Population and Life-History Characteristics of Two Micropterus Species in the Flint River System, Georgia
Steven M. Sammons, Travis R. Ingram, and John M. Kilpatrick
Abstract.—Black bass Micropterus spp. are important components of river fisheries in the southeastern U.S., but little is known about their basic life history and population characteristics in these systems. Largemouth Bass M. salmoides and Shoal Bass M. cataractae were collected from three areas in the Flint River on multiple occasions from 2005 through 2013. Collections were taken from the undammed section of the Flint River above Lake Blackshear, within Lake Blackshear, and the regulated reach of river below Lake Blackshear. Shoal Bass do not occur in Lake Blackshear, so only Largemouth Bass were collected. Population and life history data such as body condition, growth, mortality, and recruitment variability were examined for these species in all three areas. Shoal Bass and Largemouth Bass appeared to have similar scopes of growth in this system, reaching similar maximum sizes. However, Largemouth Bass grew slower than Shoal Bass in both river sections. Growth of both species was slower in the upper versus lower area of the river; growth of Largemouth Bass was similar between the lower Flint River and Lake Blackshear. Female Largemouth Bass grew faster than males in both sections of the river; whereas, growth of Shoal Bass was similar between sexes. Longevity of Largemouth Bass appeared to be slightly higher than Shoal Bass, with correspondingly lower annual mortality. Age frequencies and annual mortality was similar between the sexes for both species in all areas. Recruitment of Largemouth Bass was negatively affected by high flows in the spring in the upper Flint River and Lake Blackshear; whereas, Shoal Bass recruitment in the upper Flint River was not correlated to any flow measure. The opposite pattern was found in the lower Flint River, with recruitment of Largemouth Bass unaffected by flow but Shoal Bass recruitment negatively affected by high flows. Shoal Bass exhibited numerous differences from Largemouth Bass in the Flint River, including growth, mortality, and recruitment, demonstrating the danger in applying rate function data or basic biology concepts from one species to another closely related one. Results from this study will help biologists better understand the potential and limitations of black bass fisheries in rivers, and thereby enable more effective management.