Intensive frog farming takes giant leap forward

Shanta Barley, New Scientist 1 Sep 09;

Giant frog farms could satisfy western diners' apparently insatiable appetite for frog meat, if pioneering French research is put into practice. That's not just good news for the Europe's menus, but also for Asia's frogs, which conservationists say are in danger of being eaten to extinction.

Farming would also mean frogs could be raised close to where they're eaten, which could reduce the spread of diseases that are threatening frog populations around the world. But some ecologists and conservationists say that intensive frog farming could spawn a new range of problems.

The vast majority of frogs destined for European dinner tables are harvested from the wild in Asia, because previous attempts to farm frogs closer to home have ended in failure.

Disease spreads easily between frogs kept in close quarters, and they prefer expensive live prey to cheap food pellets, so they're not easy to raise. Another problem is that frogs hibernate for relatively long periods in cool European climates. So farming has thus far proven uneconomic.

Now, however, André Neveu at the French National Institute for Agricultural Research in Rennes says he's managed to raise common European frogs under intensive farming conditions.
Yield jump

Neveu set out to discover which of three types of European frog responded best to intensive farming: the pool frog, the marsh frog or the edible frog, an infertile hybrid of the other two species.

He raised populations of all three under the same conditions – up to 1000 froglets per square metre fed on floating pellets of fish meal, soya and other ingredients – and then measured how many of each survived, how much they grew and how much meat they yielded. His published paper is short on details of his commercially sensitive technique for persuading the frogs to eat the food, only hinting that he kept the food pellets moving on the surface of their ponds to fool the frogs into treating them like prey.

The best candidate for farming turned out to be the marsh frog. Not only was it the only strain to reach 30 grams in weight – the minimum considered acceptable for the French market – but it also did better in captivity than the other strains. Just over half the marsh frogs survived three years of intensive farming, whereas only 5 to 8 per cent of the pool and edible frogs did.

That resulted in yields of about 29 kilograms of marsh frog meat per square metre – six times higher than the yields from other strains.
Last legs

If Neveu's results can be replicated on an industrial scale, European frog-fanciers could soon be feasting on local fare, rather than on Asian imports. That would reduce the pressure on wild populations in Asia, which currently supply 95 per cent of the world's frog meat.

It would also slow the progress of amphibian diseases that have caused extinctions and declines in 200 species of frog, says Tim Halliday, international director of the Declining Amphibian Populations Task Force, based in Milton Keynes, UK.

But other specialists say frog meat is too expensive a taste. "With fish populations collapsing, should we really be harvesting fish to provide protein feeds to farmed amphibians, which are going to end up as luxury items on menus in expensive restaurants?" asks Trevor Beebee, a molecular ecologist and amphibian expert at the University of Sussex, UK.

James Collins, a frog conservation specialist at Arizona State University, Tempe, says that farming frogs could turn out to be worse for the environment than farming some other types of livestock. "Until we can find a way to feed frogs vegetable protein, rather than fish protein, it may be better to simply harvest frogs sustainably in the wild rather than building elaborate, energy-intensive farms that rely on fish meal. But we're a long way off that."

David Green of McGill University in Montreal, Canada, acknowledges that Neveu's research could make the large-scale production of frogs a viable concern, but argues we shouldn't be eating frogs – a third of which are at risk of extinction – at all.

"I hear frogs' legs taste like chicken," he says. "Eat that and leave the frogs alone."

Journal reference: Aquaculture, DOI: 10.1016/j.aquaculture.2009.06.027