Sea lice Discovery Islands 2021
April 6-25, 2021
The impact of the December 2020 Minister’s decision to honour First Nation requests to prohibit salmon farm restocking is having a significant positive impact. Sea lice infection of wild salmon in the Discovery Islands is very low compared to years where more salmon farms were active, particularly in Okisollo and Nodales Channels (green circle on right). The highest average infection per region this spring is .4 lice per juvenile salmon. This is approximately 90% lower than last year. To be sure of this number we need to wait for the next round of sampling because 2020 lice counts did not start until the 3rd week of May. In the graph above we see there are approximately 4xs more lice in the areas where salmon farms are still operating.
The study is divided into three regions:
Okisollo, the green circle on the right on the map, receives ocean currents from the east and so this area is in the path of sea lice larvae drifting out of the Cermaq Raza Island salmon farm. This site has been empty as of April 25 (according to Cermaq website), so it will be interesting to see lice numbers on young wild salmon in the Okisollo region next week.
Mid Discovery Islands, the green circle in the middle of the map, is protect by land on all sides from currents flowing out of operating salmon farms. The graph indicates an average of less than .1 louse per fish.
Western Discovery Islands, the green circle on the left, has four salmon farms still operating. Lice numbers on wild salmon are similar to Okisollo. However, they are still very low, and it will be interesting to view fish in this region next week.
Methods
50 salmon (pink and chum) were caught at each site on April 6 and April 25 (no fish were found at the sample site furthest to the east in Okisollo, Cyrus Rocks, on April 6). The fish were captured by beach seine and preserved individually in a whirlpak bag. Sea lice were identified with a 30x dissecting microscope and identified by life-stage (copepodite, chalimus A, chalimus b, preadult or adult), the, copepodite, preadult and adult stages (motile-lice) were further identified to sex and species (Lepeophtheirus salmonis or Caligus clemensi). Each fish was identified by species, measured and weighed. DNA samples were collected.
We don’t expect to see sockeye salmon migrating through this area until the 3rd week in May. I will be examining those fish alive. They will be the offspring from the adults that entered the Fraser River in 2019, the lowest return on record at that time.
SALMON FARMS – Discovery Islands
In 2021 five salmon farms are operating in the Discovery Islands. As of April 25, there are only four. In 2020 there were ten (see map below). The most critical area appears to be the Okisollo and Nodales Channel region (red circle below), because these channels are so narrow, so many young salmon use those waterways and because so many salmon farms have operated in that area in the past.
FARM LICE
All but one salmon farm (off Port Hardy) is currently reporting sea lice numbers below the federal threshold of three motile-stage (adult) lice. First Nations in the Broughton and Clayoquot Sound are demanding levels lower than this to protect collapsing wild salmon populations. I hope we can believe these farm numbers, as research published in 2020 reports that the fish farm companies using BC to grow Atlantic salmon fail to report up to 50% of their lice (Godwin et al 2020[i]). This is a critical year for wild and farm salmon. Many wild salmon runs are on the verge of extinction and the Minister of Fisheries and First Nations are severely reducing the number of farm salmon in BC waters.
[i] Bias in self‐reported parasite data from the salmon farming industry
Summary
To date I have only reported on sea lice numbers on juvenile pink and chum salmon in the Discovery Islands. The young sockeye have not arrived yet. The reduction from 10 to 4 salmon farms and complete removal of the farms from Okisollo and Nodales Channels appears to be having a significant positive effect. This work is ongoing through June.
Alexandra Morton
250-974-7086