Comparison of silver carp population demographics in an impounded and a free flowing river

Abstract

The silver carp, Hypophthalmichthys molitrix, is an invasive species that has
received increased attention due to the proximity of the population in the Illinois River
to the economically important Great Lakes and the species ability to dominate the
aquatic biomass of an ecosystem. We sought to assess the population demographics of
silver carp on two different river ecosystems, the Illinois River and Wabash River. The
Illinois River is channelized and dammed for commercial barges, whereas the Wabash
River is the longest free flowing river east of the Mississippi River and is still connected
to its natural flood plain. Silver carp were captured using DC electrofishing, weighed (g),
measured (mm), and a postcleithrum bone was removed for age estimation. The
relative density (fish/hour) of silver carp in the Illinois River (56.25 ± 15.58) was over
three times that of the Wabash River (16.9 ± 2.47). Average length (mm) was higher in
the Wabash River (563.2 ± 11.85) than in the Illinois River (517.14 ± 3.25). In both
rivers, carp exhibit quick growth reaching lengths over 300 mm in the first year. The
total annual mortatity for the Illinois was higher than on the Wabash, 0.587 and 0.317
respectively. Furthermore, the hybridization rate with bighead carp,
Hypophthalmichthys nobilis, was higher in the Illinois (72.9%) than the Wabash (24.5%).
Although silver carp in the Wabash River showed fast growth and low adult mortality,
the density was several times lower possibly due to increased resilience of the more
pristine ecosystem.

Date of Award	2012
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Robert E. Colombo II (Supervisor)