Transcript BrewerSpr07

Examining the Early Life History of Coho Salmon (Oncorhynchus
kisutch) from a Study of Otolith Microstructure
Great Lakes
West Coast
In lowland West Coast
streams, high flow events
are limited to the winter
months.
During
the
remainder of year, flooding
is rare .
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In Oregon populations of coho
salmon, emergence timing (=
date when fish swim out of
gravel nests) is drawn out over a
one month window. (Data from
Koski, 1966, Master’ Thesis
Oregon State University)
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< 0.5 mm
In Great Lakes streams,
high flow events regular in
spring and common in
summer. They are rare the
remainder of year. (Graph
based on data from USGS
Water Resources)
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Number of Fish Born
In species with prolonged hatching windows it
becomes practical for ecologists to explore
questions concerning the costs and benefits of
early and late birth dates.
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 Although survival is usually very poor during
the early life of a fish, mortality risks vary
geographically depending on ecological and
physical conditions. In coho salmon, for
example, populations of western North
American streams are exposed to flow
regimes that are very different from those
found in streams of Lake Michigan and Lake
Superior, where the species was introduced in
the late 1960s (figure to right).
 A potentially important predictor of early
mortality and growth in young fish is birth date,
which in some species can extend over a
relatively long periods of time (figure to right).
Stream spawning female salmon
will lay several thousand large
eggs in gravel nests during cold
winter months
The internal ears of fish contain bones, known as otoliths, that record many important aspects of an
individual’s life. Two of these are daily growth and metabolic rate.
 In young stream-dwelling salmon and trout the first few weeks are often associated with high levels of predation,
damaging floods and intense competition for limited spatial resources.
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Affiliation:
University of Wisconsin – Eau
Claire,
Department of Biology
Eau Claire, WI 54701
EAR BONES TELL A STORY
IMPORTANCE OF BIRTH DATE
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Advisors:
Dr. David Lonzarich
Mary Elger-Lonzarich
SALMON EARLY LIFE HISTORY:
Relative Stream Flow
Students:
Matthew
Brewer,
Yaron
Fireizen, Tim Morschauser,
David Koslov, Ernest Ruiz,
Paulina Duarte
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Days After 1st Hatch
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Hatch M
ark
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Birth Date
Metabolic Rate
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.
Otolith size at birth is correlated with metabolic rate,
suggesting that otolith diameter (shown above) is a
good indicator of growth potential in juvenile fish.
In this study, daily increments were counted by light
microscopy under oil immersion. From the total ring
counts, we estimated birth date by back-calculation for over
200 fish in the two streams.
Otoliths were measured at the hatch mark along the
long axis. In the present study, we generated data
from 52 fish from the Cranberry River population.
 Especially in salmon, the timing of birth can be a very important determinant of growth and survival.
 In part this is true because birth date may be linked to developmental (or metabolic) rate, which in turn is positively
correlated with competitive success and growth (e.g., Yamamoto and Higashi, 1998, J. Fish Biol 52:281-290).
 Birth timing also may be important in situations where competitive success and predation risk are associated with
size and abundance. We present below two scenarios depicting plausible advantages associated with early and
late birth dates.
Advantages of an early birth date
RESULTS AND DISCUSSION
Objective 1: Patterns of Hatching and emergence in the two populations
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Advantages of a late birth date
Birth Date
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Hatch
Emergence
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Frequency (%)
Fish born late
may experience
lower per capita
predation risk
because more
prey are present
in the stream
Because competitive
success is affected by
size, fish born early have
advantage in securing
limited territory space.
They also experience a
longer growing season
Mean Emergence Time (days)
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Forks Creek
Cranberry River
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Young salmon hatch following
several months of incubation and
reside as alevin within their
gravel nests for more than one
month before emerging as fry.
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Forks Creek
Cranberry River
Julian Day
WA fish hatched earlier than WI fish but the hatching season
was protracted for both populations (> 2 months).
STUDY GOALS
The general aims of this study were to document hatch timing patterns in coho salmon, and to explore the
consequences of hatch timing and developmental history on growth of young fish (<2 mos of age).
Objective 2: Effect of Hatch Date on Growth
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WI fish remained in gravel nests longer than WA fish and most
emerged in April, well after the period of peak stream flows.
Objective 3: Otolith Size as Predictor of Growth
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Forks Creek
Cranberry River
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Growth Rate (g/d)
 Characterize hatch timing in coho salmon populations
from two streams in Washington and Wisconsin.
 Examine effects of hatch date on growth patterns of
juvenile salmon.
R2 = 0.77
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Birth Date (Julian Days)
Great Lakes salmon were collected
from the Cranberry River a tributary
of Lake Superior, WI.
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West coast salmon were collected
from Forks Creek a coastal stream in
western WA.
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 Determine whether development rate (or metabolism)
can predict individual variability in growth among juvenile
salmon.
Growth Rate (g/d)
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Our specific objectives were to:
R2 = 0.40
Early fish grew faster than late fish, suggesting that population
differences in size were shaped by birth date rather than locale.
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Otolith Diameter at Hatch
Otolith size at birth, previously linked to metabolic rate, here
served as a good predictor of early season growth in WI fish.
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.
 Protracted hatching periods in both populations suggest that there may be strong ecological effects of birth timing.
From the fry stage, salmon move
through several life stages before
returning to their natal streams
as adults.
ACKNOWLEDGMENTS
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.
 One possible determinant of the different emergence dates for the two populations is fine sediments (Koski 1966).
However, it has not escaped our notice that the emergence of WI fish occured after the spring floods, suggesting
that there may be strong selective pressure favoring late emergence.
 Growth patterns were correlated strongly with birth date (-) and metabolic rate (+). Although WA fish were larger
than those in WI, growth differences appear to be affected more by birth date than local environmental conditions.
 Finally, our data indicate that fish born early have a growth advantage over those born late, at least during the first
two months of life. We are currently analyzing data for older fish to learn whether this advantage erodes with time.