Thursday, 8 February 2018

Lice Kill Wild Salmonids

As if we had not already had enough studies that show fish farm lice kill wild salmonids, here is a review article from Norway that in 2018, makes the same point:

 Here is a note from the beginning, in Google translate:

"A new report has summarized research results from various studies of how salmon lice affects salmon and sea fish stocks. It concludes that there is significant evidence that there is a connection between areas with large farmed activity and spread of salmon lice to wild salmon and sea trout stocks. Many studies show that the impact can be such that it can lead to significantly increased mortality for the fish, thus reducing fish stocks, which also results in reduced harvestable surplus for fishing. Depending on file sizes, increased mortality due to salmon lice may also cause too few spawning fish to reach the spawning stock targets."

And: "Effects of salmon lice on wild fish are well researched compared to many other human influences on nature, says Eva B. Thorstad from NINA, who is one of the researchers behind the summary."

So don't let salmon farms tell you lice aren't a problem. The effects are well studied.

And just how bad is the effect? Pretty bad:

"Salmon stocks in farmed intensive areas can be reduced by an average of 12-29% fewer spawning fish. This has been demonstrated in large scale studies in nature where groups of individually marked fish have been protected from salmon lice with chemical treatment and compared to untreated fish.
In Norway, annual loss of wild salmon is estimated due to salmon lice approx. 50,000 salmon per year for the years 2010-2014, ie a loss of 10% of wild salmon due to salmon lice. Salmon lice is one of the two biggest stock threats against Norwegian salmon stocks, says Thorstad."

And: "Finstad points out that mortality in sea trout is likely to be higher than in salmon because the sea trout stays near the coast during the entire sea stay, in the same areas that the fish farms are usually located."

That means in BC, the prime species to be hit is sea-run cutthroat trout, and secondarily Dolly Varden Charr. Not Good.

No comments:

Post a Comment