Well-Managed Aquaculture Ponds Can Help Save Wild Fish in Rural Cambodia
This post was written by Wes Neal, co-principal investigator (PI) on the Fish Innovation Lab’s Increasing Fisheries Sustainability for Resilience Activity and professor at Mississippi State University.
As we weave along the Kampong Som River, each passing motorcycle splashes the orange-tinted contents of the clay road’s potholes from the recent rains. I am a fisheries specialist from Mississippi State University, and I am heading with colleagues to a remote fishing village in the foothills of the Cardamom Mountains in Cambodia.
Small-scale fisheries like these are vital for many rural communities. Unfortunately, they are frequently left unmanaged and subject to overfishing. Limited in both personnel and funding, government fisheries agencies must often focus their limited capacity on resources of broader importance. As a result, fishing declines and local populations suffer.
We are traveling to visit the local artisanal fishers in Bak Angrut, the northernmost village along the Sre Ambel watershed. The fishers in this village are participating in a special program funded by the U.S. Forest Service that is helping to reduce fishing pressure on the Sre Ambel River by increasing aquaculture production in the area. When combined with improved fisheries monitoring and management practices, such as those promoted through the Feed the Future Innovation Lab for Fish Increasing Fisheries Sustainability for Resilience Activity, well-managed aquaculture using locally available fish species and materials provides a good alternative source of fish for nutrition and livelihoods.
With the support of Cambodia’s Fisheries Administration and the Wildlife Conservation Society, we are helping local communities initiate small-scale fish farming within village ponds. Small ponds are often excavated as borrow pits, which are pits dug for the purpose of using the soil in another capacity, on the local peoples’ land. The soil is used to build house foundations and raised roadways, and the hole that is left fills with groundwater.
It is my job to determine the best way to use these pond resources. These ponds are generally very small but often 10-12 feet deep with shear vertical walls. Water quality is typically excellent, except oxygen issues are common. Farmers tried growing tilapia in these ponds in the past, but the fish always died when oxygen was low.
No, these ponds are not suitable for traditional fish farming. Seining fish out is not an option due to the depth, nor is the use of expensive equipment like aerators. Cage aquaculture is the way to go. Net pens are locally available and affordable, and free materials like bamboo can be used for the construction of cage frames and walkways.
However, the low oxygen poses a problem for common aquaculture species like tilapia and channel catfish, and we do not want to encourage using non-native species. We need a species that is locally occurring, grows fast, takes fish feed and can survive low oxygen. We need a Pangasius catfish. They are popular, fetch a moderate price, readily accept fish food and importantly, they are adapted to breathe air, enabling them to survive in water with little to no oxygen.
During this trip, we trained 84 people (40 men and 44 women) from three villages on the basics of raising fish. Our goal with this program was to select a few demonstration farmers, provide them with everything they needed to grow fish, and produce a proof of concept that other villagers could copy. From this group, we selected one farmer with a suitable pond from each village to enroll in the pilot aquaculture program. To our surprise, several other villagers decided to follow the plan on their own.
The approach was to initially start fish in a fingerling cage with feeding three times daily, and then transfer fish to a grow-out cage with feeding twice daily (at about three months of age). The amount of feed would be adjusted as the fish grew. We hoped fish would reach minimum harvest size in about eight months.
The results were better than we could have ever hoped for. The growth rate during the fingerling grow-out period was rapid; fish reached eight inches or more in three months and were at harvestable size in six months. Incredibly, mortality was exceptionally low at only 12%. In other words, for every 100 small fish that were stocked, 88 adult fish were harvested.
Harvest-size fish can be used to feed the farmer’s family, and excess can be sold at the market to buy cooking supplies and other necessities. The program’s inputs averaged about $833 per farmer, while gross income averaged about $1,378. That’s a 65% return on investment in six months, with an average profit of $523. Whereas the mean household income in Cambodia is about $135 per month.
It remains to be seen how far this approach can be scaled up. At some point, production could flood the market, and profits could decline, but the goal is not just to produce a profitable aquaculture business. The primary goal is to provide reliable fish protein to families and villages and to take some pressure off the wild fisheries that are strained to their limit.