Suitability of single-pass backpack electrofishing to estimate fish abundance and describe assemblage structure in prairie streams

Electrofishing is commonly used by fisheries professionals to assess fish assemblage structure and species abundance in streams. Accurate estimates of fish abundance and, consequently assemblage metrics, are typically generated with mark-recapture or maximum-likelihood depletion techniques, but doing so requires considerable sampling effort. Less intensive sampling approaches may be beneficial to fisheries managers, particularly in cases where frequent sampling of many streams is preferred. We used regression and Spearman rank-order correlation analyses to compare species catch rates and the assemblage metrics generated from single-pass electrofishing samples with multiple-pass depletion abundance estimates in Nebraska streams. We examined the influence of instream habitat features on the regression residuals to further examine the effectiveness of single-pass electrofishing. Our results suggest that single-pass electrofishing is suitable for wadeable prairie streams with relatively little habitat diversity. With few exceptions, fish species were detected and captured in similar quantities regardless of electrofishing effort, suggesting that single-pass sampling can be used to quickly assess species occurrence and relative abundance. The single- and multiple-pass electrofishing methods generated slightly different values for each assemblage metric; however, these values were not significantly different. Abundance was over- or underestimated in areas where certain species were congregated (e.g., overhanging vegetation: Red Shiner Cyprinella lutrensis, Bigmouth Shiner Notropis dorsalis, large substrates: Stonecat Noturus flavus, and darters) or difficult to sample (e.g., woody debris: Largemouth Bass Micropterus salmoides and Western Mosquitofish Gambusia affinis) using only one electrofishing pass. Single-pass electrofishing offers a reliable alternative to the more intensive multiple-pass depletion techniques; however, caution should be applied in difficult to sample areas with unique habitats

Morphological and genetic analyses in the Melanoplus packardii group (Orthoptera: Acrididae)

Melanoplus packardii Scudder was described in 1897. Three additional closely-related species were later described and their status as species has been questioned on numerous occasions. We examined morphology from specimens collected in Nebraska which fit descriptions of three of the four forms and specimens that appeared to be hybrids. We found distinct morphological characters suggesting species status for M. foedus and M. packardii, but not for M. foedus fluviatilis. Examination of aedeagi of these three forms suggests that M. foedus and M. packardii are each distinct, but that the aedeagi of M. f. fluviatilis and M. f. foedus cannot be distinguished. Molecular analyses of the three groups did not produce clear separations and suggest gene exchange between these three forms may be ongoing. Together, these data suggest that M. foedus and M. packardii should be recognized as sibling species, but M. foedus fluviatilis is best considered a form of M. foedus, typically found in low lying areas

Morphological and genetic analyses in the Melanoplus packardii group (Orthoptera: Acrididae)

Melanoplus packardii Scudder was described in 1897. Three additional closely-related species were later described and their status as species has been questioned on numerous occasions. We examined morphology from specimens collected in Nebraska which fit descriptions of three of the four forms and specimens that appeared to be hybrids. We found distinct morphological characters suggesting species status for M. foedus and M. packardii, but not for M. foedus fluviatilis. Examination of aedeagi of these three forms suggests that M. foedus and M. packardii are each distinct, but that the aedeagi of M. f. fluviatilis and M. f. foedus cannot be distinguished. Molecular analyses of the three groups did not produce clear separations and suggest gene exchange between these three forms may be ongoing. Together, these data suggest that M. foedus and M. packardii should be recognized as sibling species, but M. foedus fluviatilis is best considered a form of M. foedus, typically found in low lying areas

Oklahoma's bird grasshoppers

The Oklahoma Cooperative Extension Service periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Does Tribolium brevicornis Cuticular Chemistry Deter Cannibalism and Predation of Pupae?

