Final research surveys of 2022 shed light on the status of transboundary small pelagic stocks in Africa

16/12/2022

Capacity building and exchanging knowledge is an important part of surveys on the Dr Fridtjof Nansen. Here are scientists discussing the sampling procedures in the fish lab. © IMR

16 December 2022, Las Palmas, Tenerife – The EAF-Nansen Programme has successfully completed two research surveys to study transboundary small pelagic fish stocks off the west coast of Africa. Small pelagic fish are one of the most important resources in the area, providing food and job security for thousands of people.

From July to December the research vessel (R/V) Dr Fridtjof Nansen was at sea for 118 days, bringing together a total of 80 scientists and technicians from 16 countries, including local scientists from Namibia, Angola, Senegal, The Gambia, Mauritania, Morocco, Liberia and Côte d'Ivoire, to gather data and information that will be used to assess these stocks and provide scientific advice on how to sustainably manage them.

“Understanding these transboundary species that move across national borders, is a challenging task” said Merete Tandstad, EAF-Nansen Programme Coordinator, and explained that the data from the Programme research surveys have been the backbone of regional fisheries assessments for years.

With the aim to increase the regional coverage of pelagic resources, the R/V Dr Fridtjof Nansen first made its way to waters off the coast of Namibia and Angola, covering an important part of the Benguela Current Large Marine Ecosystem (BCLME) that is an important upwelling area that is rich in resources.

“The Benguela current ecosystem is one of the most productive ocean areas in the world due to its distinctive features characterized by the upwelling of cold, nutrient-rich water” said Maik Tiedemann, researcher at the Norwegian Institute of Marine Research (IMR), and one of the cruise leaders. “Coming from the deep, the water contains high amounts of nutrients boosting phytoplankton growth at the surface that sustains the Benguela ecosystem food web”, he explained.

Next, the vessel covered small pelagic resources off the coast of Northwest Africa. This survey is a continuation in a series of surveys in this region, dating back to 1996, providing local authorities with vital information on the pelagic fish resources. In this area, the Canary Current Large Marine Ecosystem (CCLME), which stretches from the Atlantic coast of Morocco southwards to the Bijagos Archipelago of Guinea Bissau and westwards to the Canary Islands (Spain), is an extremely important ecosystem in terms of productivity and has the highest fisheries production of any African large marine ecosystem (LME) with annual catches ranging between 2 to 3 million tonnes.

During these surveys that aim to assess the status of the stocks of commercially important small pelagic fish species in both LMEs, specific species are targeted. However, in both areas, different species of horse mackerels, sardines and sardinellas, as well as the European anchovy, are all important for peoples’ livelihoods and food security, economies, and marine life. For this reason, the participating scientists worked hard to collect high quality data needed for the biomass estimation indices of these species.

“We assess the target species through acoustic sampling, to obtain information on the distribution and size of the stocks” said Kathrine Michalsen, senior researcher from IMR and the cruise leader of the survey in Angolan waters. “Trawls are used to collect samples from which we gather biological data like length, weight, sex and maturity,” she added.

Improving the understanding of fishery resources and the environment

Plastic pollution is a major challenge for the sustainability of marine resources, and microplastics are widely found around the globe. Here, scientists from Senegal and The Gambia collect samples from a Manta trawl to study the presence of microplastics. © IMR

While fishery resources were a key priority, other aspects were also addressed to improve knowledge on the composition and diversity of pelagic stocks and habitats, and to improve the understanding of the environment within which they are found, including the presence of marine debris.

Along the southern coast of Angola, extensive sampling took place using various plankton nets. As the survey took place in the middle of the upwelling period, the nets caught a lot of plankton, fish larvae and eggs.

“In total, around 13 000 fish larvae were sorted and identified to the lowest possible taxonomic level, and we were proud to be able to deliver the first ichthyoplankton data to Angola,” said Stamatina Isari, senior scientist at IMR in the field of zooplankton and ichthyoplankton taxonomy from Greece, serving as the plankton team leader during the survey.

Another important aspect of the research expeditions is training and providing experience in marine research techniques to local scientists. During one of the survey legs, six PhD students from Morocco and Senegal presented their studies on topics ranging from phyto- and zooplankton to invasive crabs, as well as monitoring of pollution and predicting landslides, to studies of climate change over past decades and centuries.

“The presentations provided an excellent opportunity to receive valuable feedback on our projects, and to practice our presentation skills, which is an important element to being a successful scientist” said Fatou Tabane from the Ecotoxicology and Environmental Safety Research Centre in Dakar, Senegal. The cruise leader at the time, Dave Boyer, added: “And the scientists aboard the vessel were able to learn about new subjects, even those who have been involved in international research for decades were introduced to real world problems that these young Africans are determined to solve.”

Collected data will be presented in a survey report and used for scientific reports and papers, as part of the EAF-Nansen Programme Science Plan. Findings will also contribute to the Benguela Current Convention (BCC) that is an initiative through which Angola, Namibia, and South Africa address challenges of the BCLME and strengthen fisheries management, as well as the FAO and the Fishery Committee for the Easter Central Atlantic (CECAF) that provides scientific advice on the management of small pelagic stocks.

Read about the additional three surveys that took place in 2022: