Transcript Archaeology Study Poster Final.ppt

Using Archaeological Freshwater Drum Otoliths to Detect Long-Term Changes in Age and Growth
Shannon Davis-Foust and Ronald Bruch
In addition to these changes, millions of pounds of the native freshwater drum
(Acipenser fulvescens), a species considered a rough fish, were removed
annually throughout most of the later half of the 20th century in a combined
effort by commercial fishermen and state-funded programs (Fig. 1). The rough
fish removal program was terminated in 1990 in part because the desired
impact on drum (fewer drum) was never detected.
Sauer Resort
9 otoliths 1390-1530
(calibrated 1317-1419)*
Despite their modern reputation as a rough fish, drum were an important part of
the diet of Native Americans inhabiting the shore of the Winnebago lakes,
evidenced by the 1000’s of drum otoliths that have been found in middens in
excavated Native American campsites and villages in the area. These
archaeological otoliths provided an opportunity to compare age and growth of
Winnebago System drum from pre-historic times to that of drum from modern
times, and perhaps provide some insight as to the impact of 60 years of
intensive drum removal in the 20th Century.
The best fit equation for the relationship between fish total length and otolith
length for drum otoliths <15.5 mm long was Log10(TL) = 1.0387 * Log10(OL) +
1.3290) r2 = 0. Winnebago
9806, and the
equation for
otoliths
≥15.52007-08
mm was Log10(TL) =
Freshwater
Drum
2003-04,
1.3683 * Log10(OL) + 0.9591, r2 = 0.8560
(n=910)(Fig. 4).
N
Doty Island
448 Otoliths 1680-1712
2.9
Menominee Park I
12 otoliths 1150-1350
2.6
2.3
2.0
1.7
60%
50%
40%
Percent
Fig. 3
Fig. 2
Objectives
Sagittal otoliths from drum provide accurate estimates of age (Davis-Foust et al.
2009) (Fig. 2), and total lengths of freshwater drum have been estimated from
their otoliths with remarkable accuracy (Witt 1960, Priegel 1963). Age has been
estimated from a small set of archaeological otoliths (Bergquist 1996). Witt
(1960) Priegel (1963) both concluded that archaeological drum grew larger than
modern drum collected from archaeological sites near the Mississippi River and
Lake Winnebago; however, no studies have used otoliths to evaluate changes
in age composition or growth rates.
We evaluated changes in age and growth of freshwater drum from prior to
European settlement (circa 1850) to modern times within the Lake Winnebago
system. We compared (1) length distribution, (2) age distribution, and (3) growth
rates between archaeological and modern drum within lotic and lentic
subclasses.
Acknowledgements
Many thanks goes to Richard Mason and Dr. Jeffrey Behm, Department of
Anthropology, UW-Oshkosh for providing archaeological otoliths, and to the
many WDNR fisheries technicians that have assisted with capturing drum and
otolith processing.
TL’s of archaeological drum were calculated using the equation derived from the
relationship between OL to TL for modern drum. TL distributions of both
archaeological and randomly sampled modern drum were examined by grouping
them into length categories proposed by Gabelhouse (1984). Mean length at age
was compared using paired t-tests between modern and archaeological drum.
Von Bertalanffy models were used to compare growth rates by calculating mean
length (OL’s and TL’s) at age. Significant differences between growth parameters
were evaluated drum using likelihood ratio tests.
To further evaluate differences between archaeological and modern drum,
subclasses were created by categorizing drum as lentic or lotic (Rypel et al.
2006). Modern drum captured during tournaments (n=287) were classified as
lotic because the majority of competitors in these tournaments target large drum
in riverine habitat. Drum captured by trawling (n=1152) were classified as lentic.
Archaeological otoliths were assumed to be lentic if they were recovered from
sites along the lakes (n=110) and considered lotic (n=508) if they were from Doty
Island, which was the only site located at the opening of a river. Differences
among length and age distributions of archaeological/lentic, archaeological/lotic,
and randomly captured modern/lentic and modern/lotic drum were examined
using two-way ANOVA.
S-Q
(200299)
Q-P
(300379)
P-M
(380509)
M-T
(510629)
T
(>=630)
Length class
The CV for age determinations between the two readers for archaeological
otoliths was 0.37%. Ages of lotic drum (M=31.66, SD=15.23) were older than
lentic drum (M=16.0, SD=10.65), F(1,1251)=178.01, p<0.001(Fig. 6). Ages of
archaeological drum (M=34.5, SD=15.82) were older than modern drum
(M=17.6, SD=9.98), F(1,1251)=234.98, p<0.001. There was no significant
interaction F(1,1251)=3.674, p=0.056 indicating that the ages of lotic drum were
greater than lentic drum during both time periods.
