David Cowley

New Mexico State University, Fish, Wildlife and Conservation Ecology, Faculty Member

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Papers by David Cowley

Optimizing the Allocation of Hatchery-Produced Fish among Multiple Stocking Sites

North American Journal of Fisheries Management, 2003

We describe a two-stage procedure to increase recreational angler use through optimal allocation ... more We describe a two-stage procedure to increase recreational angler use through optimal allocation of hatchery-produced fish among sites. In stage 1, data on historical fish stocking, angler-days, and attributes of individual fishing sites are used to formulate a regression equation that shows the relation between angler-days and the number of fish stocked (stocking elasticity). In stage 2, this stocking elasticity

Direct and Correlated Response to Selection in Osteometric Traits in the Rat

Bioscience, 1982

Aquatic resources in arid lands: Issues and opportunities

Aquatic Sciences, 2004

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Diatoms from gut contents of museum specimens of an endangered minnow suggest long-term ecological changes in the Rio Grande (USA

Journal of Paleolimnology, 2008

Diatoms consumed by Rio Grande silvery minnows (Hybognathus amarus) collected 104 years apart wer... more Diatoms consumed by Rio Grande silvery minnows (Hybognathus amarus) collected 104 years apart were used to deduce ecological requirements of this endangered species and to infer a possible cause of its decline based on environmental conditions in the Rio Grande. In 1874, foraged diatoms were largely motile, silt tolerant generalist and epipelic species (e.g. Navicula capitatoradiata, Navicula cryptotenella, Nitzschia palea, Sellaphora pupula) somewhat tolerant to pollution and indicative of eutrophic conditions, low dissolved oxygen, and high biological oxygen demand (BOD). In contrast, diatoms foraged in 1978 were mainly nonmotile epipsammic species (Fragilariaceae) sensitive to pollution and characteristic of low nutrient, oligotrophic conditions with high dissolved oxygen and low BOD. The large-scale difference in composition of the foraged diatom assemblages is consistent with a decline in nutrients and a shift in trophic state commonly associated with river regulation by dams. The results suggest that facilitating allochthonous input of detritus and nutrients into the Rio Grande ecosystem to meet foraging requirements for algivorous and detritivorous fish species such as H. amarus would be a good river restoration strategy.

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Science and Effective Policy for Managing Aquatic Resources

Reviews in Fisheries Science, 2006

Scientists often feel powerless to affect policy on natural resource conservation or management, ... more Scientists often feel powerless to affect policy on natural resource conservation or management, and managers frequently feel that there is not enough time or money to gather data to enlighten resource management decisions. This article summarizes the discussions in a facilitated workshop that brought together academicians, natural resource managers, and individuals from the private sector to discuss limitations in aquatic resource management policy and how science could be used more effectively in the decision-making process. A major impediment to including science in management and policy decision-making is insufficient dialogue between scientists and managers. For science-based resource management decisions, it is imperative to understand the distinction between science and professional judgment. The former is the acquisition of knowledge by applying the principles of the scientific method, whereas the latter may be based on science-in-progress, has not been subjected to peer review, and can be misrepresented to be science. Resource managers face significant problems making sound, science-based management decisions including: historical antecedents for resource use, changing social values, legal constraints, economics and politics, poorly focused management, plurality and diversity of stakeholders, and the credibility of agency-produced science. Effective conservation of aquatic resources can be undermined by distrust and disagreement between resource users, scientists, agencies, and even among academicians, leading to an atmosphere of "combat biology." The principles of science should be introduced early in the decision-making process because they encourage articulation of multiple perspectives and fair but rigorous assessment of all hypotheses.

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Strategies for Ecological Restoration of the Middle Rio Grande in New Mexico and Recovery of the Endangered Rio Grande Silvery Minnow

Reviews in Fisheries Science, 2006

... Numbers on the map: (1) McMillan and Avalon dams; (2) Elephant Butte Dam; (3) La Boquilla; (4... more

Across the great divide: genetic forensics reveals misidentification of endangered cutthroat trout populations

Molecular Ecology, 2007

Accurate assessment of species identity is fundamental for conservation biology. Using molecular ... more Accurate assessment of species identity is fundamental for conservation biology. Using molecular markers from the mitochondrial and nuclear genomes, we discovered that many putatively native populations of greenback cutthroat trout (Oncorhynchus clarkii stomias) comprised another subspecies of cutthroat trout, Colorado River cutthroat trout (Oncorhynchus clarkii pleuriticus). The error can be explained by the introduction of Colorado River cutthroat trout throughout the native range of greenback cutthroat trout in the late 19th and early 20th centuries by fish stocking activities. Our results suggest greenback cutthroat trout within its native range is at a higher risk of extinction than ever before despite conservation activities spanning more than two decades.

