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Traditional methods for estimating abundance of fish populations are not feasible in some systems due to complex population structure and constraints on sampling effort. Lincoln's estimator provides a technique that uses harvest and harvest rate to estimate abundance. Using angler catch data allows assumptions of the estimator to be addressed without relying on methods that could be prohibitively field-intensive or costly. Historic estimates of White Sturgeon Acipenser transmontanus abundance in the Sacramento–San Joaquin River basin have been obtained using mark–recapture methods; however, White Sturgeon population characteristics often cause violations of model assumptions, such as population closure and independent capture probabilities. We developed a version of Lincoln's estimator using a joint likelihood, estimated abundance of White Sturgeon in the Sacramento–San Joaquin River basin in 2015 using this method and empirical data and assessed accuracy and precision of estimates in a simulation study. Estimating abundance using harvest and harvest rate, as represented by our model framework, has the potential to be precise and accurate. The joint likelihood–based approach fitted using Bayesian methods is advantageous because it includes all sources of variation in a single model. Precision of abundance estimates was low with application of the model to White Sturgeon in the Sacramento–San Joaquin River basin and to similar conditions in a simulated dataset. Using simulation, precision and accuracy increased with increases in the number of high-reward and standard tags released, tag reporting rate, tag retention rate, and harvest rate. Results demonstrate potential sources of error when using this approach and suggest that increasing the number of tagged fish and tag reporting rate are potential actions to improve precision and accuracy of abundance estimates of the model. [ABSTRACT FROM AUTHOR]

The main objectives of “conservation aquaculture” are the protection, restoration and multiplication of rare and endangered species or individual fish populations. Hatchery reproduction is an effective means of preserving wild populations, but can only be used in extreme cases when the population is on the verge of extinction. The US “Conservation Aquaculture” methods are considered using the example of an isolated white sturgeon population Acipenser transmontanus Kootenai river, who lost the possibility of natural replenishment. The main features of plant reproduction in the framework of “conservation aquaculture” are: 1) preservation of genetic diversity, 2) elimination of unintentional artificial selection and domestication, 3) tagging of juvenile individuals released and control of their survival in natural conditions. [ABSTRACT FROM AUTHOR]

Abstract: The issue of deep hooking is of concern in white sturgeon, Acipenser transmontanus Richardson, fisheries because nearly all anglers use bait with a stationary presentation on the river bottom to catch them, and bait fishing is often associated with higher instances of deep hooking and hooking mortality. Deep hooking rates, landing success and catch rates were investigated for anglers bait fishing for white sturgeon using circle and J hooks with inline and offset alignments fished with both active and passive hook‐setting methods. Anglers hooked 578 white sturgeon and landed 508 fish, ranging in size from 60 to 316 cm total length (mean = 137 cm). Deep hooking rates averaged 0.6% and did not differ between hook types, hook alignments or hook‐setting methods. Landing success (the proportion of hooked sturgeon that were successfully landed) and catch rates were also equivalent between hook types, hook alignments and hook‐setting methods; landing success averaged 88% and catch rates averaged 0.27 fish/hr. Results of this study indicate that deep hooking is rare when angling for white sturgeon using standard bait‐fishing gear regardless of hook‐setting method or whether circle or J hooks were used; regulations restricting hook type in sturgeon bait fisheries are therefore unwarranted. [ABSTRACT FROM AUTHOR]

Off-site angler surveys are commonly administered via two or more survey modes in the form of a mixed-mode survey. Mixed-mode surveys allow survey administrators to attain the benefits inherent to different survey modes, reduce total survey error, and control survey cost. However, these benefits can only be simultaneously attained after undertaking sample size planning. Sample size planning is a trade-off analysis wherein a researcher concurrently assesses survey administration cost, the accuracy and precision of estimates, the magnitude and direction of biases, and variance of the test statistic to determine an optimal sample size. We used data from an off-site angler survey administered to anglers targeting White SturgeonAcipenser transmontanusto illustrate a systematic approach to sample size planning. Our survey design included a mixed-mode design with three survey modes (e-mail, mail, and telephone) and a two-phase sampling design that had a first contact and a follow-up contact with a subsample of nonrespondents. Sample size planning was undertaken in the form of a sensitivity analysis wherein four survey design alternatives were simulated and assessed based on four criteria (i.e., bias, precision, accuracy, and cost). We also incorporated tests for nonresponse bias and survey mode effect. We found that (1) response rates were lower for e-mail surveys (22%) than for mail surveys and telephone surveys (39–44%); (2) nonresponse bias did not have a substantial effect on survey estimates from the mixed-mode design; and (3) estimates (total effort and total catch) from the mail and e-mail survey modes were significantly different, indicating a survey mode effect. The high variability of anglers’ annual catch made survey estimates highly imprecise at lower sample sizes. The level of acceptable error varies for each study. Therefore, a systematic approach to sample size planning is necessary to determine the point where acceptable error is reached while considering multiple survey design alternatives. Received September 25, 2016; accepted April 24, 2017 Published online June 19, 2017 [ABSTRACT FROM PUBLISHER]

