Sea lice and salmon in the news again
The issue of lice from salmon farms and its effect on wild salmon population is the subject of a report published in the magazine Science last week. This latest in a series of reports that have somehow managed to get through the peer-review process of normally respected journals adds little to the information base about the interaction between farmed and wild salmon. It is at best an exercise in hypothetical mathematics, based on assumptions established by the authors themselves.
With half of the references to previous reports about lice and fish farms in B.C. pointing to publications by the authors themselves, or other well known critics of salmon farming in British Columbia, this report is built on a long list of false pretences. For example, this report is based on previously published reports that assume that the health of wild Pacific salmon smolt is seriously compromised by the exposure to some 1.3 lice per gram of fish. While this may be true for Atlantic salmon in Europe, it is not supported by research on Pacific salmon in B.C. To the contrary- government researchers that have spent years in the Broughton Archipelago- the area in question- have found little or no evidence of harm to juvenile Pacific salmon caused by lice.
The Department of Fisheries and Oceans (DFO) has undertaken extensive research concerning salmon farms, sea lice and wild salmon both in the field and in laboratories. The Department states that "some recent papers have, however, generated media reports stating that sea lice produced from salmon farms are a major cause of losses in wild salmon populations. DFO does not support the close association between salmon farms, sea lice, and loss of wild salmon reported by others".
Other reports published by industry critics and widely distributed to world wide media show increased sea lice infestations on wild, out-migrating juvenile Pacific salmon in locations near salmon farms- even salmon farms that did not have fish in them at the time. Huge numbers of other wild fish in the area have been shown to harbour sea lice, but no consideration to this was given in these series of publications.
This latest report also contradicts itself by referring to the "fallow year of 2003" as a year with increased marine survival, but with "elevated louse abundance". The Provincial Government points out that DFO research showed relatively low infection rates on wild salmon throughout all parts of the Broughton area during 2003. It goes on to state that in 2004, when previously fallowed sites were active, there was again no difference in lice levels between fish found in the "fallowed area" and other areas of the Broughton. There was also no evidence that the fallowed route was more significant as a migration route than other Broughton waterways. Differences were found in lice loads and species of lice between the two years 2003 and 2004.
The main contributor to the pink salmon population in the Broughton area is the Glendale spawning channel, and its salmon production was excluded from this latest study "because any increased salmon abundances in these rivers confound our estimates of natural changes in abundance", according to the authors. That leaves watersheds like the Ahnuhati, the Kingcome and the Wakeman Rivers to be included in their study. These rivers showed an increase in returns of pink salmon this year (2007- preliminary and worst case data) of 33, 272 and 748 per cent, respectively compared with the brood year of 2005.
No consideration was given in this report to commercial and sport-fishing catches of pink salmon throughout their migration in the Pacific Ocean, where salmon of British Columbian origin is frequently targeted by Alaskan and northern B.C. salmon harvesters.
Please note that in B.C., the term "sea lice" is not species specific, although most people associate the term with the salmon lice- Lepeoptheirus salmonis. The Pacific version of this lice has been found to differ significantly in its genetic make-up compared to its Atlantic counterpart. Salmon farmers in B.C. seldom have to treat their fish for lice, as infection levels have historically been low, and little damage to farm fish has been experienced.
