SIZE AND BAG LIMITS IN RECREATIONAL FISHERIES: THEORETICAL AND EMPIRICAL ANALYSIS

Size and bag limits are among the most common forms of regulations for recreational fisheries. In this paper, we theoretically study and compare the short- and long-term impacts of these policies on individual anglers and fish stocks. Particular attention is paid to the issue of release mortality, which can have important consequences for policy effectiveness. Theoretically, we show the conditions under which these policies will be successful in achieving biological objectives. Implications for recreation demand analysis are discussed. We also study these policies using a simulation model of various policy combinations for the Gulf of Mexico red snapper fishery.Resource /Energy Economics and Policy,

ECONOMIC EFFICIENCY OF ALTERNATIVE BYCATCH-REDUCTION POLICIES AND BYCATCH REDUCTION DEVICES

This paper examines the ability of two new policies to reduce bycatch of red snapper by the shrimp fishery in the Gulf of Mexico: Fractional License and Fractional Gear Programs, as proposed by Townsend, reduce bycatch by reducing the effort levels of shrimp vessels. The policies are evaluated both theoretically and using a simulation model, and they are compared with the current regulatory policy requiring shrimp vessels to use bycatch reduction devices to rebuild red snapper stocks. We find that either a FL program or a FG program could reduce effort and the related problem of bycatch resulting in improving red snapper stocks, while at the same time increasing economic welfare in the fishery.Resource /Energy Economics and Policy,

Transferable Rights of Recreational Fishery: An Application to Red Snapper Fishery in the Gulf of Mexico

Transferable rights (TRs) programs are being increasingly considered in fisheries to overcome current overfishing situation. This paper will focus on developing a conceptual foundation, investigating advantages of the TRs program in fishery management, and answering critical issues to implement recreational TRs programs. Implication is to the Gulf of Mexico red snapper fishery.Transferable Rights, Individual Transferable Quota, Recreational Fishery, Resource /Energy Economics and Policy, Q22,

Joint Estimation of Revealed and Stated Preference Data: An Application to Recreational Red Snapper Valuation

This study extends the joint estimation of revealed and stated preference data literature by accounting for truncation in the revealed preference data. The analytical model and estimation procedure are used to estimate the value of recreational red snapper fishing in the Gulf of Mexico. This recreational red snapper valuation is decomposed into its direct and indirect components. As expected, the value of recreational red snapper fishing using the joint revealed-stated preference model proposed in this analysis is bracketed on the upper limit by the value obtained using the contingent valuation method and on the lower limit by the travel cost method. The results also indicate that the joint model improves the precision of estimated recreational red snapper valuation.Resource /Energy Economics and Policy,

ESTIMATED COSTS AND RETURNS FOR CATFISH FARMS WITH RECIRCULATING PONDS ALONG THE UPPER TEXAS COAST

Cost, returns, and economies of scale for small, medium and large catfish farms with recirculating ponds are presented for the upper Texas coast. Internal rates of return are 0.150, 0.183 and 0.219, respectively. Total investment is higher than farms with static ponds but investment per unit production capacity is 7 percent to 16 percent lower. Average total cost per pound is between $0.565 and$0.541, (11 percent –20 percent lower than farms using current technology). These results have implications for regional comparative advantage of catfish production as well as incentive for adoption of new technology in conventional ponds.Aquaculture, Catfish, Economics, Off-flavor, Livestock Production/Industries,

Combined liver-kidney transplantation: Analysis of patients with preformed lymphocytotoxic antibody

In this report, we address combined liver-kidney transplantation, with particular attention to the apparent phenomenon of protection of kidney allografts to antibody mediated destruction by liver allografts. Four patients were found to have positive crossmatch before the liver phase of the combined transplant (pre-OT/KT samples). These positive crossmatches were due entirely to anti-HLA class I antibodies, as demonstrated by their removal by immunoabsorption on pololed platelets. In three of these patients, post-OT/pre-KT samples showed a conversion to a negative crossmatch (in the fourth patient this was not done). A kidney allograft, harveted from the same donor, was then placed into the recipient, and in patients no. 3, 7, and 12, good initial function was noted. In one of these patients was there evidence of hyperacute rejection. Post-OT/KT samples were collected in patients no. 3, 7, and 8, and then analyzed for the reappearance of donor specific lymphocytotoxic antibodies in the posttransplant period (data on patient no. 12 was not available at time of preparation). Lymphocytotoxic antibodies with donor specificity could not be detected in any of the samples during the first week posttransplant. The decrease in %PRA and conversion of a positive to negative crossmatch following liver transplantation was correlated to the HLA specificty of the antibody found in the pretransplant serum and the HLA type of the tranplanted organs. In the two instances where an HLA specificity could be determined by panel analysis, transplantation with donor organs bearing these HLA specificities led to a specific disppearance of these antibodies during the postransplant phase

Self-consistent perturbation expansion for Bose-Einstein condensates satisfying Goldstone's theorem and conservation laws

Quantum-field-theoretic descriptions of interacting condensed bosons have suffered from the lack of self-consistent approximation schemes satisfying Goldstone's theorem and dynamical conservation laws simultaneously. We present a procedure to construct such approximations systematically by using either an exact relation for the interaction energy or the Hugenholtz-Pines relation to express the thermodynamic potential in a Luttinger-Ward form. Inspection of the self-consistent perturbation expansion up to the third order with respect to the interaction shows that the two relations yield a unique identical result at each order, reproducing the conserving-gapless mean-field theory [T. Kita, J. Phys. Soc. Jpn. 74, 1891 (2005)] as the lowest-order approximation. The uniqueness implies that the series becomes exact when infinite terms are retained. We also derive useful expressions for the entropy and superfluid density in terms of Green's function and a set of real-time dynamical equations to describe thermalization of the condensate.Comment: 15 pages, 6 figures, to appear in Phys. Rev.

Hydrodynamic modes in a trapped Bose gas above the Bose-Einstein transition

We discuss the collective modes of a trapped Bose gas in the hydrodynamic regime where atomic collisions ensure local thermal equilibrium for the distribution function. Starting from the conservation laws, in the linearized limit we derive a closed equation for the velocity fluctuations in a trapped Bose gas above the Bose-Einstein transition temperature. Explicit solutions for a parabolic trap are given. We find that the surface modes have the same dispersion relation as the one recently obtained by Stringari for the oscillations of the condensate at $T=0$ within the Thomas-Fermi approximation. Results are also given for the monopole ``breathing'' mode as well as for the $m=0$ excitations which result from the coupling of the monopole and quadrupole modes in an anisotropic parabolic well.Comment: 4 pages, no figure, submitted to Phys. Rev. Let

First Results from SPARO: Evidence for Large-Scale Toroidal Magnetic Fields in the Galactic Center

We have observed the linear polarization of 450 micron continuum emission from the Galactic center, using a new polarimetric detector system that is operated on a 2 m telescope at the South Pole. The resulting polarization map extends ~ 170 pc along the Galactic plane and ~ 30 pc in Galactic latitude, and thus covers a significant fraction of the central molecular zone. Our map shows that this region is permeated by large-scale toroidal magnetic fields. We consider our results together with radio observations that show evidence for poloidal fields in the Galactic center, and with Faraday rotation observations. We compare all of these observations with the predictions of a magnetodynamic model for the Galactic center that was proposed in order to explain the Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude that the observations are basically consistent with the model.Comment: 11 pages, 2 figures, 1 table, submitted to ApJ Let