Population Characteristics and Parasite Burdens of Spotted Bass in the Wabash River, Illinois

We collected Spotted Bass (Micropterus punctulatus) from the Wabash River in 2013 and 2014, to address the relative lack of information regarding the population dynamics or the parasite burdens of these fish along their northern boundary.  Relative abundance (CPUE) was significantly higher in 2013 compared to 2014.  For both years, the length distributions were primarily composed of fish below stock length.  Spotted Bass in the Wabash River were infected with at least five different helminth species, the most common being the trematode white grub.  During both 2013 (n=46) and 2014 (n=72), prevalence of white grub was approximately 50% in below stock bass and near 100% in stock, quality, and preferred size bass. Mean intensity of white grub in the visceral organs increased with fish age as well, with the highest numbers being found in the liver and near the brain stem.  Larval stages of white grub infect fish by burrowing through the skin, so infections should be more successful in still water.  Conversely, Spotted Bass serve as definitive hosts for other parasites, and infections should be more related to diet.  Thus, parasite assemblages across size classes may provide useful information for fisheries management regarding habitat usage and diet shifts.