Stock assessment of the Atlantic menhaden, Brevoortia tyrannus, fishery

A stock assessment of the Atlantic menhaden, Brevoortia tyrannus, fishery was conducted with purse-seine landings data from 1940 to 1984 and port sampling data from 1955 to 1984. These data were analyzed to determine growth rates, maximum sustainable yield (MSY), spawner-recruit relationships, and yield per recruit. Virtual population analysis was used to estimate stock size, year class size, and fishing mortality rates. Surplus production models produced estimates of MSY from 450 to 490 kmt compared with yields of 416to 436 kmt based roughly on maximum recruitment from a weak spawner-recruit relationship. Recruitment to age-I ranged from 1.2 to 14.8 billion fish for year classes 1955-81. Recent mean recruitment to age-I for the 1975-81 year classes averaged 5.7 billion fish and compared favorably with the mean of 7.7 billion age-I fish recruited during the late 1950's. Mean recruitment from recent years suggests possible coastwide yields of 416 to 481 kmt. Continued dominance of late age-2 spawners among the spawning stock is of concern, since the stock is at greater risk through poor recruitment if recent favorable environmental conditions change. Yield-per-recruit estimates ranged from 46 g to 59 g since 1970. The high dependency of the modern fishery on prespawners has increased concerns about fluctuations in year-to-year availability and catches. To increase yield and enhance the stability of the resource, the number of age classes contributing significantly to the fishery should be increased, creating a butTer against future poor recruitment years and lessening the year-to-year fluctuations in landings. (PDF file contains 24 pages.

Estimating the Inflation-Output Variability Frontier with Inflation Targeting: A VAR Approach

This paper (i) illustrates how a VAR model can be used to evaluate inflation targeting, (ii) derives the policy frontier available to the central bank using counterfactual experiments with real time data, and (iii) estimates how this frontier has changed over time in terms of the position and slope of the available tradeoff between output gap variability and inflation variability under inflation targeting. Various inflation targets are considered as are tolerance bands of varying width around these targets. The results indicate that over time (i) a given reduction in inflation variability is associated with a smaller rise in output variability and that (ii) a given inflation variability is achieved with smaller interest rate volatility. Consistent with the data, our results require federal funds rate persistence, though no instrument instability was observed.

Inflation Forecast Targeting: A VAR Approach

We show how to implement inflation forecast targeting using a VAR model and derive the implied inflation-output variability frontier. Our approach is based on dynamic, stochastic simulations of the average inflation rate over a two-year horizon using the moving average representation of the VAR model. Using real time data over two samples, we estimate the inflation-output variability frontier for the U.S. and show that it has shifted favorably over time. We consider the frequency and nature of the policy interventions required to achieve target inflation in both samples and compare these interventions over time.

Estimating the Inflation-Output Variability Frontier with Inflation Targeting: A VAR Approach

This paper (i) illustrates how a VAR model can be used to evaluate inflation targeting, (ii) derives the policy frontier available to the central bank using counterfactual experiments with real time data, and (iii) estimates how this frontier has changed over time in terms of the position and slope of the available tradeoff between output gap variability and inflation variability under inflation targeting. Various inflation targets are considered as are tolerance bands of varying width around these targets. The results indicate that over time (i) a given reduction in inflation variability is associated with a smaller rise in output variability and that (ii) a given inflation variability is achieved with smaller interest rate volatility. Consistent with the data, our results require federal funds rate persistence, though no instrument instability was observed. One interpretation of these results is that they reflect the growing credibility of the Federal Reserve.

Multipole Expansions of Aggregate Charge: How Far to Go?

Aggregates immersed in a plasma or radiative environment will have charge distributed over their extended surface. Previous studies have modeled the aggregate charge using the monopole and dipole terms of a multipole expansion, with results indicating that the dipole-dipole interactions play an important role in increasing the aggregation rate and altering the morphology of the resultant aggregates. This study examines the effect that including the quadrupole terms has on the dynamics of aggregates interacting with each other and the confining electric fields in laboratory experiments. Results are compared to modeling aggregates as a collection of point charges located at the center of each spherical monomer comprising the aggregate.Comment: 6 page

The GZK Bound and Strong Neutrino-Nucleon Interactions above 10^19eV: a Progress Report

Cosmic ray events above 10^19 eV have posed a fundamental problem for more than thirty years. Recent measurements indicate that these events do not show the features predicted by the GZK bound. The events may, in addition, display angular correlations with point sources. If these observations are confirmed for point sources further than 50 - 100 Mpc, then strong interactions for the neutrino are indicated. Recent work on extra spatial dimensions provides a context for massive spin-2 exchanges capable of generating cross sections in the 1 - 100 mb range, as indicated by data. Applications of extra-dimension physics are controversial, and we comment on several contentious issues.Comment: 4 pages, 1 figure; talk by JPR at 7th Conference on the Intersections of Particle and Nuclear Physics, Quebec City, May, 200