The San Francisco Estuary (SFE) is heavily influenced by anthropogenic activities, including historic and chronic contaminant inputs. These contaminants can adversely affect SFE fish populations, particularly white sturgeon, because they are a benthic dwelling, long-lived species. We measured a suite of metals and organic contaminants in liver and gonad tissues of 25 male and 32 female white sturgeon as well as several physiological indicators of sturgeon health. Most sturgeon (68% of males and 83% of females) were estimated to be between 13 and 17 years of age. Sturgeon tissues had elevated concentrations of several metals, including As, Ba, Cd, Cu, Cr, Pb, Hg, Ni, Se, and Zn. The most frequently detected organic contaminants in sturgeon livers and gonads were DDE, PCBs, PBDEs, and galaxolide. Selenium was detected at levels similar to those shown to cause impaired liver physiology and reproductive success in white sturgeon. Observed Hg levels were higher than those shown to result in lower condition factor and gonadosomatic indices in white sturgeon. Liver galaxolide levels correlated with decreased plasma estradiol levels in female sturgeon. The Cd, As, and Cu warrant further investigation, because they were detected at levels known to impair fish health. Our results suggest contaminants are negatively affecting SFE white sturgeon health and fitness. Future SFE white sturgeon contaminant research is suggested. [ABSTRACT FROM AUTHOR]

Despite showing similar abundance estimates, population surveys of wild white sturgeon ( Acipenser transmontanus Richardson, 1836) in the Bliss and Hells Canyon reaches of the Snake River display very different stock structures. To better understand these differences, an individual based model was developed using empirical mark-recapture metrics from 343 white sturgeon recaptured in the Bliss reach [at-large 1.0-19.9 years], and 580 white sturgeon recaptured in the Hells Canyon reach [at-large 1.0-21.2 years]. After calculating annual growth increments from these recaptures, individuals from each reach were assigned to size bins then randomly chosen from within each bin to 'grow' theoretical fish. This process was bootstrapped 1000 times, producing a mean length-at-age trajectory for each reach. From these data, mark-recapture samples were assigned estimated ages and fitted to a three-parameter logistic growth curve. Results indicate a wide disparity in length-at-age of white sturgeon between reaches, with the Bliss population displaying an intrinsic rate of increase [K = 0.118] twice that of the Hells Canyon population [K = 0.059]. This is due primarily to slow juvenile growth in the Hells Canyon population relative to juvenile growth in the Bliss population. The much slower growth rate of juveniles in the Hells Canyon reach has consequences to population demographics, such as age at first maturity. Although growth differences are large, both populations appear to be stable or increasing in abundance despite being regulated by very different mechanisms. [ABSTRACT FROM AUTHOR]

Abstract: Many fish of aquacultural importance including sturgeon and paddlefish have a history of polyploidy in their evolutionary lineages. Spontaneous autopolyploids have been detected in several sturgeon species in culture despite the fact that the induction of triploidy is not a management tool in farming sturgeon for meat and caviar. In 2010, we discovered two female spontaneous autopolyploid white sturgeon (Acipenser transmontanus) on a commercial caviar farm that had successfully produced offspring of intermediate ploidy in crosses with normal males. Here we use flow cytometry and microsatellite genotyping to screen a second aquaculture program for the presence of spontaneous autopolyploids. Flow cytometry of female parents and their progeny in the 2011 year class created by the Kootenai River white sturgeon conservation aquaculture program revealed that wild caught females used as dams possessed normal ploidy (8N). Five of ten families sampled from the 2011year class contained spontaneous autopolyploids possessing DNA content consistent with dodecaploidy (12N). The percent of autopolyploid individuals sampled ranged from 0 to 33% per family, and the total number of spontaneous autopolyploids in the 2011 year class was 12/150 (8%). Microsatellites were not useful in detecting spontaneous autopolyploids in the conservation aquaculture program due to low levels of genetic diversity in the endangered Kootenai River population. The two families with the highest incidence of spontaneous autopolyploids (33% and 26% of offspring sampled) were sired by a single male, suggesting a paternal effect on the generation of spontaneous autopolyploids in white sturgeon. [Copyright &y& Elsevier]

