Experts debate fish farming limits

Aquaculture is overtaking traditional fishing in global production, the United Nations Food and Agriculture Organisation reported. But a scientist with the organisation predicted that growth would slow as space for the food farms dwindled and concerns grew about their effects on the environment.

Fish farming is the fastest growing area of animal food production, having increased at a 6.6 per cent annual rate from 1970 to 2008, the agency said in the report. Over that period, the global per-capita supply of farm-raised fish soared to 17.2 pounds from 1.5 pounds. In volume, aquaculture now makes up 46 per cent of the world’s supply of consumed fish, and the sector appears to have overtaken wild fisheries in commercial value, reaching $98.4 billion in 2008, compared with $93.9 billion for fish caught in the wild.

“In terms of capture fisheries, we’ve now more or less peaked” at a current harvest of 90 million tons for fish caught in the wild, Kevern Cochrane, director of the U N Food and Agriculture Organisation’s resources use and conservation division, said. But fish farms will also run into limits, he warned. “We’re going to run into constraints in terms of space availability, water availability – particularly fresh water – and also environmental impacts and supply of feed,” Cochrane said. The challenge for fishing countries will be to ensure that traditional fisheries production is sustained at current levels without depleting stocks, he said. Countering Cochrane’s predictions, Wally Stevens, executive director of the Global Aquaculture Alliance said that the industry’s goal was to increase its annual output.

China, which raises carp, tilapia etc now accounts for 62 per cent of global farmed fish production. That nation and some of its Asian neighbours have gone a long way toward fully developing their aquaculture potential, Cochrane said, while other regions, particularly Latin America and Africa, still have significant room to increase output.

David Jolly
New York Times News Service

Now, you can sense the charged air

Nuclear experts rushed to the shop in Mayapuri junk market and found a radioactive material, cobalt-60, of the size of a pen cap. It took them nearly two days of rigorous search to isolate several small pieces of cobalt- 60.

Since existing devices like Geiger counter detect radioactive substances only when placed near it, experts had to check every bunch of scrap metal. To avoid such problems, two US scientists have proposed a concept that could lead to a technology to find radioactive material from a distance. If materialised, it would help nuclear experts scan a large area for hidden radioactive materials in a short time and avert incidents like radiation poisoning, said Victor and Gregory of the Institute for Research in Electronics and Applied Physics of University of Maryland in USA.

As a radioactive material decays it emits gamma rays, which ionizes its immediate surrounding air, meaning air particles surrounding the radioactive material contain free electrons. The scientists said if a high-powered pulsed electromagnetic wave hits the region, the amount of ionisation would increase exponentially, creating a flood of electrons in the small area. This phenomenon, dubbed breakdown of air, can be detected even from hundreds of metres away, the scientists noted in the Journal of Applied Physics. The scientists said high-powered electromagnetic devices such as a gyrotron, can be used to experimentally validate the concept.

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