Accurate estimates of the number of adults contributing to offspring (Ns), effective breeding number (Nb), and individual adult contributions to recruitment are required for recovery planning for endangered White Sturgeon Acipenser transmontanus populations, many of which are suffering from prolonged periods of recruitment failure. We show that genetic techniques can be used to characterize important features of White Sturgeon reproductive ecology in large rivers where census data are extremely difficult to obtain. We used 12 microsatellite loci and likelihood‐based pedigree analysis to estimate Ns, Nb, number of kin groups (Nk), and individual reproductive success of White Sturgeon contributing to viable eggs and larvae collected in the upper Columbia River in each of 2 years. Estimated mean ±SD annual Ns was 121.5 ± 34.7, Nb was 86.5 ± 10.6, and Nk was 73.5 ± 17.3. Large variations in estimates of Ns, Nb, and Nk were observed between three spawning areas, in which one spawning site representing 61% of total adult spawning population. Variation in adult reproductive success was observed within and among sites. Estimated mean ±SD individual spawning duration was 1.9 ± 1.1 d, and number of mates per adult was 2.9 ± 2.5, which also varied spatially and temporally. Based on age of collected eggs and larvae, number of spawning days ranged from 5 to 19 d between years and among sites. Genetically derived estimates of Ns were lower but generally concordant with empirical estimates of available spawners (Nc), based on sex ratios and maturation staging of adults captured independently (Ns/Nc ratio = 0.683). Results increase our understanding of White Sturgeon reproductive ecology and recruitment and allow projections of cohort levels of genetic diversity. Similar data can be applied to recovery planning and aquaculture programs for this and other species of conservation concern. Received January 6, 2014; accepted May 28, 2014

Summary The effects of stream environmental conditions on inter individual variability were quantified for lake sturgeon, Acipenser fulvescens (Rafinesque, 1817) yolk sac larvae in the expression of behavioral and morphological traits. Simulated experimental treatments including food availability (brine shrimp), presence of chemosensory predator cues (adult crayfish and odonate larvae), and conspecific density (2 verses 1 larvae) were applied to determine the effects on the duration of time in substrates following hatch and growth from hatch until emergence. In spring 2010, larvae from two full‐sib families were individually placed into 240 mL perforated plastic containers (n = 263) with gravel substrate immediately following hatch. Containers were maintained in stream water at ambient temperatures and constant flow (~0.03 m/sec) in 4 m experimental flowing streams. Duration of time (days) each individual remained in the substrate was recorded. Morphological traits including total length (mm), body area (mm2), and yolk‐sac area (mm2) were measured at hatch and at the time of emergence from substrate to compare growth and amount of endogenous yolk reserves used in individuals among experimental treatments. Environmental conditions significantly affected emergence time. Individuals emerged earlier in treatments exposing larvae to chemosensory predator odorants and higher conspecific density. Use of endogenous reserves (yolk‐sac area) at the time of emergence did not differ among treatments. Growth was significantly greater when individuals were provided a food source compared to all other treatments. Quantifying the magnitude and direction of phenotypic responses to environmental conditions is important to understand potential factors affecting survival during early life stages and population viability under conditions of increasing environmental variability.

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We describe the overall composition and prey selectivity in the diet of hatchery‐reared juvenile White Sturgeon Acipenser transmontanus in the upper Columbia River, Canada. The efficacy of two sampling methods, nonlethal gastric lavage and lethal sampling to remove stomach contents, were evaluated across different ages, size‐classes, and river sections. Gastric lavage samples were collected from 108 fish angled in October 2012 and 2013. In 2012 only, a subsample of 48 individuals were euthanized following gastric lavage, and stomach contents were collected. To describe food availability, 45 benthic grabs were collected from areas of juvenile capture. Identifiable prey taxa were recovered from 60.3% of lavage and 98% of lethal stomachs sampled. While the diet of juvenile White Sturgeon was composed of 16 diverse prey taxa, most were selected less than their availability in the river. Prey diversity in lethal samples was influenced by river section, not by fish size or age; fish in deeper, slower water consumed the highest number of prey taxa (mean = 4.6). Further, there was no significant overlap in diets among river sections, the dominant prey taxa selected differing among river sections and years. Prey in the lethal samples included 56% of the 25 total prey taxa identified, lethal included 60%, and the bottom grabs included 76%. Gastric lavage was 69% efficient at describing lethal samples. A minimum of 100 lavage samples were required to describe the diet to a level comparable to lethal sampling. Where lethal sampling is not an option, our results indicate gastric lavage, if conducted on appropriate numbers of fish, is effective at describing sturgeon diets and provides data that can be used to study the feeding ecology of threatened or endangered species. Received August 24, 2015; accepted November 24, 2015 Published online March 31, 2016