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Study Suggests Habitat Restoration Efforts Need Increase To Produce Measurable Fish Abundance
Posted on Friday, February 25, 2011 (PST)

Researchers at the National Oceanic and Atmospheric Administration, Northwest Fisheries Science Center’s Watershed Program have completed a study demonstrating that a larger, more concentrated effort is required to produce measurable changes in fish abundance at a watershed scale.


“Our study found that a larger amount of habitat must be restored if you want to see a significant increase in fish production,” said Phil Roni, NOAA Watershed Program manager/research scientist.


The study, “Estimating Changes in Coho Salmon and Steelhead Abundance from Watershed Restoration: How Much Restoration Is Needed to Measurably Increase Smolt Production?” was published online in the North American Journal of Fisheries Management on Jan. 17.


The listing of many Pacific salmon populations as threatened or endangered under the U.S. Endangered Species Act has led to extensive recovery efforts. Several factors have contributed to their decline, including hatcheries, harvest, hydropower and habitat degradation.


Much of the recovery effort for salmon and other endangered fishes have focused on minimizing the impacts of the first three factors, combined with habitat improvement and restoration efforts.


An estimated one billion dollars has been spent each year on watershed restoration in the United States since 1990, says the study. More than 60 percent of projects completed during this period were for salmon and trout habitat restoration efforts in the Pacific Northwest and California. For instance, in the Pacific Northwest, nearly $100 million are spent every year on restoring watersheds to recover endangered Pacific salmon.


According to the study, biologists and restoration practitioners focus on the physical and biological effects of restoration projects on endangered species. On the other hand, resource managers, funders and developers of recovery plans are typically more concerned with questions such as:


1. How many more fish are produced by various restoration techniques?

2. How much habitat needs to be restored to significantly increase fish abundance? and

3. How much habitat needs to be restored to achieve ‘‘recovery’’ of a threatened, endangered, or depressed fish population?


Whether restoration efforts should be spread widely across a basin or region, or concentrated in key areas is an important question, said Roni.


Current restoration efforts generally are spread out over a larger geographic area. The NOAA Watershed program’s study states that even within a single watershed, other modeling efforts conducted recently suggest that concentrating restoration efforts in specific “subwatersheds” will have better results – producing larger increases in salmon than spreading restoration actions equally across subwatersheds.


The study is significant because NOAA’s Watershed Program evaluates the effectiveness of various habitat and watershed restoration strategies or techniques. The program’s scientists provide technical support to NOAA Fisheries policy makers and regulatory staff, and collaborate with other agencies, tribes, and educational institutions on research and outreach related to the management of Pacific salmon.


“We looked at a couple of different scenarios,” Roni said. “We had estimates of increases in coho and steelhead for different types of restoration. Based on those, we did some modeling to find out how much restoration would be needed if we were going to increase a fish population by 25 percent.”


Common techniques used to improve salmon habitat and restore watersheds include riparian planting, grazing reduction road improvements to reduce runoff and fine sediment, removal of culverts and other barriers to fish migration, rehabilitation of floodplain habitats, conservation easements and acquisitions, nutrient enrichment, gravel augmentation, and placement of instream structures such as logs, boulders, and logjams. The NOAA study looked at some of the most common of these techniques including barrier removal, floodplain rehabilitation and placement of instream structures.


“We looked at a typical Puget Sound watershed, and studied how much habitat is present and how much needs to be restored to see a boost in fish production,” Roni said. “We used estimates from empirical studies of restoration effectiveness from various projects over the past 10 years, and we applied them to the watershed.”


The team selected the Puget Sound basin (PSB) as an area to develop its model watershed because (1) much of the fish data in their analysis was collected in western Washington and the PSB, (2) the team has been involved in many restoration-planning efforts in the basin, and (3) data on habitat conditions across the basin were readily available.


“Our study found that approximately 20 percent of a watershed would have to be restored in order to produce a 25 percent increase in fish numbers. Clearly this means we have to do a lot more habitat restoration.”


However, according to NOAA Watershed program’s study, given the large variability in fish response to different restoration techniques, 100 percent of the habitat would need to be restored to be 95 percent certain of achieving a 25 percent  increase in smolt production. The total cost of restoring all in-channel and floodplain habitat in the model watershed alone is estimated to be approximately $123 million, while restoring 20 percent of the habitat (the amount needed to produce a mean increase of 25 percent) would cost approximately $25 million.


“Improving the effectiveness or our restoration efforts and targeting limiting habitats should also lead to greater efficiencies and success in salmon habitat restoration efforts,” Roni said.


The paper can be found at


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