Acadjas in Lake Nokoué, Benin (c) Maxime Eiselin

Involving communities to adopt sustainable fishing methods

Lake Nokoué in Benin is so filled with fishing nets, it is hardly navigable anymore. Whereas the majority of local inhabitants depend on fisheries for their livelihoods, fishing constructions made from mangrove wood actually pose a threat to the fish stocks. Partner organization Benin Education and Environment Society (BEES) uses drone images to involve local fishermen and the authorities to find a solution.

Header photo: Acadjas in Lake Nokoué, Benin © Maxime Eiselin

For over two hundred years, Beninese fishermen have confided in the acadja method to catch fish. They place a structure of mangrove branches in the water to create an artificial habitat for fish. The structure of branches provides fish with protection against predators, good spawning grounds for reproduction and a large quantity of food from algae and other organism living on the decaying wood. Thanks to these favorable conditions, significantly higher populations of fish live in these acadjas than in the surrounding areas of the lake. This is ideal to the fishermen: after a few months, they only have to put their nets around the acadja and pull up the harvest.

Centuries-old tradition no longer sustainable

But after the fishermen have pulled up their nets, the wooden constructions remain on the bottom of the lake. “They are not being reused,” says Maximin Djondo, director of BEES. “People just cut more wood to build new constructions. This way mangrove forests disappear and the lake slowly silts up.”

The removal of mangrove wood for the acadja constructions, results in the disappearance of the natural spawning grounds for fish. This eventually leads to lower fish stocks, while a large part of the local population depends on fish from lake Nokoué. Moreover, logging of mangroves leads to instable riverbeds, resulting in erosion. That puts both the quantity and quality of the water at risk.

“The acadja method is a centuries-old tradition,” Djondo explains. “The problem is related to population growth: now that ever more fishermen use this technique, it is no longer sustainable.” As little remains of the mangrove forest, over the last decennia people have resorted to illegal logging of inland acacia species in upstream forest reserves in the Ouémé basin, causing further soil erosion. “Reforestation measures cannot keep up with the high deforestation rate, so now they even use palm tree branches that will eventually end up on the bottom of the lake,” Djondo states.

Raising awareness with aerial pictures

To map the scale of the problem, with support of IUCN NL through the program Shared Resources Joint Solutions, BEES is going to use a drone to take aerial pictures of the situation in and around the lake. “This way we can plot where in the lake the acadja technique is being used and we can show the condition of the remaining forest around the lake,” Djondo explains. “First, we take that information to the communities using the acadja method to provide for their families. They will be able to confirm whether the information gathered is valid. And it’s important for them to become aware of the consequences of the use of these wooden constructions. They will want to organize their fisheries in a sustainable manner, because they cannot live without fish.”

Once the fisher communities are convinced of the need to adopt sustainable practices, BEES will arrange a joint meeting with the local authorities. “With regularly updated drone images, we can show how the acadjas are spreading and how this affects the mangrove forest and other vegetation. The next step is to make a plan – together with the fisher communities and authorities- to organize fishing in a sustainable manner.”

Conservation of mangrove forests in lake Nokoué is not only needed to safeguard the food and income from fisheries of local communities. Mangroves also provide protection against climate-related impacts, such as floods, sea-level rise and other extreme weather events, that are becoming more frequent through climate change.

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Maxime Eiselin
Senior Expert Nature-based Solutions