STUDIES ON REPRODUCTIVE BIOLOGY AND ENDOCRINOLOGY IN A PRIMITIVE TELEOSTEI, THE AMERICAN SHAD (Alosa sapidissima)

American shad is an anadromous fish that displays asynchronous ovarian development. In an effort to enhance our understanding of the reproductive cycle of this primitive Teleostei species, and provide better management tools for the Chesapeake fishery, we have conducted studies of its gonadal and hormonal cycles. We developed various assays to measure reproductive endocrine factors including: 17,20β-dihydroxy-4-pregnen-3-one (DHP) and GnRH. Fish were collected from the Susquehanna River during their spawning migration. One group of fish was sacrificed on site to assess reproductive parameters of wild shad. A second group was transported to a Maryland State hatchery and treated with gonadotropin-releasing hormone agonist (GnRHa) using several delivery systems. These treatments were followed during a two-week period by measurement of various hormonal levels. In addition, fecundity and fertilization of the hatchery groups were measured daily. Our results shed light on the reproductive physiology and endocrinology of the American shad and lay the foundation for usage of GnRHa to induce shad spawning in captivity.