Aerial Survey of the Namibian coast

by Ruth Leeney:
from:

The aim of this mission was to fly the entire Namibian coastline over two days, in order to provide a snapshot of the whales, dolphins and other large marine species using Namibia’s coastal waters. We flew along a line parallel to the coast, approximately 150-200 m from the surf zone. On the first day, the sea conditions were reasonably calm and the mist had cleared as we flew towards the town of Walvis Bay and turned northwards. We covered the entire coastline from Walvis Bay to the Kunene River mouth, stopping at Palmweg to refuel. By the end of the day we had recorded 64 sightings of Heaviside’s dolphins, one ocean sunfish and one bottlenose dolphin.

The following day, we set out to cover the southern part of the coast. As we flew over the salt pans and the Walvis Bay lagoon, flamingos flying far below us, the sea ahead was calm and turquoise. This section of the coast was covered in a previous survey, also supported by the Bataleurs, flown in November 2010, where we gained the first insight into the large numbers of Heaviside’s dolphins found south of Walvis Bay. We again sighted an abundance of these small dolphins, found only in the Benguela ecosystem, during our recent survey, with an apparent hotspot just south of Sandwich Harbour. The waters south of Lüderitz proved surprising, not for any of the focal species such as dolphins but for another ocean giant – Mola mola, the ocean sunfish. This is the heaviest bony fish in the sea (sharks can weigh more, but they are cartilaginous fish), with the heaviest individual on record as weighing 2235 kg! Their Latin name ‘mola’ means millstone, and refers to their round shape. In total we sighted 25 sunfish, and no doubt there were many more further offshore. Along the southern section of coast we had 69 sighting events; as well as the sunfish we saw 88 Heaviside’s dolphins and one bottlenose dolphin.

The data collected provide a unique and novel picture of nearshore marine vertebrate distribution, and especially provide insight into the way in which Heaviside’s dolphins use almost the entire Namibian coastline. A more complete picture of Namibia’s coastal marine life allows managers and conservators to better predict the effects of human activities on our unique and vulnerable marine life. The results of these aerial surveys, along with ongoing research by the NDP in the Namibian Islands Marine Protected Areas, thus forms the first step towards a more comprehensive picture of the key marine species present and important areas for them in Namibian waters.

Many thanks to our pilot Nico Louw, volunteer observers Naude Dreyer and Francois du Toit, and photographer Karl Terblanche. These surveys were supported by the Bataleurs (www.bataleurs.co.za) and the Rufford Small Grants Foundation.