Parasite Communities of Bluntnose Minnow (Pimephales notatus) from Several Creeks in East Central Illinois

Abstract

Parasites of freshwater fish play a vital functional role in aquatic ecosystems, but the spatial and ecological determinants of their prevalence and characteristics are still poorly understood. The current study quantified the diversity, prevalence, and environmental determinants of whole parasite burdens in bluntnose minnows across multiple creeks in central Illinois. Fish sampling and the collection of stream habitat data were conducted during the summers of 2023 and 2024. Fish were examined for parasites using necropsy and histology. A total of 20,817 parasites, predominantly trematodes (Posthodiplostomum spp.), cestodes (Proteocephalus spp), and protozoans, were identified. The most prevalent and abundant species group was Posthodiplostomum spp. 94% prevalence. Parasite prevalence was significantly different among creeks, ranged from 70.6–100% and was strongly influenced by the morphometrics of the host and by environmental factors. Statistical analysis showed that female and larger fish harbored more parasites, and length was the most important determinant. Infection intensities were generally highest in the stomach and intestine. Multivariate models indicated that pH was positively correlated with the parasite prevalence, while dissolved oxygen (DO) and conductivity were negatively correlated with the parasite prevalence. Canonical correspondence analysis (CCA) indicated that more than half the community variation was explained by environmental factors measured. These findings revealed significant spatial variability in the parasite communities over the area, likely due to a combination of host characteristics and stream water quality. The study of fish parasites as bioindicators is a vital approach to better understand their combined changes to host condition and environmental change.

Date of Award	2025
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Elliott A. Zieman (Supervisor)