Though seafood invokes images of trawlers crashing against waves, aquaculture now generates the bulk of fish protein consumed. Fish farming overtook wild catch fishing more than a decade ago, around 2009 according to studies published by the Proceedings of the National Academy of Sciences and the UN Food and Agriculture Organization. Fish farming is a booming business, and few have ridden this boom better than tilapia farmers. A relatively tiny industry in the late 1980s, tilapia today is a sprawling enterprise covering 120 countries and raking in more than $11 billion annually. The reasons for this success are clear—the most commercially successful tilapia species are easy to care for, grow fast, tolerate crowding, and are known for pleasant taste, ease of preparation, and a knack for absorbing other flavors well.
Modern tilapia aquaculture is dominated by commercial operations in China and Brazil, but tilapia farming originated as an artisanal activity in Africa. Today, the smallholder tilapia farmers are struggling to compete. African smallholder tilapia farmers face four main challenges.
Tilapia is native to warm-weather climates of Africa and the Levant, yet the geographic reach of tilapia farming extends well beyond these regions. As Brazilian scientist Machado Fracalossi and colleagues noted in the pages of Aquaculture Reports last September, the “ideal temperature range for Nile tilapia is 26-30 degrees Celsius,” because, as researchers have found, “there is a reduction in feed consumption, which leads to a significant decrease in growth, when Nile tilapia are raised at a cold suboptimal temperature of 22 degrees Celsius.” In other words, tilapia farming productivity plummets when temperatures drop. Conditions at many tilapia farms routinely fall below 22 degrees C, so how should farmers cope? On that question, the jury is still out, say Fracalossi and team at the Federal University of Santa Catarina.
Some farmers try moving tilapia indoors during cooler months, or covering ponds with greenhouses. Smaller farmers may not have either option available to them. There is some evidence that adjusting the diets of farmed tilapia to include more fatty acids can improve their ability to tolerate colder waters, but Fracalossi et al. find this evidence lacking. “Further research is needed to ascertain the relationships between nutrition, genetics, and husbandry practices more accurately,” they conclude.
Can’t take the heat, either?
In a world of global warming, scientists warn that it’s hotter temperatures farmers really need to worry about, not cooler ones. It’s no different for fish farmers, as African and Chinese researchers argue in a separate study also issued in Aquaculture Reports late last year. They note that higher water temperatures combined with pen crowding can stress farmed tilapia, producing biological symptoms resembling hypoxia. Heat stress can even weaken tilapia immune systems. Seeking ways to make tilapia more resilient to both heat and cold, a research team from Ghana and Guangdong province experimented with mixtures of beneficial bacteria and traditional Chinese herbs. Indeed, Emmanuel Abarike and colleagues say feeding tilapia a mixture they call “CHBS2” over a 56-day period enhanced the animals’ ability to stand the heat. “Among the herbal-probiotic groups, tilapia fed with CHBS2 diet showed enhanced values in most of the indices measured under the different stress conditions,” they wrote, while highlighting a need for further investigation.
Cages vs. ponds
Another factor limiting tilapia farming success in much of Africa is many farmers’ preference for cage rearing over ponds. In Ghana, most farmed tilapia are raised in nets or cages in lakes. This practice may be less labor intensive than pond aquaculture, but cage tilapia aquaculture generates more waste–cage farmers tend to let nature deal with waste, sometimes violating water-quality regulations, while pond managers actively remove it. Cage farming also generally results in lower productivity and higher costs, especially where feed costs are high.
So is convincing farmers to dig ponds the solution to improving smallholder tilapia production? It’s not quite that simple.
“Marginal” in Africa
Africans may have been the first to experiment with tilapia cultivation, but others have benefited far more from the past decade’s tilapia boom. Fish farming in general and tilapia raising in particular has been more of a bust in Africa. Carine Temegne Nono of the University of Yaoundé I writes in the International Journal of Oceanography and Aquaculture that tilapia farming in her native Cameroon “still remains marginal,” despite decades of government efforts. It’s much the same story in Zambia, where CGIAR-funded research found tilapia farmers struggling. “The profits earned by smallholders are low, and there has been a noticeable decline in the production and productivity over the past years,” authors Kyra Hoevenaars and Jona Wiza Ng’ambi note in a manual advising better tilapia management practices.
Some of the problems plaguing African tilapia farmers are rather basic. For example, many farmers rely too heavily on exotic species of tilapia when they might see better outcomes from species native to their regions. Tilapia ponds are generally dug using hand tools and manual labor, so they tend to be shallow, limiting production. This could be resolved by supplying fish farmers with excavators, but Hoevenaars and Ng’ambi argue that Zambia’s tilapia farmers can enhance both environmental integrity and profitability with better pond construction. “Selection of sites with proper soils and protection against floods will reduce long-term expenses associated with water use and replacement of escaped stock,” they note.
Further research on improving heat and cold tolerance isn’t the only thing African tilapia farmers need, but it’s the area Grow Further may be able to best contribute.
— Grow Further