Theses and Dissertations

Title: Effects of a drip-delivery fluridone treatment on largemouth bass Micropterus salmoides activity patterns and populations characteristics in the Spring Creek embayment of Lake Seminole, Georgia

Name: Sammons, Steven M.

Degree: PhD

Chair: Michael J. Maceina


University: Auburn University

Location: Auburn, Alabama

Date: 2004

Pages: 158

Keywords: drip-delivery, fluridone, largemouth bass, Micropterus salmoides, population, Spring Creek embayment, Lake Seminole, Georgia, aquatic vegetation, hydrilla, Chattahoochee River, diet, feeding


Submersed aquatic vegetation (SAV) is a powerful structuring influence on fish populations, providing both a source of food and refuge from predation. Although dense SAV can benefit insectivorous fishes by increasing their food supply, dense SAV communities can be detrimental to piscivorous fishes by restricting their food supply through a reduction in predation efficiency, leading to reduced growth, condition, and fecundity. A drip-delivery herbicide (fluridone) system was initiated in May 2000 to reduce the high density of the exotic submersed macrophyte hydrilla Hydrilla verticillata in Spring Creek, a 2,343-ha embayment of Lake Seminole, Georgia, that has a history of excessive aquatic vegetation. Fluridone was applied throughout the growing season from 2000-2003 and a total of 1,800 ha of hydrilla was eliminated. To address potential fishery concerns, the effects of the hydrilla reduction on largemouth bass Micropterus salmoides activity patterns and population characteristics were examined over a 3-year period. Two groups of largemouth bass (total of 35) were implanted with radio tags and tracked once per month from May 2000 until December 2001 to document the effects of the fluridone treatment and hydrilla reduction on behavior and movement of the fish. Food habits were quantified about every 3 months from August 2000 - March 2003 to assess diet composition and feeding characteristics throughout the study. On each sampling date, about 200 largemouth bass were collected from the Spring Creek arm. Fish under 281 mm were placed in a 300 mg/L solution of MS-222 until expired, then placed on ice and stomachs were excised from these fish in the lab. Food items were removed from larger fish using clear acrylic tubes and the fish were released. An additional 200 largemouth bass were collected on each sampling date from the Chattahoochee River arm, where no hydrilla reduction has occurred, to serve as a control. Diets were quantified using the Relative Importance Index for five size groups of largemouth bass (substock, stock, quality, preferred, and memorable) in each arm. Diet overlap was compared among size groups and seasons and between periods of high and low SAV density for each arm. Food consumption of largemouth bass was simulated using the Wisconsin bioenergentics model in both arms, consumption was simulated before and after hydrilla reduction in the Spring Creek arm. Finally, about 300 largemouth bass were collected from the Spring Creek, Chattahoochee River, and Flint River arms in March 2003. Otoliths were extracted from all fish for ageing, and eggs were removed from all mature females for fecundity analysis. Total annual survival, growth, condition, and fecundity of largemouth bass were described from all three arms and compared to data collected in 1998 to document any changes in these metrics related to the fluridone treatment or changes in vegetation in the Spring Creek arm. Largemouth bass movement increased and the fish inhabited deeper water after hydrilla reduction, however, home range size did not change. Habitat use shifted from primarily hydrilla to large woody debris. This behavior may have resulted from a shift in feeding modes from ambush predation to roaming predation. Diet of largemouth bass differed little among fish sizes, embayments, or seasons, and no change was observed before and after hydrilla reduction in the Spring Creek arm. However, bioenergetics models predicted an increase in total food consumption of largemouth bass in Spring Creek of 38% after plant cover declined. Growth, condition, and fecundity of largemouth bass in Spring Creek showed a concomitant increase with food consumption after hydrilla was reduced. Growth of age 1-5 fish in Spring Creek increased an average of 16% in length after hydrilla was reduced, and fecundity nearly doubled. Abundance of hydrilla was an important factor influencing largemouth bass population characteristics in Lake Seminole through mediation of prey

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