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Back-calculation of length-at-age from otoliths and spines is a common technique employed in fisheries biology, but few studies have compared the precision of data collected with this method for catfish populations. We compared precision of back-calculated lengths-at-age for an introduced Ictalurus furcatus (Blue Catfish) population among 3 commonly used cross-sectioning techniques. We used gillnets to collect Blue Catfish (n = 153) from Lake Oconee, GA. We estimated ages from a basal recess, articulating process, and otolith cross-section from each fish. We employed the Frasier-Lee method to backcalculate length-at-age for each fish, and compared the precision of back-calculated lengths among techniques using hierarchical linear models. Precision in age assignments was highest for otoliths (83.5%) and lowest for basal recesses (71.4%). Back-calculated lengths were variable among fish ages 1-3 for the techniques compared; otoliths and basal recesses yielded variable lengths at age 8. We concluded that otoliths and articulating processes are adequate for age estimation of Blue Catfish. [ABSTRACT FROM AUTHOR]

The life history of Cambarus halli, a crayfish endemic to the Tallapoosa River Basin, GA, was studied at four sites within the Tallapoosa River. Two sites had allopatric populations of C. halli, and two sites had populations of C. halli sympatric with C. englishi. Three age classes existed across sites. For Cambarus halli, total number of pleopodal eggs was positively related to carapace length, but egg size was only weakly positively related to carapace length. Cambarus halli were smaller across age classes at sympatric sites, hut had greater growth rates than at allopatric sites. Cambarus halli density estimates were lower at sympatric sites, while proportions of reproductively active age-1 and age-2 individuals were higher at allopatric sites (63% vs. 33%). [ABSTRACT FROM AUTHOR]

Pteronotropis welaka (Bluenose Shiner) has a fragmented range throughout the Southeast, but its apparent rarity may reflect a low probability of detection during surveys. Our objectives were to obtain up-to-date status information for populations in southwest Georgia and to account for incomplete detection in our estimate of the proportion of sites occupied. We detected Bluenose Shiner at 5 of 39 sites (13%) sampled during 2004 and 2005 and estimated detection probability (p) and the proportion of sites occupied (psi) from seine-haul data. Models containing habitat covariates as predictors of p and psi provided a better description of the data than models without covariates for Bluenose Shiner and three other minnow species. Regardless of the model structure, the probability of detecting Bluenose Shiner during a single seine haul was substantially lower than for the other minnow species (3-8% vs. 13-33%). However, estimates of the proportion of sites occupied (corrected for incomplete detection) were similar to observed occupancy rates for all four species because of the large number of seine hauls we made at each site. The modeling approach we followed increased our confidence in survey results and provided information on where and how much to sample in future surveys. It has broad application to future surveys and monitoring programs for rare aquatic species in the southeastern United States. [ABSTRACT FROM AUTHOR]