Reproductive Development and Related Observations during the Spawning Migration of Hickory Shad

Abstract

AbstractHickory shad Alosa mediocris were sampled for two consecutive years in coastal North Carolina at various points of their ascent in salt water, brackish water, and freshwater to examine reproductive development and related variables during the spawning migration. Fish averaged 3 years of age; however, the proportion of repeat spawners and the proportion of individuals in older age‐classes were greater for females than for males, and females were larger than males of the same age. Nearly all fish had identifiable food items in their stomachs early in migration. Feeding decreased significantly as fish entered freshwater, and energy reserves became depleted with movements upstream. Reproductive development was positively correlated with inland movements, as indicated by increases in the gonadosomatic index and oocyte size and based on histological examination. Separate oocyte size‐classes were observed within the same individuals, and postovulatory follicles were also present; these observations indicate that hickory shad are batch spawners with indeterminate fecundity and group‐synchronous development of oocytes. Postspawn females with yolked oocytes were captured while feeding in the estuary after the reproductive season. Migratory timing was similar in both years, and a strong positive correlation between water temperature and fish movements was evident. Results indicate that reproductive development in migrating hickory shad is significantly related to size, age, energy reserves, geographic location, and time of year. This information contributes to a better understanding of the relatively unstudied hickory shad and serves as a basis for further research on alosine fishes in the eastern United States.