0.40
Archae/Lentic
Modern/Lentic
Archae/Lotic
Modern/Lotic
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0
Fig. 6
Age
Archae
700
600
Predicted
Archae
500
400
300
Archae
604.323
0.033
-14.814
0.9
Linf
K
t0
r^2
200
100
Modern
Modern
603.394
0.044
-9.286
0.84
Predicted
Modern
0
0
10
20
30
40
50
60
70
80
Conclusions
0%
S-S
(100199)
6 10 14 18 22 26 30 34 38 42 46 50 54 58 62 67 71
Age (years)
20%
Proportion of total in age class
Fig. 1
Error bars represent +/- one standard error
Using mean total length at age for archaeological drum ages 2-64 and modern
drum ages 2-41, archaeological drum grew slower yet attained similar lengths to
modern drum (likelihood ratio test, F(3,96)=3.8886, p=0.011) (Fig. 8). Similar
differences between von Bertalanffy parameters were obtained between lotic
von Bertalanffy model comparing actual TL of modern and
modern and lotic archaeological
drum.
predicted
TL of archaeological drum
Fig. 8
Archae/Lentic
Archae/Lotic
Modern/Lentic
Modern/Lotic
30%
Fig. 5
10
800
10%
Sagittal otoliths were obtained from modern drum (n=148 in 1986, n=177 in 2003,
n=126 in 2004, n=107 in 2005, n=184 in 2006, n=351 in 2007, n=240 in 2008,
and n=106 in 2009) captured by fall assessment trawling and angling at
tournaments. A random otolith length (OL) (left or right) was used from 1016
drum to determine the model the best described the relationship between OL and
total body length (TL). Modern otoliths were embedded and sectioned following
the same methods as the archaeological otoliths.
15
Fig. 7
The TL’s of the lotic drum (M=502.3, SD=96.3) were greater than lentic drum
(M=362.7, SD=103.2), F(1,1214)=405.619, p<0.001 (Fig. 5). However, the
length distributions between the two time periods were not significantly different,
F(1,1214)=3.667, p=0.056, and there was significant interaction between habitat
type and time period, F(1,1214)=66.11, p<0.001.
*Calibrated by quickcal2007 ver.1.5
20
2
Log otolith length (mm)
Fahrney Point
38 otoliths 1728-1730
25
5
Fig. 4
Bell Site
2 otoliths 1222-1275
58 otoliths 1680-1730
Archaeologic
Modern
3.2
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4
Kargus Site
50 otoliths 1330-1390
30
Mean otolith length (mm)
Sagittal otoliths for this study were recovered from archaeological sites
surrounding the Lake Winnebago system (Fig. 3). The lengths of 690 otoliths were
measured in mm on the longest axis, weighed to the nearest tenth of a mg,
embedded in epoxy, sectioned with a low-speed diamond bladed saw, and
examined through a dissecting scope for age determination. Age determinations
were made by two experienced readers by counting the opaque zones as the
boundary for annual growth increments (Casselman 1987). Precision was
evaluated by calculating the coefficient of variation (Campana 2001).
Metzig Garden
1 otolith 8500-6500 BC
Results (cont.)
Results
Log fish fish total length (mm)
Freshwater drum (Aplodinotus grunniens) have been a dominant part of the
aquatic community of the shallow Lake Winnebago System for centuries. Since
European settlement in central Wisconsin began in the early 1800’s, the Lake
Winnebago system has faced an onslaught of anthropogenic changes including
loss of thousands of acres of emergent wetlands, eutrophication, and invasions
of non-native species such as carp and zebra mussels.
Methods
Mean total length (mm)
Introduction
5 10 15 20 25 30 35 40 45 50 55 60 65 70
Age class
An inflection point was detected between modern and archaeological mean OL’s
at age (Fig. 7). Mean OL’s at age for archaeological drum were greater than
modern drum from age 2-9 (one tail paired Student’s t test: t=2.29, p=0.028),
and mean OL’s for modern drum were greater than archaeological drum from
ages 10-49 (one tail paired Student’s t test: t=-6.56, p<0.001).
• Archaeological drum from lotic habitats had greater longevity and slower overall
growth rates than modern drum.
• Archaeological drum less than age 10 grew more quickly than modern drum,
suggesting that the food base for small drum may have been better and the food
base for large drum may have been poorer (in relation to population densities)
prior to European settlement.
• The inflection points observed between TL and OL, and OL and age in both
archaeological and modern drum corresponds to the length at which there is a
diet shift in modern drum (unpublished data).
• Sixty years of intensive drum removal operations may have sufficiently
decreased densities to result in a younger age composition and increased growth
rates in the adult Lake Winnebago drum population.
References
Bergquist, L.A. 1996. Development of an archaeometric dating technique
using freshwater drum otoliths: an application of biochronology. Thesis,
University of Minnesota, St. Paul. 111 pp.
Campana, S.E. 2001. Accuracy, precision and quality control in age
determination, including a review of the use and abuse of age validation
methods. Journal of Fish Biology 59: 197-242.
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 & J. Janssen.
2009. Age validation of freshwater drum using bomb radiocarbon.
Transactions of the American Fisheries Society 138: 385-396.
Gabelhouse Jr, D. 1984. A length-categorization system to assess fish stocks.
North American Journal of Fisheries Management 4: 273-285.
Priegel, G.R. 1963. Use of otoliths to determine length and weight of ancient
freshwater drum in the Lake Winnebago area. Wisconsin Academy of
Science, Arts, and Letters 52: 27-35.
Rypel, A.L., D.R. Bayne & J.B. Mitchell. 2006. Growth of freshwater drum
from lotic and lentic habitats in Alabama. Transactions of the American
Fisheries Society 135: 987-997.
Witt Jr, A. 1960. Length and Weight of Ancient Freshwater Drum, Aplodinotus
grunniens, Calculated from Otoliths Found in Indian Middens. Copeia
1960:181-185.