Information on the farming of common carp in Malawi was obtained from the following sources:

(1) A compilation of existing literature on the origin and status of common carp farming in Malawi. Since farming of this fish in Malawi has been restricted, some of the literature on the subject is admittedly quite old (Betram et al., 1942; Pruginin, 1976; Balarin, 1987; Welcomme, 1988; Vanden Bossche and Bernacsek, 1990; Msiska and Costa-Pierce, 1993).

(2) Personal involvement as a research assistant in Zomba district in 1989/1990 under the International Center for the Living Aquatic Resources Management (ICLARM/GTZ Africa Project).

Further information was obtained through attendance of meetings organized by ICLARM in 19891990 and in later years by the Department of Fisheries.

 

History of common carp farming in Malawi

The farming of fish in Malawi started in 1906 with the introduction of rainbow trout (Onchorhynchus mykiss Walbaum, 1792) for angling (Balarin, 1987). As the human population at this time was low, fish stocks in the capture fisheries were considered adequate and in healthy state. A nutritional survey following the League of Nations (1935), Report on the Psychological Basis of Nutrition recommended that the farming of fish for food in upland areas of Malawi needed consideration to redress the nutritional deficiency in the diet of people living far from lakes (Betram et al., 1942). Thus, fish farming for food began in 1956/1957 using the indigenous tilapias Oreochromis shiranus Boulenger, 1897 and Tilapia rendalli Boulenger, 1897 (Pruginin, 1976). In 1969, a joint Malawi Fisheries Department (FD)/FAO survey of fish yields of Malawian species was carried out to assess the performance of these fishes. Results indicated slow growth rate (< 1 g/day), leading to low fish yields from ponds and dams of 0.1 to 0.2 t/ha/year for Northern Malawi and 0.5 to 1.0 t/ha/year for Southern Malawi (Msiska, 1993).

Presently, there are five main indigenous fish species used in Malawi’s aquaculture, the tilapias O. shiranus, Oreochromis karongae Trewavas, 1941, Oreochromis mossambicus Peters, 1852, T. rendalli, and the catfish Clarias gariepinus Burchell, 1822 (Figure 3). Tilapias and catfish make up 93 and 5% of aquaculture production, respectively. Oreochromis shiranus is the most widely cultured fish in Malawi, followed by T. rendalli. O. mosambicus is cultured in the Lower Shire river basin. These tilapias grow slowly and to small sizes, with O. shiranus and O. mosambicus reaching sexual maturity as small as 6 g and breed precociously (M’balaka et al., 2012).

 

 

In 1990, the government of Malawi stopped further distribution of common carp fingerlings, pending a decision on the future of carp farming. This, coupled with drought in that year that dried up more than 50% of farmers’ ponds, drastically reduced the number of carp farms to just about four or five in the country (Moreau and Costa-Pierce, 1997). In 1991/1992, carp withdrawn from farmers and the remaining stocks in ponds were eradicated in Malawi. All exotic fishes, including carp and even Oreochromis niloticus, were prohibited in the Lake Malawi catchment area by the Malawi Government, in order to conserve the lake's unique assemblage of native species (Msiska and Costa Pierce, 1993; Moreau and Costa-Pierce, 1997). The restriction of exotic fish farming became legalized in the 1997 Fisheries Conservation and Management Act [Part XI section 41(1) c] (Hecht and Maluwa, 2003). However, the farming of common carp was still carried out (although negligibly) in some parts of the Lower Shire and other areas in Southern Malawi (Msiska and Costa-Pierce, 1996; Andrew et al., 2003).

Reasons for banning common carp in Malawi

The decision to import common carp did not consider the ecological effects of the fish on aquatic ecosystems (Costa-Pierce et al., 1993). When reports of devastating ecological impacts of the Nile perch introduced into Lake Victoria in the 1950s began to spread in the early 1990s, scientists in Malawi were awakened to the negative effects that introduced fish species can have on native biota. Although, common carp was highly valued and already being distributed to farmers, scientists began to ponder about the potential negative impacts of this species on the unique Lake Malawi fish biodiversity. Fortunately, the fish had already been introduced elsewhere in the world and to more than 21 countries in Africa (Table 1 and Figure 5) from which lessons of its ecological effects could be learned.

