Date of Award

1999

Degree Name

Biological Sciences

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Donald Tarter

Abstract

Etheostoma osburni, the candy darter, is endemic to the lower New River drainage of West Virginia and Virginia and Gauley River drainage of West Virginia. As a result of its endemism and evidence of declining population numbers, the species has been given the status of Special Concern in both states. Candy darters occur in the Appalachian Plateau and Ridge and Valley provinces, and are influenced by different environmental selective pressures. In this study, candy darters were collected in the summer and fall of 1998 and spring of 1999 by backpack electroshocking for determination of their seasonal reproductive biology, food habits, and to establish, by means of mitochondrial DNA analyses, any genetic divergence of the two physiographically separated populations. Results of seasonal gonosomatic indices (GSI) indicated a steady increase in females, wtth the peak (7 .137) in April 1999. A peak GSI found for males in October 1998, rather than the following April, was probably indicative of the low number of adult males collected in the spring. By snorkeling, female darters were observed exhibiting behaviors of possible nest guarding on five occasions beginning early June 1999. A fecundity analysis showed females to contain a low average of 170 mature ova. The observed mature ova were of varying sizes and colors, suggesting that candy darters may spawn multiple times throughout the spawning season. Larval candy darters collected in the summer of 1999 were measured and their lengths plotted against Julian days. A test of the resulting regression equation showed the approximate date of spawning to be between April 21 and 22. Results oft-tests performed on morphometric measurements showed adult male darters have significantly longer anal rays compared to females. Males also were statistically larger in two areas of the caudal region and two areas of the head. Orbit length was the only characteristic found to be significantly greater in females. Combined reproductive studies indicated that candy darters spawn in late spring, probably from mid-April to mid-May. An analysis of gut contents revealed feeding activity to be high in the summer and low in fall and spring. The mayfly family Heptageniidae occupied the largest total percent volume within stomachs in summer and fall. In the spring, the mayfly family Baetidae was highest in volume. Families Baetidae (mayflies) and Chironomidae (dipterans) were found in all stomachs collected in the summer. Family Heptageniidae occurred most frequently in fall stomachs, while Baetidae was most common in stomachs from the spring collection. Summer forage ratio analyses showed dipteran families Chironomidae and Tipulidae to have positive selection values, indicative of active searching by candy darters for these food items. In fall stomachs, all families, with the exception of Chironomidae, had positive selection values. All benthic families taken from spring stomachs had negative selection values, with the exception of family Baetidae. However, spring data may have been obscured due to difficulty met when obtaining Surber samples. Studies conducted on food habits suggest that candy darters are most likely opportunistic feeders. Mitochondrial DNA analyses of candy darters from the Appalachian Plateau and Ridge and Valley provinces were inconclusive as to evolutionary divergence, however did show a possible high degree of similarity between the provinces.

Subject(s)

Etheostoma -- Cherry River (W. Va.)

Etheostoma -- Food.

Etheostoma -- Ecology.

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