JOHANNESBURG, Oct 24 (Reuters) - Conservationists have been casting around for ways to protect Africa's heavily exploited fish stocks without depriving coastal communities on the world's poorest continent of revenue.
With a new trap design, they may have landed the big one, and it could prove a game-changer for some aspects of Africa's multi-billion dollar fishing industry.
Scientists have modified basket traps used by Kenyan fishermen, introducing gaps allowing small and non-target species to escape while big, valuable fish are harvested.
The results of an experimental study - which have just been published in the academic journal 'Fisheries Research' - show the traps not only allowed the little ones to get away, but they also retained more large fish.
This lifted the income of the fishermen by 25 percent because there is a strong size/price relationship in this kind of fishery.
And in the longer run, it makes the fishery more sustainable because juveniles and species with little commercial value are not harvested. Referred to as "by-catch", such fish are usually used for bait, sold for a lower price or wastefully discarded.
The new traps, designed by scientists from the U.S.-based Wildlife Conservation Society (WCS) and the Kenyan Marine and Fisheries Research Institute, introduced two rectangular escape gaps on the sides measuring 4 cms (1-1/2 inches) by 30 cms.
"These new escape gaps are a game changer for Kenya's coastal fisheries," said Caleb McClennen, director for WCS's Marine Programs.
"By reducing bycatch, the new basket traps increase fish size and economic return, while limiting the bycatch that can harm entire reef systems. These innovations can also be exported to other coastal fisheries for the benefit of entire regions."
BIGGER FISH, BIGGER RETURNS
The study, which used the escape gap concept for the first time in African waters, was conducted on reef systems near a marine park on the coast of Mombasa, Kenya.
Researchers worked with an experienced fisherman who built six basket traps - three with the modification, three along traditional lines.
The experiment took place over 41 weeks and the researchers found that in the modified traps, by-catch was reduced while the average size and economic value of the harvest was increased.
"The mean length of fish retained in traps with escape gaps was significantly greater," the authors of the study wrote in 'Fisheries Research'. The average biomass or weight of the catch was also larger in the experimental traps.
As a result, the market value of the catch rose by 25 percent because "larger fish attracted better prices in this fishery, irrespective of species."
The implications for fisheries and fishing communities elsewhere in Africa, including the continent's southern and western coats, could be huge.
According to the World Bank, first sales alone in Africa's commercial fishing industry - which exclude final retail or restaurant value - are worth $5 billion a year and around 10 million people rely on the resource for their livelihood.
In countries such as Sierra Leone, the industry accounts for 9 percent of gross domestic product (GDP) and in Mozambique it supports 850,000 households.
"In most coastal countries in Africa, the fishing sector is a major contributor to rural income and employment, attracts considerable local and foreign investment, enhances food security, and in many cases is a substantial source of foreign exchange and funding for public budgets," the World Bank said in a recent report on its programme for African fisheries.
It estimates that with better governance, the sector could generate an additional $2 billion a year for African economies.
But stocks are being heavily exploited, raising ecological concerns about the sector's long-term sustainability.
"Currently, Africa's fish resources are mined as an extractive industry, but the fisheries could be transformed into a renewable and more profitable industry," the World Bank said.
The escape-gap trap design holds the promise - at least in some cases - of not exploiting the resource like an extractive industry while raising income for fishermen and their families.
Crucially, no training is required because fishing methods do not need to be changed and it only costs 50 U.S. cents to alter a trap, making it an affordable option for poor fishermen.
So in future, African fishermen may boast about the little ones that got away while cashing in on the big ones that didn't.
(Editing by Ron Askew)