Credited to Benin. Brush parks are found in many parts of West Africa, Madagascar, Sri Lanka, Bangladesh, Cambodia, China, Ecuador and Mexico, and the sources do not name a single place of origin. Benin is where the acadja form and name were recorded and where its development over two centuries has been studied.
How it began
Acadja is the name used in Benin for brush parks set in the coastal lagoons, notably Lake Nokoue and the Porto-Novo lagoon. An FAO review of lagoon fisheries notes that the historical development of acadjas in Benin has been traced over roughly two centuries, citing a 1972 study by Bourgoignie. The sources do not give a founder or a first date. They also state that brush parks of similar kinds exist in many other countries, so Benin's claim is to the developed acadja form rather than to the general idea.
How it works
An acadja is built from tree branches pushed into the muddy bottom of quiet water no more than about 1.5 meters deep. Harder woods form the outer frame and soft, heavily branched wood fills the interior. Fish colonize the structure, feed and breed inside it. To harvest a small acadja, fishers ring it with a net, pull out the branches and close the net. In large parks the net is moved inward step by step as branches are removed, and the fish are taken with traps, baskets and hand nets. Used branches are then replaced.
How it spread
The FAO review records lagoon brush parks elsewhere in West Africa, including the Keta lagoon in Ghana, the Lagos and Lekki lagoons in Nigeria, lagoons in Ivory Coast and Togo, and in Madagascar. It also reports that the practice had recently been introduced in some Mexican lagoons. The sources do not say that these all derive from Benin.
Who pushed back
FAO lists several objections. Acadjas compete, or are seen to compete, with open-water fishers for space and fish, and in Lac Togo and Lac Aheme such pressures led to their destruction or disappearance. The large quantity of branches needed can add to local deforestation, erosion and turbidity, and the parks may speed the silting of lagoons, although one researcher cited did not think that effect was large. They can also get in the way of boats.
What changed first
Measurements published by Buffe in 1958 and cited by FAO recorded yields of 13.6 and 19.2 tonnes per hectare per year in one type of acadja, with about 10 tonnes per hectare in others. A study in Benin, summarized by Welcomme and Kapetsky in 1981, showed that the parks were more than devices for gathering fish from surrounding water. In the catch by weight, the tilapia Tilapia melanotheron made up 72.6 percent and the catfish Chrysichthys nigrodigitatus 23.8 percent.
Where it stands today
By 1980 and 1981 the total acadja yield in the 15,700 hectare Lake Nokoue and Porto-Novo lagoon system was estimated at about 2,000 tonnes from about 390 hectares of installations. FAO also notes that the permanent opening of a channel between lagoon and sea brought shipworm attack on the wood and mineral deposits that reduced the growth on the branches, raising maintenance costs.
