Comparison of the fecundity rate of Caligus rogercresseyi infesting Atlantic salmon (Salmo salar L.) on farms in two regions of Chile

Monthly sampling of adult lice on a salmon farm located in Region XI was carried out between October 2011 and September 2012 to assess the reproductive behaviour of Caligus rogercresseyi (43°34′LS; 74°78.9LW). The fecundity data were compared with those obtained in Region X (Lat 42°S) for the period 2006-2007. Results have shown that those from the farm in Region XI were smaller than the female lice collected in Region X in the period 2006-2007. In contrast, the male lice collected from Region XI were 14% larger than the males collected from Region X. Even though the average length of the egg sac string and the number of eggs per string were larger in Region XI in comparison with Region X, the egg length was 10% smaller in Region XI. The differences recorded in this study could be attributed to differences in the environmental conditions observed between both regions. Region XI is highly influenced by the Humboldt current, with lower seawater temperature in comparison with Region X.