EQUIVALENCIES IN THE FISHERY

Abstract We consider the management of a resource by a sole owner whose utility depends on income and leisure. Income is generated from time spent harvesting the resource and time spent working for a wage in the nonfishing sector. Our analysis produces two results. (i) The sole owner maximizing discounted utility will seek to achieve the same steady‐state optimum as a manager seeking to maximize discounted net revenue. (ii) The approach paths to the common steady‐state optimum will be the same if the utility function is linear in income and separable in income and leisure. These equivalencies are illustrated in a numerical example.     

Recreation of Wöhler’s Synthesis of Urea: An Undergraduate Organic Laboratory Exercise

An undergraduate laboratory exercise appropriate to the upper-level organic or inorganic course is presented. The objective of the laboratory is to recreate an experiment of historical significance familiar to organic chemistry students while also incorporating modern techniques of spectroscopic characterization and purification.     

ON THE STRUCTURE OF COHOMOLOGY RINGS OF p-NILPOTENT LIE ALGEBRAS

In this paper the authors investigate the structure of the restricted Lie algebra cohomology of p-nilpotent Lie algebras with trivial p-power operation. Our study is facilitated by a spectral sequence whose E ₂-term is the tensor product of the symmetric algebra on the dual of the Lie algebra with the ordinary Lie algebra cohomology and converges to the restricted cohomology ring. In many cases this spectral sequence collapses, and thus, the restricted Lie algebra cohomology is Cohen–Macaulay. A stronger result involves the collapsing of the spectral sequence and the cohomology ring identifying as a ring with the E ₂-term. We present criteria for the collapsing of this spectral sequence and provide some examples where the ring isomorphism fails. Furthermore, we show that there are instances when the spectral sequence does not collapse and yields cohomology rings which are not Cohen-Macaulay.     

OPEN ACCESS AND EXTINCTION OF THE PASSENGER PIGEON IN NORTH AMERICA

ABSTRACT. An open access model is formulated where X is a renewable resource and E is the level of effort devoted to harvest. Net growth is assumed to exhibit critical depensation and the open access system is described by two nonlinear differential equations where r > 0 is the intrinsic growth rate, K1 is the minimum viable population level, K₂ is the environmental carrying capacity, K₂ > K₁ > 0, q > 0 is the catchability coefficient, ? > 0 is an adjustment coefficient, (p – s) > 0 is the market price net of shipping cost, and c > 0 is the unit cost of effort at the harvest site. It is shown that the E= 0 isocline is a vertical line at X∞=c/[(p‐ s)q] and that the open access system passes through a supercritical Hopf bifurcation as X∞ moves from a level above (K₁+K₂)/2 to a level below (K₁+K₂)/2. For X∞ above (K₁+K₂)/2 the open access equilibrium is locally stable. For X∞ below (K₁+K₂)/2 the open access equilibrium will be locally unstable. At X∞=(K₁+K₂)/2 the system has a stable limit cycle. This analysis is useful in interpreting the economic history of the passenger pigeon. The limited empirical evidence would suggest that X∞=c/[(p – s)q] declined below (K₁+K₂)/2 during the last half of the 19th century as a result of improved rail transport and communications (the telegraph). It is thought that the passenger pigeon was extinct in the wild by 1901. The last passenger pigeon died in captivity at the Cincinnati Zoological Gardens on September 1, 1914. X=rX(X/ K₁– 1)(1 –X/K₂)–qXE and E=α[(p – s)qXE – cE],     

DESIGNING FISHERY MODELS: A PERSONAL ADVENTURE

ABSTRACT. This paper describes my experiences designing fishery models, starting from a mathematical background in the differential equations of theoretical physics. Three examples from my early research, cited by Quinn in the lead article for this issue, illustrate a historical approach to model design. Although such analytical results provide useful tools for thought, they sometimes gloss over important assumptions and limitations. I describe the series of questions that led me from simple models to a more complete statistical framework, involving state space models and Bayes statistics. Modern fishery models often grow into complex structures that depend on numerous arbitrary choices about underlying deterministic processes, process error, and measurement error. Given this inherent ambiguity and uncertainty, I discuss scientific limits to quantitative fishery models and future prospects for devising robust management algorithms.     

