Comparing Asian Carp Between the Illinois River and Its Tributaries

Invasive bighead and silver carps have been heavily studied in mainstem rivers like the Illinois River; however, little work has been conducted in tributaries of large rivers.  This study compared the size and age structures, relative abundance, and sex ratios of Asian carp between the Illinois River main channel and four of its tributaries.  Asian carp were collected monthly from June-October from two sites per river.  Adults were sampled using pulsed-DC electrofishing at all sites and larval fish by an ichthyoplankton push.  A total of 615 Asian carp were collected, with no larval Asian carp sampled.  All tributaries differed in length distribution (p < 0.05) and mean age (df = 2,510; p < 0.05) but there were no differences in length between the tributaries and the main channel.  Although we found differences in length distribution (p < 0.001) and sex ratios (df = 3, p < 0.001) between downstream and upstream sites of tributaries, relative abundances and mean age did not differ between sites.  This preliminary data allows us to understand existing populations of Asian carp in tributaries of large rivers, ultimately allowing us to determine the size of waterway necessary to sustain an entire Asian carp’s life cycle.