Grant W. Feist

Potential Classification of Sex and Stage of Gonadal Maturity of Wild White Sturgeon Using Blood Plasma Indicators

Abstract 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 (Ca2+). 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 Ca2+ was measured spectrophotometrically. White sturgeon showed sex- and maturity-specific levels of steroids and Ca2+. Stepwise discriminant function analysis (DFA) ...

Physiological stress responses of the freshwater chondrostean paddlefish (Polyodon spathula) to acute physical disturbances

Juvenile paddlefish (Polyodon spathula) subjected to various physical disturbances showed significant increases in plasma cortisol and lactate, but little or no change in plasma glucose, chloride or hematocrit. When paddlefish were given a 30 s aerial emersion handling stressor, plasma cortisol increased from 2.2±0.6 to 11±1.8 ng ml−1 in 1 h but had returned to the prestress level by 3 h. Addition of 0.5% NaCl to the recovery tanks had no effect on plasma cortisol changes. Plasma lactate rose from 26±2.6 to 52±4.5 mg dl−1 within 3 h. Plasma cortisol increased to 14±4.8 ng ml−1 and plasma lactate rose to 67±3.7 mg dl−1 after fish were continuously chased in their home tanks for 1 h; plasma lactate remained elevated for 5 h. In fish severely confined for 6 h in cages with intermittent handling, plasma cortisol rose from 6.2±1.6 ng ml−1 to its peak level of 74±6.3 ng ml−1 by 2 h, but approached the prestress value after 18 h of recovery. Plasma lactate levels in confined fish increased from 27±2.7 to 73±6.9 mg dl−1 by 3 h but had returned to near-resting levels by 24 h. The results suggest that paddlefish do not exhibit physiological stress responses to physical disturbances similar in magnitude to those previously documented for many teleostean fishes including salmonids, although cortisol was determined to be the principle steroid released during stress.

Evidence of Detrimental Effects of Environmental Contaminants on Growth and Reproductive Physiology of White Sturgeon in Impounded Areas of the Columbia River

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.

Conditioning improves performance of juvenile chinook salmon, Oncorhynchus tshawytscha, to transportation stress☆

Abstract A positive conditioning approach was used, where a dewatering Stressor was associated with feeding, to help moderate the severity of the response of juvenile chinook salmon, Oncorhynchus tshawytscha, to transportation. Not only did this procedure attenuate the physiological response to transportation stress, as evidenced by more rapid recovery of plasma cortisol, glucose and lactate concentrations following the stressful experience, but it also enhanced survival during transport, elevated resistance to the pathogen Aeromonas salmonicida, increased seawater adaptability, and helped the animals to cope with other Stressors relative to control groups. Fish given prior exposures to Stressors not associated with feeding performed intermediately between positively conditioned fish and controls in most tests.

Effects of thermal regime on ovarian maturation and plasma sex steroids in farmed white sturgeon, Acipenser transmontanus

Abstract Recently, commercial aquaculture farms in Northern California have exposed gravid, cultured white sturgeon females to cold water (12±1°C) throughout the late phase of vitellogenesis and ovarian follicle maturation resulting in improved ovulation rates and egg quality. However, the optimum timing for transfer of broodfish to the cold water and the capacity of transferred broodfish to maintain reproductive competence over an extended time in cold water had not been evaluated. Gravid white sturgeon females that have been raised at water temperatures of 16–20°C were transported to either cold water (12±1°C; Group 1) in November 1997 or maintained in ambient water temperatures (10–19°C; Group 2) until early spring. In March 1998, half of the fish in Group 2 had regressed ovaries, but the remaining females had intact ovarian follicles and were transported to the cold water. Ovarian follicles and blood were collected from females until they reached the stage of spawning readiness (determined by germinal vesicle position and an oocyte maturation assay) or underwent ovarian regression. Exposure of gravid sturgeon females to ambient water temperatures (14.5±2.3°C, mean±S.D.) from October to March led to a decrease in plasma sex steroids and a high incidence of ovarian regression in fish with a more advanced stage of oocyte development. Transfer of females with intact ovarian follicles to cold water (12±1°C) in the fall or early spring resulted in normal ovarian development in the majority of females. Holding females in cold water does not seem to override their endogenous reproductive rhythms but extends their capacity to maintain oocyte maturational competence over a longer period of time. A temperature-sensitive phase in ovarian development may occur during the transition from vitellogenic growth to oocyte maturation, and the degree and timing of sensitivity to environmental temperature are dependent on the females endogenous reproductive rhythm.

