Sea lice not the cause of pink salmon crash
Fish farmers and their regulators in British Columbia were given an early Christmas present with the release of a study that contradicts earlier reports about lice from salmon farms causing a big drop in the returns of pink salmon to the area in 2002, following a huge return two years earlier. The lead author of the study, Dr. Gary Marty from the School of Veterinary Medicine at the University of California Davis, said that the number of lice on farmed fish in the region can not be used to predict pink salmon returns.
Many other studies have been reported regarding the situation between salmon farms, sea lice and wild salmon in B.C., most of them by researchers from the University of Alberta and the Simon Fraser University in Vancouver. The conclusions and the presentations made from these studies all predicted a major negative effect on the wild salmon populations in the Broughton Archipelago.
Most of the previous studies published about this issue were based on theoretical mathematical models with some sampling and field monitoring of wild, juvenile pink salmon, but none of the studies that predicted the destruction and demise of wild pink salmon looked at the presence or absence of lice on the fish within the farms in the study area at the time. One publication authored by scientists from the Canadian Department of Fisheries and Oceans concluded that wild and farmed salmon can co-exist in the marine ecosystem on the Pacific coast of Canada .
This particular study had free access to all data in the possession of the fish farming companies operating in the Broughton- from sea lice and other fish health records to production data such as number and age/size of the fish in individual farms. 10-20 years of farm data were analyzed, along with 60 years of pink salmon data. Along with Dr. Marty, the study was co-authored by Terrance Quinn, professor of fish population dynamics at the Juneau Center of the School of Fisheries and Ocean Sciences at the University of Alaska Fairbanks, and Veterinary Doctor Sonja Saksida, Executive Director of the British Columbia Centre for Aquatic Health Sciences in Campbell River.
The researchers pointed out that the earlier studies that concluded that sea lice from farms were to blame for the dismal 2002 return of pink salmon to the Broughton area did not perform any diagnostic investigation to rule out any other causes of mortality. They said that “..productivity of wild salmon is not negatively associated with either farm lice numbers or farm fish production, and all published field and laboratory data support the conclusion that something other than sea lice caused the population decline in 2002. We conclude that separating farm salmon from wild salmon -proposed through coordinated fallowing or closed containment - will not increase wild salmon productivity...”.
The Californian University is over 100 years old, has more than 32,000 students and over 21,000 staff, as well as an annual research budget that exceeds US$ 679 million (~€ 512 million).
