Using an Otolith Growth Chronology as an Archive of Environmental Change
Shannon Davis-Foust and Ronald Bruch
Sagittal otoliths were embedded in epoxy resin and sections were cut through
the core to a thickness of 0.25-0.48 mm with a low-speed diamond blade saw
(Fig. 2). Sections were selected based on the clarity of increments in the
images to develop the growth chronology. Edge measurements on the otolith
sections were not used because the growth for the year of capture is
incomplete. The growth chronology index was developed using a mixed-effects
linear model (Weisberg et al. 2010) in the program R. Mean daily and monthly
air temperatures from 1948 to 2008 were obtained from the National
Oceanographic and Atmospheric Administration (NOAA) Satellite and
Information Service archives, which were measured near the west side of Lake
Winnebago at Oshkosh Wittman Airport (43°59'N / -88°33'W). Growing degree
days were calculated annually from high and low daily temperatures using a
series of nine threshold (base) temperatures ranging from 0°-18.3°C.
Correlations were examined between growth chronologies and climatic data
using Pearson’s correlation coefficient (r). The chronology was also entered into
the KNMI climate explorer and correlated against gridded, monthly-resolved air
temperature, precipitation, and sea level pressure data.
-4
chironomid larva
2009
2007
2005
2003
2001
1999
1997
1995
1992
1990
2008
2004
2000
1996
> 400 mm TL
Year
2008
Fig. 6
180-362 mm TL
2004
There were a total of 22,373 increment measurements from 1632 fish; ages
ranged from 2-58 and years 1948-2008 were included. The high frequency
fluctuations of the drum growth chronologies were positively correlated to air
temperatures. CDD base 15.6°C provided the strongest correlation with the
master chronology (CDD base 15.6°C: r=0.70) (Fig. 3).
12
10
8
6
4
2
0
-2
-4
-6
-8
-10
-12
2000
Results
Growth chronologies were compared between small (n=1632) and large (n=461)
drum subsets (Fig. 6). Paired Student’s t tests with Bonferroni’s adjustment
(α=0.0021) showed that year effects were consistently significantly different
between small and large drum every year after 2000, which was shortly after the
first report of zebra mussels in Lake Winnebago in 1998. Relative weights
(Wr’s) were consistently greater for large drum post zebra mussel establishment
versus pre zebra mussel establishment (Fig. 7).
1996
The objectives of this study are to: (1) establish correlations between drum
growth chronology and environmental factors, (2) characterize drum diet in
relation to body length, and (3) determine whether drum body condition has
changed with the establishment of zebra mussels. The third step would provide
solid evidence that zebra mussels supply a nutrient-rich food source for
molluscivorous fish and therefore directly affect higher trophic positions.
1992
zebra mussel
1964
Objectives
1988
1
0.8
0.6
0.4
0.2
0
Total length (10 mm class)
1960
Fig. 1
1984
Chironomid larvae
Zebra mussels
Chironomid larvae predicted
Zebra mussels predicted
1956
1966-present: Lake sturgeon abundance recovering from low levels (Bruch 2008)
1980
The stomach contents of 987 freshwater drum between 160-640 mm TL were
examined, and a distinct body length-related ontogenetic diet shift was
observed from chironomid larvae (160-362 mm TL, classified as small drum) to
zebra mussels (≥400 mm TL, classified as large drum) (Fig 5).
1952
1955-1966: State intensive rough fish removal period (Staggs and Otis 1996)
Relative weight (Wr) values were calculated to determine if body condition of
freshwater drum corresponded to growth rates. To search for changes in Wr
trends over time in regards to zebra mussel establishment, October trawl
captured drum from 1986 through 1999, which was prior to zebra mussel
establishment, were compared to 2001 to 2008, post zebra mussel
establishment. Comparisons between Wr’s were made between the time
periods using ANCOVA where Wr’s are a function of length.
error bars = ± 1 s.e.
Conclusions
• The growth chronology developed from otoliths of freshwater drum in Lake
Winnebago, WI, reflects both ambient temperatures (as high frequency fluctuations)
and food resource availability (as a low frequency fluctuation).
