Population Biology / Ecology I
Saturday March 12:
10:20am-11:50am
Back to Concurrent Session
I
ABSTRACTS |
EFFECT OF ADULT SIZE AND LITTORAL
HABITAT ON LARVAL SUNFISH PRODUCTION IN UNEXPLOITED
LAKES
Knuth, D.S. And Garvey, J.E.
Department Of Zoology, Southern Illinois
University, Carbondale, Il 62901
Adult size structure and lake morphometry
may influence larval production and timing of spawning
in sunfish. We quantified how these factors affected
larval sunfish in seven unexploited, small (2.47-8.67ha)
coal mine lakes during the summer of 2003. Lakes were
stratified across categories of adult size structure
and littoral habitat availability. Larval tows were
conducted weekly in each of the lakes to estimate
densities throughout the spawning season. Littoral
habitat was quantified by conducting bathymetric surveys
with an echosounder and calculating percent availability.
Peak and total larval sunfish densities increased
with adult size. The earliest peak spawning occurred
in lakes with large adults. Although lakes range from
2% to 32% littoral volume, this measure did not affect
larval sunfish production among lakes. Management
that increases adult size in lakes will likely improve
reproduction and recruitment success.
Keywords: sunfish, larvae, production,
spawning
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COMPARING THE DEMOGRAPHICS OF CHANNEL
CATFISH POPULATIONS FROM FISHED AND UN-FISHED REGIONS
OF THE WABASH RIVER
Colombo, R.E., Garvey, J.E., and
Heidinger, R.C.
Fisheries and Illinois Aquaculture
Center, Southern Illinois University, Department of
Zoology, Carbondale, IL 62901
Commercial fishing alters the density,
size structure, and growth rates of fish populations.
During fall 2001, 2002 and 2003, we sampled channel
catfish Ictalurus punctatus in four 106.2 km commercially
fished river reaches and one non-commercially fished
reach of the Wabash River. Fish were sampled using
three-phase AC electrofishing, and baited 2.54 cm
and 3.18 cm bar mesh hoop nets. Because mean length
of capture differed between gear types mortality was
independently estimated for each. Growth was modeled
for both fished and un-fished river reaches using
a von Bertalanffy model. Mean electrofishing catch
per unit effort (CPUE) was significantly higher in
the un-fished reach (15.13 fish/hr) compared to the
commercially fished reaches (6.44 fish/hr) (P = 0.0022).
However, mean CPUE for both 2.54 cm and 3.18 cm mesh
hoopnets did not differ significantly between the
un-fished and fished reaches (P = 0.3132 for 2.54
cm and P = 0.6552 for 3.18 cm hoopnets). Fish sampled
in the commercially fished river reaches had a lower
mean length with greater relative weight and growth,
and had higher annual mortality compared to the un-fished
river reach. Commercial exploitation may have led
to faster growth rates and better condition by lowering
densities of large fish and increasing annual mortality,
thereby reducing intraspecific competition.
Key words: Commercial fisheries, channel
catfish, demographics
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HABITAT
USE AND MOVEMENT PATTERNS OF ASIAN CARP IN THE LOWER
ILLINOIS RIVER
DeGrandchamp, K.L., J.E. Garvey, and
R.C. Brooks
Department of Zoology, Southern Illinois
University, Carbondale, IL 62901
Asian carp have become an increasing
nuisance in recent years in the Illinois River, presenting
potential problems of resource competition for native
species in this system. Understanding when and where
these fish spawn and what habitat they are using is
essential for the management of these species. Habitat
use and movement patterns of bighead carp (Hypophthalmichthys
nobilis) and silver carp (H. molitrix) were quantified
in the lower Illinois River (River Mile 80.2 to River
Mile 0) and Swan Lake, an adjacent backwater with ultrasonic
telemetry. We implanted forty silver carp and forty
bighead carp with ultrasonic transmitters during 2004.
Long-range movement was continuously monitored with
stationary receivers (N=3). Intensive, weekly mobile
tracking during the spawning season and intermittent
tracking during fall through winter quantified habitat
use. To date, both species were frequently found in
slower water velocity habitats perhaps to forage, and
were numerous in areas with high physical complexity
(tree snags, sandbars). The lower Illinois River, particularly
near Swan Lake, provides this habitat, with greater
than 81% of the tagged fish using this area. Bighead
and silver carp also inhabited Swan Lake (44%). Side
channels (sloughs) of islands also were used by both
species, with about 20% of tagged fish occurring in
these areas. Flooding of the Illinois River during summer
2004 increased movement of fishes of both species upstream,
and more activity in general in the lower reaches was
observed. Effective management of these species requires
knowledge of behavior and life history characteristics
such as habitat use, spawning activity and seasonal
movement patterns.
