Blind cave fish research may lead to new applications.

By David Alderton

blind cave fish - Astyanax mexicanus
Blind cave fish.
Photo courtesy JohnstonDJ.
Blind cave characins (Astyanax mexicanus) have long fascinated fishkeepers, thanks to their apparent ability to “see,” even though they are totally blind. These blind cave fish occur only in the San Luis Potosi cave system in Mexico, where their ancestors became cut off by changes in the water level thousands of years ago.

The appearance of the blind cave fish has been modified, as a result of their isolation in this subterranean world. They rely on a remarkable sensory system to guide them when swimming, which scientists at the Georgia Institute of Technology in Atlanta have recently been studying.

Blind cave fish have tall, plate-like structures called cupulae along their bodies, which sense changes in water movement in their vicinity. These connect to bundles of specialized cells which in turn convey the information to the brain. This means that as a fish swims past an object, it can instantly detect its position by the water flow around its body helping it to gauge its distance and avoid a collision, or escape from a predator.

Professor Vladimir Tsukruk, who leads the research team, built corresponding cupulae by using droplets of a polymer applied to flow sensors. He discovered that these modified sensors were far more sensitive than the basic sensors currently in use. This means they could have applications in many different areas, ranging from tsunami detection to port security. “It’s a simple but robust demonstration of the potential of bio-inspired design in solving difficult engineering problems,” he said.

These modified sensors may also be valuable as a replacement for sonar in some situations, helping to protect marine life. More widespread underwater use of sonar by the world’s navies is believed to be the major reason as to why whales are now beaching themselves in increasing numbers.

The next step is to develop sufficient computing power to interpret the data coming from groups of these sensors. This, of course, is something that the blind cave fish already does as it swims through its dark environment.

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Pacific nations to cut bigeye tuna catch by 30 percent

SEOUL (Reuters) - Asia-Pacific nations have agreed to cut their catches of bigeye tuna by 30 percent by 2011 in order to help preserve the fish that is popular in the region served raw as sushi and sashimi.

The deal, announced late on Friday, calls on the 25 members of the Western and Central Pacific Fisheries Commission to implement cuts of 10 percent a year on bigeye tuna from 2009 to 2011. The group met this week in the South Korean city of Busan.

The group, which includes South Korea, Japan and the United States, also agreed to place limits on the fishing season and ban fishing of bigeye tuna in international waters, according to a summary of the meeting provided by South Korea's fisheries agency on Saturday.

Western and Central Pacific tuna stocks are the largest in the world and account for more than half the tuna consumed.

A decline in bluefin stocks has increased demand for bigeye tuna, which is fished in the Indian and Atlantic oceans and the Western and Central Pacific.

Worldwide stocks of bigeye tuna, a prime source for Japanese restaurants serving sushi and sashimi around the world, are on the verge of collapse from overfishing, conservationists say.

In November, the European Union and nations such as Russia, Japan and South Korea that fish the Atlantic and Mediterranean, cut bluefin tuna quotas by 30 percent to 19,950 tonnes in 2010.