2005 MLRR Awards


	Mineral Land Regulation and Reclamation Program, 2005 Mined Land Reclamation Awards

Oregon Plan Award - Delta Sand & Gravel Company, Lane County

Contact: Alan & Lee Babb or George Staples - 541-688-2233.

Also contact: McKenzie Watershed Council - Megan Finnessy 541-687-9076.

For more information on the Confluence Island Alcove, contact George Staples - 541-688-2233

Background:

Delta Sand & Gravel working with the McKenzie River Watershed Council created an artificial alcove along a channel of the Willamette River in Lane County.

Alcoves, those fingers of water that parallel the river and that connect with the river at their downstream end, offer special benefits to fish. During higher flows alcoves provide the fish refuge from fast moving water in the main channel. The organisms that live on alcove substrates provide a rich supply of food to fish, especially in early spring when the main channel is relatively unproductive. And, alcoves are favored breeding and rearing areas for many fishes.

Over the last 150 years many Willamette Valley alcoves were obliterated as the rivers were channelized to allow boat navigation and contain local flooding of adjacent fields and towns. In addition, upstream reservoirs now mute the big floods that once scoured the edges of the main channel and created new alcoves.

Can constructed alcoves substitute for the lost natural alcoves? An alcove excavated last summer along the Willamette River just upstream of the McKenzie River confluence is providing an opportunity to find out. The Confluence Island alcove was created on land owned by Delta Sand and Gravel and was funded by the Oregon Watershed Enhancement Board. The alcove is 963 feet long, 45 feet wide, and 3 to 5 feet deep in the summer. The excavation required over 300 dump truck loads.

Boat-mounted electo-fishing gear provides a way to sample the fish community without killing them. So far, sampling has occurred in September, 2003, several weeks after the alcove was completed, and in May 2004. Late summer and spring sampling will continue for several more years.

Even within weeks of its completion, fish used the alcove in large numbers. The fish community was dominated by native pioneer species such as redside shiner, northern pikeminnow, and largescale sucker (Table 1), which took advantage of a surge in small aquatic insects and algae that were fueled by the clean gravel substrate, released nutrients, and clear water. Eight native fish species were present, along with the non-native largemouth bass.

By spring 2004, the fish community had become increasingly complex and diverse. Sampling in May, 2004, indicated that juvenile chinook salmon made up 15% of the fish community and the number of native species had increased to 13. The only species found in the main channel of the Willamette River that were missing from the alcove were mountain whitefish, mountain sucker, rainbow trout, and white sturgeon. None of these fishes typically use natural alcoves.

The chinook salmon numbers in May were of special interest because we have rarely come across such a high density in the Willamette River. Previous sampling efforts in the spring indicate that natural alcoves typically have chinook salmon densities between 0.2 and 0.4 fish per 100 feet of bank sampled. The constructed alcove at Confluence Island had a value of 0.8. Main channel densities are typically 0.1 chinook salmon per 100 feet of bank sampled. Another constructed alcove, this one located upstream of Corvallis, had a value of 0.5 when sampled in the spring.

The constructed alcove at Confluence Island appears to be unusually productive and supports a diverse fish community. Also, it is favored habitat for chinook salmon in the spring. Further monitoring will determine how this fish productivity and physical features of the alcove change over time.

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The alcove is 963 feet long, 45 feet wide, and 3 to 5 feet deep in the summer. The excavation required over 300 dump truck loads.

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Mineral Land Regulation and Reclamation Program, 2005 Mined Land Reclamation Awards