Media Releases & Recent Articles

BACKGROUNDER on the DFO Research Papers on Sea Lice

The main objective of the Marine Monitoring Program (MMP), a main component of the Pink Salmon Action Plan announced by Fisheries and Oceans Canada Minister Robert Thibault in February 2003, was to obtain samples of wild juvenile pink salmon (Oncorhynchus gorbuscha) from marine areas throughout the Broughton to assess the incidence and severity of infection by sea lice by location and time. A secondary objective was to regularly monitor the abundance of wild juvenile pink salmon at many locations during the early sea life period, to obtain information about the spatial and temporal distribution in the Broughton. The study objectives were not designed to examine cause and effect relationships among sea lice infection rates and fish farm site location or farm management practices. Instead, the results of the study show that the 2003 Marine Monitoring Program (MMP) was an important first step in gathering base-line information and data on distribution of juvenile pink and chum salmon and current state of sea lice infection rates in the Broughton Archipelago. This information will form the basis of the experimental design of future sampling where hypothesis can be established and tested.

Paper on Sea lice on juvenile salmon and on some non-salmonid species caught in the Broughton Archipelago in 2003

Dr. Simon Jones and Amanda Nemec
Copepods of the family Caligidae (Siphonostomatoidea: Copepoda) are parasitic on the skin, fins, gills and buccal cavity of marine fishes. In British Columbia (BC) coastal waters these niches have been exploited by 11 species belonging to the genus Lepeophtheirus and one species of Caligus. There is little historic data on sea lice infection rates of juvenile salmonids in the Broughton Archipelago. In addition, prior to 2001, juvenile pink and chum salmon in the Broughton Archipelago had received virtually no scientific attention. Annual variations in the number and condition of out-migrating smolts from specific streams had been relatively poorly documented and their migratory routes through this region were speculative. The present study was an effort to systematically survey juvenile Oncorhynchus spp. for caligid copepods throughout their nearshore marine migratory phase following seawater entry. The overall objective of the study was to describe patterns of spatial and temporal variations in the prevalence and intensity (or abundance) of sea lice infections on juvenile pink and chum salmon in a limited area of coastal BC: the Broughton Archipelago and Knight Inlet. For the purpose of this study, it was hypothesized that the prevalence and intensity (or abundance) of infections on salmonid and non-salmonid fishes would be uniformly distributed temporally and spatially throughout the study.

Approximately 25% of juvenile pink and chum salmon were infected with two species of sea lice: Lepeophtheirus salmonis and Caligus clemensi. On both salmon species most infections consisted of a single chalimus stage and most of these were C. clemensi. The prevalence of motile L. salmonis increased towards the end of the study and was coincident with a decline in the proportion of L. salmonis chalimus stages. Prevalence of sea lice infections on juvenile salmon varied significantly in time and space was this variation was significantly associated with sea water salinity and temperature and with size of salmon. There was no evidence that infection with sea lice adversely affected size or condition factor of juvenile pink and chum salmon during the time that was monitored. Caligus clemensi and an unidentified Lepeophtheirus sp. were found on approximately 60% of sticklebacks. Lepeophtheirus hospitalis and C. clemensi were also found on herring.

Paper on Abundance and distribution of juvenile salmon and other fish caught in the Broughton Archipelago, Knight Inlet and Muchalat Inlet, B.C. in 2003.

Dr. Brent Hargreaves, Doug Herriott and Vic Palermo

This PSARC paper provides analyses of the catches, abundances (CPUE), and size of juvenile pink and chum salmon, and stickleback, for the Broughton and Knight Inlet. In general, juvenile pink and chum were caught throughout the Broughton and Knight Inlet in all time periods, and frequently these two species were found together. The abundances of pink and chum remained low throughout the study area during March, then gradually increased during April. The peak abundances of both pink and chum salmon occurred in Knight Inlet in mid-to-late April, about two to three weeks earlier than in the Broughton. The average size of both pink and chum remained low (30 - 40mm fork length range) during March, then increased steadily to 70-80 mm by mid-June.

This PSARC paper provides some new information on migration routes and timing of juvenile pink and chum salmon in the Broughton and Knight Inlet. One hypothesis put forward in 2002 was that juvenile pink salmon migrate through the Broughton area using a specific corridor. In 2003 the B.C. Province required that all commercial salmon farms along this route be fallowed (cease production) to protect juvenile pink and chum salmon. The results from the 2003 MMP show that juvenile pink and chum salmon were widely distributed throughout the Broughton and Knight Inlet and did not support the existence of a "main migration corridor" in the Broughton. However, these results represent only one year and the conclusion may be different in other years when the abundances of pink or chum are substantially higher or lower. Determining the migration routes and timing for juvenile pink and chum was not the primary objective for the 2003 MMP, and the sampling program was not optimal for resolving these questions.

The full reports will be available on DFO web site in early June.