HomeMy WebLinkAboutRuby Hydrokinetic Electrical Generation Project Fish Monitoring Pilot Study Summer 2009Ruby Hydrokinetic Electrical Generation Project
Fish Monitoring Pilot Study Work-plan
Summer 2009
Submitted by Yukon River Inter-Tribal Watershed Council
www.yritwc.org
The Yukon River Inter-Tribal Watershed Council, along with the Tribal Council and City of
Ruby, intend to test a hydrokinetic turbine in the Yukon River in Ruby, Alaska. One of the
concerns with in-river testing of a vertical axis low-speed hydrokinetic turbine is whether it will
have a significant detrimental effect on resident and anadromous fish. Yukon River Drainage
Fisheries Association (YRDFA) has been asked to assist in the development of a workplan to
monitor and assess fish interactions with the turbine.
The 5 kW Encurrent turbine, manufactured by New Energy Corporation, is mounted on a 10 foot
x 20 foot pontoon boat that is anchored approximately 20 -50 yards off the south bank of the
Yukon River in the vicinity of Ruby, Alaska in an area of relatively fast water currents (2.5 - 4.0
mph). The site is further characterized b y water depths of 25–30 feet, with the turbine positioned
1 – 6 feet below the water surface and 15 or more feet above the river bottom.
Fish that are commonly found in this area of the Yukon River include both anadromous and
resident species. Three species of salmon—Chinook (King; Oncorhynchus tshawytscha), Chum
(Dog; O. keta), and Coho (Silver; O. kisutch)—are common anadromous fish in this area with
the adults migrating to spawning areas. Salmon juveniles typically migrate in the spring and
summer to the sea as smolts. The major use of the Chinook, chum and Coho salmon in the
Yukon has been as a commercial and subsistence food. Chum salmon are a traditional source of
dog food and dried fish for winter use and are the most abundant harvested salmon species in
Interior Alaska. Northern pike (Esox lucius linnaeus), Burbot (Lota lota ) as well as arctic
grayling (Thymallus arcticus) and Dolly Varden (Salvelinus malma) are also important resident
freshwater species in the Yukon River system. They are utilized as a source of fresh food and
are also dried for winter use. Whitefish are the most abundant group of resident migratory fish,
inhabiting almost every type of river and freshwater habitat in this section of Alaska. Whitefish
are important as a source of subsistence food and are important in the food chain of the aquatic
community, as they are a major food item for many predatory fish. Whitefish species include the
Humpback (Coregonus oidschian) and Broad Whitefish (C. nasus), Berring (C. laurettae) and
least Cisco (C. said), and Sheefish (inconnu; Stendous leucichthys nelma). Sheefish is the largest
member of the whitefish family. Interior Alaska Sheefish typically over-winter in the lower
Yukon Delta and migrate in the spring to feeding grounds and spawning grounds in the Yukon.
Studying effects of hydrokinetic turbines on fish in the Yukon River is no easy task. Significant
debris loads as well as high turbidity and velocity limit visual observation of effects and fish
behavior. The plan for this pilot study is to use sonar devices to observe fish (target) behavior in
the proximity of turbine blades as well as capturing fish (juveniles) that have passed through the
downstream flow of the turbine. We are not planning on using gill nets to confirm the presence
of fish in the area. We intend to investigate whether the sonar unit will show individual fish and
behavior around the hydrokenitic blades and document what that behavior is.
To determine existing fish movement patterns, we will run the fike net and sonar before the
pontoon boat is deployed, but, we would expect that the abundance of smolt to change more
temporally than because of a small structure and disturbance in the water column. In any case
this baseline will be taken. The sonar will be deployed to try and identify channel areas that
adults are utilizing in migration. That data will be documented and can be utilized to site the
pontoon boat and hydrokinetic generator before and during deployment to minimize fish/prop
interaction.
In terms of sampling methodology, initially the fike net will be run for 5 minutes twice an hour
four times a day and will be run in conjunction with the sonar. The sampling plan is intended to
be an iterative process to accurately assess whether there are impacts to the outgoing smolt
flush. The sampling time will be adjusted to sample sufficient fish (>30 <50 smolt) to assess
whether: 1.) the fish pass through the hydrokinetic blade path (sonar); 2.) that the deployment of
the fyke net will sample fish that pass through the sonar; and 3.) whether the fish
sampled sustained any mechanical damage.
Detrimental impacts to adult fish by the hydrokinetic turbine could theoretically be from two
features: the turbine blade, or entrainment on a debris screen forward of the turbine. However,
we will not be deploying a debris screen this year, so there will be no impingement of fish, but
we will include this possibility in the following discussion for future consideration. Fish
swimming toward the turbine blades or debris screens are likely to experience a pressure change
as well as sense a physical object and react by swimming around it. The turbine blade area
exhibits a small target in relation to the transect area of the river giving fish a lot of room to
avoid obstacles. Also, the turbine blades rotate at a relatively low speed (30-70 rpm) that may
minimize impact if a fish encounter occurs. Fish behavior will be monitored with a multiple
beam sonar unit with its transducer mounted on a boom downstream of the pontoon boat and
pointed toward the turbine. The deployment of the sonar unit will be an iterative process to
adjust for signal strength, target acquisition, and to reduce noise. This configuration is designed
to provide a visual record of target behavior as they swim upstream and encounter the pontoon
boat, turbine, and debris screens. The sonar data will be recorded for verification and
interpretation of the data record. Impingement on the debris screens can be further monitored by
physical inspection.
Impacts to juvenile fish may also be from impingement on the upstream debris screen, from
impact with the turbine blades, or from the reduction on water pressure in the proximity of the
turbine. The efficacy of a sonar unit to monitor juvenile fish behavior in relation to turbines
may be limited as the sonar may only be able to see schools of juvenile fish as targets. Thus, a
hoop sample net (50cm x 200cm) will be deployed periodically from the downstream side of the
pontoon boat at a depth of 0 to 6 feet to monitor impacts to juvenile fish and we will attempt to
correlate the accuracy of sonar detection with our hoop sample results. Deployment will be time
limited as to not kill juveniles by river velocity and to limit the take of juveniles. A technician
will monitor net deployment, identify species sampled, release live and uninjured fish, and lastly
process takes. Takes will be evaluated for type of injury and preserved for examination and
analysis. All takes will be archived with Alaska Department of Fish and Game.
The pilot phase of the fish monitoring study is expected to commence in May 2009 and continue
throughout the summer to evaluate impacts and efficacy. A report detailing sonar deployment
and project results will be made available to permitting agencies.
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