Induced Spawning, Artificial Fertilization, and Egg Incubation Techniques for Green Sturgeon

Abstract

Establishment of hatchery breeding techniques for the threatened green sturgeon Acipenser medirostris is important for research and conservation hatcheries. Injections of either gonadotropin-releasing hormone analog (GnRHa) or GnRHa plus domperidone were used to induce ovulation in 13 female Klamath River green sturgeon and to induce spermiation in 19 males. Ovulated eggs were either rinsed in water or not rinsed before fertilization, and the eggs were fertilized with different milt dilutions and for different lengths of time. After fertilization, eggs either were allowed to adhere to the bottom of glass dishes or were silted for 1 h and then incubated in McDonald or upwelling jars. All broodfish ovulated or spermiated in all hormonal treatments, and the best treatment was GnRHa injected alone in a single dose of 10 μg/kg for males or in a 1-μg/kg priming dose and a 19-μg/kg resolving dose for females. Females were held at 12–13°C, and ovulation was observed 14 ± 3 h (mean ± SD) after the second injection. Domperidone was not required for successful ovulation and appeared to reduce the adhesion of ovulated eggs. From 49,000 to 115,000 eggs were collected from each female, and from 30 to 300 mL of milt were collected from each male. Sperm cell concentrations in milt ranged from 2.9 × 10⁸ to 5.4 × 10⁹ sperm/mL, and the sperm exhibited 90–100% motility for up to 5 min. In all experiments, egg rinsing improved fertilization success by 5–12%. Embryo survival to neurulation in the McDonald jars was lower (5–32%) than that in the upwelling incubators (60–82%). Green sturgeon eggs were sensitive to the high-impact rolling action at the bottom of the McDonald jars, probably due to the large egg diameter (mean ± SD = 4.33 ± 0.14 mm) and thinner chorion (42 ± 4 μm) relative to eggs of white sturgeon A. transmontanus (diameter = 3.79 ± 0.03 mm; chorion thickness = 115 ± 6 μm).