Critical unknowns surrounding the basic biology of White SturgeonAcipenser transmontanushave hindered management and conservation efforts. Population genetic data may be used to address some of these uncertainties, but previous examinations of population structure in White Sturgeon have been limited by the highly duplicated nature of the species’ genome. We report results from an analysis of White Sturgeon population structure within and among drainages using 13 polysomic microsatellite loci. Genetic diversity levels varied widely among regions, and the lowest levels were observed in the endangered Kootenai River Distinct Population Segment and the highest levels were detected in regions with access to estuarine and marine habitat. Patterns of within-drainage population structure varied, and no structure was detected in the Sacramento–San Joaquin drainage and a complex pattern of isolation by distance was revealed in the Columbia–Snake River drainage. These results contrast a previously published evaluation of a White Sturgeon population structure in the Fraser River, which revealed several genetically distinct populations within a single drainage. Examination of population structure among drainages, including from samples collected across the species range, revealed six populations. Populations in the Sacramento–San Joaquin, Kootenai, lower Fraser, and upper Fraser River drainages were distinct. The complex isolation-by-distance pattern discovered in the within-drainage analysis of the Columbia–Snake River drainage was supported by the among-drainage population structure analysis. Our results provide little support for the practice of managing each impounded reach of the Columbia–Snake River system as a genetically distinct population as adjacent reaches show little to no genetic divergence in these analyses. Variation in patterns of population structure across the species range indicates that the scale of spawning site fidelity for White Sturgeon varies regionally, which has implications for recruitment failure mitigation. Received May 31, 2012; accepted March 14, 2013 [ABSTRACT FROM AUTHOR]

Sturgeon (Acipenseridae) stocks worldwide are generally in decline, with many populations close to extirpation. One prominent species, the White Sturgeon (Acipenser transmontanus) with spawning populations distributed throughout three large, western North American watersheds (the Sacramento, Columbia, and Fraser rivers), has experienced population declines in the past decade. In 2003, the Committee on the Status of Endangered Wildlife in Canada designated all six populations of White Sturgeon in Canada “endangered.” To assist sturgeon recovery initiatives in the lower Fraser River (British Columbia), a stewardship‐based monitoring and assessment program was developed by the Fraser River Sturgeon Conservation Society. A descriptive population model was developed to provide reliable annual population estimates by size/age group and location, based on tag release and recapture data collected by trained volunteers. As of January 2011, the population estimate (from 40‐ to 279‐cm fork length) was 44,713 (95% confidence level 42, 634–46, 792). Group size analyses suggest that abundance decreases have been greatest for juvenile sturgeon under 100‐cm fork length. Recruitment decline may be the result of several factors, including destruction of important spawning and early life history rearing habitats; fewer successful adult spawners due to in‐river fisheries; and/or impacts of reduced food supply and ecological imbalances on both early life and adult stages. RESUMEN: en términos generates, los stocks de esturiones (Acipenseridae) alrededor del mundo están reduciéndose, e incluso varias poblaciones se encuentran cerca de ser extirpadas. Una especie importante, el esturión blanco (Acipenser transmontanus), cuenta con poblaciones reproductoras que se distribuyen a lo largo de tres cuencas hidrológicas del noroeste americano (ríos Sacramento, Columbia y Fraser), sin embargo ha experimentado reducciones poblacionales en la última década. En 2003, el Comité sobre el Estatus de la Vida Salvaje en Peligro, en Canada, designó a las seis poblaciones de esturión blanco el estado de “amenazadas”. La Sociedad para la Conservación del Esturión en el Río Fraser desarrolló un programa de evaluación y monitoreo con el fin de apoyar las iniciativas de recuperación del esturión en el bajo Río Fraser (Columbia Británica). Se desarrolló un modelo poblacional descriptive para estimar anualmente, y de manera confiable, el tamaño de la población por grupo de talla y edad y por locación, sobre la base de datos de captura‐recaptura colectados por voluntaries debidamente entrenados. La población estimada para el año 2011 (40–279 cm de longitud furcal) fue de 44,713 (95% de confianza 42,634–46,792). El análisis del tamaño por grupo indica que la reducción de la abundancia ha sido más importante en los juveniles de esturión de menos de 100 cm de longitud furcal. El decremento del reclutamiento puede ser el resultado de varies factores que incluyen la destrucción del hábitat de desove y desarrollo de los primeros estadios de vida de la especie; poca abundancia de adultos desovadores debido a la pesca en los ríos; y/o los impactos que tienen la reducción de alimento y otros desbalances ecológicos en los adultos y en los juveniles. [ABSTRACT FROM AUTHOR]

