Sea Lice Monitoring

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DFO has created a comprehensive action plan to address, assess, and observe potential risks to wild pink salmon stocks. The five part plan includes:

• a freshwater monitoring program
• a marine monitoring program
• an active salmon farm management approach
• a long-term research plan
• a public-consultation/dialogue process

There are two more common species of sea lice observed on wild and farmed salmon in the British Columbia area:

• Lepeophtheirus salmonis: infecting various species of salmon exclusively.
• Caligus clemensi: infecting a wide variety of finfish, including salmon, herring, and stickleback.

Since 2004, the numbers of L. salmonis sea lice on wild juvenile pink and chum salmon have declined in the Broughton Archipelago. DFO has conducted research and monitoring since the 2003 implementation of the Pink Salmon Action Plan but reasons for the steady decline are not conclusive.

Broughton Archipelago Monitoring Results
(Observations from 2003 – 2009)

Time of Year	Wild Pink Salmon Mass
Late March - Early April	98.9% of samples < 0.7 g
June	Less than 1% < 0.7 g

These observations serve as indicators to salmon farm operators to make important farm management decisions. For example, pretreatment of the farm in the spring to reduce sea lice levels in the summer in anticipation of the passing of smaller sized salmon fry. These decisions not only protect the salmon on the farms, but also help protect wild salmon stocks from early and potentially harmful exposure to sea lice while they are at a crucial size. 

Controlled laboratory testing showed that 35% of pink salmon (weighing < 0.3 g) died following exposure to sea lice. However, once salmon had reached 0.7 g they had become highly resistant to the potentially lethal parasites. Based on these scientific observations, L. Salmonis and C. Clemensi pose particular threat to wild juvenile salmon that are under 0.7 g. Generally, when juvenile salmon migrate through farming areas they weigh more than 0.7 g. Further research is underway to compare the observations in the controlled lab testing to field research conducted in the wild.

For more information regarding the study of critical weight for juvenile pink salmon and their resistance to sea lice, visit: http://+www3.interscience.wiley.com/journal/120751387/issue