Information on Sea Lice - Fast Facts

October 11, 2005

DO YOU KNOW?

• Sea lice are a naturally-occurring species found in every ocean and on many varieties of fish.
• Sea lice are small, salt-water parasites that graze on the mucous and skin of fish, and usually have little impact on their health and survival.
• Sea lice are very common on all Pacific salmon adults during their return to the freshwater lakes and streams in which they were born. Commercial fishermen, recreational fishers, and First Nations people are all accustomed to seeing sea lice on wild adult Pacific salmon.
• Two species of sea lice have been observed in the Broughton Archipelago since monitoring began in the area in 2001.  Lepeophtheirus salmonis is commonly found on wild and farmed salmon and has been reported throughout the Pacific in areas including the high seas and coastal areas of Russia, Alaska and Canada.  Caligus clemensi is found on several species of fish and occasionally on farmed salmon.
• Sea lice populations are affected by environmental conditions and thrive in warm water temperatures and high salinity levels. Warmer ocean temperatures and lower levels of freshwater runoff from reduced annual rainfall along the BC coast may be contributing to higher levels of sea lice.
• Juvenile pink and chum salmon experience naturally high rates of mortality during their first few months at sea. Infections with sea lice may increase mortality of individual fish during this period. DFO is examining whether sea lice infections over the life span of these salmon threatens the overall size of pink and chum populations. DFO research shows evidence that sea lice levels are not affecting pink and chum salmon stocks in the Broughton Archipelago.
• The numbers of pink salmon returning to the Broughton Archipelago in 2002 and 2003 were very poor and heightened concern about impacts of sea lice infections observed on juveniles in that area. In 2004 and 2005, the number of returning pinks has improved compared to those years. Since 1987 - the introduction of salmon farms to the area - average returns of Pink salmon have been higher than the 50 year average.
• Sea lice affect both wild and farmed fish. In British Columbia, lice from wild salmon returning from the ocean to spawn in their natal streams can transfer the parasite to farmed salmon. This can result in an increase in the levels of sea lice on fish farms in the fall and early winter.  If not treated, these infections could provide another refuge for sea lice in coastal waters. However, the incidence of sea lice is monitored regularly and veterinarians can treat these fish to reduce lice levels.
• Because of these recent controls, farm fish usually carry lower levels of sea lice than wild adult salmon.
• Every salmon farm in British Columbia is required to have a fish health management plan in place as a condition of its operating licence. Sea lice monitoring is mandatory in this plan and all producers are required to report their sampling results to the British Columbia Ministry of Agriculture and Lands.
• DFO's research during the past three years does not support the notion that juvenile salmon travel through specific "migration corridors" in the Broughton Archipelago on their way out to the ocean. These results do not support the suggestion that emptying salmon farms along a certain path will be an effective action to reduce sea lice infections to young salmon.