Masters Theses

Date of Award

3-1981

Degree Type

Thesis

Degree Name

Master of Science

Major Professor

David A. Etnier

Committee Members

A. C. Echternacht, Larry Wilson

Abstract

From December 1976 to October 1978, a study of the trispot darter, Etheostoma trisella Bailey and Richards was undertaken to determine life history data to aid preservation efforts and to assist in answering taxonomic questions. Etheostoma trisella is limited in distribution to the Conasauga River and its tributaries in northern Georgia and Tennessee. It requires two separate but interconnected habitats. When not breeding, it occupies the peripheral zones of the main river in areas of slow current, gravel-silt substrate, and aquatic vegetative or leaf litter cover. In the study area, the breeding habitat is a small seepage stream with heavy aquatic vegetation and relatively warm water temperatures, which is located in a pasture 2.5 km from the main river.

The principal food items in every habitat are Ephemeroptera nymphs and Chironomidae larvae, which account for 19% and 70%, respectively, of the annual numerical intake. A relative biomass index indicates more equal contributions from both groups. Feeding observations indicate that the trispot darter is a highly selective, visual feeder. Parasitism is minimal and predation is not evident.

Trispot darters spawn from January to March. Males exhibit bright orange-red and green breeding colors and have tubercles on the anal fin rays. The observed spawning behavior is typical of the ritualized patterns in the genus Etheostoma. Fecundity estimates range from 56 to 154 per female counting mature eggs only, and from 42 to 292 per female including developing eggs.

The eggs hatch in 30 days at 12°C and larval development is rapid, reaching the juvenile stage in 41 days. First year individuals grow to an average size of 36 mm SL whereas second year individuals average 44 to 45 mm SL. The maximum size was 49.4 mm SL for an aquarium raised specimen. The darters live to 2+ years in age and as adults have a 1:1 sex ratio. The uncommon habitat association required for successful reproduction indicates that E. trisella is vulnerable to human impact and its threatened species designation is justified.

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