The Fraser River system consists of five white sturgeon ( Acipenser transmontanus) management units, two of which are listed as endangered populations under Canada's Species at Risk Act. The delineation of these management units was based primarily on population genetic analysis with samples parsed by collection location. We used polysomic microsatellite markers to examine population structure in the Fraser River system with samples parsed by collection location and with a genetic clustering algorithm. Strong levels of genetic divergence were revealed above and below Hells Gate, a narrowing of the Fraser canyon further obstructed by a rockslide in 1913. Additional analyses revealed population substructure on the Fraser River above Hells Gate. The Middle Fraser River (SG-3) and Nechako River were found to be distinct populations, while the Upper Fraser River, although currently listed as an endangered population, represented a mixing area for white sturgeon originating from SG-3 and Nechako. Differences between these results and previous genetic investigations may be attributed to the detection of population mixing when genetic clustering is used to infer population structure. [ABSTRACT FROM AUTHOR]

We applied a spatially and seasonally structured stock reduction analysis (SRA) model to white sturgeon ( Acipenser transmontanus) in the lower Fraser River, British Columbia, to estimate trends in abundance since the 1800s and evaluate the current status of the population. We used a sequential Bayesian state-space estimation approach to incorporate prior information from other analyses and evaluate the updating of prior knowledge within the SRA model. The estimated ratio of the abundance of spawning fish in 2004 to relative to unfished conditions was slightly higher than estimates from other studies; on average, 27% of the posterior probability was associated with a 2004 spawning stock abundance of 50% or less of the unfished abundance. Estimates of the current abundance of fish vulnerable to the lower Fraser River recreational fishery were higher than those obtained in other recent SRAs that ignored spatial structure. We also performed the analysis using a spatially aggregated version of the SRA model and obtained lower estimates of unfished biomass and depletion and higher estimates of fishing mortality rates compared with the spatially structured model. We evaluated two structural hypotheses about age-specific vulnerabilities in the historical commercial fishery; assumed vulnerabilities had a marked impact on estimated fishing mortality rates. [ABSTRACT FROM AUTHOR]

Summary A combined analysis of capture/recapture, sonic tracking, and genetics was carried out to examine population structure of White Sturgeon of the Kootenay and Upper Columbia rivers. Analysis of capture/recapture and sonic telemetry data identified spatial patterns in habitat use, with individuals showing a preference for one of four high-use zones. Mitochondrial DNA analysis of groups of fish defined by zonal preference and age suggests there is genetic population structure across this region, even between groups frequenting different zones in the contiguous river system. This population structure likely has its origin in patterns of habitat use established prior to the impacts of human development when White Sturgeon in the region existed as assemblage of semi-reproductively isolated populations. Identification of this historical population structure reveals unrecognized complexity regarding the spatial extent of historic habitat use and breeding structure of White Sturgeon in the region, which must be considered in further research and recovery efforts. [ABSTRACT FROM AUTHOR]

Our objective was to evaluate recovery goals for endangered white sturgeon Acipencer transmontanus in the Kootenai River, Idaho. We used demographic statistics for white sturgeon in the Kootenai River in a stochastic density-dependent population model to estimate recruitment rates needed for population recovery. We simulated future abundance of white sturgeon in the Kootenai River over a 25-year period and a range of hypothetical recruitment rates to estimate the level of recruitment that would lead to population recovery (7,000 fish, the number present before the population suffered recruitment failure). We compared simulations of future abundance at enhanced levels of recruitment with those based on the present status of the population and with the recruitment criterion in the Koolenai River White Sturgeon Recovery Plan. We found that the population would decline to only 57 individuals after 25 years and only 6 individuals after 50 years if recruitment failure continued. The population would reach the target carrying capacity of 7,000 individuals within 25 years only when each adult produced 0.4 age-1 recruits, a recruitment rate equivalent to reaching the target level of recruitment in the recovery plan every year. In contrast, the population would grow to only 1,200 individuals if the target level of recruitment in the recovery plan was produced in only 3 of every 10 years, as specified in the recovery plan. We suggest that recovery goals for white sturgeon in the Kootenai River can be modified as follows: (1) a population goal of 7,000 subadults and adults; (2) population recovery within 25 years; and (3) a minimum recruitment rate of at least 20 age-1 juveniles detected from each year-class in each of 10 years by use of a standardized monitoring protocol. [ABSTRACT FROM AUTHOR]

