Changes in Fish Catch Rates in the Presence of Air Gun Sounds in Prudhoe Bay, Alaska

Air guns used in oil industry seismic surveys have the capacity to change fish catch rates, but no previous work has demonstrated this effect in shallow water or in Arctic oilfields. Long-term monitoring of fish catches using four fyke nets allowed assessment of changes in catch rates during a 2014 seismic survey in Prudhoe Bay, Alaska. Fyke net locations were instrumented with both conventional hydrophones and vector sensors. Catch rates were generally within the range of those found in 27 previous sampling seasons. The effect of air guns on eight species was assessed using a modified Before-After/Control-Impact analysis, with historical data and 2014 data as the Before-After components of the analysis and days without and with air gun activity as the Control-Impact components. Results showed significant changes associated with air guns in catch rates at one or more nets at p < 0.1 for all eight species and at p < 0.05 for seven of the eight. Changes included both increased and decreased catch rates, perhaps reflecting displacement of fish in response to air gun sounds throughout the study area. Measured sound pressure levels associated with air gun pulses were low and usually undetectable close to the fyke nets, reflecting the loss of low frequencies in shallow water (~1.5 m). Attempts to measure particle velocities failed when wind-driven surface waves overwhelmed vector sensors. However, fish responses may have been related to changes in particle motion associated with air gun sounds.Les armes à air comprimé dont on se sert pour faire les levés sismiques dans l’industrie pétrolière ont la capacité de changer le taux de capture des poissons, mais aucune étude n’a jamais démontré l’effet de ces armes dans les eaux peu profondes ou dans les champs pétrolifères de l’Arctique. La surveillance à long terme des prises de poissons à l’aide de quatre verveux a permis d’évaluer les changements en matière de taux de prises pendant un levé sismique qui a eu lieu à Prudhoe Bay, Alaska, en 2014. Les emplacements de verveux ont été munis d’hydrophones classiques et de capteurs de vecteur. De manière générale, les taux de prises coïncidaient avec la gamme répertoriée au cours des 27 saisons d’échantillonnage précédentes. L’effet des armes à air comprimé sur huit espèces a été évalué au moyen d’une analyse modifiée avant-après/contrôle-impact, les données historiques et les données de 2014 représentant les composantes avant-après de l’analyse, puis les jours avec et les jours sans activité d’armes à air comprimé représentant les composantes contrôle-impact de l’analyse. Les résultats ont permis de constater d’importants changements liés à l’emploi d’armes à air comprimé pour ce qui est des taux de prises à un ou plusieurs verveux, à p < 0,1 pour les huit espèces, et à p < 0,05 pour sept des huit espèces. Les changements se sont caractérisés à la fois par des taux de prises plus élevés et moins élevés, ce qui reflétait peut-être le déplacement des poissons en raison du son des armes à air comprimé dans la zone visée par l’étude. Les niveaux de pression sonore mesurés en lien avec les impulsions d’armes à air comprimé étaient faibles et habituellement indétectables à proximité des verveux, signe de la perte des ondes kilométriques dans l’eau peu profonde (~1,5 m). Les tentatives de mesure des vitesses acoustiques des particules ont échoué lorsque les ondes de surface poussées par le vent submergeaient les capteurs de vecteur. Toutefois, la réaction des poissons aurait pu être liée aux changements sur le plan du mouvement des particules découlant du son des armes à air comprimé

Itinerant electron metamagnetism in LaCo9_9Si4_4

The strongly exchange enhanced Pauli paramagnet LaCo$_9$Si$_4$ is found to exhibit an itinerant metamagnetic phase transition with indications for metamagnetic quantum criticality. Our investigation comprises magnetic, specific heat, and NMR measurements as well as ab-initio electronic structure calculations. The critical field is about 3.5 T for $H||c$ and 6 T for $H\bot c$, which is the lowest value ever found for rare earth intermetallic compounds. In the ferromagnetic state there appears a moment of about 0.2 $\mu_B$/Co at the $16k$ Co-sites, but sigificantly smaller moments at the 4d and $16l$ Co-sites.Comment: 11 pages, 5 figures, PRB Rapid Communication, in prin

