Lake Malawi is the third-largest lake in Africa and the world’s ninth largest. It is home to around 470 species of fish, most of them from the Cichlidae family. Chambo, the local name for an especially prized member of the Tilapia genus, is a key source of protein and a basic food. Known taxonomically as Oreochromis karongae, this is an endemic commercial species but has been subject to drastic overfishing in recent years. In a project entitled “Ich liebe Fisch – Fish for life,” researchers from Fraunhofer EMB are now seeking to improve the nutrition status of Malawi’s rural population. Working together with local and foreign partners – the Gesellschaft für Marine Aquakultur mbh (GMA) in Büsum, Germany; the Lilongwe University of Agriculture and Natural Resource (LUANAR) in Malawi; the Quantum for Urban Agriculture and Environmental Sanitation (QUALIVES) and the Innovative Fish Farmers Network Trust (IFFNT) in Malawi – the research team has launched a diverse range of strategies designed to boost hatchery and production yields, make chambo farming more efficient and sustainable and thereby work to remedy the precarious food situation. The project, which is scheduled to run until the end of 2020, is being funded by Germany’s Federal Office for Agriculture and Food (BLE) to the tune of 1.65 million euros.
Aquaculture is one way in which the supply of chambo to Malawi’s rural population might be increased. At present, however, local fish farming is still on a low level and inefficient. A major problem for this budding industry is sourcing a reliable supply of fingerlings – young fish just bigger than the fry stage. A key task that the project partners face will therefore be to establish methods to ensure that fish farmers have access to a stable stock of juvenile fish, which they can then rear to a salable size.
Hatcheries for rearing fish from own brood stocks
The “Ich liebe Fisch” team has designed and installed a new hatchery at Bunda College of Agriculture. The hatchery, which is solar powered and therefore not dependent on the local electricity grid, offers an efficient method of rearing large volumes of fish larvae until they have reached the fingerling stage, at which point they weigh around ten grams. These fingerlings are sold to local fish farmers at a favorable price. “The fish are then reared in ponds to a marketable weight of between 250 and 330 grams,” explains Dr. Sebastian Rakers, scientist at Fraunhofer EMB in Lübeck.
The research team is working with a number of local communities. Some of them have many years of fish-farming experience, whereas others are just making a start. The aim is to harmonize the level of expertise. “We’ve got a whole variety of technology on offer,” says Rakers. “For example, we show fish farmers what kind of ground is best for their ponds and also teach them in cryopreservation technologies, which will enable to produce fish the whole year round.”
Using cryopreservation to increase reproductive performance
To date, cryopreservation has not been used in Malawian fish farming. Now, however, project partners are devising new methods for freezing chambo sperm, the aim being to breed a spawning population with an increased reproductive performance. The first step is to select promising-looking fish strains that are resistant to disease, for example, and display good growth parameters. Sperm is taken from the males of this strain and then frozen. In order to prevent the formation of ice crystals, it is mixed with antifreeze substances. The frozen sperm is then stored in liquid nitrogen at a temperature of -196 °C. “From time to time you have a situation in which the males and females of the population are not ready to spawn at the same time. This lowers the reproduction rate. To counteract this problem, we use cyropreserved sperm in order to increase the number of fertilized eggs and hence hatchlings,” Rakers explains. Cryopreservation is meanwhile being tested by several Malawian partners.