A Spatial Model of Dolphin Avoidance in the Eastern Tropical Pacific Ocean

This paper examines the impact of dolphin-safe eco-labeling and how it fundamentally altered the spatial distribution of fishing effort and fishermen's willingness to pay to avoid dolphins. To do this, a dynamic discrete choice econometric model is applied to the Eastern Tropical Pacific tuna fishery. This econometric approach combines a dynamic programming component with the static discrete site choice model. This estimator couples the current period projected profits associated with fishing a specific site with the value of all future location choices on the cruise, assuming choices are made optimally. The key feature of this model is that it recovers behavioral parameters and solves the dynamic programming problem recursively. The dynamic site choice model reveals a markedly higher impact on producers as compared to the commonly used static model following the labeling regime. Further, in all but a few cases the common practice in dynamic choice models of setting discount factors equal to one is rejected.Environmental Economics and Policy,

SHORT-RUN WELFARE LOSSES FROM ESSENTIAL FISH HABITAT DESIGNATIONS FOR THE SURFCLAM AND OCEAN QUAHOG FISHERIES

In this paper, we present a spatial model of fishing that can be used to assess some of the economic welfare losses to producers from setting aside essential fish habitat (EFH) areas. The paper demonstrates how spatially explicit behavioral models of fishing are estimated, how these models can be used to measure welfare losses to fishermen, and how these models can then, in turn, be used to simulate fishing behavior. In developing the spatial model of fishing behavior, the work incorporates ideas of congestion and information effects, and we show a modification of standard welfare measures that accounts for these spillover effects. Using this methodology, these effects are traced through to the policy simulations, where we demonstrate how these welfare and predicted shares need to be modified to account for spillover effects from fleet activity.Resource /Energy Economics and Policy,

Stellar and Molecular Gas Kinematics of NGC1097: Inflow Driven by a Nuclear Spiral

We present spatially resolved distributions and kinematics of the stars and molecular gas in the central 320pc of NGC1097. The stellar continuum confirms the previously reported 3-arm spiral pattern extending into the central 100pc. The stellar kinematics and the gas distribution imply this is a shadowing effect due to extinction by gas and dust in the molecular spiral arms. The molecular gas kinematics show a strong residual (i.e. non-circular) velocity, which is manifested as a 2-arm kinematic spiral. Linear models indicate that this is the line-of-sight velocity pattern expected for a density wave in gas that generates a 3-arm spiral morphology. We estimate the inflow rate along the arms. Using hydrodynamical models of nuclear spirals, we show that when deriving the accretion rate into the central region, outflow in the disk plane between the arms has to be taken into account. For NGC1097, despite the inflow rate along the arms being ~1.2Msun/yr, the net gas accretion rate to the central few tens of parsecs is much smaller. The numerical models indicate that the inflow rate could be as little as ~0.06Msun/yr. This is sufficient to generate recurring starbursts, similar in scale to that observed, every 20-150Myr. The nuclear spiral represents a mechanism that can feed gas into the central parsecs of the galaxy, with the gas flow sustainable for timescales of a Gigayear.Comment: accepted by Ap

AN INTRODUCTION TO SPATIAL MODELING IN FISHERIES ECONOMICS

Resource /Energy Economics and Policy,

Visualization of flows in a motored rotary combustion engine using holographic interferometry

The use of holographic interferometry to view the small- and large-scale flow field structures in the combustion chamber of a motored Wankel engine assembly is described. In order that the flow patterns of interest could be observed, small quantities of helium were injected with the intake air. Variation of the air flow patterns with engine speed, helium flow rate, and rotor position are described. The air flow at two locations within the combustion chamber was examined using this technique

Diffusion and Transport Coefficients in Synthetic Opals

Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the termal and electrical conductivity makes possible to estimate the transport coefficients of opal structures. We estimate this changes as function of the neck size and the mean-free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures.Comment: Submitted to PR

Short-run Welfare Losses from Essential Fish Habitat Designations for the Surfclam and Ocean Quahog Fisheries

In this paper, we present a spatial model of fishing that can be used to assess some of the economic welfare losses to producers from setting aside essential fish habitat (EFH) areas. The paper demonstrates how spatially explicit behavioral models of fishing are estimated, how these models can be used to measure welfare losses to fishermen, and how these models can then, in turn, be used to simulate fishing behavior. In developing the spatial model of fishing behavior, the work incorporates ideas of congestion and information effects, and we show a modification of standard welfare measures that accounts for these spillover effects. Using this methodology, these effects are traced through to the policy simulations, where we demonstrate how these welfare and predicted shares need to be modified to account for spillover effects from fleet activity

Strategic Substitutes or Complements? The Game of Where to Fish

The ‘‘global game with strategic substitutes and complements’’ of Karp et al. (2007) is used to model the decision of where to fish. A complete information game is assumed, but the model is generalized to S \u3e 1 sites. In this game, a fisherman’s payoff depends on fish density in each site and the actions of other fishermen which can lead to congestion or agglomeration effects. Stable and unstable equilibria are characterized, as well as notions of equilibrium dominance. The model is applied to the Alaskan flatfish fishery by specifying a strategic interaction function (response to congestion) that is a non-linear function of the degree of congestion present in a given site. Results suggest that the interaction function may be non-monotonic in congestion

A Close Look at Star Formation around Active Galactic Nuclei

We analyse star formation in the nuclei of 9 Seyfert galaxies at spatial resolutions down to 0.085arcsec, corresponding to length scales of less than 10pc in some objects. Our data were taken mostly with the near infrared adaptive optics integral field spectrograph SINFONI. The stellar light profiles typically have size scales of a few tens of parsecs. In two cases there is unambiguous kinematic evidence for stellar disks on these scales. In the nuclear regions there appear to have been recent - but no longer active - starbursts in the last 10-300Myr. The stellar luminosity is less than a few percent of the AGN in the central 10pc, whereas on kiloparsec scales the luminosities are comparable. The surface stellar luminosity density follows a similar trend in all the objects, increasing steadily at smaller radii up to 10^{13}L_sun/kpc^2 in the central few parsecs, where the mass surface density exceeds 10^4M_sun/pc^2. The intense starbursts were probably Eddington limited and hence inevitably short-lived, implying that the starbursts occur in multiple short bursts. The data hint at a delay of 50--100Myr between the onset of star formation and subsequent fuelling of the black hole. We discuss whether this may be a consequence of the role that stellar ejecta could play in fuelling the black hole. While a significant mass is ejected by OB winds and supernovae, their high velocity means that very little of it can be accreted. On the other hand winds from AGB stars ultimately dominate the total mass loss, and they can also be accreted very efficiently because of their slow speeds.Comment: 51 pages, including 27 figures; accepted by ApJ (paper reorganised, but results & conclusions the same