Declines in fish catches lead directly to increased hunting and consumption of wildlife, according to a study published today (12 November) in Science. The research shows that unsustainable fishing practices can have far-reaching consequences for poverty alleviation, food security and biodiversity conservation.
By comparing fish catches in Ghana between 1970 and 1998 with mammal populations in six of the country's nature reserves, researchers from Ghana, Canada, the United Kingdom and United States found that when fish was plentiful, mammal populations increased. When fish was scarce, numbers of mammals fell.
Fish supplies were highly variable during the study period — varying by up to 24 per cent between consecutive years. Changes in the abundance of mammals could not be linked to other factors, such as rainfall, temperature, oil prices, and gross national product.
The researchers did, however, find other evidence of a link between fisheries and wildlife consumption. Sightings of hunters in nature reserves increased in years when fish supplies were low. Bushmeat sales in markets increased in months following a drop in fish supply and increase in fish price. And the link between declines in wildlife and reduced fish supplies was greatest in reserves nearer to the coast.
Increased consumption of bushmeat in apparent compensation for declines in other foods has long been suspected, but this is the first time this 'protein limitation hypothesis' has been tested. It suggests that wildlife is not consumed as a luxury good but as an essential source of protein in Ghana.
Between 1970 and 1998, the biomass of the 41 studied mammal species fell by 76 per cent in nature reserves. The species that declined most were large carnivores including lion, wild dog, hyena and leopard, certain primates and several herbivores such as hippopotamus and giant hog.
"Both for the reserves we studied and the wider region, it appears most wildlife species cannot endure current levels of harvest," says Justin Brashares, lead author of the Science paper.
"The greatest foreseeable problem of unsustainable harvest, in my opinion, is the loss of the economic and dietary benefits that bushmeat provides," Brashares told SciDev.Net. "The loss of all of that food and income for people in developing countries could result in a real humanitarian crisis."
During the same period, fishing activity off Ghana's coast intensified. Since 1977, fish biomass in Ghana's near and offshore waters fell by at least 50 per cent.
Together, these statistics suggest that this collapse of local protein availability is a very real threat. Increasing crop and livestock production sufficiently in the region could take decades and, instead, existing sources of protein need to be exploited in a more sustainable way, say the researchers.
One way of approaching this problem would be to increase protection of both marine and terrestrial species, say the authors.
Another approach would be to restrict access to Ghana's waters by large foreign fishing vessels. European Union (EU) vessels increased their fish catches off West Africa 20-fold between 1950 and 2001. EU subsidies of this fleet increased from US$6 million dollars in 1988 to US$350 million in 2001, artificially increasing their profits.
"EU fishing fleets appear to be a small part of the problem, but also one that can be quickly addressed through changes in EU fishing policy," says Brashares. "Our study does not show that the EU is solely responsible for fish declines; many countries are involved and the question now is who can take the lead in providing solutions?"
"Local, regional and foreign governments must look closely at their fisheries policies and work together to find sustainable levels of harvest to ensure a steady food supply in West Africa to maintain the millions of people in the region whose livelihoods are tied to fishing."
Brashares told SciDev.Net that the researchers think their findings will apply in other countries.
"Bushmeat is an important contributor to household income and food supply not only in much of Africa but also South and Central America, and parts of Asia," says Brashares. "Ongoing work in other parts of West and Central Africa, and the Americas and Asia suggests a strong link between fish supply and people's reliance on wildlife on land for food and income."
Link to full paper by Bashares et al in Science Reference: Science 306, 1180 (2004)