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Growing Trout in New Mexico Ponds

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Estimation of introgression in cutthroat trout populations using microsatellites

Conservation Genetics, 2007

Introgressive hybridization, mediated by anthropogenic activity, poses a threat to numerous and d... more Introgressive hybridization, mediated by anthropogenic activity, poses a threat to numerous and diverse taxa. The management of introgressed individuals or populations within species of conservation concern is currently the subject of scientific and political debate. We investigate the utility of 10 nondiagnostic microsatellite loci for investigating admixture from introduced Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri) and rainbow trout (O. mykiss) within 25 putative Rio Grande cutthroat trout (O. c. virginalis) populations. We apply five different approaches (correspondence analysis, maximum-likelihood assignment tests, an admixture estimator based on allele frequencies, an admixture estimator based on coalescent theory and an admixture estimator implementing a Bayesian method) and use two alternative O. c. virginalis reference samples. All approaches were capable of identifying one population that consisted entirely of introduced O. c. bouvieri, and three out of five approaches enabled us to discriminate those populations with relatively high levels of nonnative introgression from those populations with little or none. Actual estimates of admixture coefficients within a test population, varied, however, with the approach and reference sample used. These results have important implications for policies dividing populations into different management categories according to the estimated proportion of non-native genetic material that they contain.

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Population Genetics and Fishery Management. Edited by N. Ryman and F. Utter. Seattle, WA

Genetics Research, 1988

Effects of salinity on specific gravity and viability of eggs of a North American minnow (Cyprinidae

Scientia Marina, 2009

The influence of salinity on survival, specific gravity, and size of eggs of the endangered Hybog... more The influence of salinity on survival, specific gravity, and size of eggs of the endangered Hybognathus amarus (Rio Grande silvery minnow) was studied to provide insight into factors affecting their potential dispersal and fate. Under low salinity conditions egg specific gravity declined significantly in the first hour after spawning as the perivitelline space of the egg filled with water. Egg specific gravity achieved a minimum value approximately 1 h post-spawning and remained approximately constant until hatching, which occurred near 48 h post-spawning at 20ºC. Specific gravity of the egg depended on the salinity of the water surrounding the egg: hardened eggs changed rapidly in diameter and specific gravity when exposed to water of higher salinity. Size and specific gravity of H. amarus eggs also differed when the eggs were incubated in different groundwater sources. Experiments indicated that calcium chloride saline solution had a greater effect on egg specific gravity and size than did solutions of sodium or potassium chlorides. Survival of H. amarus eggs declined sharply at salinity greater than 3 (practical salinity units, PSU) and was only 5% at a salinity of 8. Habitat restoration to benefit H. amarus should consider the salinity of habitats in which eggs incubate.

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Preface: Conservation and Management of Aquatic Resources in Arid Lands

Reviews in Fisheries Science, 2006

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Competition between Hatchery-Raised Rio Grande Cutthroat Trout and Wild Brown Trout

North American Journal of Fisheries Management, 2007

... Brown Trout BARAK SHEMAI,1 ROSSANA SALLENAVE, AND DAVID E. COWLEY* Department of Fishery and ... more

Evolutionary Divergence, Shape Change, and Genetic Correlation Structure in the Rodent Mandible

Systematic Biology, 1992

... WILLIAM R. ATCHLEY, DAVID E. COWLEY, CLAUS VOGL, AND TRACY MCLELLAN1 Department of Genetics, ... more

Genetic prenatal maternal effects on organ size in mice and their potential contribution to evolution

