Salmon even more harmful that originally thought
Nothing new here....this is a perspective from Europe.....
Farmed salmon pose greater risk to wild species than thought
Wed Jun 4, 2:40 PM ET
PARIS (AFP) - Farmed salmon are a bigger risk to wild species than previously thought, according to a study which says young captive fish that escape their pens beat their native counterparts at the mating game.
Salmon farms are a thriving industry in Canada, Chile, Ireland, Norway and Scotland but biologists have long feared that the native gene pool could be destroyed if too many penned fish escape their confinement and inter-breed with wild fish.
Until now, those fears have been dampened by findings that escapees are less successful at reproducing than native fish.
But a new study says the picture is more complex, the British weekly New Scientist reports in its forthcoming June 7 issue.
Farmed salmon may be less fertile than wild fish but young males among them more than make up for it. Their early sexual maturity and aggressiveness enables them to sneak in front of larger wild fish to fertilise the female's eggs.
Experiments conducted on farmed, wild and hybrid species of Norwegian salmon by Oxford University scientist Dany Garant and colleagues found that farmed yearlings were four times as successful as wild ones at fertilising eggs.
Even the hybrids were twice as good at it as their wild rivals.
Given the faster life cycles of farmed salmon, these young fish could very quickly spread their genes through wild populations, says Garant's study, published in a specialist journal, Ecology Letters.
William Muir, an expert on farmed and transgenic fish at Purdue University in the US state of Indiana, told New Scientist that the study shed "incredibly important" light on the dilemma of farmed fish.
"(Escapees) could swamp the gene pools with maladapted genes and quickly cause extinction of wild fish," he warned.
Seven countries that have big salmon farming industries signed an agreement in 1994 aimed at minimising the impact of fish farming in the North Atlantic.
But the measures set out in the accord are only voluntary guidelines and do not hold countries accountable for damage wrought by escaped fish.
Escapees are a major problem, said Garant. "In Norway, some rivers are completely invaded by farmed fish."
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