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| Styrofoam and reference Maria |
The relationship of sea lice and coho salmon is investigated in two recent studies, published in the Journal of Applied Ecology. The first study investigated the potential role that predation plays in transmitting sea lice between salmon species. The authors - two of which hail from DFO's Pacific Biological Station - report that when coho salmon prey upon pink salmon that are carrying sea lice, the lice move to the coho - causing the coho to have substantially higher louse loads than they would otherwise. While the coho are larger and therefore should be expected to be more robust in the face of louse parasitism, the authors suggest that the magnification of louse loads due to predation may 'undermine' the benefits of their size advantage. The second study reports that coho in a region with open net-pen salmon farms had a seven-fold reduction in productivity during a time of recurrent sea lice outbreaks on the farms; the authors attribute this reduction to the transmission of sea lice from farm to coho via the predation effect noted in the first study, and via direct transmission of lice from farm to juvenile coho. Taken together, these studies offer an intriguing look into potential post-farm ecosystem effects of the release of sea lice from open net-pen salmon farms, and the authors point out that the results suggest that the broader ecosystem impacts of sea lice should be taken into consideration in the management of such farms.
And finally, the big news of the past few days: in a stirring display of snacking solidarity, the North American snack chip consuming public - a sizable demographic in every sense of the word - stood as one to deliver a unified message to would-be snack masters of the universe: do not make our chip bags noisy. It seems that Frito Lay, the corporate giant that gives us so many salty snacks and 'yo mama' joke punchlines, had the temerity to try putting Sun Chips in compostable bags. The problem? The bags were loud. Very, very loud. As someone who actually ran across one of these on a road trip a few week ago, I can attest that even trying to get just one or two chips out of one of those bags would pretty much stop conversation. It had the same effect as just yelling "PARDON ME BUT I'M JUST GOING TO GET SOME CHIPS WHILE YOU'RE TALKING". Anyway, the deafening nature of these bags proved too great a sacrifice for even the hippies that eat Sun Chips, and therefore Frito Lay has announced that the eardrum-perforating bags are being discontinued. So, consumers will be able to line their arteries in peace and quiet. Intellectuals are predictably apoplectic.
So, on October 8, 2010, we find more evidence that open net-pen salmon farms harm wild salmon, yet they are allowed to continue to do their thing - but we deep-six a potentially compostable chip bag because it is too loud. Yep, I'd say that pretty much sums up the zeitgeist.
Hmmm we're these studies conducted by the same people who predicted the collapse of the pink salmon in the broughton and the sockeye in the fraser?
ReplyDeleteFirst of all, it's worth noting that two of the authors on one of the papers are from DFO's Pacific Biological Station. Hardly a hotbed of fish-hugging activism.
ReplyDeleteSecond, re: the commonly-repeated assertion that the "pinks will go extinct" prediction was wrong. You're probably referring to Krkosek et al 2007. The authors of that paper, which dealt with pinks, found that the growth rate of populations that migrated past salmon farms was significantly lower than non-exposed populations. The authors reported a significantly negative growth rate for exposed populations, and based upon this they predicted collapse of pink salmon population abundance in four generations if outbreaks were to continue. Note those last words - it's a direct quote: "If outbreaks continue.."
So – did the pinks go extinct? No. Did something change? Yes.
This is what happened: CAAR negotiated the CAMP with Marine Harvest and the company started fallowing all the farms on alternating migratory routes during the wild juvenile out-migration period AND coordinating treatment of lice outbreaks on all their farms, AND only stocking sub-adult fish on the non-fallowed route (research in Norway has shown sub-adults are less prone to heavy lice infestation), AND treating pro-actively – which means instead of waiting until lice levels hit the treatment trigger level of 3 per fish, then calling in the vet, getting the prescription, ordering the medicated feed, waiting a week or two for it to be milled, shipped and administered and days more for it to take effect – by which time lice levels would have reached 10 or 15 per fish or more, MHC agreed to start treating prophylactic ally. So the lice never got to the very high levels they had been reaching in the past.
So – was the Krkosek et al extinction prediction wrong? No – they said the pinks would collapse if nothing changed. Preliminary results on the scientific field monitoring undertaken jointly by CAAR and MHC indicates that in 2009, when the CAMP program began, the lice levels on wild out-migrating juveniles were significantly lower than in previous years. In other words – the interim plan appeared to be working. It was put in place again in 2010 and the data from the field work are being analyzed now. So it looks like a success for the short-term.
BUT – the CAMP is an interim measure at best. First, it relies on fallowing (good) but also on dumping pesticide-laden feed pellets into the ocean (bad). Secondly, it does not address ALL the other impacts of the farms – escapes, predator kills, chemical and antibiotic use, waste deposition, etc. So it’s not a long term solution, but an emergency measures to try to reduce infection of wild juvenile salmon while we move towards the longer term solution – closed containment.
Great response! This is all a terrific reminder of the importance of understanding assumptions in modeling--not that relying on assumptions (which is 100% necessary) makes modeling less valuable, just that the whole point of modeling is to show what will happen under certain conditions. Changing those conditions doesn't prove the model wrong, as much as people love to hate the word 'assumption'.
ReplyDelete