Viewed in cross-section, daily growth increments of calcium carbonate are evident. Hatching is a physiologically stressful event, which produces a distinctive landmark upon the otolith. Daily increments were counted by light microscopy under oil immersion. From the total ring counts, we estimated birth date by back-calculation.

Back Calculation of Birth Date Growth Assessment

Examining the Early Life History of Coho Salmon (Oncorhynchus kisutch) from a Study of Otolith Microstructure

Students: Matt Brewer

Advisors: Dr. David LonzarichMary Elger-Lonzarich

Affiliation:University of Wisconsin – Eau Claire, Department of BiologyEau Claire, WI 54701

CONCERNS FOR YOUNG FISH

Determine the hatching window for populations of coho salmon in Washington and Wisconsin

Determine the effect of birth timing on growth of young coho salmon in these two different populations

EAR STONES TELL A STORY

ACKNOWLEDGEMENTS

By examining otoliths of young coho salmon we have gained a rare glimpse into the very early life of this species. From our findings we are able to make the following observations and conclusions.

Emergence of salmon in Wisconsin is delayed; possibly in response to spring flood regime

Washington salmon show compensatory growth (younger fish grow more rapidly in summer)

However, end of summer size remains linked to birth date in Washington fish.

Flow variability has effects on population growth patterns

Many students have participated in the project since it began nearly three years ago. In addition to the six involved in the production of this poster, they include Rachel Schoen, Rachel Haazert, Carissa Pannell, Patrick Murack, Bill Hintz, Kristine Funk, Rebecca Kitzman, Kristine Dahlheimer and Nalee Xiong. Mary Lonzarich and Dr. Steven Campana (Bedford Oceanographic Institute in Halifax, Canada) are owed special thanks. Mary for her extraordinary work in organizing and managing a large collection of specimens and data files and Dr. Campana for his generous support of time and expertise in training our lab group in the fine art of otolith analysis. We also wish to thank the UWEC Office of Research and Sponsored programs, which provided funds to support 12 students and the UWEC Diversity Mentoring program, which provided funds for two others. Funding for the printing of this poster was provided by UWEC Differential Tuition and the Office of Research and Sponsored Programs.

Hatch Mark

12

34

56

78

910

1112

13

Hatch Mark

12

34

56

78

910

1112

13

STUDY GOALS

RESULTS AND DISCUSSION

• Length of growing season

• Risk of predation

• Access to resources

• Establishment of dominance hierarchies

Birth Date

Emergence Date

0

0.1

0.2

0.3

0.4

0.5

30 50 70 90 110 130

Freq

uenc

y

Washington

Wisconsin

Jan

Feb

Mar

Apr

0

50

100

150

200

250

Jan

Mar

May Ju

lSep Nov Ja

nM

arM

ay Jul

Sep Nov

Rel

ativ

e S

trea

m F

low

In Great Lakes streams, high flow events regular in spring, but also occur in summer, creating environmental instability.

250

0

50

100

150

200

Jan

Mar

May Ju

lSep Nov Ja

nM

arM

ay Jul

Sep Nov

Rel

ativ

e S

trea

m F

low

In West Coast streams, high flow events are limited to the winter months, resulting in summer stability.

0

20

40

60

80

0 20 40 60 80 100

Birth Date

Length

(m

m)

Early Season

Late Season

0

20

40

60

80

0 20 40 60 80 100

Birth Date

Length

(m

m)

Early Season

Late Season

WASHINGTON

WISCONSIN0

0.1

0.2

0.3

0.4

30 40 50 60 70 80 90 100Length (mm)

Fre

quen

cy

Washington

Wisconsin

70 mm70 Days

1 mm/ day

140 mm

2 mm/ day

The total size of the fish was recorded at the time of capture. By dividing age by size, we can obtain a daily growth estimate for each fish.

R² = 0.8158

R² = 0.0793

0

0.1

0.2

0.3

0.4

0 20 40 60 80 100

Gro

wth

(m

m/d

)

Birth Date (J ulian Day)

Washington Wisconsin

Stream Flow and Environmental Stability

In Oregon populations of coho salmon, emergence timing (date when fish swim out of gravel nest) is drawn out over a one month period. (Data from Koski, 1966, Masters Thesis, Oregon State University)

0

50

100

150

200

250

300

350

400

2 6 10 14 22 28

Days After 1st Hatch

Num

ber

of

Fis

h B

orn

Consequences

Consequences• Maintenance of dominance hierarchies

related to flow stability

• Break down of hierarchies may equalize summer growth of young fish