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'Irrefutable evidence' sea lice are killing wild salmon
Written By: John Fiorillo
On Date: 11/10/2006
Up to 95 percent of wild juvenile salmon that migrate past fish farms die as a result of sea lice infestation from the farms, according to a new study published in the Proceedings of the National Academy of Sciences. The study found an increasing number of salmon were killed over the migration season, from 9 percent in early spring, when the sea lice population was low, to 95 percent in late spring, when the sea lice population was higher.
"We know that fish farms raise sea lice levels, and we know that sea lice kill fish," said the study's lead author, Martin Krkosek, a Ph.D. student at the University of Alberta Center for Mathematical Biology. "This is the first study to combine field surveys, experiments and mathematical modeling in one system to estimate the total impact of the farms."
The primary sea lice hosts are adult salmon. Under natural conditions, the adults are far offshore when the juveniles are migrating out to sea. Fish farms put adult salmon in net pens along the migration routes. The result is a cloud of sea lice through which the juveniles must migrate. "It takes only one or two sea lice to kill a juvenile pink or chum salmon," said Krkosek. "The juveniles are so vulnerable because they are so small ? only one to two inches long."
The research was conducted by a team of biologists and mathematicians working in coastal British Columbia. "We counted sea lice on more than 14,000 juvenile salmon migrating past fish farms, and conducted mortality experiments with more than 3,000 fish," said Krkosek. "We then used mathematical models to combine this information and estimate the total impact of the farms."
"A mathematical model is only as good as the data put in, and in the past the data put in has been very questionable because of sampling errors and some overt ways the study was done to slant the data," said Alex Trent, spokesman for Salmon of The America's (SOTA), a trade group representing salmon farmers. "Over time the returns of pink salmon have increased since the introduction of salmon farms. So all the projections aside, what actually happens in nature over time, which is what we need to worry about, does not support the computer model," Trent told IntraFish on Monday.
The research was funded primarily by the National Research Council of Canada and the Natural Sciences and Engineering Research Council of Canada. Further support came from the David Suzuki Foundation, the Canadian Sablefish Association, and the British Columbia Wilderness Tourism Association.
"The debate is over," said study co-author Alexandra Morton, a biologist with the Raincoast Research Society. "This paper brings our understanding of farm-origin sea lice and Pacific wild salmon to the point where we know there is a clear severe impact."
Written By: John Fiorillo
On Date: 11/10/2006
Up to 95 percent of wild juvenile salmon that migrate past fish farms die as a result of sea lice infestation from the farms, according to a new study published in the Proceedings of the National Academy of Sciences. The study found an increasing number of salmon were killed over the migration season, from 9 percent in early spring, when the sea lice population was low, to 95 percent in late spring, when the sea lice population was higher.
"We know that fish farms raise sea lice levels, and we know that sea lice kill fish," said the study's lead author, Martin Krkosek, a Ph.D. student at the University of Alberta Center for Mathematical Biology. "This is the first study to combine field surveys, experiments and mathematical modeling in one system to estimate the total impact of the farms."
The primary sea lice hosts are adult salmon. Under natural conditions, the adults are far offshore when the juveniles are migrating out to sea. Fish farms put adult salmon in net pens along the migration routes. The result is a cloud of sea lice through which the juveniles must migrate. "It takes only one or two sea lice to kill a juvenile pink or chum salmon," said Krkosek. "The juveniles are so vulnerable because they are so small ? only one to two inches long."
The research was conducted by a team of biologists and mathematicians working in coastal British Columbia. "We counted sea lice on more than 14,000 juvenile salmon migrating past fish farms, and conducted mortality experiments with more than 3,000 fish," said Krkosek. "We then used mathematical models to combine this information and estimate the total impact of the farms."
"A mathematical model is only as good as the data put in, and in the past the data put in has been very questionable because of sampling errors and some overt ways the study was done to slant the data," said Alex Trent, spokesman for Salmon of The America's (SOTA), a trade group representing salmon farmers. "Over time the returns of pink salmon have increased since the introduction of salmon farms. So all the projections aside, what actually happens in nature over time, which is what we need to worry about, does not support the computer model," Trent told IntraFish on Monday.
The research was funded primarily by the National Research Council of Canada and the Natural Sciences and Engineering Research Council of Canada. Further support came from the David Suzuki Foundation, the Canadian Sablefish Association, and the British Columbia Wilderness Tourism Association.
"The debate is over," said study co-author Alexandra Morton, a biologist with the Raincoast Research Society. "This paper brings our understanding of farm-origin sea lice and Pacific wild salmon to the point where we know there is a clear severe impact."