J. P. Van Eenennaam

Reproductive conditions of the Atlantic sturgeon (Acipenser oxyrinchus) in the Hudson River

Ninety-four prespawning adult Atlantic sturgeon (Acipenser oxyrinchus) were sampled in the Hudson River for age, sex, body size, gonad weight, fecundity, mature oocyte size, and plasma concentrations of gonadotropins, sex steroids, and vitellogenin during the spring spawning migrations in 1992 and 1993. In males, the age and total length ranged from 12 yr to 19 yr and from 133 cm to 204 cm and in females from 14 yr to 36 yr and from 197 cm to 254 cm. The majority of males were 13–16 yr old, and females were 16–20 yr old. Some females had residual atretic ovarian bodies, presumably remaining from a previous spawning and indicating iteroparity. Pre-ovulatory condition was recognized by migration of the germinal vesicle or by germinal vesicle breakdown and by significantly elevated plasma gonadotropins, progesterone, and vitellogenin. All pre-ovulatory females were captured upriver from Hudson River kilometer 136. Individual fecundity ranged from 0.4 million to 2.0 million eggs and oocyte diameter from 2.4 mm to 2.9 mm, and both characters exhibited a significant (p<0.05) positive relationship with female body size. Iteroparous females, tentatively identified by the presence of atretic bodies remaining in the ovary from a previous spawning, had significantly (p<0.05) higher fecundity and produced larger eggs, compared with females spawning presumably for the first time.

Effect of ovarian stage on plasma vitellogenin and calcium in cultured white sturgeon

Abstract We developed an enzyme immunoassay for plasma vitellogenin (VTG) of white sturgeon Acipenser transmontanus , cultured in California. The assay, based on polyclonal rabbit antibody to purified VTG, was tested for specificity and applied on sturgeon broodstocks (age 4–12 years) reared at three locations. Plasma VTG concentrations were correlated with total plasma calcium and stage of ovarian maturity. Females in the previtellogenic ovarian stage and at the onset of yolk deposition had low VTG concentrations, but plasma VTG and calcium increased after onset of yolk deposition in the oocytes. Total plasma calcium exhibited a linear relationship with plasma VTG. Concentrations of both metabolites in plasma discriminate previtellogenic and vitellogenic females, but fail to discriminate specific stage of ovarian vitellogenesis. The immunoassay for plasma VTG or flame photometry for total plasma calcium can be utilized to segregate vitellogenic females in cultured sturgeon broodstocks.