Life History Plasticity of the Blacktail Shiner (Cyprinella venusta) across Disturbance Gradients in Alabama Streams

Abstract

Four populations of the blacktail shiner, Cyprinella venusta were studied to determine life history parameter variation across disturbance gradients in Alabama streams. Consistent with life history theory, fishes from the degraded site were significantly smaller than fishes from sites with minimal disturbance. Fishes from the degraded site had the smallest size at maturity and the smallest propagule size. Clutch sizes adjusted for standard length (SL) varied among populations. Egg diameters were not related to SL among populations. There was no significant difference in mature egg diameters; however ripening egg diameters differed among populations. There was no difference in gonad mass in females for all spawning months; however, there were differences in gonad mass in males in July. Gonadosomatic index (GSI) peaked in July for both males and females. Reproductive males were still present in September for three populations but all females from all populations had become latent by September, indicating that spawning season has ended. The results of this study suggest that Cyprinella venusta has the ability to alter life history parameters in harsh environments and may be a factor contributing to its persistence in habitats where other species are declining.