Date of Award

8-2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Committee Member

Dr. Yoichiro Kanno, Committee Chair

Committee Member

Dr. Patrick Jodice

Committee Member

Mr. Jason Bettinger

Abstract

Dams and altered flow regimes impact riverine fish. In addition to ecological impacts, unpredictable changes in flow influence the ability to access rivers and effectively sample fish populations. Fisheries management practices are often influenced by water regulation and hydropower generation, thus designing distinct methods of monitoring populations in regulated rivers is critical for effective management. Recurrent changes in river flow also influence behavior of fish inhabiting the flow-regulated portions of rivers, and such individual behavior may ultimately have population-level effects (e.g. fish abundance). I investigated population abundance and movement of smallmouth bass (Micropterus dolomieu) within a regulated portion of the Broad River, SC, located below a small hydropower dam. In Chapter 1, I developed a novel approach to estimating bass abundance within a 4.2-km section immediately below the dam where fluctuations in discharge might influence capture efficiency over different sampling days. The number of smallmouth bass was estimated based on mark-recapture data utilizing two gears, angling and electrofishing. The closed population assumption was confirmed using radio telemetry, and closed population capture-mark-recapture models were fit in the Bayesian hierarchical modelling framework with an estimated number of 2,380 bass (95% Credible Interval: 1,578-3,693) over 200 mm TL. Integrating the two gear types into a mark-recapture study can be an effective method for assessing abundance in spatially or temporally heterogeneous habitats where changing conditions can cause variable sampling environments. In Chapter 2, to inform the sampling strategy to detect a temporal trend in bass abundance, I implemented a power analysis comparing the ability to detect a 2.5% or 5% annual declining trend in abundance after 5, 10, and 15 years based on various levels of sampling effort. The primary interest was to optimize the allocation of effort in terms of number of survey occasions within a year and intensity of effort for each survey occasion. Results indicated that increased effort intensity of each survey occasion (e.g. more boats to be used on each survey to increase capture probability) was more important than adding more occasions with lower effort/bass detection levels within each. In general, power increased with the larger decline (5%) and more sampling effort. In the third and final chapter, I evaluated the effects of river discharge variation on diurnal fish movement every 30 minutes during daylight hours to establish linkage between hydro-power generation and fish behavior. Generalized additive mixed models (GAMMs) suggested that movement distances slightly increased with river discharge associated with hydro-power generation in winter, but not in summer. The physiological impacts of this altered behavior was not known, but if rapid and major changes in flow magnitude act as a stressor to individual bass, then population-level effects could follow and impact fisheries resources within the study area.

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