Statistical Theory of Spin Relaxation and Diffusion in Solids

A comprehensive theoretical description is given for the spin relaxation and diffusion in solids. The formulation is made in a general statistical-mechanical way. The method of the nonequilibrium statistical operator (NSO) developed by D. N. Zubarev is employed to analyze a relaxation dynamics of a spin subsystem. Perturbation of this subsystem in solids may produce a nonequilibrium state which is then relaxed to an equilibrium state due to the interaction between the particles or with a thermal bath (lattice). The generalized kinetic equations were derived previously for a system weakly coupled to a thermal bath to elucidate the nature of transport and relaxation processes. In this paper, these results are used to describe the relaxation and diffusion of nuclear spins in solids. The aim is to formulate a successive and coherent microscopic description of the nuclear magnetic relaxation and diffusion in solids. The nuclear spin-lattice relaxation is considered and the Gorter relation is derived. As an example, a theory of spin diffusion of the nuclear magnetic moment in dilute alloys (like Cu-Mn) is developed. It is shown that due to the dipolar interaction between host nuclear spins and impurity spins, a nonuniform distribution in the host nuclear spin system will occur and consequently the macroscopic relaxation time will be strongly determined by the spin diffusion. The explicit expressions for the relaxation time in certain physically relevant cases are given.Comment: 41 pages, 119 Refs. Corrected typos, added reference

Meta-analysis of nature conservation values in Asia & Oceania: Data heterogeneity and benefit transfer issues

We conduct a meta-analysis (MA) of around 100 studies valuing nature conservation in Asia and Oceania. Dividing our dataset into two levels of heterogeneity in terms of good characteristics (endangered species vs. nature conservation more generally) and valuation methods, we show that the degree of regularity and conformity with theory and empirical expectations is higher for the more homogenous dataset of contingent valuation of endangered species. For example, we find that willingness to pay (WTP) for preservation of mammals tends to be higher than other species and that WTP for species preservation increases with income. Increasing the degree of heterogeneity in the valuation data, however, preserves much of the regularity, and the explanatory power of some of our models is in the range of other MA studies of goods typically assumed to be more homogenous (such as water quality). Subjecting our best MA models to a simple test forecasting values for out-of-sample observations, shows median (mean) forecasting errors of 24 (46) percent for endangered species and 46 (89) percent for nature conservation more generally, approaching levels that may be acceptable in benefit transfer for policy use. We recommend that the most prudent MA practice is to control for heterogeneity in regressions and sensitivity analysis, rather than to limit datasets by non-transparent criteria to a level of heterogeneity deemed acceptable to the individual analyst. However, the trade-off will always be present and the issue of acceptable level of heterogeneity in MA is far from settle

Recovery of the cave crayfish (Decapoda: Cambridae) population in Peacock Springs, Florida?

Volume: 22Start Page: 61End Page: 6

A Comparison of Fish Populations from Natural and Constructed Freshwater Marshes in Central Florida

In Florida, freshwater marshes are constructed as mitigation for wetland loss associated with phosphate strip mining, but little is known regarding the similarity of fish communities in natural and constructed marshes. Fish from five constructed and eight natural marshes were sampled quarterly via throw-traps for one year. Gambusia holbrooki, Heterandria formosa, Poecilia latiuinna, Elassoma everqladei, Fundulus chrysotus, Jordanella floridae, Fundulus rubifrons, and unidentified juvenile centrarchids were found in both constructed and natural marshes, while Lucania goodei was found only in constructed marshes. A comparison between constructed and natural marsh populations showed that differences in mean abundance and biomass at p \u3c 0.05 (Wilcoxon rank-sum teat) were present for G. holbrooki and E. everqladei. Differences in populations may be attributed to differences in conditions found in constructed and natural marshes