Sarah McCarthy

1
Trophic performance of Oncorhynchus mykiss along
forest gradients in the South Fork Trinity River
watershed

• Sarah McCarthy

2
South Fork Trinity River
Photo courtesy of J. Duda
3

• Klamath River tributary
• Trinity River dam 1962
• South Fork Trinity undammed
• Klamath Mountains Province steelhead ESU unlisted

4
Objectives

• What factors control O. mykiss production in CA?
• Temperature Effects
• Prey Quality
• Feeding Rate
• Use bioenergetics modeling to identify effect of
  season, age, forest cover, and temperature on O.
  mykiss consumption and growth efficiency (GE).

5
Study Design

• 9 streams
• 3 forest cover categories
• 2 temperature regimes

6
Study Design
7
Bioenergetics Model
FISH GROWTH
C G M W
DIET COMPOSITION
PREDATOR ENERGY DENSITY
THERMAL EXPERIENCE
PREY ENERGY DENSITY
Proportion of maximum consumption (p) C/Cmax
G/C Growth efficiency (GE)
CONSUMPTION
8
Model Inputs

• Stream Temperature
• (constant temperature monitoring)
• Prey Quality
• (invertebrate drift sampling)
• O. mykiss Growth Measurements
• O. mykiss Diet Composition

9
Fish Sampling

• Electrofished 9 streams during June, August, and
  October 2003

10
Fish Sampling

• Electrofished 9 streams during June, August, and
  October 2003
• Measured length weight

11
Fish Sampling

• Electrofished 9 streams during June, August, and
  October 2003
• Measured length weight
• Collected scales

12
Fish Sampling

• Electrofished 9 streams during June, August, and
  October 2003
• Measured length weight
• Collected scales
• Collected stomach contents

13
Fish Sampling

• Weight Trajectories

Conifer-cool highest weight, but all groups had
slow growth
Warm streams had sharpest growth increase
Hardwood-cool and conifer-cool grew most
14
Diet Composition

• Prey items
• Immature aquatic sources
• Aquatic larvae (Diptera, Coleoptera, Trichoptera,
  etc)
• Aquatic nymphs (Ephemeroptera, Plecoptera, etc)
• Aquatic other (Gastropoda, Isopoda, Crustacea,
  Acarina, Ostracoda, etc)
• Adult invertebrates
• Aquatic (Ephemeroptera, Plecoptera, Trichoptera,
  Diptera)
• Terrestrial (Coleoptera, Hymenoptera, Araneae)

15
Diet Composition

• Contribution of adult insects increased with age

16
Diets varied by season and age
17
Bioenergetics Modeling

• Low proportion of maximum consumption (avg0.25)

1.0
Cmax
0.8
Consumption
0.6
Specific rate (g/g/d)

• Summer
• temps
• 14-18C

0.4
0.2
Respiration
0.0
5
10
15
20
25
Temperature (C)
C G M W
18
Simulating Increased Summer Temperature Effects
Age 0
Age 0
Age 1
Age 1
Age 2
Age 2
Most growth occurs during winter/spring
19
Simulating Increased Summer Temperature Effects
11.5
18.8
5.4
8.9
With 2oC temperature increase, O. mykiss required
to grow more over winter.
20
Summary

• Increased consumption of adult insects with age
  and season
• Higher consumption of adult invertebrates in
  conifer-cool category
• Decreased or negative growth during late summer
• Low feeding rates throughout summer
• Decreased summer growth after 2oC temperature
  increase

Photo courtesy of J. Duda
21
Summary

• Increased consumption of adult insects with age
  and season
• Higher consumption of adult invertebrates in
  conifer-cool category
• Decreased or negative growth during late summer
• Low feeding rates throughout summer
• Decreased summer growth after 2oC temperature
  increase

Photo courtesy of J. Duda
22
Summary

• Increased consumption of adult insects with age
  and season
• Higher consumption of adult invertebrates in
  conifer-cool category
• Decreased or negative growth during late summer
• Low feeding rates throughout summer
• Decreased summer growth after 2oC temperature
  increase

Photo courtesy of J. Duda
23
Summary

• Increased consumption of adult insects with age
  and season
• Higher consumption of adult invertebrates in
  conifer-cool category
• Decreased or negative growth during late summer
• Low feeding rates throughout summer
• Decreased summer growth after 2oC temperature
  increase

Photo courtesy of J. Duda
24
Summary

• Increased consumption of adult insects with age
  and season
• Higher consumption of adult invertebrates in
  conifer-cool category
• Decreased or negative growth during late summer
• Low feeding rates throughout summer
• Decreased summer growth after 2oC temperature
  increase

Photo courtesy of J. Duda
25
Conclusions

• Isnt summer the growing season?
• O. mykiss may be food-limited across the
  watershed
• Heightens concern for effects of interannual
  variability and/or climate shifts
• Implications for other steelhead stocks in CA
• high temperatures exacerbated by low prey supply
• even minor shifts in temperature or food supply
  could push population further into negative
  growth patterns
• Recommend extending study to neighboring
  populations

26
Acknowledgements
Graduate committee Dr. David Beauchamp, Dr.
John Emlen, Dr. Thomas Quinn
USGS Jeffrey Duda, C. Ostberg, Dr. R.
Reisenbichler, Dr. S. Rubin, K. Larsen, S.
Dufrene, L. Pascoe, C. Chambers, C. Galitsky, J.
Steinbacher UW School of Aquatic and Fishery
Sciences Dr. C. Grue, Dr. L. Conquest, V.
Blackhurst, E. Chia, D. ODonnell, A. Van Mason,
A. Lind, C. Sergeant, S. Damm, J. Matilla, E.
Duffy, A. Cross, J. Moss, M. Mazur, N. Overman,
S. Wang, E. Schoen USFS Redwood Sciences
Laboratory, Arcata, CA Dr. H. Welsh, G.
Hodgson, Dr. B. Harvey USFS Ranger Station,
Hayfork, CA J. Lang, J. Fitzgerald
27
(No Transcript)
28
Effects of Food and Temperature on Growth
Energetics
Consumption rate reduction reduced optimal
temperature for growth and growth potential.
29
Effects of Food and Temperature on Growth
Energetics
25 Cmax
Absolute growth very low when costs associated
with metabolism and waste are accounted for.
30
Physical Stream Characteristics

• Stream Temperature
• Temperature loggers deployed April-October 2003
• Temperature recorded every 20 minutes
• Avg daily temp gt17C warm
• Avg daily temp lt17C cool

31
Prey Sampling

• Drift Composition
• Drift samplers deployed before dusk collected
  after dawn
• Evaluated relative proportion of invertebrate
  drift
• Invertebrates used for bomb calorimetry

32
Relative Prey Supply

• Drift Composition
• Higher volume of immature aquatic invertebrates
• Higher prey supply in hardwood-cool

• Drift sampler bias

33
Cumulative Consumption
2.9 - 8.9
-2.3 9.7
-7.3 7.2
GE Growth/Consumption
Lower growth efficiencies during late summer
34
Cumulative Consumption
-1.1 11
-42 15.2
-3.8 15.4
GE Growth/Consumption
Lower growth efficiencies during late summer
35
Cumulative Consumption
3.7 7.1
-2.7 13.2
-12.2 15.9
GE Growth/Consumption
Lower growth efficiencies during late summer