Aquaculture for all

Sea Lice On Farmed Salmonids In Chile

Salmonids Health

Research by Sandra Bravo, from the Aquaculture Institute at the Universidad Austral de Chile, has identified that sea lice Caligus rogercresseyi, a Caligidae species not previously documented, occurs widely in both the South of Chile and Southern Argentina.

Studies carried out in conjunction with the Chilean project Fondef D04I1255 documented resistance development in this parasite towards both emamectin benzoate and deltamethrin - two important compounds used to control sea lice in Chile as well as in the Northern hemisphere. The studies also revealed that hydrogen peroxide only has a limited ability to control C. rogercresseyi.

Furthermore, the studies showed that, after a single mating, the C. rogercresseyi female could produce up to 11 broods. Female parasites adapted to suboptimal conditions better than males and under these conditions their reproductive rate increased. Under normal conditions, C. rogercresseyi produced about 50 eggs per egg string, but under suboptimal conditions, such as low temperature or low salinity, the egg production was higher.

Since 1992, Chile has been the second largest salmon producer (after Norway), and since 1997 C. rogercresseyi has been proved to be the most serious parasite infestation affecting the Chilean salmon industry. The parasite has a substantially negative effect on the survival and growth of salmon, as well as increasing their susceptibility to other infections. This has had a serious economic impact on the salmon industry. The most vulnerable salmonid species are Atlantic salmon (Salmo salar) and Rainbow trout (Oncorhynchus mykiss), while Coho salmon (Oncorhynchus kisutch) appears to be resistant to this particular parasite species.

Sandra Bravo’s thesis is based on several studies carried out in Chile in connection with various research projects during the period from 1998 to 2008. The primary aim of the thesis was to characterize this Caligidae species as well as to study its dispersal, biology, ecology and the efficacy of control treatments. Due to the severe effects of C. rogercresseyi on farmed salmon, an integrated parasite management approach (IPM) was suggested in order to improve the level of control.

On 9th of December 2010, Sandra Bravo gave two trial lectures before defending her doctoral thesis at The Norwegian School of Veterinary Science: Lessons learned in integrated disease management strategies for salmonid farming: a global perspective and Predominant fish diseases in Chilean aquaculture.

The thesis, entitled Caligidae ectoparasites on farmed salmonids in Chile: Classification, distribution, biology, control and resistance development, was publicly defended on 10th of December 2010.

December 2010