Evaluation of a Re-established Walleye Population within a Hydropower Reservoir Recovering from Acidification

Abstract

Cheat Lake, a hydropower reservoir in northern West Virginia, was impacted for decades by acid mine drainage and acid precipitation. Acidification of Cheat Lake likely reduced fish species richness and fish abundance. From 1952-1977, only 15 fish species were collected, cumulatively. Additionally, the fish community was dominated by acid tolerant species such as Brown Bullhead (Ameiurus nebulosus) and White Sucker (Catostomus commersonii) (82% of mean annual relative abundance), while acid intolerant species such as Walleye were extirpated. Due to legislative action and subsequent funding of water quality treatment within the watershed (e.g., Surface Mining Control and Reclamation Act of 1977), acidification issues have been mitigated over time. My study aimed to quantify temporal changes in the fish community of Cheat Lake, as they might be related to improvements in water quality. Additionally, from a fishery management perspective, I focused on evaluating population characteristics and spatial ecology of a reestablished Walleye (Sander vitreus) population in Cheat Lake. I examined changes in water quality data (1952-2015) and fish community data (1952-2015) from Cheat Lake. Main lake pH averaged less than 5.0 prior to 1990 and averaged 5.8 in 1990. Since 1997, pH has averaged greater than 6.0 every year indicating reduction in acidification of Cheat Lake. Based on boat electrofishing and gill net surveys, I found that the fish community of Cheat Lake has significantly changed over time, likely owing to improvements in water quality. From 1990-2015, 18,387 fishes were collected using these methods. Additionally, 44 species were collected representing a substantial increase in species richness. The mean annual relative abundance of fishes captured from 2011-2015 was over 4 times greater than that from 1990-2001. Also, fish community composition significantly changed over time from 1990-2015. Changes in fish community composition were largely driven by increases in abundance of acid intolerant fish species such as Smallmouth Bass (Micropterus dolomieu). I also evaluated population characteristics of the Walleye population. As expected, initiation of stocking significantly increased abundance of Walleyes within Cheat Lake as indicated by increases in gill net catch per unit effort (CPUE). Age and growth analysis indicated that the Cheat Lake Walleye population was characterized by fast growing individuals that reach large maximum sizes. Both male and female Cheat Lake Walleyes reach quality size (≥ 380 mm) after two years of growth. Specifically, female Walleyes reached larger maximum sizes (female L∞ = 754 mm; male L∞ = 502 mm) and grew faster after age-3 than male Walleyes. Increasing natural reproduction was also evident as indicated by collection of young of year in the fall of non-stocking years and through evaluation of year classes from age and growth data. Telemetry data provided information on distribution and movement patterns of Cheat Lake Walleyes. Walleyes exhibited seasonal and sex-based differences ...