Escapes from Aquaculture are a serious problem when they intermingle with wild populations, causing disease and adverse genetic change. Various attempts are being made to control the problem.
The
impact of Salmon Farming on wild Salmon
It may
be odd, but at a time when there is growing concern about the abundance of wild
Atlantic salmon stocks, the number of Atlantic salmon in the sea has never been
higher. The salmon farming industry has developed extremely rapidly and now has
a production, on a worldwide basis, of more than 1 million tonnes a year,
approximately 400 times the harvest of the wild salmon stocks.
There
are major issues concerning the sustainability of catching sufficient small fish
to feed all of these salmon but the principal impacts of salmon farming are
principally the risks of transmission of diseases and parasites, particularly
sea lice, to the wild stocks. Any direct impact of disease or parasites is
exacerbated through the loss of genetic diversity in wild stocks caused by
interbreeding with escaped farmed salmon. Recent research (Ref?) suggests that
such interbreeding, and poorly planned stocking practices, are having serious
consequences for the genotypes of wild salmon, each population of which (each
ESU – Evolutionarily Significant Unit in the jargon) has been adapted by
evolution to the specific environmental conditions appertaining in its home
river. In contrast, most farmed salmon have been held in captivity for many
generations, are often very inbred and have been selected for traits which
favour survival in captivity, not in the wild.
Other
serious genetic issues are raised by trying to grow species outside their home
range and there are now plans to raise transgenic salmon (fish with transplanted
genes from other species) in the
| Atlantic Salmon Escapes. |
Recent News : Impact of escapes in Scotland
|
| On Sept. 29, 2000, the British Columbia provincial cabinet reportedly approved a government order that would require more stringent measures to prevent escapes of Atlantic salmon from 104 BC salmon farms. The new regulations are to be formally announced on Oct. 4, 2000, and would become effective on Oct. 31, 2000, requiring all BC fish farmers to submit written escape prevention and response plans that include measures for predator avoidance, descriptions of existing and proposed containment mechanisms, and inspection and maintenance schedules. | {{In addition, net pens will be randomly inspected and additional streams will be surveyed for escaped Atlantic salmon. At the same time, the federal Canadian government approved four aquaculture pilot projects with C$9.7 million in funding.}} [Canadian Press, Environment News Service] |
Do escaped farm salmon jeopardise native populations?A MAJOR row has broken out in Canada over a proposal to import Norwegian salmon to stock fish farms. The government's Office of Aquaculture and the farming industry have dismissed fears of escaped salmon wreaking havoc, saying they will enrich the genetic diversity of wild stocks. But last week in Montreal the government's fisheries scientists warned that escapees could jeopardise the survival of Canada's wild salmon. Canadian salmon farmers want to import breeding stock from Norway's highly successful farms. "They want the same opportunity to improve their stock as other livestock producers," says Dave Conley, a spokesman for the Office of Aquaculture. The office wants the government to lift its ban on importing farmed salmon. In October, Ray Peterson, a retired cattle geneticist at the University of British Columbia, wrote a paper for the department claiming wild salmon would benefit from some new genes. "Isolation of salmon stocks should be avoided," writes Peterson. He says they have lost their genetic diversity. |
"Nonsense," says Carl Walters, a
fish biologist at the University of British Columbia. Wild salmon are
genetically very diverse, he says, while farmed fish are less diverse
selections from wild stocks. He says that salmon, unlike cattle, are
highly adapted to local conditions that do not restrict genetic
diversity.
Fisheries scientists are concerned that the sheer number of escaped farmed salmon could overwhelm native stocks. At a meeting in Montreal last week, scientists working for the Department of Fisheries and Oceans recommended continuing the ban on Norwegian salmon. And a leaked report by the scientists says studies have shown that wild fish are much more genetically diverse than Peterson claims. Debora MacKenzie (From New Scientist no 2224 5 Feb 2000 p12 ) |
Page Author: Dr Rick T Leah, Univ of L'pool - Contents last reviewed 05/01/2007