Induced Spawning of Wild American Shad Alosa sapidissima Using Sustained Administration of Gonadotropin-Releasing Hormone Analog (GnRHa) |
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| Authors: | Costadinos C Mylonas Yonathan Zohar Brian M Richardson Steven P Minkkinen |
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| Institution: | Center of Marine Biotechnology, University of Maryland Biotechnology Institute and Maryland Agricultural Experiment Station, Columbus Center, 701 E. Pratt St., Baltimore, Maryland 21202 USA;Maryland Department of Natural Resources, 580 Taylor Ave., Annapolis, Maryland 21401 USA |
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| Abstract: | 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 ± 109 (±163 ± 109) 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. |
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