Distribution, abundance, and population characteristics of shoal bass in tributaries of the Chattahoochee River, Alabama
Type of DegreeThesis
DepartmentFisheries and Allied Aquacultures
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The shoal bass Micropterus cataractae is the most recently described black bass species and in east-central Alabama, this fish only occurs in streams that flow into the Chattahoochee River. Recently, shoal bass were listed as a species of special concern in Alabama. Shoal bass are considered habitat specialists and prefer shoals, but little information exists on the current status, habitat use, movement, and home range size. Fifty km of 4 tributaries (Wacoochee, Halawakee, Little Uchee, and Osanippa) of the Chattahoochee River were surveyed and about 6 km of shoal bass habitat were found. Only one substantial population of shoal bass was found (Moffits Mill on Little Uchee Creek). On the three other streams, these fish were infrequently collected or rare. A multiple census mark-recapture study in April 2005 estimated a population size of 72 shoal bass (90% CI = 48, 130) with a density and biomass of 42 fish/ha and 11.7 kg/ha of shoal bass (> 150 mm TL) residing in the Moffits Mill shoal. Estimates of shoal bass population size were similar in November 2005 (N = 107) and April 2006 (N = 69), but declined dramatically in November 2006 (N = 13) and April 2007 (N = 23) due to mortality and some migration from the shoal as this site dewatered in summer-fall 2006. From November 2005 to April 2006, survival was 82% based on mortality sensors in radio telemetered fish, but declined to 22% over a 6-month period after this time. Radio telemetry of 24 shoal bass revealed that these fish exhibited relatively sedentary behavior with little movement outside of the shoal. However, as dry conditions persisted through summer and fall 2006, movement increased and 3 individuals moved to a refuge area just downstream of the dewatered shoal. Shoal bass were strongly associated with boulder substrate, lower-than-available current velocity (=0.10 m/s), and average available depth (0.30 m - 0.50 m). Home range analysis revealed that 92 % of radio tagged shoal bass remained within the total area of the Moffits Mill shoal and indicated that these fish primarily used the shoal throughout the year. Eighty-seven shoal bass (=150 mm TL) were collected from the Moffits Mill shoal between April 2005 and April 2007 to describe the weight:length relationship (log10(Wt) = -5.490 + 3.235*log10(TL)). Shoal bass from the Flint River, Georgia were in better condition and exhibited greater growth rates in total length (mm) and weight (g) than for fish from Moffits Mill. Based on anecdotal evidence, shoal bass have likely declined (except for 1 population) in Chattahoochee River tributaries in Alabama. Land use changes, population fragmentation, and habitat changes may have caused this decline. Possible conservation strategies include protection of the upper and middle Little Uchee Creek basin, water withdrawal protection within watersheds of the 4 tributaries I sampled, and stocking shoal bass in the 3 other tributaries. A moratorium of shoal bass harvest in Alabama was put into effect on 1 October, 2006 in an attempt to protect this population.