3,3′,4,4′-Tetrachlorobiphenyl affects cortisol dynamics and hepatic function in rainbow trout

Abstract This study investigates the impact of 3,3′,4,4′-tetrachlorobiphenyl (TCBP), a polychlorinated biphenyl (PCB) congener and cytochrome P -450 inducer, on cortisol dynamics in rainbow trout ( Oncorhynchus mykiss ). Trout were given either an intraperitoneal implant of corn oil alone or corn oil containing TCBP (5 mg kg −1 body weight) and sampled 6 weeks later. TCBP-implanted fish had significantly lower condition factor and plasma glucose concentration, whereas plasma cortisol and protein, and hepatocyte protein concentration and liver ethoxyresorufin- O -deethylase (EROD) activity was significantly higher compared with the sham group. There was no significant difference in plasma lactate and amino acid concentration, hepatocyte glycogen content or liver cytosolic cortisol binding affinity or capacity between the two groups. [ 3 H]Cortisol uptake was significantly higher in hepatocytes isolated from TCBP-treated fish compared with the sham fish. Also, our preliminary results suggest that the catabolism of [ 3 H]cortisol by hepatocytes of TCBP-treated fish was enhanced as noted by a decrease in cortisol-specific radioactivity and an increase in tetrahydrocortisone (a cortisol metabolite) specific radioactivity. These results support a role for TCBP in enhancing cortisol clearance by hepatocytes of trout and suggest that toxicants like PCBs may impair the ability of trout to elicit a physiological response normally associated with cortisol stimulation.

EARLY IDENTIFICATION OF SEX IN CULTURED WHITE STURGEON, ACIPENSER TRANSMONTANUS, USING PLASMA STEROID LEVELS

Abstract In sturgeon aquaculture, it is advantageous to sex fish as early as possible so that males can be used for meat production and females reserved for caviar production. Currently, growers wait 3 to 4 years before fish are sexed by an invasive surgical examination of the gonads. The goal of this study was to determine when sex could be determined by examining levels of plasma steroids. Populations of white sturgeon were held at three locations and water temperatures (Oregon—13±0.1 °C, Idaho—15±0.1 °C and California—18±0.5 °C). Blood was sampled every 3 months and plasma testosterone (T), 11-ketotestosterone (KT) and estradiol (E2) concentrations were measured by radioimmunoassay (RIA). By 18 months of age, males from California had significantly higher levels of T and KT than females. By 21 months, all males could be separated from females based on T and KT content (>2 ng/ml). However, males and females from Idaho and Oregon had similar levels of T and KT up to 36 and 34 months of age, respectively, and sex could not be delineated based on plasma sex steroid content. There were no differences in E2 levels between males and females in all populations, and at all sample periods. Histological analysis of gonads revealed that all but one of the males from California had well differentiated testes with spermatogonia undergoing mitosis in cysts (stage 2), whereas the testes of all fish from Idaho and Oregon had just begun to differentiate (stage 1). Growth rates of fish were highest in California, intermediate in Idaho and lowest in Oregon. It appears that proliferation of spermatogonia is necessary for production of androgens and that growth rate, as influenced by water temperature, is the main contributor to the early onset of this process. This study has developed a less invasive technique for ascertaining sex in white sturgeon that can be used 1 to 2 years earlier than current methodologies.

The effect of food deprivation on the cortisol response to crowding in juvenile steelhead.

Abstract Routine salmonid hatchery procedures include food deprivation, handling, and crowding of fish before sorting, transporting, or stocking. Although several studies have examined the effects of food deprivation or husbandry stressors on salmonid physiology, few have examined the effects of food deprivation and standard hatchery procedures, such as handling and crowding. The objective of this study was to determine whether food deprivation of juvenile steelhead (anadromous rainbow trout Oncorhynchus mykiss) affects the cortisol response to stress from low-water crowding. Plasma cortisol levels of fish held in circular fiberglass tanks at 8°C under normal daily feeding conditions were compared with levels in fish subjected to 3 d of food deprivation; both groups were held at 3.8 kg/m3 (control density). Additionally, these groups were compared with fed and food-deprived fish held at a density of 12.8 kg/m3 for 3 h (low-water crowding stressor). There was a significant increase in plasma cortisol level...