The cuticular hydrocarbons of insects are species-specific and often function as semiochemicals. The activity of Tribolium brevicornis cuticular hydrocarbons as feeding deterrents that ostensibly function to prevent pupal cannibalism and predation was evaluated. The cuticular hydrocarbons of T. brevicornis pupae were characterized and flour disk bioassays conducted with individual and combined extract components incorporated into artificial diets on which Tribolium adults fed for six days. Feeding by T. brevicornis and T. castaneum on flour disks containing cuticular extracts of T. brevicornis pupae resulted in reduced consumption and weight loss relative to feeding on control flour disks. In both cases, feeding deterrence indices exceeded 80% suggesting that T. brevicornis cuticular hydrocarbons could function to deter cannibalism and predation of pupae by larvae and adult beetles. Sixteen different cuticular hydrocarbons were identified in T. brevicornis pupal extracts. Eight of the commercially available linear alkanes were tested individually in feeding trials with eight Tribolium species. One compound (C28) significantly reduced the amount of food consumed by three species compared to control disks, whereas the compounds C25, C26, and C27 elicited increased feeding in some species. Four other compounds had no effect on consumption for any species. When four hydrocarbon mixtures were tested for synergistic deterrence on T. brevicornis and T. castaneum, none significantly influenced consumption. Our results indicate that the cuticular chemistry of T. brevicornis pupae could serve to deter predation by conspecific and congeneric beetles

Short-term acclimation in adults does not predict offspring acclimation potential to hypoxia

Abstract The prevalence of hypoxic areas in coastal waters is predicted to increase and lead to reduced biodiversity. While the adult stages of many estuarine invertebrates can cope with short periods of hypoxia, it remains unclear whether that ability is present if animals are bred and reared under chronic hypoxia. We firstly investigated the effect of moderate, short-term environmental hypoxia (40% air saturation for one week) on metabolic performance in adults of an estuarine amphipod, and the fitness consequences of prolonged exposure. We then reared the offspring of hypoxia-exposed parents under hypoxia, and assessed their oxyregulatory ability under declining oxygen tensions as juveniles and adults. Adults from the parental generation were able to acclimate their metabolism to hypoxia after one week, employing mechanisms typically associated with prolonged exposure. Their progeny, however, did not develop the adult pattern of respiratory regulation when reared under chronic hypoxia, but instead exhibited a poorer oxyregulatory ability than their parents. We conclude that species apparently hypoxia-tolerant when tested in short-term experiments, could be physiologically compromised as adults if they develop under hypoxia. Consequently, we propose that the increased prevalence of hypoxia in coastal regions will have marked effects in some species currently considered hypoxia tolerant

Generating route-level mutually exclusive service areas: comparative study of alternative methods

Willing-to-walk distance was investigated as a means of measuring spatial accessibility of bus stops and of examining the effectiveness of alternative methods of generating mutually exclusive transit service areas at the route level. First, the walking distance to and from a transit stop was investigated with onboard survey data. Two methods in geographical information systems - the combination of Thiessen polygon and buffer and the network distance-based service area - were compared as strategies for generating mutually exclusive service areas. For the examination of the effectiveness of these two methods, all mutually exclusive service areas were validated with a spider diagram generated from an onboard survey. Measures of urban form were also statistically tested for comparison of the two methods. A case study of a single route, serving the Minneapolis-Saint Paul, Minnesota, metropolitan area, was performed with data from various sources, such as Google's General Transit Feed Specification, an onboard survey, parcel-level land uses, and the U. S. Census street network. Validation with onboard survey data demonstrates the strengths of each method. Results also show that the network-based service area, a popular geographical information system method for service area analysis, does not yield a more meaningful strategy for generating mutually exclusive transit catchment areas, especially when spacing between stops is very small

Can Oxygen Set Thermal Limits in an Insect and Drive Gigantism?

Contains fulltext : 111575.pdf (publisher's version ) (Open Access

GW190412: Observation of a Binary-Black-Hole Coalescence with Asymmetric Masses

We report the observation of gravitational waves from a binary-black-hole coalescence during the first two weeks of LIGO’s and Virgo’s third observing run. The signal was recorded on April 12, 2019 at 05∶30∶44 UTC with a network signal-to-noise ratio of 19. The binary is different from observations during the first two observing runs most notably due to its asymmetric masses: a ∼30 M_⊙ black hole merged with a ∼8 M_⊙ black hole companion. The more massive black hole rotated with a dimensionless spin magnitude between 0.22 and 0.60 (90% probability). Asymmetric systems are predicted to emit gravitational waves with stronger contributions from higher multipoles, and indeed we find strong evidence for gravitational radiation beyond the leading quadrupolar order in the observed signal. A suite of tests performed on GW190412 indicates consistency with Einstein’s general theory of relativity. While the mass ratio of this system differs from all previous detections, we show that it is consistent with the population model of stellar binary black holes inferred from the first two observing runs