Thursday, November 04, 2010

The great salmon carcass caper

Restoration of ecosystems is good except when it's not.

What do you think about putting the dead rotting bodies of salmon into streams with water quality problems caused by excess nutrients? If you're like me, that sounds bad.

So why are smart and earnest conservationists doing it in the Molalla River, which is on Oregon's nutrient-polluted streams list? Because swarms of salmon used to die and rot in streams, so restoration means putting dead salmon bodies in streams where they "should" be. This seems to work in nutrient-limited streams, but a stream with nutrient excess may respond differently.

When salmon streams are healthy, then the rotting bodies feed bugs and fish. When salmon streams are degraded, lacking native species, and already burdened with excess nutrients, then adding more nutrients isn't likely to restore anything.

There's nothing magic about salmon carcasses. They will feed and make more of whatever lives there. It what lives in a stream is algae and non-native fish, then salmon carcasses will only feed the unwelcome guests.

I like the idea of salmon carcasses in streams. But only at the end of a restoration process when habitat is good, native species are present, and the ecosystem is fairly healthy. I'm happy when the rotting bodies are native fish that just spawned after swimming upstream naturally.

But putting salmon in streams to jump-start the process may just worsen existing problems. All things in good time.

1 comment:

Ray Kinney said...

All nutrients are not equal. Marine-derived nutrients (MDN)are chock full of essential micronutrients that the evolving salmonids and supporting species had been adapted to. They rely on these particular suites of micronutrients for completing their fitness for ocean entry.Many easily leached nutrients and micronutrients are quickly washed into the ocean by copious, relatively acidic, rainfall flushing down out of systems that no longer have the nutrient-retentive stream morphology that was characteristic of prehistoric conditions. As salmon habitat acidification pressures increase with our habitat alterations,the problem of lack of essential micronutrients gets greater.It's a 'chicken or egg' situation.The quality of the bioavailable nutrient assemblage is what is important, not just the total 'nutrient' polluting a stream. there could be an anthropogenic overabundance of N and P but a critical deficiency of essential micronutrients that allow health 'fit' smolt that can survive better to later return MDN to our watersheds.We desperately need better escapement to provide the MDN (from lamprey as well as salmon). Anthropogenic NPS 'nutrient' pollution needs to be agressively reduced, AND,MDN needs to be increased.Both actions are essential... and this is an aquatic emergency.
Ray Kinney
Siuslaw watershed