Journal of Evolutionary Biology, 1991

were carried out in order to estimate the magnitude of prenatal maternal effects, independent of ... more were carried out in order to estimate the magnitude of prenatal maternal effects, independent of postnatal maternal factors, on the growth of internal organs and fat pads in mice. Reciprocal embryo transfers between the inbred mouse strains C3HeB/FeJ and SWR/J yielded three significant findings. First, all traits were not equally influenced by prenatal maternal factors. Genetic prenatal maternal factors, stemming from the genotype of the uterine mother, had a significant effect on testis weight, subcutaneous fat pad weight and epididymal fat pad weight in 21 day old progeny, but they had no effect on cranial capacity, an index of brain size, kidney weight, or liver weight. Prenatal litter size, defined as the sum of live and dead pups at birth, had a significant negative relationship with 21 day testis weight and kidney weight, and a significant positive association with subcutaneous and epididymal fat pad weights. Cranial capacity and liver weight at 21 days postnatally were not influenced by prenatal litter size. Second, the experiments demonstrated that there was ontogenetic variability in the strength of prenatal maternal effects. At 70 days of age, only subcutaneous fat pad weight was significantly influenced by genetic prenatal effects, and prenatal litter size had a significant negative relationship only with subcutaneous fat pad weight and body weight. Third, genetic prenatal effects had a significant influence on the among-trait covariances at 21 days postnatally, but not at 70 days. Because multivariate evolution involves covariances among characters, the latter results suggest that prenatal effects due to the mother's genotype can affect phenotypic evolution of mammals, especially for selection imposed early in life.

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Estimating required habitat size for fish conservation in streams

Aquatic Conservation-marine and Freshwater Ecosystems, 2008

1. A procedure is described to estimate viable population size and the area of habitat needed to ... more 1. A procedure is described to estimate viable population size and the area of habitat needed to support an endangered stream fish population. Monte Carlo simulations were used to evaluate population fates with stochastic demography and random variation simulated to cause age class 0 failures in some years. Viable population was defined in this paper to be large enough to have less than a 10% chance of extinction in 100 years and to have a long-term effective size of at least 500 breeding adults, although the method could be applied for any assumed extinction rate and effective size.

format_quoteRecommendation to manage for larger populations rather than minimum sizes to account for habitat quality variability and temporal demographic shifts.format_quote

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Ecology of the Rio Grande Silvery Minnow (Cyprinidae: Hybognathus amarus) Inferred from Specimens Collected in 1874

Reviews in Fisheries Science, 2006

... obtained from the literature; habitat types associated with specific taxa of diatoms were giv... more

Altering Developmental Trajectories in Mice by Restricted Index Selection

A restricted index selection experiment on mice was carried out for 14 generations on rate of ear... more A restricted index selection experiment on mice was carried out for 14 generations on rate of early postnatal development (growth rate from birth to 10 days of age) 11s. rate of development much later in ontogeny (growth rate from 28 to 56 days of age). Early rate of development ( E ) approximates hyperplasia (changes in cell number) and later rate (I,) reflects hypertropy (changes in cell size). The selection criteria were as follows: E+LO was selected to increase early body weight gain while holding late body weight gain constant; E-LO was selected to decrease early body gain while holding late gain constant; EOL+ was selected to increase late gain holding early gain constant; and EOL-was selected to decrease late gain holding early gain constant. After 14 generations of selection, significant divergence among lines has occurred and the changes in the growth trajectories are very close to expectation. The genetic and developmental bases of complex traits are discussed as well as the concept of developmental homoplasy.

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Development and Quantitative Genetics of Correlation Structure Among Body Parts of Drosophila melanogaster

American Naturalist, 1990

QUANTITATIVE GENETICS OF DROSOPHILA MELANOGASTER. I. SEXUAL DIMORPHISM IN GENETIC PARAMETERS FOR WING TRAITS

Sexual dimorphism in genetic parameters is examined for wing dimensions of Drosophila melanogaste... more Sexual dimorphism in genetic parameters is examined for wing dimensions of Drosophila melanogaster. Data are fit to a quantitative genetic model where phenotypic variance is a linear function of additive genetic autosomal variance (common to both sexes), additive genetic X-linked variances distinct for each sex, variance due to common rearing environment of families, residual environmental variance, random error variance due to replication, and variance due to measurement error and developmental asymmetry (left us. right sides). Polygenic dosage compensation and its effect on genetic variances and covariances between sexes is discussed. Variance estimates for wing length and other wing dimensions highly correlated with length support the hypothesis that the Drosophila system of dosage compensation will cause male X-linked genetic variance to be substantially larger than female X-linked variance. Results for various wing dimensions differ, suggesting that the level of dosage compensation may differ for different traits. Genetic correlations between sexes for the same trait are presented. Total additive genetic correlations are near unity for most wing traits; this indicates that selection in the same direction in both sexes would have a minor effect on changing the magnitude of difference between sexes. Additive X-linked correlations suggest some genotype X sex interactions for X-linked effects.

format_quoteX-linked variance plays a crucial role in estimating narrow-sense heritability, confounding standard heritability measures for each sex.format_quote

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