Disease threatens aquaculture in developing world

Disease may damage fish farming, hitting food security and economies

Flickr/IvanWalsh

[CAIRO] Disease may challenge the ability of fish farming to feed the growing human population even as wild fish stocks decline and climate change hampers food production from other sources, a study shows.

Aquaculture is the fastest growing food sector in the world, according to the UN Food and Agriculture Organization, with 90 per cent of production coming from the developing world, where it makes a significant contribution to many nations' economies.

But fish and shellfish disease will increasingly present a major problem for aquaculture in tropical countries, many of which rely on this form of food production for dietary protein, according to the study, which calls for better disease-response strategies and infrastructure in developing countries.

The study, published in February's issue of the Journal of Applied Ecology, is the first analysis of the global pattern of disease outbreaks in aquaculture, according to its lead author, Tommy Leung, a lecturer in parasitology and evolutionary biology at the University of New England, Australia. 

By examining published reports of disease-induced mortalities in commercial aquaculture, it found that outbreaks were more deadly and progressed quicker in the tropics than in temperate regions, after controlling for differences in veterinary and disease-reporting infrastructure.

Leung says the results show that outbreaks in tropical regions can wipe out entire fish stocks in a relatively short space of time, with devastating consequences for both the economy and food security.

"As aquaculture continues to expand as a means of food production, achieving food security and bolstering the domestic economy of those countries, it becomes ever more crucial to ensure that such ventures are protected from the impact of diseases," Leung tells SciDev.Net.

The results highlight the importance of developing and maintaining disease-monitoring infrastructure and training to identify pathogens and parasites, he says.

They also indicate the need for rapid response strategies for disease outbreaks, he adds.

Leung now wants to examine what environmental factors are driving the disease pattern.

Judith Weis, a biology professor at Rutgers, the state university of New Jersey, United States, says that disease spreads faster at warmer temperatures and that the excessive use of antibiotics in aquaculture causes antibiotic resistance, which may explain the pattern the study found.

"You can't do anything about the temperature but you can reduce the use of antibiotics," she says.

Martin Krkosek, assistant ecology and evolutionary biology professor at the University of Toronto, Canada, says: "For the first time, we have a global perspective on the dynamics of infectious diseases in aquaculture".

He adds that disease may turn out to "ultimately be the limiting constraint on growth of this industry".

But he sees hope in continuous disease monitoring which may help better understand and eventually minimize outbreaks, instead of "relying on emergency reactions once a crisis has already arrived".

And he adds that, as a precaution measure, areas of coastal waters should be designated no-farming zones in order to protect other sectors such as fisheries, tourism, and wildlife outbreaks in aquaculture.

Link to full paper