Population dynamic of early stages of Caligus rogercresseyi in an embayment used for intensive salmon farms in Chilean inland seas

Abstract

Around the world several strategies for the management and control of sea lice infestations have been implemented. In Chile where the salmon harvest is significantly higher than other countries and where salmonids are not endemic species, information concerning how farm locations and local oceanographic conditions interact in regulating the dispersal of parasites and their impact on farmed and native fish populations is required urgently. In this work we studied the spatial and temporal dynamics of the early stages of Caligus rogercresseyi in a semi-enclosed area where eight salmon farms are located in southern Chile. Plankton samples were collected in three modes (fortnightly, diurnal and semidiurnal spatial), which were complemented by studying circulation patterns inside the bay. Simultaneously, records of ovigerous female C. rogercresseyi per fish, treatments for caligids, biomass, and the average weight of fish were obtained from salmon farms in the study area. Our results suggest that the population dynamics of the early stages of C. rogercresseyi is strongly associated to salmon farm, which could be magnified by the effect of the local circulation pattern. In this context it seems unlikely to control, through current caligid treatments, the caligid pest in this semi-enclosed area without a drastic decrease of salmon biomass inside the bay. The salmon farms should be located distant enough between them to minimize risks and maximizes benefits to all concerned parties.