 

 

Lessons from other countries in  Africa  suggested  that carp’s habit of digging up lake’s sediment could destroy tilapia breeding areas, thereby lowering tilapia recruitment due to disruption of nesting. The stirring of sediment by carp also hasten eutrophication by mobilizing sediment-bound nutrients (mostly phosphorus) into the water column (Costa-Pierce and Pullin, 1989; Breukelaar et al., 1994). However, considering the high economic value of carp farming, no country in Africa, beside Malawi, has rejected the fish on account of its ecological effects. The Malawi government was concerned about the potential threat of carp to the unique fish biodiversity of Lake Malawi if it escaped into the lake (Vanden Bossche and Bernacsek, 1990; Costa-Pierce et al., 1993).

Impacts of common carp ban in Malawi

Declining contribution of carp to fish supply and continued slowing of aquaculture growth

The contribution of common carp to aquaculture production declined from about 9% of total aquaculture production in the early 1990s to less than 0.5% by the early 2000s (Figure 6). During the same period, the contribution of common carp to global aquaculture production increased from 5.4% of global aquaculture production to 5.9%. 

 

 

In Malawi, fish farming became less profitable for most of the farmers who were used to carp, prompting over 80% of them to quit fish farming altogether. Farmers’ trust and confidence in the Malawian Fisheries Department declined sharply, setting the government on frantic but futile confidence rebuilding campaigns (Msiska and Costa-Pierce, 1993). Growth in Malawi’s aquaculture has slowed. For instance the contribution of aquaculture to total fish supplies in Malawi has remained low, estimated at 2% (Sanudi et al., 2015). It is widely believed that if Malawi were to adopt common carp farming, aquaculture development would accelerate (GoM, 2011).

Search for indigenous aquaculture species

Aquacultural farmers demanded a replacement of the common carp to maintain profitable fish farming in Malawi. The search for suitable native aquaculture species had already proved difficult when such efforts began in the 1960s. However, the scientists believed a lack of success in this direction was attributable to an absence of sustained project commitment to screen and test indigenous fish species (Msiska and Costa-Pierce, 1993). Such a project came along in late 1999 with funding from Japan International Cooperation Agency (JICA). A number of indigenous fish species were assessed. By the end of the 5-year project period (1999-2004), no suitable indigenous fish species  was  identified that could replace carp (SSC, 2005).

Pressure on policy review

Failure by government to identify a better-performing native aquaculture species has attracted widespread calls from farmers for a reversal on common carp ban (GoM, 2011). Slow-growing and stunting native fish species have been cited as a major impediment to aquaculture growth in Malawi (GoM, 2011, 2012). The National Aquaculture Strategic Plan (NASP) (2005-2015) calls for impact studies to provide information that would form the basis for policy review on the use of carp in Malawi’s aquaculture. The National Biodiversity Strategy and Plan (NBSP) also calls for impact assessment of alien species as potential candidates for aquaculture development in Malawi (Environmental Affairs Department, 2006). The government has emphasized the need to do more research on the ecological impacts of carp before it can consider reviewing its policy (Msiska and Costa-Pierce, 1993; Bandula, 1997; SSC, 2005).

