Report on Gamba Area collaborative marine surveys July 2015


Minton, G.



Place Published

Gamba, Gabon




Sousa teuszii, humpback dolphin, Humpback whale, Megaptera novaeangliae, tursiops, bottlenose dolphin, photo identification, distribution, relative abundance, platforms of opportunity, Hydrocarbons, Gabon, Gulf of Guinea, Mitigation, fishing gear


Following the successful survey season from July 2013-June 2014, a request was made by the Smithsonian Institution to Shell Gabon to continue monthly marine surveys on board the SMIT operated vessel “Cachimba”. These surveys were to take place in collaboration with WWF, the Gamba fisheries brigade, and the National Parks Agency, with WWF playing a coordinating role. A number of logistical issues, SBM repairs and a prolonged nation-wide fuel strike prevented the vessel from being available for marine surveys from August 2014 through January 2015. As such, only five surveys were conducted in the period covered by the latest agreement between Shell and Smithsonian. Surveys conducted in February, March, April, June and July 2015 followed the same transects as in 2013/14, and comprised 39 hours and 886 kms spent on the vessel. Fisheries observations were limited, and were similar to those made in 2013/14 again, revealing a higher density of artisanal fishing effort in and around the Nyanga rivermouth and occasional observations of industrial trawlers further offshore. The persistent setting of nets in and just outside the Nyanga rivermouth, despite this being prohibited in the fisheries code, presents a risk both to the sustainability of fishing and to navigation, and requires more stringent surveillance and enforcement. The most frequently observed marine mammal species observed in 2015 was the bottlenose dolphin sightings made during each survey with the exception of June. The lack of Atlantic humpback dolphin sightings is of concern, as the species, known to occur in shallow waters close to shore, is at risk in other parts of its range. The survey on July 3rd yielded the first humpback whale sightings of the season, consistent with their seasonal migrations in Gabon. Analysis of data collected over the entire survey period from 2013-15 allowed for mapping of bottlenose dolphin distribution in the area offshore from Gamba. Results show that the species uses the entire area covered by surveys, including both inshore and offshore waters. Photographs of bottlenose dolphin dorsal fins were entered into a photo-identification catalogue, allowing the recognition of specific individuals that were re-sighted between surveys. This analysis shows that the waters offshore from Gamba host a resident population of bottlenose dolphins that range at least as far as the area from the Nyanga Rivermouth to the Sette Cama rivermouth, and move between 500m and 12kms offshore. Bottlenose dolphins were observed with small calves, and were also observed feeding, indicating that the area where Shell conducts its operations constitutes an area of biological importance for this resident population, and that all environmental impact assessments for activities planned in the nearshore/offshore area should take this species into account.