Investigation into Bias and Variability in Estimates of Population Size and Biomass when Catches of Individuals are Large Relative to the Total Population

Biomass of fish populations has traditionally been estimated by multiplying the average weight of captured fish by the estimated number of fish, with its variance estimated as the product of two variances. We present a method for estimating fish biomass in small streams (< 5 m wetted width) that uses a finite population correction factor (FPC) to take advantage of the fact that a relatively high proportion of the total population is normally captured and can be weighed during removal estimates. For these captured fish, measurement error is related to scale accuracy and field conditions. For the portion of the population that is not captured, we used a randomly stopped sums estimator (RSS) to estimate the total weight and variance of this non-captured proportion of the population. We also evaluated FPC and RSS methods individually to determine which of the four methods--(1) combination of FPC and RSS (FPCRSS), (2) traditional (hereafter OLD), (3) FPC, or (4) RSS—performed best. We also incorporated biomass estimates for fish that were captured, but not weighed, using length-weight regression predictions (FPCRSSreg). Performance of these estimators was evaluated using both simulated and field data. We based performance on reduction in the coefficient of variation (CV) of the biomass estimate and coverage of 95-percent confidence intervals (proportion of trials for which the 95-percent estimated biomass confidence intervals included the true biomass). The FPCRSS method had the narrowest CVs and the OLD method had the widest CVs for both the field and simulated data. Because of the high variance for the OLD method, 95-percent CIs for this method included the true biomass for a higher proportion of trials (nearly 100%) than 95-percent CIs for the FPCRSS method, but the coverage of the FPCRSS method for two-pass removal estimates was 80 percent or better for capture probabilities of 0.5 or higher. Using simulated data, we found that removal estimators are biased and that these biases are more pronounced at lower capture probabilities and lower population sizes. This bias in removal population estimators causes a bias in biomass estimates and was partly responsible for poorer coverage of 95-percent CIs. Our attempts to correct for population estimate bias resulted in much wider confidence intervals for both population and biomass estimates. For 607 field biomass estimates where all captured fish were weighed, the median CV for the FPCRSS method (0.05) was significantly lower (Wilcoxon sign-ranked test: P < 0.001) than the OLD method (0.76). When a portion of captured fish was not weighed, but estimated using length-weight regression relationships, the FPCRSSreg method had significantly lower CVs (median = 0.06; Wilcoxon sign-ranked test: P < 0.001, n = 130) than the old method (median = 0.86)

Observing the Effects of Inbreeding and Local Adaptation on Fitness in Westslope Cutthroat Trout Populations in a Common Garden

Montana Westslope cutthroat trout (Oncorhynchus clarkii lewisi, WCT) populations, particularly those east of the continental divide, are predominantly small and isolated from one other. Small population size inevitably leads to a more inbred population and can lead to lowered fitness (inbreeding depression). Isolated populations may experience local adaptation, which increases the fitness of a population within its native habitat. If inbreeding is the greatest threat to a population, introducing individuals from another population might be the best management decision. However, if local adaptation has also occurred, introducing new individuals might lower the fitness of the population. Our goal was to evaluate the relative importance of inbreeding and local adaptation on fitness in several WCT populations. This study combines eggs from several populations of WCT into several different natural habitats. Remote-site incubators were used to introduce eggs to six sites over four years in the Cherry Creek drainage. Each year a colder and warmer site was selected to test for the potential of local adaptation to stream temperature. Electrofishing was used to sample above and below introduction sites one, two, and three years after eggs were introduced. DNA sequencing of microsatellite loci in parents and offspring were then used to determine the population of origin of 511 offspring sampled in Cherry Creek in 2008 and will ultimately be used for over 750 offspring sampled in 2007 and 2009. Preliminary results suggest that a colder common habitat produces larger differences in relative fitness than a warmer habitat

Performance of Westslope Cutthroat Trout Released into the Upper Cherry Creek Drainage Using Remote Stream Incubators

A major effort to conserve westslope cutthroat (Oncorhynchus clarkii lewisi; WCT) is underway throughout Montana. One of the larger WCT conservation projects is onging in the Cherry Creek drainage of the Madison River. About 105 km of stream and a mountain lake are being treated with piscicides to remove nonnative trout, and WCT are being introduced into the drainage using remote stream incubators (RSIs). We are evaluating the relative success of different wild and hatchery stocks of WCT released into Cherry Creek. Here, we report on survival, abundance, growth, condition, and dispersal of WCT in the upper Cherry Creek drainage during the first three years of releases. Two streams of similar size, upper Cherry Creek and Cherry Lake Creek, meet to form main Cherry Creek. Cherry Lake Creek is colder than upper Cherry Creek (average August temperature about 3?C colder).Known numbers of WCT embryos were placed into RSIs at two sites in upper Cherry Creek during 2006 and 2007, one site in Cherry Lake Creek during 2006 and 2007, one site in Pika Creek (a tributary to Cherry Lake Creek) during 2008, and in an un-named spring-fed tributary to main Cherry Creek just below the mouth of Cherry Lake Creek during 2008. Fry that hatched in each RSI were captured and counted prior to release. Population abundances were estimated by single and multiple-pass electrofishing in 100-m sample sections located systematically throughout the upper reaches of the drainage. Estimated survivals from egg to fry, fry to age- 1, age-1 to age-2, and age-2 to age-3 ranged from 13 to 80 percent, 7 to 80 percent, 21 to 100 percent, and 100 percent, respectively. Survivals in the colder stream, Cherry Lake Creek, were lower than in the warmer stream. Over 3500 WCT occupied the upper Cherry Creek drainage by 2009. Fish dispersed short distances upstream and long distances downstream, but downstream dispersal appeared relatively discrete, with WCT filling available habitat near RSIs before occupying reaches further downstream. Early growth of WCT was much slower in colder streams, but by age-3 little difference existed among streams. Conversely, condition factors of WCT were slightly lower in upper Cherry Creek (averaging 0.88 to 0.95) than in Cherry Lake Creek (0.92 to 1.11). The introduction of WCT in upper Cherry Creek has been successful to date; however, natural reproduction by introduced WCT has not yet occurred, but is expected to occur next year

