Nonlethal tools (plasma sex steroid concentrations and ultrasound) for assigning sex and reproductive condition in Burbot Lota lota from Lake Roosevelt, Washington, were assessed. Gonadal tissue, blood plasma, and gonadal sonograms were collected monthly from November 2016 to March 2018. Gametogenesis was described by gonadal histology during an entire reproductive cycle to confirm sex and reproductive condition. Plasma testosterone (T) and estradiol‐17β (E2) concentrations were measured by radioimmunoassay. Plasma 11‐ketotestosterone (11‐KT) concentrations were measured by liquid chromatography–mass spectrometry. Plasma sex steroid profiles, gonadosomatic index, and ovarian follicle diameter were also described during an entire reproductive cycle. Plasma 11‐KT concentration was used to assign sex with 82% accuracy during the entire reproductive cycle, and plasma 11‐KT and E2 concentrations were used to assign sex with 98% accuracy when fish were reproductive (i.e., November–March in Lake Roosevelt). Plasma T and E2 concentrations were used to assign reproductive condition in females with 98% accuracy, and plasma T concentration was used to assign reproductive condition in males with 90% accuracy. Ultrasound was used to assign sex with 96% accuracy but was not useful for assigning reproductive condition. Nonlethal tools to assign sex and reproductive condition will enable fisheries biologists to assess reproductive indices of the Burbot population in Lake Roosevelt to inform management decisions.

Woundfin Plagopterus argentissimus are a small, endangered cyprinid found solely in the Virgin River across Utah, Arizona, and Nevada. As of now, only three facilities culture Woundfin for conservation propagation purposes, but there is growing concern that current extensive culture protocols are not meeting the conservation recovery goals outlined in the Virgin River Resource Management and Recovery Program. The development of alternative rearing methodology, like effective intensive culture conditions, could help increase production to more effectively meet the conservation propagation needs for this species. Our goal was to assess the effect of different sex ratios and fish densities on reproductive success at indoor facilities. We measured fertilization success at three different sex ratios (1:1, 1:3, 1:5; female:male) and three different fish densities (0.05, 0.21, and 0.47 fish/L) in a laboratory setting. Sex ratio did not significantly affect fertilization success (P = 0.73). Fertilization was completely inhibited at a density of 0.05 fish/L, but there was no difference in fertilization success between the two other density treatments (P = 0.92). Our findings suggest that a density greater than 0.05 fish/L and a sex ratio of 1:1, 1:3, or 1:5 will likely enhance fertilization success. The results and conclusions of this paper provide valuable rearing information for the Virgin River Resource Management and Recovery Program and hatchery managers attempting to increase production of Woundfin in an intensive culture setting.

Summary A sanctuary targeting the time and space occupied by reproductively active white sturgeon, Acipenser transmontanus, during spawning can be an effective method for reducing angling‐related stressors. A catch and release (C&R) fishery targeting over the legal limit (oversize; ≥137 cm fork length) white sturgeon had been intensifying since 1990 and grew in popularity through the 2000s in the lower Columbia River. A research project to describe the reproductive structure of the adult white sturgeon population below Bonneville Dam (rkm 220‐233) was initiated in 2000 and provided the first detailed observations of trauma linked to this C&R fishery. Fish captured from 2003 to 2011 were examined for evidence of in‐season angling damage (hook marks, leaders and lines in buccal cavity) from June through August each year. Carcass surveys were conducted weekly from June through August within a 24.8 km stretch downstream from Bonneville Dam. Catch rates were determined through angler interviews and aerial counts of boat and bank anglers. Four major regulation changes occurred during the course of the study affecting the seasonal spawning sanctuary in space and time. A total of 679 oversize white sturgeon were examined for evidence of in‐season angling damage. The proportion of individuals with evidence of angling, damage indicators per individual, number of carcasses found and the number of carcasses with observed evidence of angling or retained gear, and the total number of oversize fish handled by boat anglers declined after each fishing regulation change. The trends suggest that the sanctuary influenced the number of encounters between anglers and white sturgeon and that increases to the sanctuary in time and space reduced stress endured by oversize white sturgeon.

Summary Determining the age at which farmed sturgeon begin storing ovarian fat will potentially enable sturgeon farmers to adjust husbandry practices, such as feeding different dietary fat levels at an early age. We investigated the influence of dietary fat on the size of ovarian adipocytes in farmed age‐2 white sturgeon Acipenser transmontanus. At age 1 month, all fish were fed a commercial high fat (HF; 17% fat) diet. At age 6 months, half were transitioned to an experimental low fat (LF; 9% fat) diet. Fish at this time averaged 160 g (±30 g), and individual tank density was 4.1 kg/m3. Tanks were 3.7 m in diameter, 1.3 m deep, each with a volume of 13.7 m3. Each tank maintained a flow rate of 150 L/min using groundwater with water temperatures ranging from 19 to 21°C and dissolved oxygen ranging from 6.5 to 12.0 ppm. All fish were fed the diet assigned to their tank for an additional 18 months prior to sampling. At age 25 months (now referred to as “age 2”), tissue was collected from fish and processed histologically. Adipocytes were measured along the ovarian fold (anterior), furthest from the ovarian fold (posterior), and randomly in between the anterior and posterior sections. Randomly chosen adipocytes from each location were measured histologically. Mean adipocyte size did not statistically differ among sample locations in fish fed the same diet. Once pooled by sampling location, average adipocyte size was 5,491.18 μm (±98.97) in fish fed the HF diet and 3,348.62 μm (±40.85) in fish fed the LF diet. Fish fed the HF diet had larger adipocytes than fish fed the LF diets (t = 20.01, df = 78.54, p < .01). The results demonstrate that diet can influence the size of adipocytes found in juvenile white sturgeon ovaries. Additional research is needed to determine whether the accumulation of large adipocytes as a juvenile confers to adulthood and influences reproductive ability and caviar yield and quality.