A synthetic "chemical sex smell" could help rid North America's Great Lakes of a devastating pest, scientists say. US researchers deployed a laboratory version of a male sea lamprey pheromone to trick ovulating females into swimming upstream into traps. The sea lamprey, sometimes dubbed the "vampire fish", has parasitised native species of the Great Lakes since its accidental introduction in the 1800s. The work is reported in Proceedings of the National Academy of Sciences. The Great Lakes on the US-Canada border support recreational fishing worth billions of dollars a year, which the lampreys would wreck but for a control programme costing about $20m annually. This is thought to be the first time that pheromones have been shown to be the basis of a possible way of controlling animal pests other than insects. "There's been extensive study of pheromones in animals and even in humans," said lead researcher Weiming Li from Michigan State University in East Lansing, US. "But most researchers have presumed that as animals get more complex, their behaviour is regulated in a more complex way, not by just one pheromone," he told BBC News. Professor Li's team released the synthetic version of a lamprey hormone from a trap placed in a stream where lampreys come to breed. Females scenting it would swim vigorously upstream until they found the source, some becoming trapped in the process. Death wish The sea lamprey's natural life cycle takes it from birth in a stream to adulthood in the ocean, where it gains its vampirical appellation. Circular jaws lock on to another, larger fish, and a sharp tongue carves through its scales. From then on the lamprey feeds on the blood and body fluids of its temporary host, often killing it in the process. Eventually, the satiated lampreys - both males and females - find a suitable stream to swim up, breed and die. Unlike salmon, which seek out the stream they were born in, lampreys appear willing to take any stream indicating a suitable breeding place; and perhaps pheromones play a role in identifying streams worth selecting. In their native Atlantic Ocean, their numbers are controlled by predation; but in the Great Lakes they have no predators. They first appeared in the 1800s after completion of the Erie Canal linking the lakes to New York. Colonisation was completed a century later when other canals provided unfettered access to the upper lakes. What followed was decimation of native fish. "It was one of the worst things to hit the Great Lakes in the history of European settlement," said Marc Gaden from the Great Lakes Fishery Commission (GLFC), the body responsible for controlling the lamprey problem. "Before it, we had a thriving fishery largely dependent on native fish such as the lake trout... but by 1940 they had colonised thousands of streams and fishermen were beginning to see the devastation." Getting fresh Many fish can survive only in fresh water or only in the oceans - or, like salmon, have a set migration between the two - but the lamprey appears to have thrived on its move from the saline Atlantic to the fresh environs of the five lakes. Each individual devours a total weight of up to 20kg of trout or other host fish during its parasitic lifetime. The GLFC has established a complex set of control measures, including dusting the streams with pesticides specific to the lamprey, building barriers to block their upstream migration, and releasing sterile males to reduce breeding. "Why we're so enthusiastic about the pheromone work is that we see it as another tool in the arsenal," said Dr Gaden. "We see it as away of tricking these spawning lampreys, and then you can do things to manipulate their behaviour in ways that would work against them - for example you could lure them into streams without suitable spawning habitat, or just into traps." Professor Li's team is now planning a larger experiment, using the pheromone to trap female lampreys in 20 streams feeding into the lakes, which will take three years to complete.
GAZA CITY, Gaza Strip – Israeli warplanes, gunboats and artillery units bombarded more than 40 Hamas targets Saturday, including weapons storage facilities, training centers and leaders' homes as Israel's offensive against Gaza's Islamic militant rulers entered a second week.
There were tentative signs that the current phase of fighting may be nearing an end. Most of the airstrikes targeted empty buildings and abandoned sites, suggesting Israel may be running out of targets.
In another indication the campaign was entering a new phase, Israeli artillery units attacked Gaza for the first time, military officials said. The shelling was directed at open areas, but was seen as a possible signal that a ground invasion could be nearing.
Israeli defense officials said some 10,000 troops, including tank, artillery and special operations units, were massed on the Gaza border and prepared to invade. They said top commanders are split over whether to send in ground forces, in part because such an operation could lead to heavy casualties but also because they believe Hamas already has been dealt a heavy blow. The officials spoke on condition of anonymity because they were classified discussions.
At the same time, international cease-fire efforts were also gaining momentum. French President Nicolas Sarkozy is visiting the region next week to try to end the violence, and President George W. Bush and U.N. chief Ban Ki-moon both spoke in favor of an internationally monitored truce.
But Hamas, in its first reaction to the proposal on Saturday, reacted coolly to the idea of international monitors.
Israel launched the offensive on Dec. 27 in response to intensifying rocket fire by Hamas militants in Gaza. The operation has killed more than 430 Palestinians, including dozens of civilians, according to Palestinian and U.N. counts. Four Israelis have also been killed, and rocket attacks on southern Israel persist.