Radial shortening following a fracture of the proximal radius: Degree of shortening and short-term outcome in 22 proximal radial fractures

Background and purpose: The Essex-Lopresti lesion is thought to be rare, with a varying degree of disruption to forearm stability probable. We describe the range of radial shortening that occurs following a fracture of the proximal radius, as well as the short-term outcome in these patients. Patients and methods Over an 18-month period, we prospectively assessed all patients with a radiographically confirmed proximal radial fracture. Patients noted to have ipsilateral wrist pain at initial presentation underwent bilateral radiography to determine whether there was disruption of the distal radio-ulnar joint suggestive of an Essex-Lopresti lesion. Outcome was assessed after a mean of 6 (1.5-12) months using clinical and radiographic results, including the Mayo elbow score (MES) and the short musculoskeletal function assessment (SMFA) questionnaire. One patient with a Mason type-I fracture was lost to follow-up after initial presentation. Results 60 patients had ipsilateral wrist pain at the initial assessment of 237 proximal radial fractures. Radial shortening of ≥ 2mm (range: 2-4mm) was seen in 22 patients (mean age 48 (19-79) years, 16 females). The most frequent mechanism of injury was a fall from standing height (10/22). 21 fractures were classified as being Mason type-I or type-II, all of which were managed nonoperatively. One Mason type-III fracture underwent acute radial head replacement. Functional outcome was assessed in 21 patients. We found an excellent or good MES in 18 of the 20 patients with a Mason type-I or type-II injury. Interpretation The incidence of the Essex-Lopresti lesion type is possibly under-reported as there is a spectrum of injuries, and subtle disruptions often go unidentified. A full assessment of all patients with a proximal radial fracture is required in order to identify these injuries, and the index of suspicion is raised as the complexity of the fracture increases.</p

Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Concurrent Sessions C: A Cooperative Approach to Solving Fish Habitat Recovery - Determining the Need for Fish Passage Versus Fish Barriers

Yellowstone Cutthroat trout (YCT) have disappeared from more than 70% of their historic range during the past200 years. With over 350 miles of occupied habitat, the Shields River Subbasin is a rare stronghold among watersheds supporting YCT in Montana, as this species is spread throughout the basin, rather than being relegated to headwater stream reaches. Unfortunately, nonnative brook trout which outcompete YCT for food and space, have been exponentially increasing in distribution and abundance in the upper basin over the past decade and if left unchecked, could entirely displace YCT in the headwaters. This has left managers with the task of assessing the tradeoffs between improving fish passage to preserve the unique interconnected YCT population (metapopulation) versus constructing barriers to secure the YCT population in the upper basin from invasion and displacement by brook trout. To inform agency management decisions, the Wildlife Conservation Society began a multi-year fish movement study using passive integrated transponder (PIT) tags in 2011. Data suggest that brook trout abundance and distribution is increasing faster than anticipated and that management action, including the use of fish barriers, is needed to secure the upper Shields River basin from brook trout invasion and the associated consequences. Agencies are currently formulating a strategy which maintains as much connected habitat as possible while also reducing or excluding brook trout from critical habitats

Dual-Biometric Human Identification Using Radar Deep Transfer Learning

Accurate human identification using radar has a variety of potential applications, such as surveillance, access control and security checkpoints. Nevertheless, radar-based human identification has been limited to a few motion-based biometrics that are solely reliant on micro-Doppler signatures. This paper proposes for the first time the use of combined radar-based heart sound and gait signals as biometrics for human identification. The proposed methodology starts by converting the extracted biometric signatures collected from 18 subjects to images, and then an image augmentation technique is applied and the deep transfer learning is used to classify each subject. A validation accuracy of 58.7% and 96% is reported for the heart sound and gait biometrics, respectively. Next, the identification results of the two biometrics are combined using the joint probability mass function (PMF) method to report a 98% identification accuracy. To the best of our knowledge, this is the highest reported in the literature to date. Lastly, the trained networks are tested in an actual scenario while being used in an office access control platform to identify different human subjects. We report an accuracy of 76.25%

Patterns of Gendered Performance Differences in Large Introductory Courses at Five Research Universities

Significant gendered performance differences are signals of systemic inequity in higher education. Understanding of these inequities has been hampered by the local nature of prior studies; consistent measures of performance disparity across many disciplines and institutions have not been available. Here, we report the first wide-ranging, multi-institution measures of gendered performance difference, examining more than a million student enrollments in hundreds of courses at five universities. After controlling for factors that relate to academic performance using optimal matching, we identify patterns of gendered performance difference that are consistent across these universities. Biology, chemistry, physics, accounting, and economics lecture courses regularly exhibit gendered performance differences that are statistically and materially significant, whereas lab courses in the same subjects do not. These results reinforce the importance of broad investigation of performance disparities across higher education. They also help focus equity research on the structure and evaluative schemes of these lecture courses