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Because white sturgeon Acipenser transmontanus show no readily discernible external signs of gender, management agencies use surgical biopsies to determine the sex and stage of gonadal maturity of individuals. This procedure is highly invasive and can be difficult under field conditions. Therefore, gonadal tissue and blood were collected from white sturgeon captured in tribal and commercial fisheries (fishery fish) and by fish and wildlife agencies (oversize fish) in the Columbia River basin to develop a method of determining sex and stage of maturity using the blood plasma indicators testosterone (T), 11-ketotestosterone (KT), estradiol (E2), and calcium (Ca 2ϩ ). The sex and stage of maturity was determined by histology or by visual examination in maturing fish. Plasma sex steroid levels were measured by radioimmunoassay, and plasma Ca 2ϩ was measured spectrophotometrically. White sturgeon showed sex-and maturity-specific levels of steroids and Ca 2ϩ . Stepwise discriminant function analysis (DFA) was used to choose the best variable(s) for predicting sex and stage of maturity, and quadratic DFA was conducted to classify fish into two groups of sex or four groups of sex and stage of maturity. In the classification of the fishery plus oversize fish, plasma T and E2 were the best predictors of sex and stage of maturity. Of the 151 females and 106 males, 85% of the females and 79% of the males were correctly classified; 88, 72, 98, and 96% of the immature females, immature males, maturing females, and maturing males, respectively, were correctly classified. The greatest error of misclassification occurred with immature males classified as immature females. In the analysis of immature fishery fish only, plasma T and fork length led to the correct classification of 88% of the females and 86% of the males. In the analysis of oversize fish only, 100% of the females and 95% of the males were correctly classified using plasma T and E2; 93, 100, 98, and 100% of the immature females, immature males, maturing females, and maturing males, respectively, were correctly classified using these variables. The derived classification functions for the prediction of sex or sex and maturity may replace the need for surgical biopsies if the error associated with the misclassification of immature fish is acceptable.

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We investigated the effects of stress over the final stages of sexual maturation on the reproductive performance of female rainbow trout, Oncorhynchus mykiss. Stress was administered over the period of early vitellogenesis (1.5 mo), late vitellogenesis-final maturation (1.5 mo), or during both periods (3 mo). Each stress treatment and control was triplicated, with eight females in each replicate (n = 24 fish per treatment). The eggs and progeny of each female were kept separate, and observations were made for 4 mo after transfer to rearing tanks. Fish that experienced stress during final maturation and those that were under stress during the whole experiment ovulated on average 2 wk earlier than the control group. In contrast, fish stressed during the period of early vitellogenesis ovulated at the same time as controls. Absolute fecundity and fertilization were not significantly affected in any treatment group, but significant differences in relative fecundity were found. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry. No significant differences were found in juvenile weight 8 wk after hatching. Furthermore, we found no differences in survival of the progeny or resistance to the fish pathogen Vibrio anguillarum. Thus, mild acute stresses applied to rainbow trout females may affect certain reproductive performance parameters such as timing of ovulation and relative fecundity; however, the progeny of such stressed females perform as well as controls with regard to juvenile growth and disease resistance.

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This study sought to determine whether wild white sturgeon from the Columbia River (Oregon) were exhibiting signs of reproductive endocrine disruption. Fish were sampled in the free-flowing portion of the river (where the population is experiencing reproductive success) and from three reservoirs behind hydroelectric dams (where fish have reduced reproductive success). All of the 18 pesticides and almost all of the 28 polychlorinated biphenyls (PCBs) that were analyzed in livers and gonads were detected in at least some of the tissue samples. Metabolites of p,p′-dichlorodiphenyltrichloroethane (DDT) [p,p′-dichlorodiphenyldichloroethylene (DDE) and p,p′-1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD)] were consistently found at relatively high levels in fish. Some males and immature females showed elevated plasma vitellogenin; however, concentrations were not correlated with any of the pesticides or PCBs analyzed. Negative correlations were found between a number of physiologic parameters and tissue burdens of toxicants. Plasma triglycerides and condition factor were negatively correlated with total DDT (DDD + DDE + DDT), total pesticides (all pesticides detected – total DDT), and PCBs. In males, plasma androgens and gonad size were negatively correlated with total DDT, total pesticides, and PCBs. Fish residing in the reservoir behind the oldest dam had the highest contaminant loads and incidence of gonadal abnormalities, and the lowest triglycerides, condition factor, gonad size, and plasma androgens. These data suggest that endocrine-disrupting chemicals may be accumulating behind dams over time. Overall, results of this study indicate that exposure to environmental contaminants may be affecting both growth and reproductive physiology of sturgeon in some areas of the Columbia River.

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