Sea lice on farmed Salmonids in Chile

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. Read more...

This blog is written by Martin Little The Aquaculturists, published and supported by the International Aquafeed Magazine from Perendale Publishers.