Do Sea Lice from Salmon Farms Kill Wild Stocks?

Mr Gourlay claims that sea lice from salmon farms cause infestations that decimate the population of wild salmon (CH 2 Feb 2012). Before taking a position, I like to examine the evidence. I searched a bibliographic database, called Scopus, for peer-reviewed publications that addressed the question. I downloaded the three most recent measurement-based papers (1, 2, 3) that were free via Scopus. PNAS also have a recent publication on the issue. None of these publications supported the notion that salmon farms caused sea lice infestations that destroyed natural stocks.

A 9 year study of Atlantic salmon from Ireland found "infestation with the salmon louse to be a minor component of marine mortality". Of all the studies, the most lice-infected salmon were quite isolated from fish farms. That infestation was tentatively associated with spawning Pacific herring.

My interest piqued, I downloaded a paper that set out to measure sea lice infestation of wild fish due to ranched tuna, in Australia. Hold your breath, it turned out that it was wild fish that caused the ranched fish to become infested!

We should always be sceptical and we should always examine the evidence. But here is the rub, many scientific publications are not freely available to all --- even though most of the science is funded from the public purse of one country or another. The system for scientific publishing needs to be reformed, it is no longer acceptable for the public to pay to be kept in the dark. Neither is it acceptable for our journalistic media to be dumb, blind, and ignorant of science!

The Saga Continues

On 8 Feb 2012 Bruce Hancock published an opinion that "There is no scientific evidence that salmon farming causes harm to wild stocks". This is a very broad statement since there are many ways in which salmon farming might cause harm to wild stocks --- quite apart from sea lice. For example, if farmed salmon are fed with wild fish then one could argue that this diminishes the food supply for wild salmon etc. But to take this line of reasoning, we would have to fest up to the ugly truth that the mere existence of a large number of human beings is a threat to salmon and many other species. Never mind marine farming, look at the ecological carnage caused by farming the land! Going back 150 years, if we had gathered all of the planet's mammalian flesh in a big pile, weighed it and then worked out the proportion of it from human and domesticated animals and pets, it would have amounted to 15 per cent. If we were able to perform that exercise now the figure would be about 90 per cent. Ten thousand years ago, it would have been 0.1%! Just look out of the window next time you fly, all the arable land is consumed by us. So why isolate the salmon farmer to be societies whipping boy?

Now, on 12 Feb 2012 we have Mr Gourlay writing to refute Mr Hancock. Apparently Mr Gourlay has dozens of authoritative studies. Where? Perhaps at the Atlantic Salmon Federation website, where we see the publication by Jonathan Carr and Dr Fred Whoriske, Sea Lice rates of infestation?

The weaker the evidence, the bigger the claims! Well, I guess it all helps to sell a newspaper or two...