The Israeli army would not say when the operation might end, repeating its position that it would continue as long as necessary. But officials confirmed that the number of airstrikes is down, from more than 100 a day in the first days to 60 or so a day now.
The Israeli offensive has sparked large protests around the world over the past few days. Tens of thousands rallied Saturday in about a dozen European countries against the Israeli action. Some hurled shoes at iron gates near the British prime minister's residence in London, in an echo of the Iraq journalist who angrily threw his shoes at President George W. Bush while he was visiting Iraq last month.
Tens of thousands of Israeli Arabs demonstrated in the northern town of Sakhnin, by far the biggest protest in Israel so far. Marchers held Palestinian flags and a smattering of green Hamas flags. But there were no reports of violence.
In the latest attacks, the Israeli army struck the homes of two Hamas operatives, saying the buildings were used to store weapons and plan attacks. Hamas outposts, training camps and rocket launching sites also were targeted, it said.
The army also struck the American International School, the most prestigious educational institution in Gaza. The school is not connected to the U.S. government, but it teaches an American curriculum in English.
The airstrike demolished the school's main building and killed a night watchman. Two other Palestinians were killed in a separate airstrike, while four others, including a mid-level militant commander, died of wounds sustained earlier, Gaza health officials said.
Early Saturday, it dropped leaflets in downtown Gaza City ordering people off the streets.
Palestinian militants fired at least 10 rockets into southern Israel, lightly wounding one person, police said. One rocket scored a direct hit on a house in the southern city of Ashkelon and another struck a bomb shelter there, leaving its above-ground entrance scarred by shrapnel.
The Israeli airstrikes have badly damaged Gaza's infrastructure, knocking out power and water in many areas and raising concerns of a looming humanitarian disaster.
Israel briefly opened its border Friday to allow nearly 300 Palestinians with foreign passports to flee the besieged area. The evacuees told of crippling shortages of water, electricity and medicine.
Maxwell Gaylard, U.N. humanitarian coordinator for the Palestinians Territories, estimated that a quarter of the Palestinians killed were civilians and a "significant number" of the dead were women and children. He said some 2,000 people have been wounded in the past week.
"There is a critical emergency right now in the Gaza Strip," he said.
Israel denies there is a humanitarian crisis in Gaza and has increased its shipments of goods into Gaza. It says it has confined its attacks to militants while trying to prevent civilian casualties.
While ground troops remained poised to enter Gaza, Israel also has left the door open to a diplomatic solution, saying it would accept a cease-fire if it is enforced by international monitors.
This latest round of violence erupted after the expiration of a six-month cease-fire that was repeatedly marred by sporadic rocket attacks on Israel.
Israel's call for international monitors appeared to be gaining steam.
At the United Nations, Ban urged world leaders to intensify efforts to achieve an immediate cease-fire that includes monitors to enforce the truce and possibly protect Palestinian civilians.
In Washington, Bush on Friday branded the rocket fire an "act of terror" and outlined his own condition for a cease-fire in Gaza, saying no peace deal would be acceptable without monitoring to halt the flow of smuggled weapons to terrorist groups.
"The United States is leading diplomatic efforts to achieve a meaningful cease-fire that is fully respected," Bush said in his weekly radio address.
The spokesman for the Hamas government in Gaza, Taher Nunu, said the group would not allow Israel or the international community to impose any arrangement, though he left the door open to a negotiated solution.
"Anyone who thinks that the change in the Palestinian arena can be achieved through jet fighters' bombs and tanks and without dialogue is mistaken," he said.
With time running out on the Bush presidency, the crisis in Gaza is likely to carry over to President-elect Barack Obama. Secretary of State Condoleezza Rice continued telephone diplomacy to arrange a truce, but said she had no plans to make an emergency visit to the region.
Palestinian President Mahmoud Abbas delayed a planned trip to the United Nations so he could meet with Sarkozy and a high-level EU delegation on Monday. He now plans on speaking at the U.N. on Tuesday, said Abbas aide Saeb Erekat.
At the U.N., Abbas is expected to urge the Security Council to adopt an Arab draft resolution that would condemn Israel and demand a halt to its bombing campaign in Gaza.
Abbas, whose forces in Gaza were ousted by Hamas in June 2007, still claims authority over the area.
The council is expected to discuss the draft resolution on Monday. But the United States said the draft is "unacceptable" and "unbalanced" because it makes no mention of halting Hamas rocket attacks.
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Federman reported from Jerusalem. Associated Press writer Ben Feller in Washington contributed to this report.