Presentation on theme: "Investigation of Avian Predation Upon Salmonid Smolts With the Use of an Active Acoustic / PIT Tag Combination Curt Dotson – Grant PUD Suzie Rizor – Blue."— Presentation transcript:
Investigation of Avian Predation Upon Salmonid Smolts With the Use of an Active Acoustic / PIT Tag Combination Curt Dotson – Grant PUD Suzie Rizor – Blue Leaf Environmental
Project History To meet relicensing agreements Grant PUD is in the process of conducting survival studies. Despite excellent concrete survival, steelhead reservoir survival is low.
Why Low Steelhead Survival? Piscivorous Fish Avian Predation
In 2007, acoustic tags were returned to Grant PUD by Real Time Research and confirmed that a subset of our study fish were consumed by birds.
Questions Where were the fish removed from the river? Did the take impact survival numbers? Taken after the project = No Impact Taken in project = Impact
Combined technologies –Acoustic tag mated to PIT tag Goals –Explore impacts of avian predation In 2008, after Grant PUD became aware of tag origin issues, study designs were modified.
Combination Acoustic / PIT tag “Best of Both Worlds” Hydroacoustic Technology, INC Model 795 acoustic tag Biomark RFID Model TXP B PIT Tag Limited battery life Limited detection efficiency
Tag Dimensions 2008 and 2009 combined tag dimensions 6.8 x 21.8 mm, 1.65 g in air combined tag dimensions 5.0 x 17.5 mm, 0.76g in air.
Goals/Objectives 1.Quantify Avian Predation –Species –Nesting and roosting locations –Estimate depredation rates 2.Estimate areas of highest predation –Forebay, tailrace, mid-reservoir 3.Differences in susceptibility of passage –Powerhouse, Bypass/Top-spill, Spillway 4.Evaluate effectiveness of hazing and wire arrays
Year Steelhead2,2002,1002,500 Chinook1,000 Sockeye 2,100 Releases
Loafing Area Potholes Reservoir Crescent Island Banks Lake
Quantity of Fish Taken
Avian Prey Selection No difference –Release groups –Condition factor = (10 * weight^(1/3))/length –Dam passage routes Preference –Steelhead –Fork length range ( mm) –Hatchery stock
Steelhead Taken by Reach
Steelhead Taken by River Mile
Percent of Steelhead Tags Recovered
64% of recovered tags came from Potholes Reservoir –Predominantly Caspian terns Detection Rate at Potholes was estimated to be 52% (A. Evans, pers. comm. 2010) Deposition rate unknown We extrapolated that a minimum of 3.3% steelhead released by Grant PUD were consumed above Vernita Bridge. Impact of Potholes Reservoir Avian Colonies on 2010 Steelhead Survival
Crescent Island In 2009, there were 6,500 nesting pairs of California gulls and 350 nesting pairs of Caspian terns on the island. In 2010, a total of 8,255 PIT tags were detected in the tern colony and 3,985 PIT tags were detected in the gull colony. (A. Evans, AFEP presentation 2010)
Hazing and Wire Arrays Deterrents are effective in the immediate tailraces of both dams. Avian predation pressure has shifted downstream of both dams. Overall avian predation within the project has not decreased.
Next Steps Locate predation “hot spots” within the reservoirs Estimate the effects of piscivorous fish
Acknowledgements NOAA Fisheries USGS-Oregon Cooperative Fish and Wildlife Research Unit Oregon State University Real Time Research