• The correlation of growth rates with food resource availability is supported by the
body length-related ontogenetic diet shift from chironomid larvae to zebra mussels
and improved body condition of large drum corresponding to the diet shift.
• Had the growth chronologies not differed between size classes that had been
defined by a diet shift, then another variable such as long-term climate trends could
have been implicated as the factor in controlling the recent increase in growth rates.
• Zebra mussels can provide enough nutrition to directly enhance drum growth
rates, whereas most studies have reported direct effects of zebra mussels only at
lower trophic levels.
Fig. 4
1948
1936-1990: State rough fish removal (emphasizing drum) (Staggs and Otis 1996)
Fig. 2
Year
References
Year effect
2000-present: Improved water clarity (Bruch 2008)
1998-present: Zebra mussels present (WDNR memo, unpublished)
error bars = ± 1 s.e.
The drum growth chronology was positively correlated on a regional scale to
summer temperatures in the Midwest and negatively correlated to sea surface
temperatures in the tropical Pacific (Fig. 4; maps from KNMI Explorer). There
were no other significant correlations with climatic data.
Fig. 5
1984-present: Best Management Practices reduce nutrient loading (WDNR 2004)
1970-present: Rusty crayfish present (Hobbs III and Jass 1988)
1976
Year
1969: Severe and prolonged flooding event (WDNR 1993)
1900-present: Carp present (WDNR memo, unpublished)
1972
1968
1964
1960
1956
1952
1948
Fig. 3
Fig. 7
1988
60
1960: Severe and prolonged flooding event (WDNR 1993)
1973: Severe and prolonged flooding event (WDNR 1993)
90
70
1992
1960-2000: Reduced water clarity (WDNR, unpublished anecdotal reports)
-2
-6
Freshwater drum stomach contents were qualitatively examined (volume was
not measured) from 2006-2009. Contents were identified for the presence or
absence of the taxonomic levels: Amphipoda, Isopoda, Chironomus spp. larvae, Chironomus spp. - adults, Oligochaeta, Hirudinea, Gastropoda, Bivalvia clams, Bivalvia - Dreissena sp., crayfish, fish, Limnephilidae, Ephemeroptera,
microcrustaceans - general, or Mollusca - unknown. In particular,
microcrustaceans were all microscopic arthropods, which were likely to be either
Cyclops sp., ostracods, Leptodora sp. or Daphnia sp., as described in the diet of
Lake Winnebago freshwater drum by (Priegel 1967). For the diet selectivity
analysis, 10 mm total length (TL) classes were constructed and proportions of
diet items selected were calculated. To determine the mean length at which
drum began to consume or stopped consuming major food items, the proportion
of drum selecting each food item was calculated and plotted as a function of
length. A double logistic model was fitted to the proportion selecting particular
food items.
180- 362 mm TL
> 400 mm TL
80
1988
1960-2000: High nutrient loading (WDNR, unpublished data)
0
1984
1960-2000: Decline of macrophytes (WDNR, unpublished anecdotal reports)
100
1980
1937-1960: Replacement of floating bog by other macrophytes (WDNR 1993)
2
1976
1850-1937: Large scale formation and disintegration of floating bog (WDNR 1993)
110
1972
1850-present: Water levels maintained at unnaturally high levels (WDNR 1993)
120
4
1968
1850 1875 1900 1925 1950 1975 2000
CDD 15.6°C
160
200
240
280
320
360
400
440
480
520
560
600
640
Growth chronologies have been correlated to temperature for freshwater drum
(Aplodinotus grunniens) in Minnesota (Pereira et al. 1995), but not for any other
environmental factor, including food availability. Drum are a dominant part of
the aquatic community of the shallow Lake Winnebago System. Since
European settlement began in central Wisconsin in the early 1800’s, the Lake
Winnebago system has faced an onslaught of anthropogenic pressures
including loss of thousands of acres of emergent wetlands, hypereutrophication,
six decades of rough fish removal, and invasions of non-native species such as
common carp, rusty crayfish, and zebra mussels (Fig. 1).