A PREDICTIVE MODEL TO INFORM ADAPTIVE MANAGEMENT OF DOUBLE‐CRESTED CORMORANTS AND FISHERIES IN MICHIGAN

The proliferation of double‐crested cormorants (DCCOs; Phalacrocorax auritus) in North America has raised concerns over their potential negative impacts on game, cultured and forage fishes, island and terrestrial resources, and other colonial water birds, leading to increased public demands to reduce their abundance. By combining fish surplus production and bird functional feeding response models, we developed a deterministic predictive model representing bird–fish interactions to inform an adaptive management process for the control of DCCOs in multiple colonies in Michigan. Comparisons of model predictions with observations of changes in DCCO numbers under management measures implemented from 2004 to 2012 suggested that our relatively simple model was able to accurately reconstruct past DCCO population dynamics. These comparisons helped discriminate among alternative parameterizations of demographic processes that were poorly known, especially site fidelity. Using sensitivity analysis, we also identified remaining critical uncertainties (mainly in the spatial distributions of fish vs. DCCO feeding areas) that can be used to prioritize future research and monitoring needs. Model forecasts suggested that continuation of existing control efforts would be sufficient to achieve long‐term DCCO control targets in Michigan and that DCCO control may be necessary to achieve management goals for some DCCO‐impacted fisheries in the state. Finally, our model can be extended by accounting for parametric or ecological uncertainty and including more complex assumptions on DCCO–fish interactions as part of the adaptive management process.     

ON THE ECONOMICS OF BIOLOGICAL INVASION: AN APPLICATION TO RECREATIONAL FISHING

Abstract The paper demonstrates four general mechanisms that may affect economically valuable species when exposed to biological invasion. We distinguish between an ecological level effect and an ecological growth effect. In addition, we present an economic quantity effect working through demand. Finally, we suggest that there is an economic quality effect that reflects the possibility that invasions affect the harvesting agents directly through demand‐side forces. For example, this may occur because the state of the original species or the ecosystem is altered. We depart from the existing literature by revealing ecological and economic forces that explain why different agents may lack incentives to control invasions. The theoretical model is illustrated by the case where escaped farmed salmon (EFS) influence wild Atlantic salmon fisheries.     

丰中子奇A核145,147Ce的集体带结构

通过对²⁵²Cf自发裂变产生的瞬发γ谱的测量,对丰中子奇A核^145,147Ce的高自旋态进行了研究,首次识别了¹⁴⁵Ce的集体带结构,扩展了¹⁴⁷Ce的集体带结构,扩展了¹⁴⁷Ce的能级,并新识别了3个边带,粒子–转子模型的计算指出,^145,147Ce的晕带可能来自于νi_13/2轨道的耦合,¹⁴⁵Ce基态起源于(νh_9/2νf_7/2)组态混合,而¹⁴⁷Ce基态则起源于νh_9/2轨道.在这两个核中未观测到明显的八极形变带,然而,在¹⁴⁷Ce中观测到的一个边带,可能显露出八极关联的迹象.     

Collective Band Structures in Neutron-Rich Odd-A 145,147Ce Nuclei

Through study of the prompt r-rays emitted in the spontaneous fission of ²⁵²Cf, high spin states of neutron-rich odd-A ^145,147Ce nuclei have been investigated. The levels in ¹⁴⁷Ce have been extended. A collective band in ¹⁴⁵Ce have been identified for the first time. The results from the particle rotor model calculations indicate that the yrast bands in ¹⁴⁵Ce and ¹⁴⁷Ce originate from vi_13/2 orbital coupling and the ground states of ¹⁴⁵Ce and ¹⁴⁷Ce originate from (vh_9/2,vf_7/2) and vh_9/2 configiration, respectively. No obvious octupole deformation was observed in these two isotopes, but a side band obtained in ¹⁴⁷Ce may show some octupole correlations.