Fifty white sturgeon ( Acipenser transmontanus) eleutheroembryos (average size 0.17 g) were placed onto each of four quadrants (0.45 m2 quadrant−1; 200 fish tank−1) of different sized substrates in four circular tanks (approximately 562 L). Each of three quadrants had a different size substrate and the fourth quadrant was left bare. We used one replicate of smaller size substrates (0.5–11.9 mm) and one replicate of larger size substrates (21.7–88 mm). It was found that the white sturgeon eleutheroembryos preferred substrate with an average size (longest diameter) of 12 mm (11.9) in the smaller substrate range and 22 mm (21.7) in the larger substrate range. These data improve our knowledge of white sturgeon early life history, and if confirmed in the wild can be used to protect areas that are crucial for white sturgeon recruitment and survival. [ABSTRACT FROM AUTHOR]

The six North Pacific members of the genus Acipenser have generally similar environmental requirements and share several specific morphological features. This Pacific group consists of green sturgeon, Acipenser medirostris, Sakhalin sturgeon, A. mikadoi, white sturgeon, A. transmontanus, Chinese sturgeon, A. sinensis, Dabry’s sturgeon, A. dabryanus and Amur sturgeon, A. schrenkii. A qualitative morphological examination of these species revealed synapomorphic characters that suggest close phyolgenetic relationships resulting from common ancestry of eastern and western species within the Pacific Rim. An evolutionary taxonomic approach, considering a reduction of characters from east to west, would suggest an Asian ancestry for all Pacific sturgeons. In contrast however, a phylogenetic approach using derived character states suggests a North American ancestry. Besides a common ancestry for Chinese and American sturgeons, the taxonomic status of A. mikadoi is discussed. [ABSTRACT FROM AUTHOR]

River fragmentation by dams has often preceded declines in sturgeon populations, which suggests that reconnecting populations would contribute to their recovery. This study used a population viability model to quantify the effects of upstream passage at dams on white sturgeon (Acipenser transmontanus) metapopulations inhabiting a series of long (source) and short (sink) river segments. Simulated river systems with high interspersion of long and short segments and a long segment far upstream supported the healthiest metapopulations, suggesting biological criteria for siting dams. Contrary to expectation, the model predicted that upstream passage, without screening or downstream passage, was harmful to the metapopulation as a whole. However, upstream passage was beneficial when downstream migration was either restricted (by screening larger fish) or made safe (by providing downstream passage). The combination of upstream and downstream passage was most beneficial at dams above a long river segment. Screening, alone or combined with upstream passage, was most beneficial at dams below a long segment. These theoretical results highlight the need for field research to evaluate management options and provide practical guidance for restoring sturgeon metapopulations in large rivers. [ABSTRACT FROM AUTHOR]

White sturgeon (Acipenser transmontanus) in the Columbia River in Canada have recently been listed as Endangered/Critically Imperiled, based on a shift in size and age-class composition from a population dominated by juveniles in the early 1980s to one presently dominated by adults. This shift has been attributed to a poor survival of early life stages. To determine the causes for this poor survival, investigations conducted annually since 1990 have focussed on identifying white sturgeon movement patterns, population dynamics, reproductive biology, and critical habitats. The reasons for the low recruitment remain poorly understood but river regulation and reservoir formation due to dam construction and pollution from municipal and industrial effluent inputs are suspected as contributing factors. The history of dam development on the Columbia River and implications to white sturgeon are discussed from a historical perspective. A synopsis of post-1990 study results is provided and discussed in the framework of management strategies that include: 1) angling regulations, 2) flow enhancement strategies during spawning, 3) development of a population stabilization plan, 4) investigations into the feasibility of artificial stock supplementation, and 5) proposed future study programs to identify factors limiting recruitment. [ABSTRACT FROM AUTHOR]