Geology topics

M.A.H. Webb

Publications and source records attributed to M.A.H. Webb.

6 recordsLinked to original sources

USGS2012

Shovelnose sturgeon spawning in relation to varying discharge treatments in a Missouri River tributary

Many lotic fish species use natural patterns of variation in discharge and temperature as spawning cues, and these natural patterns are often altered by river regulation. The effects of spring discharge and water temperature variation on the spawning of shovelnose sturgeon Scaphirhynchus platorynchus have not been well documented. From 2006 through 2009, we had the opportunity to study the effects of experimental discharge levels on shovelnose sturgeon spawning in the lower Marias River, a regulated tributary to the Missouri River in Montana. In 2006, shovelnose sturgeon spawned in the Marias River in conjunction with the ascending, peak (134 m 3 /s) and descending portions of the spring hydrograph and water temperatures from 16°C to 19°C. In 2008, shovelnose sturgeon spawned in conjunction with the peak (118 m 3 /s) and descending portions of the spring hydrograph and during a prolonged period of increased discharge (28–39 m 3 /s), coupled with water temperatures from 11°C to 23°C in the lower Marias River. No evidence of shovelnose sturgeon spawning was documented in the lower Marias River in 2007 or 2009 when discharge remained low (14 and 20 m 3 /s) despite water temperatures suitable and optimal (12°C-24°C) for shovelnose sturgeon embryo development. A similar relationship between shovelnose sturgeon spawning and discharge was observed in the Teton River. These data suggest that discharge must reach a threshold level (28 m 3 /s) and should be coupled with water temperatures suitable (12°C-24°C) or optimal (16°C-20°C) for shovelnose sturgeon embryo development to provide a spawning cue for shovelnose sturgeon in the lower Marias River.

Montana↗

USGS2012

Lake sturgeon population attributes and reproductive structure in the Namakan Reservoir, Minnesota and Ontario

Quantified were the age, growth, mortality and reproductive structure of lake sturgeon ( Acipenser fulvescens ) collected in the US and Canadian waters of the Namakan Reservoir. The hypotheses were tested that (i) age and growth of lake sturgeon in the Namakan Reservoir would differ by sex and reproductive stage of maturity, and (ii) that the relative strength of year-classes of lake sturgeon in the reservoir would be affected by environmental variables. To quantify age, growth and mortality of the population, existing data was used from a multi-agency database containing information on all lake sturgeon sampled in the reservoir from 2004 to 2009. Lake sturgeon were sampled in the Minnesota and Ontario waters of the Namakan Reservoir using multi-filament gillnets 1.8 m high and 30–100 m long and varying in mesh size from 178 to 356 mm stretch. Reproductive structure of the lake sturgeon was assessed only during spring 2008 and 2009 using plasma testosterone and estradiol-17β concentrations. Ages of lake sturgeon >75 cm ranged from 9 to 86 years (n = 533, mean = 36 years). A catch-curve analysis using the 1981–1953 year classes estimated total annual mortality of adults to be 4.8% and annual survival as 95.2%. Using logistic regression analysis, it was found that total annual precipitation was positively associated with lake sturgeon year-class strength in the Namakan Reservoir. A 10 cm increase in total annual precipitation was associated with at least a 39% increase in the odds of occurrence of a strong year class of lake sturgeon in the reservoir. Plasma steroid analysis revealed a sex ratio of 2.4 females: 1 male and, on average, 10% of female and 30% of male lake sturgeon were reproductively mature each year (i.e. potential spawners). Moreover, there was evidence based on re-captured male fish of both periodic and annual spawning, as well as the ability of males to rapidly undergo gonadal maturation prior to spawning. Knowledge of lake sturgeon reproductive structure and factors influencing recruitment success contribute to the widespread conservation efforts for this threatened species.

