Sea lice monitoring baseline studies show low but variable results

September 7, 2015 - Campbell River, B.C.

Marine Harvest Canada has publicly posted this year's report of wild fish sea lice monitoring undertaken in the waters northeast of Vancouver Island. This year's results - sampled in April and May - show continued low overall abundance of sea lice on wild fish and mirrored 2011 results that saw elevated levels of sea lice on wild fish in some zones of study.

The 43 page report is the fourth such study since 2011 and is published by Pacificus Biological Services on behalf of Marine Harvest Canada, the Tlatlasikwala First Nation, and Gwa'sala Nakwaxda'xw First Nation. The primary objective of the study is to create baseline data of sea lice abundance on wild fish species in an area where no historical data exists. Target species included five species of salmon, cutthroat trout, Dolly Varden, and Pacific herring.

The report shows that, while highly variable, sea lice intensity on wild fish within all sampling zone remains far below the known threshold of health concern to pink salmon (Jones et al, 2007).

Interesting observations were also noted, including a spike in sea louse species commonly associated with Pacific herring, Caligus clemensi. Abundance of C. clemensi in Zone 1 was significantly higher than all other Zones. Additionally, while the study confirms that 2015 sea lice abundance is below levels of concern, the numbers mirrored 2011 results that found levels to be slightly higher than average. These observations support recent anecdotal information that higher temperatures and salinity, combined with a strong return of adult wild salmon the previous fall, have provided for ideal growing and reproducing conditions for sea lice.

Future objectives of this study will include determining life history characteristics of sea lice, as well as the timing, abundance, and distribution of juvenile wild salmon migrations.

Read the full report here.