Model type, predictor variables, Deviance Information Criteria (DIC), ΔDIC, and DIC weights () for the candidate set of logistic regression models relating misidentification of sex with personal background information.

<p>DIC is a measure of model fit, ΔDIC measures the relative difference between the best model (ΔDIC = 0) and all subsequent models in the model set, and is the relative likelihood of a model given the data.</p

Biplots from principal component analysis (PCA) of traditional morphometrics.

<p>(A), geometric morphometrics (B), and Fourier morphometrics (C). Colors and shapes of points correspond to females (black circle; <i>n</i> = 44) and males (gray diamond; <i>n</i> = 61) of <i>Lampsilis teres</i> (Yellow Sandshell) from Yegua Creek and the East Fork of the Trinity River. Polygons enclose convex hulls of each sex (solid line = females; dashed line = males).</p

Flow chart exploring pros and cons of different approaches to determine sex for mussels as it relates to time, effort, lethality, and accuracy.

<p>Note that Geometric or Fourier morphometrics have similar accuracy as gonadal fluid sampling but requires more effort.</p

Summary of misidentification rates by personal background information, sex of specimen, and location of where the survey was administered.

<p>N (number of observers), median, min, max, and 25th and 75^th percentile summarize the central tendency and spread of misidentification rates per background information trait.</p

Biplot from principal component analysis (PCA) of Fourier morphometrics.

<p>Shapes of points correspond to female (circle; <i>n</i> = 20) and males (diamond; <i>n</i> = 30) of <i>Lampsilis teres</i> (Yellow Sandshell) from Yegua Creek; gradient colors correspond to observer misidentification rates for each specimen. Polygons enclose convex hulls of each sex (solid line = females; dashed line = males). Outlined shell shapes represent a mean shape (top-right) and ± 2 × standard deviations on PC1 and PC2 axes.</p

Parameter estimates, standard errors (SE), 95% highest posterior probability density (95% HPD) intervals, odds ratios (OR), and median odd ratios (MOR) based on logistic regression models relating misidentification of sex with personal background information.

<p>Parameter estimates, standard errors (SE), 95% highest posterior probability density (95% HPD) intervals, odds ratios (OR), and median odd ratios (MOR) based on logistic regression models relating misidentification of sex with personal background information.</p

Misidentification of sex for <i>Lampsilis teres</i>, Yellow Sandshell, and its implications for mussel conservation and wildlife management

<div><p>Correct identification of sex is an important component of wildlife management because changes in sex ratios can affect population viability. Identification of sex often relies on external morphology, which can be biased by intermediate or nondistinctive morphotypes and observer experience. For unionid mussels, research has demonstrated that species misidentification is common but less attention has been given to the reliability of sex identification. To evaluate whether this is an issue, we surveyed 117 researchers on their ability to correctly identify sex of <i>Lampsilis teres</i> (Yellow Sandshell), a wide ranging, sexually dimorphic species. Personal background information of each observer was analyzed to identify factors that may contribute to misidentification of sex. We found that median misidentification rates were ~20% across males and females and that observers falsely identified the number of female specimens more often (~23%) than males (~10%). Misidentification rates were partially explained by geographic region of prior mussel experience and where observers learned how to identify mussels, but there remained substantial variation among observers after controlling for these factors. We also used three morphometric methods (traditional, geometric, and Fourier) to investigate whether sex could be more correctly identified statistically and found that misidentification rates for the geometric and Fourier methods (which characterize shape) were less than 5% (on average 7% and 2% for females and males, respectively). Our results show that misidentification of sex is likely common for mussels if based solely on external morphology, which raises general questions, regardless of taxonomic group, about its reliability for conservation efforts.</p></div

Population Structure of Alligator Gar in a Gulf Coast River: Insights from Otolith Microchemistry and Genetic Analyses

<p>Growing interest in the Alligator Gar <i>Atractosteus spatula</i> among anglers and fishery managers has inspired efforts to better manage populations. Successful management requires identifying population structure and understanding the distribution of stocks and associated differences in life history. This is particularly important in river systems along the coast of the Gulf of Mexico, where transitions from freshwater rivers to saltwater bays provide the potential for life history diversification. We used otolith microchemistry and genetics to assess population structure of Alligator Gars in the Guadalupe River–San Antonio Bay system, Texas. Lifetime Sr:Ca revealed three, distinct life histories that differed in prevalence across the system. River-resident fish (i.e., fish exclusive to freshwater) were present throughout the river but were most common in the uppermost river reach (74% of upper river fish). Transient fish that used both river and bay habitats were also found throughout the river but were most prevalent in the lowermost river reach (66% of lower river fish) and bay (91% of bay fish). Bay residents (i.e., fish exclusive to salt water) were detected but comprised only 9% of bay fish. Haplotype diversity based on mitochondrial DNA was lowest in the upper river, indicating limited gene flow compared with the lower river and bay. Similarly, nuclear DNA analyses indicated nonrandom mating between fish from the upper river, lower river, and bay. The differences in Alligator Gar movement and genetics along the river–bay continuum suggest the presence of a river resident stock that predominates the upper river, and a transient stock that predominates the lower river and bay. Therefore, a local-scale management approach, consistent with the spatial partitioning between stocks, would conserve life history and genetic diversity within the system and provide opportunities to meet the needs of a diverse angling constituency. Understanding how population dynamics differ between stocks is needed to develop appropriate fishery management objectives and corresponding regulations for Alligator Gar.</p> <p>Received May 20, 2016; accepted December 2, 2016 Published online February 27, 2017</p