AUTHORS: Adam Musolf, Student Conservation Association; Benjamin Marcek, US Fish & Wildlife Service
ABSTRACT: Silver Carp (Hypophthalmichthys molitrix) have invaded much of the Mississippi River Basin, including the Ohio River. Although understanding the health of individuals within this population is critical to its management, little information is available regarding the body condition of Silver Carp in the Ohio River. To better understand the body condition of Silver Carp in the Ohio River, we used Le Cren’s Relative Condition Factor (Kn) to compare body condition between six pools in the Ohio River (J.T. Myers-Meldahl pools), and to examine temporal patterns during 2014-2024. We found that Silver Carp in the lower three pools of our study area (J.T. Myers, Newburgh, and Cannelton pools) had similar mean Kn values that were substantially lower than the overall mean Kn. The highest mean Kn values, which exceeded the overall mean Kn and were similar to each other, occurred in the upper two pools (Markland and Meldahl pools). The mean Kn of McAlpine pool was greater than the overall mean but lower than that of the upper pools. When examining Ohio River Silver Carp body condition among years, we found the greatest mean Kn values occurred during 2015, 2019, and 2023 and were greater than the overall mean Kn. The lowest mean Kn values occurred during 2016 and 2021 and were lower than the overall mean Kn. The mean Kn for 2014, 2017, 2020, and 2022 is similar to the overall mean Kn. Density dependent factors may explain the spatial differences in mean Kn, but the drivers of the annual fluctuations are harder to explain. Climate, water quality, year class effects, or sampling bias could all play a role. Understanding the causes of these fluctuations could better help predict population changes for use by management agencies and commercial fishers.
