Illinois Natural History Survey Reports

              1
I LLINOIS
NATURAL
HI STORY
S U R V E Y R e p o r t s
Autumn 2003
No. 377
I N S I D E
Egg-powdering in
Leafhoppers
2
Impact of Red Im-ported
Fire Ants on the
Black-capped Vireo,
an Endangered Species
3
“Eat and Run:” Soy-bean
Herbivory Infl u-ences
Western Corn
Rootworm Behavior
and Egg-laying
4
Understanding the
Public in Natural
Resource
Management
5
Announcing New
INHS Publications
6
Species Spotlight:
American White
Pelican
8
Naturalist's Appren-tice:
Pelican Math
9
Continued on back page
The most recent invasive species
threatening Illinois’ aquatic eco-systems
are the bighead and silver
carps, two of four species com-monly
called Asian carps. These
fi sh grow quickly to more than
50 lbs by consuming 30–50%
of their body weight each day in
small algae and other tiny
organisms. They also repro-duce
quickly and migrate
long distances to spawn.
Currently, in the Mississippi
and Illinois rivers, these
Asian carp are spreading
rapidly upriver toward the
Chicago Sanitary and Ship
Canal (CSSC) where they
could enter Lake Michigan
and affect the entire Great
Lakes basin. Because of
the immediate danger of
Asian carps crossing into the
Great Lakes basin through
the CSSC and the more gen-eral
and persistent threat of
invasive fi shes passing this
artifi cial connection be-tween
the Great Lakes and
Mississippi River drain-ages,
an electric barrier to
fi sh movement was constructed in
the CSSC near Romeoville, ap-proximately
28 miles downstream
from Chicago Harbor. Currently,
Asian carp have been found
about 22 miles downstream of
the dispersal barrier location in
Romeoville.
This barrier creates a graded
electric fi eld that should repel fi sh
as they sense the fi eld, creating a
nonlethal barrier. Because opti-
Evaluating the Effectiveness of an Electric
Dispersal Barrier
mal barrier performance depends
on current velocity, temperature,
conductivity, etc., we are evaluat-ing
the performance of this dis-persal
barrier. One evaluation
technique is a series of experi-ments
being conducted under con-trolled
conditions that evaluate
a scale model barrier emulating
the Romeoville barrier. We also
are testing combined barrier tech-nologies
that focus on the effi cacy
of an integrated sound-bubble
barrier and both technologies
combined (electric and sound-bubble)
in hatchery raceways at
the Illinois Department of Natural
Resources’ Jake Wolf Memorial
Hatchery. Our preliminary results
suggest that bighead carp are very
sensitive to the electric fi elds
created by the electric barrier,
making this barrier a promising
technology for preventing further
range expansion of this species.
The integrated sound-bubble
barrier and the combined tech-nology
barrier have also given
good results by preventing over
90% of fi sh from moving through
each barrier type. We continue
to evaluate and modify these bar-riers
to increase their effective-ness
with the goal of stopping all
attempts to move through each
barrier type. Additionally, the
combined technologies barrier is
an appealing approach because
Researchers track fi sh at electric dispersal barrier on the Illinois River. Photo by Dr.
Scudder Mackey, Great Lakes Protection Fund