Keywords: Asian carp, invasive species,
Illinois River, habitat use
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ONTOGENETIC
DIVERGENCE IN SECONDARY SEXUAL CHARACTERISTICS IN THE
SLIDER (Trachemys scripta)
Readel A.M.1,2, M.J. Dreslik3, J.K.
Warner3, and W.J. Banning2,3
1Ecology and Evolutionary Biology,
University of Illinois, Champaign, IL 61820
2Department of Integrative Biology, University of Illinois,
Champaign, IL 61820
3Illinois Natural History Survey, Center for Biodiversity,
Champaign, IL 61820
Although secondary sexual characteristics
(SSCs) can distinguish sexes and indicate maturity in
male turtles, interpopulational variability in growth
rates may result in geographic differences in their
development. Because of the potential for such variability,
we studied a population of slider turtles (Trachemys
scripta) in southern Illinois to determine 1) at what
size SSCs develop, 2) how young turtles could be sexed
using SSCs, and 3) interpopulational variation of SSC’s
between Illinois and southern populations of the same
species. We measured the following SSCs from 209 T.
scripta: plastron length, foreclaw length (all five
claws on the left fore-foot), and pre- and postanal
tail lengths. For males, foreclaws 2, 3, and 4 grew
longer and more rapid relative to plastral length compared
to females, such that, sexual differences were present
at age 3. Male preanal tail lengths diverged from females
at approximately 100 mm PL to lengths 2 times longer
than females. The combined SSCs resulted in males diverging
from females at 100 mm plastron length between ages
3 and 5.
Keywords: Trachemys scripta,
secondary sexual characteristics, sexual dimorphism,
Emydidae
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HABITAT
USE OF JUVENILE SLIDER TURTLES (Trachemys scripta)
Banning, W.J.1,2, M.J. Dreslik2, J.K.
Warner2, and A.M. Readel2,3
1 School of Integrative Biology, University
of Illinois, Champaign, IL 61820
2 Illinois Natural History Survey, Center for Biodiversity,
Champaign, IL 61820
3 Ecology and Evolutionary Biology, University of Illinois,
Champaign, IL 61820
Life history studies often detail ontogenetic
changes such as differences in habitat use. Several
freshwater turtle species exhibit marked differences
in habitat use patterns across ages and sizes. We investigated
differential habitat use in a population of red-eared
slider turtles (Trachemys scripta) from a floodplain
lake located in Gallatin County, Illinois. We used 25
baited hoop traps for 26 days and all T. scripta captured
were aged, measured, and sexed. At each trap location
we measured water depth, distance from shoreline, canopy
cover, presence/absence of logs, presence/absence of
bushes, and bank slope for comparison among age classes.
Our results suggest that juvenile turtles prefer areas
with basking sites such as logs to those without.
Keywords: Trachemys scripta,
ontogenetic, habitat use, juvenile
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VOCAL VERSATILITY IN LEOPARD FROGS:
DOES MALE CALL COMPLEXITY ADVERTISE BEAUTY OR BRAWN?
(ORAL PRESENTATION WINNER!)
Larson, K.A.
Department Of Biological Sciences,
Purdue University, W. Lafayette, In 47907
The study of communication is of paramount
importance for understanding how animals interact
and what kinds of information individuals convey to
one another. In many species, competition between
males and mate choice decisions by females are based
on highly elaborate morphological, behavioral, or
acoustical male displays. My research focuses on a
highly exaggerated acoustic trait, the complex advertisement
call of a common North American anuran. Northern leopard
frogs (Rana pipiens) migrate from overwintering sites
to temporary ponds in early spring after which they
breed for a period of several weeks. Males neither
defend territories nor appear to interact directly
with each other, but instead partition their time
between calling and searching for mates. In contrast
to this otherwise simple mating system, northern leopard
frogs have a remarkably complex advertisement call.
Males use a repertoire of several distinct notes in
variable numbers and combinations to generate hundreds
of unique calls (perhaps equivalent to the way people
put words together to form sentences). Why northern
leopard frogs have developed such a complex vocalization
system is far from clear. It is not known, for example,
if different calls serve different functions. I conducted
field and laboratory playback experiments using advertisement
calls of varying complexity to test for differential
responses of male and female receivers. Males changed
their calling behavior in response to call playbacks;
some playbacks elicited call matching (responding
with the same call as the playback), others resulted
in males switching to aggressive vocalizations, and
others caused the males to cease calling altogether.
Females exhibited a strong preference for complex
calls over simple calls; however, this preference
was eliminated when call duration was controlled.
I will discuss the potential communicative significance
of call complexity in anurans and explore the relationship
between the development and production of a complex
advertisement call repertoire and the proclivity for
speciation events in the leopard frog species group.
Keywords: anurans, call complexity,
mating behavior, vocalizations
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III
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