Senegal Tests Adding Fish to Rice Fields to Reduce Snails and Raise Yields

Researchers and farmers in Senegal's river valley released hundreds of tilapia and several African bonytongue into rice fields as part of an experiment to reduce disease and increase harvests. The team placed about 600 tilapia per field across 60 sites, with the larger fish added to consume snails that transmit schistosomiasis.

Momy Seck Ndao, an environmental engineer leading the work, said the fish also fertilize the rice through their waste.

A pilot study published earlier in 2026 found that adding fish raised yields by about 25 percent, increased farmer income, and slightly lowered snail counts. The current phase more than doubles the number of fields under study. Dam construction along the Senegal River that began in the 1980s created steady irrigation but allowed snail populations to grow after cutting off migratory prawns that once ate them.

Schistosomiasis now affects about one-third of children in the area and more than 200 million people worldwide each year. Rice farmer Dgibi Dia said he has suffered repeated infections that cause nighttime itching, stomach pain, bloody diarrhea, and fever lasting months. Farmers report that treatment drugs are often unavailable or too expensive.

African bonytongue can eat large numbers of snails daily, according to Ndao. The team transported the fish from a farm in Dagana and collection points near Saint Louis, acclimating them to field water temperatures before release. Senegal imports about half the rice it consumes.

One participating farmer, Abou Diallo, said his seasonal rice sales rose from about 60 bags to 90-95 bags after adding fish, allowing him to buy sheep and renovate his house. He also eats and sells the fish, which he said taste better than ocean-caught varieties. Ndao contacts each farmer by phone every two days until harvest.