A new study from UC Davis is in contradiction with earlier reports that salmon farms were responsible for the 2002 wild Pink salmon population crash in the West of the Canada Broughton archipelago.
Broughton crash became a rallying for people concerned about the potential environmental effects of salmon open-net, agriculture, which became a $ 10 billion industry worldwide event, generating nearly 1.5 million tonnes of fish per year.
The new study, which will be published online this week in proceedings of the National Academy of Sciences, determines not what caused the accident, but it is the first suspect: skin small parasites called pou.
Principal author of the study is Gary Marty, a veterinary pathologist and research associate at the UC Davis School of Veterinary Medicine. An expert in diseases of fish, Marty is studying health Pink salmon since 1989 oil spill Exxon Valdez, Alaska.
"For anyone who worried about the effect of salmon farm on wild salmon, it is good news" Marty said. "Sea lice from fish farms have no significant effect on the productivity of the population of wild salmon."
The new study is the first to analyze 20 years of data for the production of fish and sea lice each salmon farm counts 10 years in the Broughton archipelago and compare them against 60 adult salmon population figures.
The study concludes that farmed fish are the main source of sea lice on juvenile salmon pink wild region, but it found no statistical correlation between levels on farms and the survival of the lifetime of the wild populations Pink salmon lice.
Pink salmon (Oncorhynchus gorbuscha) are the most abundant wild salmon species in the Broughton archipelago. When they are older than a few months, Pink salmon juveniles leave streams where they were born. They mature at sea, then return to their native stream to spawn and die two years after their parents.
Because of their lifetime of two years, salmon pink, born in odd-numbered years are genetically different from those who were born in odd-numbered years. Registration of 60 years, two rows of Pink salmon took huge population, unexplained swings, before even the farms were established at the end of the 1980s.
Sea lice is natural parasites of adult salmon. Adult louse, about the size of a small watermelon seed attaches to the skin of a fish and feed its host. Minor lice infestations are not harmful to pink, but a severe infestation can weaken or kill smaller fish (those of the size of a paper clip). Farm fish, veterinary treat fish with medicated when lice populations become too high.
Broughton fish farms raise of salmon (Salmo salar) in enclosures bâchées on the net into the water. Salmon pink wild is separated as farmed fish by mesh net enclosures. Lice password freely farmed wild fish and vice versa.
Save a large number of wild Pink salmon returns to spawn in the rivers of the archipelago of Broughton in 2000 and 2001, but only 3 percent of this number returned in 2002 and only 12% in 2003.
Also in 2001, the first review of Pink salmon juveniles Broughton concluded that more than 90 per cent had lice. In the next two years, when salmon numbers collapsed, the assumption is that sea lice from fish farms is responsible for.
Calls went into closed containers open net pens fish farm. And regulatory agencies ordered farmers to use stricter summer treatments.
In the new study, Marty and his colleagues were able to see, year by year, lice how was in farms where young Pink salmon went to the sea, and how these salmon return to spawn. The results are surprising.
"Salmon returned in these low numbers in 2002 was exposed to the juvenile stage unless lice that salmon returned in numbers high record in 2001," said Marty. "Louse of farmed fish could not have the crash of the wild salmon population 2002."
Marty co-authors are Sonja Saksida, Director of the British Columbia Centre for Aquatic Health Sciences in Campbell River and Terrance Quinn, Professor of population dynamics of fish in the Juneau School of fisheries and the sea at the University of Alaska Fairbanks sciences centre. Quinn is a world authority on the mathematical modelling of fish populations. Saksida is a veterinarian, and the first researcher given access to confidential documents all Broughton aquaculture enterprises.
Marty is also the pathologist fish for the Ministry of agriculture of British Colombia and a member of faculty affiliate school Alaska of fisheries and marine science.
Marty said that even if the trio used a large part of the fish data and the same lice used in previous studies, they have reached a different conclusion for two reasons: firstly, the farmers give Saksida their records, and secondly, the old and new data were analyzed for common methods in veterinary medicine which were not used in most previous studies.
"The lesson to be drawn from this study is that we cannot solve simple explanations for the decline of populations of wild animals." There are very complex interactions between animal disease, the environment and the health of populations. Sustainability studies should engage all specialties of science to pursue a better understanding of these relationships, "said Marty."
None of the authors received compensation from any source for this analysis. Quinn ever worked for any company hatchery. Marty has never worked for any company hatchery to the Canada. United States, he consulted for the industry in 2000 and 2001. Since 2004, Marty analyzed samples from fish-farm for the provincial Government of British Colombia is sometimes paid a fee for these services by agricultural enterprises. Saksida in veterinary practice private for 15 years, has done work contract for all three farm fish companies operating in the study area.
More than 100 years, the UC Davis is engaged in teaching, research and public service in California and to transform the world. Located near the capital of the State, UC Davis has more than 32,000 students, teachers and 2 500 and more than 21 000 members of staff, an annual budget in excess of $ 679 million, an overall health system research and 13 specialized research centres. Interdisciplinary offers graduate and 100 majors undergraduate four colleges - agriculture and environment, biological sciences, and engineering and letters and sciences science and University. It boasts six professional schools - education, law, management, medicine, veterinary medicine and Betty Irene Moore School of nursing.
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