chinook salmon supplementation in the imnaha river basin- a comparative look at changes in abundance...

Chinook Salmon Supplementation in the Chinook Salmon Supplementation in the Imnaha River Basin- A Comparative Look at Imnaha River Basin- A Comparative Look at

Changes in Abundance and ProductivityChanges in Abundance and Productivity

Richard W. Carmichael and Tim HoffnagleOregon Department of Fish and Wildlife

Eastern Oregon UniversityLa Grande, OR 97850

Management Objectives

•Enhance natural production while maintaining long term fitness (productivity) of the natural population.

•Re-establish historic tribal and recreational fisheries

•Operate the hatchery program so we maintain the genetic and life history characteristics of the natural population and hatchery fish characteristics mimic those of the wild fish, while achieving management objectives.

Today’s Presentation

•Illustrate one approach to assessing success in supplementation programs

•Has the Imnaha Chinook salmon supplementation program increased the number of total spawners and natural origin spawners?

•How has the hatchery program influenced natural spawner productivity?

•Are the life history and spawning characteristics of hatchery origin fish the same as natural origin fish?

Broodstock Development History

•Wild adults were collected for broodstock beginning in 1982.

•The majority of broodstock were wild through 1988.

•Wild and hatchery adults were used for broodstock from 1989-2007 (14 to 71% wild).

•Due to logistical constraints of weir installation, the broodstock comes from middle to end of run.

• In 2007, it appears that we were able to collect broodstock from across the entire run.

Management of Wild Returns andNatural Escapement

•Nearly all wild salmon collected were kept for broodstock from 1982- 1986.

•Percentage of wild salmon retained for broodstock after 1986 was 50% or less, except 1995.

•Few hatchery salmon were released to spawn naturally until 1990.

•Naturally spawning hatchery fish were those that passed the weir site prior to weir installation and those that spawned below the weir.

•The percent of naturally spawning salmon that were hatchery origin has ranged from 30-80% since 1990.

Estimated Spawners in Nature 1960-2005

0

1,000

2,000

3,000

4,000

5,000

6,000

1960 1970 1980 1990 2000

Return year

Sp

awn

ers

in n

atu

re

0

10

20

30

40

50

60

70

80

90

100

Per

cen

t hat

cher

y

Spawners

Percent hatchery

Abundance/Productivity Comparison Approach

• Compiled spawner and recruit adult abundance and productivity (R/S) datasets for Imnaha and unsupplemented Idaho Salmon River Chinook populations (ICTRT/ODFW/IDFG) including harvest adjusted values.

• Determined level of correlation in abundance and productivity between Idaho and Imnaha populations for the pre-supplementation time period (late 1950’s-1985 for abundance and late 1950’s-1981 for productivity) to evaluate adequacy as reference populations.

• Calculated and compared Imnaha-to-Idaho population ratios for total spawner abundance, natural origin spawner abundance and productivity (year specific and means) for pre- and post-supplementation time periods (abundance 1986-2004 return years and R/S 1986-1999 broodyears).

• If we have increased natural origin abundance then the ratio should be higher in post supplementation period and if we have maintained productivity the post period ratio should be equal to or higher than pre period ratio.

Abundance/Productivity Comparison Stocks

Abundance of Total SpawnersAbundance of Total Spawners

Year

1960 1970 1980 1990 2000

Nu

mb

er o

f ad

ult

sp

awn

ers

0

1000

2000

3000

4000

5000

6000

Imnaha RiverBear Valley Creek

Abundance of Total SpawnersAbundance of Total Spawners(harvest adjusted)(harvest adjusted)

Year

1960 1970 1980 1990 2000

Nu

mb

er o

f ad

ult

sp

awn

ers

0

2000

4000

6000

8000

10000

12000


Abundance of Natural Origin SpawnersAbundance of Natural Origin Spawners

Year

1960 1970 1980 1990 2000

Nu

mb

er o

f ad

ult

sp

awn

ers

0

1000

2000

3000

4000

5000

6000


Abundance of Natural Origin RecruitsAbundance of Natural Origin Recruits(harvest adjusted)(harvest adjusted)

Brood year

1960 1970 1980 1990 2000

Nu

mb

er o

f ad

ult

rec

ruit

s

0

1000

2000

3000

4000

5000

6000

7000


Recruits per Spawner RatioRecruits per Spawner Ratio

Year

1960 1970 1980 1990 2000

R:S

rat

io

0

1

2

3

4

5

6

7

8


Pre-Supplementation Natural-Origin Abundance CorrelationsPre-Supplementation Natural-Origin Abundance CorrelationsImnaha Population vs. Idaho PopulationsImnaha Population vs. Idaho Populations

Natural origin abundance R:S ratio

Idaho stream rho P-value rho P-value

Bear Valley Creek 0.56501 0.0026 0.47290 0.0262

Big Creek 0.53876 0.0026 0.36653 0.0715

Camas Creek 0.67431 0.0004 0.65674 0.0023

Lemhi River 0.47824 0.0087 0.40587 0.0441

Loon Creek 0.64394 0.0002 0.60903 0.0016

Marsh Creek 0.62440 0.0003 0.53570 0.0058

Sulphur Creek 0.52331 0.0043 0.35625 0.0805

Valley Creek 0.75378 <0.0001 0.58447 0.0027

Total Abundance Ratio Total Abundance Ratio (Imnaha River / Bear Valley Creek)(Imnaha River / Bear Valley Creek)

Year

1960 1970 1980 1990 2000IR /

BV

C t

ota

l ab

un

dan

ce r

atio

0

2

4

6

8

10 SupplementedUnsupplemented

Total Spawner Abundance RatiosTotal Spawner Abundance Ratios(Imnaha Abundance / Unsupplemented (Imnaha Abundance / Unsupplemented

