Adding fertilizer to streams! What's next?
We usually think about keeping nutrients out of streams and lakes,because it stimulates too much biological activity.
This article appeared this week in the Vancouver Sun (British Columbia) newspaper. Biologists are adding nitrogen and phosphorus fertilizer to streams to enhance aquatic productivity. This practice is not uncommon in the Pacific Northwest, but not recommended for most conditions.
Fertilizer in streams holds promise in rebuilding salmon stocks
VANCOUVER — Young steelhead and salmon showed a dramatic growth in streams seeded with sacks of slow-release fertilizer, a method that shows real promise to help rebuild collapsed salmon and steelhead spawning populations, according to B.C. biologists.
The method has proven effective at improving steelhead growth and survival in Vancouver Island streams in programs dating back to 1989.
Steelhead fry in treated areas are typically about 95 per cent larger than those in untreated streams, while coho fry are about 40 per cent bigger. Fish counts in the Keogh River found a 50 per cent increase in the number of coho that survived the freshwater stage of life.
Fisheries biologists are using fertilizers to replace the nutrients that would be added to the stream naturally by the rotting carcasses of fish that die after spawning, said Kevin Pellett of the B.C. Conservation Foundation. Enhancement programs are operating in 15 watersheds and 28 rivers on Vancouver Island and southwestern B.C.
The fertilizers are designed to stimulate growth of certain algaes that in turn cause the populations of insects such as mayfly and stonefly to thrive. Juvenile salmon and steelhead fry feed on those insects.
Steelhead fry growing downstream from the fertilizer caches are bigger and typically 75 to 250 per cent heavier than those upstream, which would not be expected to benefit from the improved food supply, according to the most recent data. Larger more robust fish are more likely to survive and return as spawning adults.
"We've switched to a new product called Crystal Green," he said.
Crystal Green is a slow-release agricultural fertilizer comprised of nitrogen and phosphate recovered from municipal waste water using a technology invented by civil engineers at the University of British Columbia. The Vancouver-based manufacturer, Ostara, is harvesting a waste material called struvite for the fertilizer from the sewage stream in suburban Portland, Oregon.
More about about struvite and Ostara in a later post.
This success of this practice actually doesnt suprise me. We have been working with the USBR here in Southern California on the restoration of the Colorado River floodplain with Riparian plant species over the last few years. The idea is to plant "native" species to attract endangered birds and the like to the areas (MSCP). Before we came on board the thought was to establish the trees and irrigate in a manner consistent with the flood pattens of the ancient Colorado River. They were unhappy with the response of the wildlife. What we found was, where we fertilized and irrigated in a conventional "stewardship" manner, based on soil and plant tissue analysis that the wildlife returned like they had not before. My opinion is that an ecological system can respond to fertilizer much the same was as modern agriculture. The yields are just counted differently.
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