Investigation of Avian Predation Upon Salmonid Smolts With the Use of an Active Acoustic / PIT Tag Combination

Curt Dotson – Grant PUDSuzie 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

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.

Wanapum Dam

Priest Rapids Dam

Mattawa

Rock Island Dam

Vernita Bridge Ringold

Study Site

WashingtonOregon

RM 453

RM 388

RM 408

RM 416

RM 397

RM 361

0 5 10 Miles

Flow

Detection Array

Hydro Project

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 148511B PIT Tag

Limited battery lifeLimited detection efficiency

Tag Dimensions

• 2008 and 2009 combined tag dimensions 6.8 x 21.8 mm, 1.65 g in air.

• 2010 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

Wanapum Dam

Priest Rapids Dam

Mattawa

Rock Island Dam

Vernita Bridge Ringold

Study Site

WashingtonOregon

RM 453

RM 388

RM 408

RM 416

RM 397

RM 361

0 5 10 Miles

Flow

Detection Array

Hydro Project

  Year

  2008 2009 2010

Steelhead 2,200 2,100 2,500

Chinook 1,000

Sockeye     2,100

Releases

Wanapum Dam

Priest Rapids Dam

Rocky Reach Dam

Mattawa

Rock Island Dam

Vernita BridgeRingold

RM 453

RM 388

RM 408

RM 416

RM 397RM 361

0 4 8 Miles

Flow

Detection Array

Hydro Project

Potholes Reservoir

Banks Lake

Crescent Island

Loafing Area

Banks Lake

Crescent Island

Loafing Area

Potholes Reservoir

Crescent Island

Banks Lake

Quantity of Fish Taken

Potholes Reservoir Crescent Island

Num

ber o

f Fis

h

0

20

40

60

80

100

120

Steelhead Sockeye Chinook

2008 2009 2010 2009 2010

Tern Gulls Tern/Mix Tern Mix Tern Tern Gulls

Avian Prey Selection

• No difference– Release groups– Condition factor = (10 * weight^(1/3))/length– Dam passage routes

• Preference– Steelhead– Fork length range (190-210 mm)– Hatchery stock

Reach

RIDM - WADM WADM - MATT MATT - PRDM PRDM - VEBR VEBR - RING

Perc

ent o

f Tag

s Re

cove

red

by R

each

0

1

2

3

4

5

6

7

8

9

10200820092010Cumulative % 2008Cumulative % 2009Cumulative % 2010

Reach

RIDM - WADM WADM - MATT MATT - PRDM PRDM - VEBR VEBR - RING

Perc

ent R

ecov

ered

by

Reac

h

0

1

2

3

4

5

6

7

8

9200820092010Cumulative 2008Cumulative 2009Cumulative 2010

Steelhead Taken by Reach

Steelhead Taken by River Mile

Reach

RIDM - WADM WADM - MATT MATT - PRDM PRDM - VEBR VEBR - RING

Perc

ent R

ecov

ered

Per

Rive

r Mile

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16200820092010

Percent of Steelhead Tags Recovered

Year

2008 2009 2010

0%

2%

4%

6%

8%

10% Percent TakenPercent Effecting Survival

4.3%

2.3%

6.4%

2.6%

8.1%

2.2%

• 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

Questions?