Open AccessInduced Spawning of Wild American Shad Alosa sapidissima Using Sustained Administration of Gonadotropin‐Releasing Hormone Analog (GnRHa)
Author(s) -
Mylonas Costadinos C.,
Zohar Yonathan,
Richardson Brian M.,
Minkkinen Steven P.
Publication year - 1995
Publication title -
journal of the world aquaculture society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 60
eISSN - 1749-7345
pISSN - 0893-8849
DOI - 10.1111/j.1749-7345.1995.tb00252.x
Subject(s) - milt , biology , broodstock , alosa , hormone , zoology , andrology , fishery , endocrinology , fish <actinopterygii> , aquaculture , medicine , fish migration
American shad Alosa supidissima broodstock were collected from the Susquehanna River during their spawning migration. Mean volume of expressible milt (± standard deviation) was 2.5 (±1.7) mL/kg body weight; mean spermatozoid count was 66.2 ± 10 9 (±163 ± 10 9 ) spermntozoa/mL; and duration of 50% motility was 36.5 (±10.3) see. Ovarian biopsies indicated the presence of oocytes of various sizes (200–2,000 μm in diameter) and stages of development. Fish were implanted with a delivery system loaded with gonadotropin‐releasing hormone analog (GnRHa) and started spawning 2 d after treatment. Fertile eggs were collected daily for the next 9 d, for a total of 50,100 eggs/kg body weight with a mean fertilization success of 62%. Upon cessation of spawning, the ovaries of all females still contained large numbers of oocytes at various stages of development, as at the beginning of the experiment, but with a greater number of atretic oacytes. Our observations show that American shad have an asynchronous ovarian development, and treatment with a GnRHa delivery system is effective in inducing several successive spawns of fertile eggs.