastal Studies, USA) who are working closely with the Ministry of Fisheries and Marine Resources (MFMR), Namibian NGOs and the local community, particularly the commercial marine-tour operators. This project is funded by grants from international and local agencies including the Rufford Small Grants Foundation, the British Ecological Society, Namibia Coast Conservation Management (NACOMA) and the Nedbank Go Green fund. The principle study site is in the Walvis Bay region. This is the largest area of human coastal habitation in Namibia, and is thus the area where human threats to the dolphin populations are likely to be the highest. Comparative data is now also being collected in Lüderitz.
The project is aimed at generating an estimate of the abundance of these populations, and investigating the habitat use and behaviour of the dolphins, and the potential human impacts in the environment. Several techniques are being used, including photographically identifying individual dolphins from natural marks and scars, which allows the team to look at individual dolphin movements and interactions and estimate the number of animals using the bay. Simultaneously, moored hydrophones continuously listen for dolphin presence in key areas, which complements the visual observations of habitat use made during daylight hours.
Initial results from the 2008 pilot study have revealed clear differences between the bottlenose and Heaviside’s dolphin populations in Walvis Bay. The bottlenose dolphin population is small (less than 100) and predominantly uses the inshore environment along the open coast and the bay itself, where the animals are regularly seen feeding. The population of Heaviside’s dolphins is much larger (several hundred to a thousand) and mostly aggregate at the tip of the bay or are scattered further from shore. These are only preliminary results and much more work is needed to confirm the abundance estimates and look at how habitat use varies seasonally.
The Namibian Dolphin Project is working closely with the CETN (Coastal Environmental Trust of Namibia), MFMR and NACOMA to reinvigorate the strandings network, to train people who will be able to assist in rescue and to collect data from stranded whales, dolphins and turtles.
This article appeared in the 2009/10 edition of Conservation and the Environment in Namibia.