Master
Proportion
It is well-established that growth chronologies developed from relatively stable
anatomical structures reflect ecosystem structure and function and can serve as
valuable tools to interpret fish community health and regulating factors. Many
field studies have established a link between fish otolith growth and temperature,
but the effect of resource abundance on incremental growth, while intuitive, has
not been reported for fish in a natural environment. Defining relationships
between incremental growth and resource abundance is more ambiguous partly
because obtaining data to create indices can be intensive, while climatic indices
are usually readily available. As a consequence, fish growth chronologies are
often hypothesized to be indirectly related to resource availability, such as from
eutrophication related to fluctuating water levels or nutrient loading or population
density changes related to fluctuating water levels or exploitation.
6
1986
Most of the freshwater drum samples were collected by Lake Winnebago
assessment trawling from 1984-2009. Additional samples were collected from
fishing tournaments in 2003, 2006, 2009; boom electroshocking and angling in
2009; and from bridge construction blasting in 2007. Total length to the nearest
tenth of an inch (mm in 2009) and weight to the nearest tenth of a pound were
recorded, and sagittal otoliths were collected for age determination. From 20062009 sex and maturity were determined by the appearance of the gonads.
Results (cont.)
1984
The identification of environmental parameters that control biological growth
rates is vital to understanding ecological interactions within a community.
Growth rates are controlled by the interplay of endogenous and exogenous
variables; endogenous variables include age, maturation, and individual growth
rates; and exogenous variables include effects from the biotic and abiotic
environment (e.g. temperature, photoperiod, precipitation, dissolved oxygen).
The summation of these variables constitutes the growth of an individual within
a given time frame, and the mean relative contribution of variables influencing
total annual growth can be mathematically partitioned to provide information on
regulation of growth of an organism or serve as an archive of environmental
change.
Results (cont.)
Wr
Methods
Year effect
Introduction
error bars = ± 1 s.e.
Bruch, R.M. 2008. Modeling the population dynamics and sustainability of lake
sturgeon in the Winnebago system, Wisconsin. Dissertation. University of
Wisconsin - Milwaukee.
Casselman, J.M. 1987. Determination of age and growth. pp. 209–242. In: S. Gill
(ed.) The Biology of Fish Growth, Academic Press, London.
Davis-Foust, S.L., R.M. Bruch, S.E. Campana, R.P. Olynyk and J. Janssen. 2009.
Age validation of freshwater drum using bomb radiocarbon. Transactions of
the American Fisheries Society 138: 385-396.
Hobbs III, H., and J. P. Jass. 1988, The crayfishes and shrimp of Wisconsin
(Cambaridae, Palaemonidae). Milwaukee Public Museum Milwaukee, WI
(USA).
KNMI (Koninklijk Nederlands Meterologisch Instituut) Climate Explorer. (n.d.).
Retrieved from http://climexp.knmi.nl/
Pereira, D. L., C. Bingham, G. R. Spangler, Y. Cohen, D. J. Conner, and P. K.
Cunningham. 1995. Growth and recruitment of freshwater drum (Aplodinotus
grunniens) as related to long-term temperature patterns. Canadian special
publication of fisheries and aquatic sciences 121:617-629.
Staggs, M. D., and K. J. Otis. 1996. Factors affecting first-year growth of fishes in
Lake Winnebago, Wisconsin. North American Journal of Fisheries
Management 16(3):608-618.
Weisberg, S., G. Spangler, and L. Richmond. 2010. Mixed effects models for fish
growth. Canadian Journal of Fisheries and Aquatic Sciences 67(2):269-277 .
Wisconsin Department of Natural Resources. 1993. Aquatic Macrophyte Ecology
in the Upper Winnebago Pool Lakes, Wisconsin.
Wisconsin Department of Natural Resources. 2004. Water quality in the Lake
Winnebago pool. Wisconsin Department of Natural Resources, Publication
FH-229-04, Madison.
Acknowledgements
This project would not have been possible without the WDNR Fisheries
Management crew members who have assisted with obtaining drum samples.