Abundance)Abundance)Mean

StreamPre-

supplementationPost-

supplementation

P-value

(t-test)

Bear Valley Creek 2.13 3.20 0.0308

Big Creek 4.84 6.27 0.0746

Camas Creek 7.77 24.04 0.0007

Lemhi River 1.89 9.54 <0.0001

Loon Creek 10.08 15.22 0.0244

Marsh Creek 2.57 4.97 0.0089

Sulphur Creek 7.35 18.91 0.0157

Valley Creek 11.74 18.94 0.0003

Natural-Origin Abundance Ratio Natural-Origin Abundance Ratio (Imnaha River / Bear Valley Creek)(Imnaha River / Bear Valley Creek)

Year

1960 1970 1980 1990 2000

IR /

BV

C n

atu

ral o

rig

in a

bu

nd

ance

rat

io

0

2

4

6

8

10

12 SupplementedUnsupplemented

Natural Origin Abundance RatiosNatural Origin Abundance Ratios(Imnaha Abundance / Unsupplemented Abundance)(Imnaha Abundance / Unsupplemented Abundance)

Mean

StreamPre-


supplementation

P-value

(t-test)


Big Creek 6.66 2.87 0.0076

Camas Creek 10.07 10.38 0.8866

Lemhi River 2.51 4.18 0.0244

Loon Creek 12.63 8.57 0.2503

Marsh Creek 3.36 2.66 0.2310

Sulphur Creek 9.81 8.06 0.5699

Valley Creek 13.53 8.79 0.2464

Recruits per Spawner RatioRecruits per Spawner Ratio(Imnaha River R:S / Bear Valley Creek R:S)(Imnaha River R:S / Bear Valley Creek R:S)

Year

1960 1965 1970 1975 1980 1985 1990 1995

IR /

BV

C R

:S r

atio

0

1

2

3

4

5

6SupplementedUnsupplemented

Recruit per Spawner RatiosRecruit per Spawner Ratios (Imnaha R:S / Unsupplemented R:S)(Imnaha R:S / Unsupplemented R:S)

Mean

StreamPre-


supplementation

P-value

(t-test)


Big Creek 1.63 0.96 0.1335

Camas Creek 1.90 1.63 0.0942

Lemhi River 1.64 1.28 0.0489

Loon Creek 2.13 1.75 0.0209

Marsh Creek 1.49 1.41 0.5106

Sulphur Creek 2.11 2.20 0.7618

Valley Creek 1.59 1.25 0.0495

22.822.8 31.131.1

Imnaha Recruit-per-Spawner Ratios

0

2

4

6

8

10

12

14

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000

Brood year

Rec

ruit

s p

er S

paw

ner

Natural

Hatchery

Abundance and Productivity Summary

•We have not observed a trend of increased number of natural-origin spawners through time since supplementation started.

•We have achieved a significant life cycle survival advantage for hatchery fish with progeny-to-parent advantage of seven to one.

•Recruits per spawner for naturally spawning hatchery and natural fish have averaged less than one and have been above one for only four of the last fifteen broodyears.

•It does not appear that we have increased natural origin abundance with supplementation even though we have increased the total number of spawners.

•It appears that we have depressed productivity of the natural spawners in the Imnaha population since supplementation was initiated.

Life History and Spawning Comparison Approach

Compiled data from weir collections, spawning ground surveys, and hatchery spawning to examine:

•Age composition – based on tags and scales to determine age

•Run timing – based on time of arrival at the weir and the composition of marked and unmarked carcasses recovered on spawning ground surveys.

•Spawn timing – based on time of collection of female carcasses on spawning ground surveys and time of spawning of females at Lookingglass Fish Hatchery.

•Spawning distribution – based on the location of female carcass recovery on spawning ground surveys.

•Spawning characteristics (age, size, fecundity, egg size, ovosomatic index, timing) – based on females spawned at Lookingglass Fish Hatchery.

•Our objective is for hatchery origin fish to have the same life history and spawning characteristics as natural origin fish.

Life History and Hatchery Spawning Summary

•Hatchery adults return at an earlier age for both males and females.

•Younger females means smaller females that are less fecund and have smaller eggs, on average, than natural females.

•Smaller hatchery smolt size-at-release has not resulted in an older age at return.

•Hatchery salmon typically return later than natural salmon.

•Hatchery salmon spawn later, in both nature and the hatchery, and mean spawn date of natural females is shifting to later.

•Hatchery salmon are distributed more downstream, near the smolt release location.

Life history and spawning characteristics of hatchery salmon are not matching those of natural salmon.

Why Not More Natural Origin Fish and Why Does Productivity Appear Depressed?

Some Hypotheses•Poor reproductive success of hatchery fish?

•Likely given the relatively low PNI, selective broodstock and resulting life history effects (spawn timing and younger age)

•Competitive and other ecological effects on natural origin juveniles?•Highly uncertain due to lack of information, however the number of hatchery produced smolts far exceeds the natural smolt production

•Other genetic and ecological effects?•Likely given selective broodstock collection, high proportion of hatchery origin fish spawning naturally, differences in spawn timing and spawning distribution of natural and hatchery origin fish, unnaturally high proportions of jacks spawning in nature and potential weir effects on adult spawning distribution

•Density dependent effects of increased total spawners•Likely some influence, however many post supplemetation years were low spawner abundance (1986-2000) in the Imnaha

What To Do

•Improve adult collection to get broodstock in a non selective manner

•Increase proportion of natural origin broodstock

•Reduce proportion of hatchery spawners in nature

•Reduce the size of the program

•Distribute juvenile releases throughout the spawning area

•Harvest as many hatchery fish as possible

chinook salmon supplementation in the imnaha river basin- a comparative look at changes in abundance...

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