03/04/2010 23:19

Hungry Nile Perch threatens to deprive local fishermen of their main source of protein. Also: TAU group develops sensitive electro-mechanical sensors.

Nile Perch used to be so prolific in Africa’s Lake Victoria that it was called “Princess of the Nile” in Israel to encourage consumers to buy it. But the lake, discovered some 160 years ago, is currently in a poor state of health, and its fish population is depleted. The clear waters have turned murky and stinky, and it is full of algae. Some native fish species have even disappeared from the lake, which borders on Uganda, Tanzania and Kenya.

Now researchers at the Hebrew University in Jerusalem and Makerere University in Kampala have established unique “boutique” fish farms in small villages around the lake to help Uganda fight the declining fish population.

Locals used to catch carp and perciform fish near the shores of the lake, but half-a-century ago, Nile Perch were introduced into Lake Victoria to increase local fishing. The authorities did not realize that the species is a predator that feeds on most of the other fish.

While the Nile Perch became the primary export of the countries around the lake, over the past decade it has devoured many smaller fish around the shores of the lake and deprived local fishermen of their main source of protein. Furthermore, fishing for the larger Nile Perch was unfeasible for local fishermen, as the fish reside in the middle of Lake Victoria, and larger fishing boats are required to catch them.

To combat this increasing problem, Prof. Berta Levavi-Sivan of HU’s Robert Smith Faculty of Agriculture, Food and Environment found a way to spawn several species of African carp and cultivate them in Ugandan fish farms. The project was initiated five years ago, and has been financed by the US Agency for International Development, in collaboration with Dr. Justus Rutaisire of Makerere University.

LAST YEAR, the developers began establishing ponds in small villages, stocking them with carp from the fish farms and enabling the local population to eat them. The project has since developed, and now four large fish farms whose owners were trained in Israel produce enough fingerlings to be raised in the ponds. Residents of each village – and especially their children – eat the carp as their main source of protein. Levavi-Sivan hopes that soon, every village around the shores of Lake Victoria will have its own “boutique” fish farm, and that the project will be expanded to include other countries in Africa. “We succeeded in inducing spawning in the carp – and these 14 villages are the success story.”

The effort is part of a program organized by Mashav (Foreign Ministry agency for international development cooperation) and the HU’s division of external studies to study inland water aquaculture and help develop the existing project in Uganda.

The scientists are now facing another challenge – with the depletion of the lake’s smaller fish, the Nile Perch have nothing to eat and are themselves dying off. So they are launching a new project, financed by the World Bank, to find ways of cultivating the Nile perch – thus helping boost Uganda’s fish exports, as well as the nutrition of the local population.


Electro-mechanical sensors tell the airbag in your car to inflate and rotate your iPhone screen to match your position on the couch. Now a research group of Tel Aviv University’s engineering faculty is making the technology even more useful. Prof. Yael Hanein, Dr. Slava Krylov and their doctoral student Assaf Ya’akobovitz have set out to make sensors for microelectromechanical systems (MEMS) much more sensitive and reliable than they are today. And they’re shrinking their work to nano-size to do it.

More sensitive sensors means more thrilling videogames, bette prosthetic limbs, cars that can detect collisions and dangerous turns before they occur, and – in the defense industry – missiles that can reach a target far more precisely.

Able to sense the movement of individual atoms, the researchers’ new MEMS sensing device uses carbon tubes about one-billionth of a meter long. Creating these tiny tubes using a process involving methane gas and a furnace, Hanein enables the atoms to “arrange themselves” on a silicon chip to accurately sense tiny movements and changes in gravity.

In the device the team developed, a nanometer-scale tube is added onto much larger micrometer-scale MEMS devices. Small deformities in the crystal structure of the tubes register a change in the movement of the nano object, and deliver the amplitude of the movement through an electrical impulse. “It’s such a tiny thing,” she says. “But at our resolution, we are able to feel the motion of objects as small as a few atoms. Originally developed for the car industry, miniature sensors are all around us,” she adds. “We’ve been able to fabricate a new device where the nano structures are put onto a big surface – and they can be arranged in a process that doesn’t require human intervention. We can drive these nano-sensing tubes to wherever we need them to go, which could be very convenient and cost-effective across a broad spectrum of industries.”

Until now, the field of creating sensors for nanotechnology has been based mostly on time-consuming manual operation. but the team members have developed a sensitive but abundant and cost-effective material that can be coated onto prosthetic limbs, inserted into new video games for more exciting play and used by the auto industry to detect a potential collision.

The market for MEMS devices, which take mechanical signals and convert them into electrical impulses, is estimated to be worth billions. “The main challenge facing the industry today is to make these basic sensors a lot more sensitive, to recognize minute changes in motion and position. Obviously there is a huge interest from the military, which recognizes the navigation potential of such technologies, but there are also humanitarian and recreational uses that can come out of such developments,” Hanein stresses. More sensitive MEMS could play a role in guided surgery, for example.