Semester

Summer

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Patricia Mazik

Committee Member

Vicki Blazer

Committee Member

Stuart Welsh

Committee Member

Christopher Rota

Abstract

Fish kills, increased disease prevalence, and endocrine disruption have been observed in multiple freshwater fish populations of the Chesapeake Bay watershed (CBW). Some of these health issues occur in conjunction with declining abundance. A combination of multiple stressors is believed to be weakening sensitive fish species in non-tidal regions of the CBW. Fish health indices such as Deformity, Erosion, Lesion, and Tumor counts (DELTs), and the Health Assessment Index (HAI) are simple tools designed to evaluate the general health of fish populations. Both indices could be widely applied in the watershed because they require limited training and equipment. However, their utility in the CBW needs to be demonstrated. Fish health concerns in the CBW often occur in areas dominated by forested and agricultural land. The research in this thesis evaluates the influences of agricultural land-use, season, seasonal stream discharge, species, age, and sex on DELTs and the HAI. Two studies are included. The first occurred in the Shenandoah Valley of Virginia and West Virginia and applies the DELT index to fish aggregations and the HAI to white sucker and fantail dater in wadable streams. These streams were spread over a gradient of catchment pastureland. The second looked at DELTs and the HAI applied to smallmouth bass at 5 sites, 2 in the Potomac River watershed and 3 in the Susquehanna River watershed, sampled from 2013 to 2020 in the spring and fall. These sites varied in catchment agricultural and forested land with small areas of development. The utility of the two indices in agricultural regions of the CBW was not demonstrated. Both DELTs and HAI scores were correlated with the age and sex of fish sampled, and not with any of the included environmental variables. Future research directions and other concerns surrounding the use of DELTs, and the HAI are discussed.

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