Selective Spawning: Dworshak NFH B-Run Steelhead

Brett Bowersox, Idaho Department of Fish & Game Chris Peery, Idaho Fishery Resource Office, USFWS

What are the points of concern?

Issues with stock: • Are population characteristic changing? Importance of stock: • Unique Dworshak/North Fork B-Run Population • Economics of a Popular Fishery Brood Management: • What are viable strategies for maintaining what

makes them unique • Genetic analysis, why are we doing this and does

it work

Snake River A-Run Snake River B-Run

Importance of Fishery

~ $24 million in angler expenditures

So what’s going on with the hatchery stock?

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014

So what’s going on with the hatchery stock?

Smolt Releases

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

50,000Adult Returns

0.000

0.005

0.010

0.015

0.020

0.025

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

Smolt to Adult Ratio

So what’s going on with the hatchery stock?

Dworshak Population Age Structure

0.00.10.20.30.40.50.60.70.80.91.0

1980 1985 1990 1995 2000 2005 2010 2015

1-Ocean 2-Ocean 3-Ocean

600

650

700

750

800

850

900

950

1000

Leng

th (m

m)

Run Year

3-ocean 2-ocean 1-ocean

DWOR Stock Length at Ocean age

Broodstock Management Strategies

Multiple Spawn Crosses For Males

0

10

20

30

40

50

60

70

80

550 580 610 640 670 700 730 760 790 820 850 880 910

# Fi

sh

Length (mm)

Male Steelhead

Outlook for 2016

USFWS, 2016

Minimum Size Criteria for Females

0

10

20

30

40

50

60

70

80

90

100

550 580 610 640 670 700 730 760 790 820 850 880 910

# Fi

sh

Length (mm)

Female Steelhead

Minimum Size Criteria

USFWS, 2016

Why could this make a difference? And

How will we know?

Selection

Three conditions must be met for selection to occur in a population:

Variation: Individuals in the population must differ with respect to the trait in question.

Heritability: The variation found in the population must (at least partially) be heritable, e.g. transmitted from parent to offspring.

Differential Mortality: Finally, individuals must have a probability of survival that is a function of the value of the trait in question. If all individuals, regardless of there trait value, had an equal probability of survival and fecundity, no predictable change in the mean value of the population would occur.

Heritability

• Heritability is the proportion of variance in a particular trait, that is due to genetic variation among individuals in the population

• A simple way to estimate the heritability of a trait is to plot the offspring’s traits against the average of their parents

Heritability in Steelhead

y = 0.1977x + 650.15 R² = 0.0579

650.0

700.0

750.0

800.0

850.0

900.0

950.0

650 700 750 800 850 900 950

Avg.

Len

gth

of O

ffspr

ing

spaw

ned

in 2

013

Avg. Length of Parents Spawned in 2009

Heritability of Fork Length

Summary

• Clearwater River B-Run Steelhead are unique

• It is the responsibility of USFWS to maintain the population integrity

• The Age Structure and Size-At-Age are changing – a basin-wide trend

• Broodstock selection may help maintain age and size structure for this population

• Close monitoring is needed to assure is effective and not causing un-intended consequences.