Research directions related to policy on common carp farming

Government insistence on judicious research on common carp before policy review is understandable and logical. However, government has not suggested any potential policy research direction on the issue. This paper suggests the following possible research avenues:

(1) Comparison of ecological impacts between common carp and C. gariepinus: Both of these species are benthivorous (Koekemoer and Steyn, 2002; Rahman, 2015). Anecdotal field observations of the impacts of these fishes in Malawi suggest they may impact on ecosystems in the same way. These observations contradict Msiska and Costa-Pierce (1993) who opined that common carp occupies a niche that no other farmed fish occupies in Malawi. Reports of common carp displacing C. gariepinus from its benthic niche in Zimbabwean reservoirs (Costa-Pierce et al., 1993) corroborate observations of similarity of niche occupation by the two species. If these observations are true, the introduction of one of them into a system already containing the other may not significantly alter the ecosystem.

(2) Assessment of colonization and establishment of common carp and its environmental impacts in the Lake Chilwa and Lower Shire drainage systems: Common carp is reported to have escaped from fish ponds into natural waters in these ecosystems in the 1988-1990 period (Msiska and Costa-Pierce, 1993). The escapees have not been followed to determine if they are established and what impacts, if any, they cause.

(3) Evaluation of common carp farming in the Lake Malawi catchment area in Tanzania and Mozambique: These riparian countries are reported to be farming common carp in their side of the lake’s catchment (Costa-Pierce et al., 1993; Chirindza, 2010). Mozambique is one of the main African producer countries of common carp (Figure 5). If the species is already in the lake’s watershed, the questions of what impacts the common carp is causing and what justification Malawi has for its unilateral rejection of the fish when other countries in the same watershed are farming it will need addressing.

(4) Invasion history of common carp in lakes of similar morphometry and physico-chemical conditions to Lake Malawi: Across-ecoregion analysis has shown that the invasivity of common carp is regulated by a number of ecological filters such as depth and trophic status of a water body (Bajer et al., 2015). However, no studies have been conducted to establish invasion history of common carp farmed in catchment areas of lakes with depth and trophic status similar to Lake Malawi. Lessons learned in these ecosystems can be used to make inference about the potential vulnerability or invasion potential of Lake Malawi to common carp.

Common carp was introduced in Malawi to complement tilapia aquaculture production with an aim of increasing overall  production  from  the  fish  farming  industry.  The indigenous tilapias were slow-growing, stunting and breeding precociously. The catfish C. gariepinus was economically a difficult fish for the majority of farmers as the species’ protein requirements made it costly to feed. The species was also difficult to breed under prevailing pond conditions. Thus, these species had received farmers’ disapproval as early as the 1960s. With common carp (1985-1991), the farmers’ interest in fish farming surged as profits from fish farming began to increase. Government’s withdrawal of common carp and its ultimate ban left many farmers disillusioned and wondering what the real justification was. The government insisted it was concerned with the effects the fish would have on Lake Malawi once the species found its way to the lake’s catchment. Farmers were promised that a more suitable indigenous aquaculture species would be identified for use in Malawi’s aquaculture sector.

To date, a more suitable native aquaculture species has not been identified in Malawi, despite the existence of well-resourced project investments in this effort. Lack of better performing indigenous fish species is continually being cited as a major constraint in the growth of aquaculture industry in Malawi. The Malawi government has persistently resisted calls to reverse its ban of common carp until it could be shown that carp’s farming in the Lake Malawi catchment would not negatively affect the lake’s unique fish biodiversity. This paper has outlined potential research areas that are relevant to policy decision-makers on the question of whether common carp would harm Lake Malawi.

Due to inconsistent and fragmentary documentation of the farmers involved in carp farming, this study has not been able to chronicle the trends of carp farmers in Malawi from the time of distribution of the fish to farmers to the time the fish was withdrawn from the farmers. Although it is recorded that carp was still being farmed after banning it (Andrew et al., 2003), the farmers could not make public declaration of the activity for fear of government reprisals. The study has therefore not been able to provide up-to-date records of carp production in Malawi. In addition, there are unconfirmed reports that farmer-to-farmer distribution of carp has occurred in Malawi, and that the fish is illicitly farmed in the Lake Malawi catchment area. This study has not been able verify these reports as the farmers fear to provide information.

The authors have not declared any conflict of interests.