Matt Sloat and Gordon Reeves

Fisheries and Wildlife ManagementOregon State University

and

USFS PNW Research Station, Corvallis, OR

Influence of changing thermal regimes on steelhead growth and life history expression

Climate change will alter the thermal regimes of aquatic ecosystems

How will aquatic organisms with complex life histories respond to these alterations?

O. mykiss life cycle

Boughton et al.

J. Tomelleri

J. Tomelleri

Males exhibit alternative mating tactics

Anadromous- delay maturation and mature at

large size

FW resident- mature early at small size

O. mykiss life histories

photos: J. McMillan

Prob

abili

ty o

f ear

ly m

atur

ity

1

0

20%

90%

Length-at-age

McMillan et al. (2011) Env. Bio. Fish.

Lipid storage greater in cold streams and growth (i.e., length) greater in warm streams.

(Wilcoxon rank sum test, p >0.001)(Wilcoxon rank sum test, p = 0.02)

0.0

0.2

0.4

0.6

0.8

1.0

1

2

3

4

5

6

7

60 80 100 120 140 160 180 200

Pro

babi

lity

of m

atur

ity

Who

le b

ody

lipid

%

Fork length (mm)

Redrawn from McMillan et al. (2011) Env. Bio. Fish.

warmer

colder

Prob

abili

ty o

f ear

ly m

atur

ity

Length-at-age (mm)

0.0

0.2

0.4

0.6

0.8

1.0

40 60 80 100 120 140 160 180 200

Pro

babi

lity

of e

arly

mat

urity

Length-at-age (mm)

Warmer

Length-at-age

Prob

abili

ty o

f ear

ly m

atur

ity1

0

Study objective:

Determine the influence of thermal regimes on energy allocation and life history expression in O. mykiss

• Obtained fertilized eggs from a single pair of Clackamas River steelhead from the Clackamas River Hatchery

• Incubated at OSU Salmon Disease Lab

• 2 thermal regimes• 12 replicates per thermal regime• 24 tanks total

Difference in thermal regimes representsa 2.5°C increase in mean annual watertemperature

Month

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul

Mea

n d

aily

te

mpe

ratu

re

6

8

10

12

14

16

18

20

Overview of experimental design

30 individually marked fish per

tank

post hoc analysis:sex ratio ~ 1:1

• 30 fish per tank• 24 tanks total• 720 individually marked fish VIE marks identify individual fish

Overview of experimental design

Methods

•Monthly growth measurements (FL, mass) of individual fish

•Life history categorization•Assessment of smolt status April – June 2011

•Assessment of maturity Aug 2011

•Retrace growth trajectories of fish within life history categories

•Whole body lipid analysis (forthcoming)

Results

Male growth trajectories: length

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

For

k le

ngth

(m

m)

20

40

60

80

100

120

140

160

180

200

Warm regimeCold regime

*

*

**

**

*

20mm

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

Mas

s (g

)

0

20

40

60

80

Warm regimeCold regime

Male growth trajectories: mass

**

*

*

*

**

22g

Smolts Mature males

Smolts: 46% *

Mature: 49% *

Smolts: 16% *

Mature: 76% *

UN: 8% UN: 5%

Male life history expression for steelhead offspringreared under different thermal regimes

Cold thermal regime Warm thermal regime

Cold regimeWarm regime

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

UNDIFFERENTIATEDSMOLT MATURE

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

Fo

rk le

ng

th (

mm

)

20

40

60

80

100

120

140

160

180

200

UNDIFFERENTIATEDSMOLT MATURE

Male growth trajectories by life history type: length

* * **

**

Month Month

Leng

th (m

m)

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

Mas

s (g

)0

20

40

60

80

UNDIFFERENTIATEDSMOLTMATURE

Month

AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE

Mas

s (g

)

0

20

40

60

80

UNDIFFERENTIATEDSMOLT MATURE

Cold regimeWarm regime

Male growth trajectories by life history type: mass

*

*

* * **

*

*

*

Month Month

Mas

s (g

)

Len

gth

(m

m)

80

100

120

140

160

180

200

220

240

260

Warm regime Cold regime

smolt mature smolt mature

smolt mature smolt mature

Mas

s (g

)

0

20

40

60

80

100

120

140

160

180

200

Leng

th (

mm

)

80

100

120

140

160

180

200

220

240

260

Mas

s (g

)

0

20

40

60

80

100

120

140

160

180

200

Conclusions:

• Despite higher rates of somatic growth, fish experiencing warmer temperatures had lower rates of maturation

• Temperature may alter energy allocation in important ways that are not captured by measuring somatic growth alone

• A mechanistic understanding of physiological responses to altered thermal regimes is needed to forecast effects of climate change

Acknowledgments:Funding provided by USFS PNWRS with additional support from USGS FRESC, Corvallis, ORAFS Carl Bond Memorial Scholarship.

Thanks to: Jason Dunham, India Sloat, Jill Pridgeon, Haley Ohms, Amy Lindsley, Stephanie Saunders, Matt Stinson, and staff at ODFW Clackamas Hatchery.

photo: Becky Sloat