Minnesota, Ontario↗

USGS2011

Effects of acclimation on poststocking dispersal and physiological condition of age-1 pallid sturgeon

The objective of this study was to evaluate the effects of acclimation to flow and site‐specific physicochemical water conditions on poststocking dispersal and physiological condition of age‐1 hatchery‐reared pallid sturgeon. Fish from three acclimation treatments were radio‐tagged, released at two locations (Missouri River and Marias River), and monitored using passive telemetry stations. Marias treatment was acclimated to flow and site‐specific physicochemical conditions, Bozeman treatment was acclimated to flow only, and controls had no acclimation (reared under traditional conservation propagation protocol). During both years, fish released in the Missouri River dispersed less than fish released in the Marias River. In 2005, Marias treatment dispersed less and nearly twice as many fish remained in the Missouri River reach as compared to control fish. In 2006, pallid sturgeon dispersed similarly among treatments and the number of fish remaining in the Missouri River reach was similar among all treatments. Differences in poststocking dispersal between years were related to fin curl which was present in all fish in 2005 and only 26% in 2006. Pallid sturgeon from all treatments in both years had a greater affinity for the lower reaches of the Missouri River than the upper reaches. Thus, release site influenced poststocking dispersal more than acclimation treatment. No difference was observed in relative growth rate among treatments. However, acclimation to flow (i.e., exercise conditioning) prevented fat accumulation from rupturing hepatocytes. Acclimation conditions used in this study did not benefit pallid sturgeon unless physiological maladies were present. Overriding all treatment effects was stocking location; thus, natural resource agencies need to consider stocking location carefully to reduce poststocking dispersal.

Montana↗

USGS2007

Identification of plasma glucocorticoids in pallid sturgeon in response to stress

Compared to teleosts, little is known about the stress response in chondrosteans, and the glucocorticoid(s) most responsive to stress have never been definitively determined in sturgeon. In terms of cortisol production, pallid sturgeon (Scaphirhynchus albus) have a low physiological response to stress compared to other sturgeons (Acipenser sp.). Because of this, our null hypothesis was that cortisol is not the predominant glucocorticoid secreted in response to stress in pallid sturgeon. Our objective was to identify the putative glucocorticoids present in the plasma of pallid sturgeon during the stress response. Pallid sturgeon were subjected to a severe confinement stress (12 h) with an additional handling stressor for the first 6 h. Control fish were not subjected to confinement but were handled only to collect blood. Blood plasma was collected at time 0, 6, and 12 h. Gas chromatography/mass spectrometry was used to screen the plasma for the spectrum of glucocorticoids and determine the putative steroid secreted during the stress response. Cortisol was the primary glucocorticoid detected in stressed pallid sturgeon. In addition, the cortisol metabolites cortisone, alloTHE (5??-pregnane-3??,17??,21-triol-11,20-dione), allo-??-cortolone (3??,17??,20??,21-tetrahydro-5??-pregnan-11-one), and allo-??-cortolone (3??,17??,20??,21-tetrahydro-5??-pregnan-11-one) were detected. Plasma cortisol increased from a resting concentration of 0.67 ng/ml to 10.66 ng/ml at 6 h followed by a decrease to 6.78 ng/ml by 12 h. Plasma glucose increased significantly by time 6 and 12 h in both stressed and unstressed groups and remained elevated at time 12 h, while resting lactate concentrations were low to non-detectable and did not increase significantly with the stressor over time. Cortisol was the primary glucocorticoid synthesized and secreted in response to a stressor in pallid sturgeon. Though the proportional increase in plasma cortisol in stressed pallid sturgeon was lower than many other species of sturgeon, the concentration was high enough to elicit a secondary stress response as seen by changes in plasma glucose. ?? 2007 Elsevier Inc. All rights reserved.

General and Comparative Endocrinology↗

USGS2005

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.

Environmental Health Perspectives↗

USGS2001

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

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 female's endogenous reproductive rhythm. ?? 2001 Elsevier Science B.V. All Rights reserved.

Aquaculture↗