Keep it simple: three indicators to deal with overfishing

Three simple fisheries indicators are presented: (i) percentage of mature fish in catch, with 100% as target; (ii) percent of specimens with optimum length in catch, with 100% as target; and (iii) percentage of ‘mega-spawners‘ in catch, with 0% as target, and 30–40% as representative of reasonable stock structure if no upper size limit exists. Application of these indicators to stocks of Gadus morhua, Sardinella aurita and Epinephelus aeneus demonstrate their usefulness. It is argued that such simple indicators have the potential to allow more stakeholders such as fishers, fish dealers, supermarket managers, consumers and politicians to participate in fisheries management and eventually hold and reverse the global pattern of convenience overfishing, which is defined here as deliberate overfishing sanctioned by official bodies who find it more convenient to risk eventual collapse of fish stocks than to risk social and political conflicts

"We Knew no North, no South": U.S.-Mexican War Veterans and the Construction of Public Memory in the Post-Civil War United States, 1874-1897

In 1874, American veterans of the U.S.–Mexican War 1846–1848 formed the National Association of Veterans of the Mexican War (NAVMW). Until the organization’s demise in 1897, NAVMW members crafted and celebrated a vision of their war with Mexico as a national triumph which had united Americans from all sections of the Union in a common cause. This article examines how, by promoting this particular memory of the war to the American public, NAVMW members sought to remind their countrymen of their shared national history, and so aid the process of reconciliation between North and South in the post-Civil War era

The Decline of the Model Republic: Images of Mexico in U.S. Public Discourse, 1860 - 1883

Mexico had a fixed place in the antebellum American imagination. It was, most agreed, a failed republic whose chronic political turbulence proved the United States’ exceptional stability. The Civil War, however, shattered the notion that the United States was immune to the forces of internal dissension which had plagued Mexicans for decades. This realisation destabilised Mexico’s place in U.S. public discourse. During the 1860s, an awareness of their own fallibility caused some Americans to sympathise with their sister republic. As political factionalism persisted in the United States into the 1870s, however, a growing number of them invoked images of Mexican anarchy as portents of their own nation’s future. It was not until the early 1880s, as Americans extended their commercial reach south of the Rio Grande, that they viewed Mexico as their nation’s protégé and therefore a reflection of its resilience and strength. By tracing of images of Mexico in U.S. public discourse between 1860 and 1883, this dissertation uncovers a current of anxiety regarding what some Americans saw as a dangerous spirit of factionalism in U.S. politics during this period. Historians often view concerns about the condition of the nation’s political culture as a conservative force that fuelled opposition to the innovations of the Civil War era. This study, however, demonstrates that fears of factionalism transcended party and sectional lines. Moreover, it reveals that actors in public discourse used images of Mexico to harness these anxieties behind a range of policies - emancipation, Radical Reconstruction, and even commercial expansion were all were presented to Americans as programmes to harmonise national politics and so restore the United States to its proper standing as the exceptional New World republic. This dissertation argues that Americans could embrace some revolutionary measures, so long as they believed they could bring them lasting domestic peace

"The rising sun of empire": William H. Seward's Mexican policy 1861-1865

Historians argue that Secretary of State William H. Seward abandoned the pursuit of his expansionist vision during the Civil War. They interpret his conduct of wartime Mexican policy as a case in point for this argument. Although Seward wished to see the Mexican republic stabilised and eventually incorporated into the United States, he allegedly remained neutral towards the French invasion of Mexico 1862-67 in order to prevent Emperor Napoleon III from striking up an alliance with the Confederacy. This thesis argues that Seward never gave up expansionism and that his wartime Mexican policy was designed to facilitate the future absorption of that country into the U.S. republic. Seward believed the Civil War signalled the coming demise of slavery, which had complicated previous instances of national territorial growth, in the United States. He also saw the French invasion of Mexico as an opportunity for the Mexicans to prove their commitment to republicanism and therefore their readiness to become citizens of the U.S. republic. Once both these crises had passed, Seward predicted, the next stages of U.S. expansionism – the peaceful incorporation of Mexico into the United States – would follow. As secretary of state, Seward used his influence over Mexican policy to facilitate the realisation of this goal. This thesis tracks the development of Seward’s pre-war expansionist outlook and compares it to his approach to wartime relations with Mexico, an undertaking not yet attempted by historians. During the antebellum era Seward advocated a method for expansion whereby the United States would build relations based on non-intervention, ideological affinity, and commercial cooperation with those countries it wished to absorb. These same principles guided and shaped Seward’s Mexican policy and his response to the French invasion in 1862. In regards to Mexico, Seward made significant advances towards furthering his expansionist ambitions during the Civil War

Empirical equations for estimating maximum length from length at first maturity

10.1111/j.1439-0426.2009.01215.

Predicting reference points and associated uncertainty from life histories for risk and status assessment

To assess status of fish populations and the risks of overexploitation, management bodies compare fishing mortality rates and abundance estimates with reference points (RP). Generic, “data-poor” methods for estimating RP are garnering attention because they are faster and cheaper to implement than those based on extensive life history data. Yet data-poor RP are subject to many unquantified uncertainties. Here, we predict fishing mortality RP based on five levels of increasingly comprehensive data, to quantify effects of parameter and structural uncertainty on RP. Level I RP (least data) are estimated solely from species' maximum size and generic life history relationships, while level V RP (most data) are estimated from population-specific growth and maturity data. By estimating RP at all five data levels, for each of 12 North Sea populations, we demonstrate marked changes in the median RP values, and to a lesser extent uncertainty, when growth parameters come from data rather than life history relationships. As a simple rule, halving the median level I RP gives almost 90% probability that a level V median RP is not exceeded. RP and uncertainty were substantially affected by assumed gear selectivity; plausible changes in selectivity had a greater effect on RP than adding level V data. Calculations of RP using data for successive individual years from 1984 to 2014 showed that the median RP based on data for any given year would often fall outside the range of uncertainty for RP based on data from earlier or later years. This highlighted the benefits of frequent RP updates when suitable data are available. Our approach provides a quantitative method to inform risk-based management and decisions about acceptable targets for data collection and quality. Ultimately, however, the utility and extent of adoption of data-poor methods for estimating RP will depend on the risk aversion of managers

Transborder capitalism and national reconciliation: The American press reimagines U.S.-Mexican relations after the Civil War

The end of the Civil War did not eradicate Americans’ concerns regarding the fragility of their republic. For many years after Appomattox, newspapers from across the political spectrum warned that the persistence of sectionalism in the postwar United States threatened to condemn the country to the kind of interminable internal disorder supposedly endemic among the republics of Latin America. This article examines how, from the early 1870s onward, growing numbers of U.S. editors, journalists, and political leaders called on Americans to concentrate on extending their nation’s commercial reach into Mexico. In doing so, they hoped to topple divisive domestic issues—notably Reconstruction—from the top of the national political agenda. These leaders in U.S. public discourse also anticipated that collaboration in a project to extend the United States’ continental power would revive affective bonds of nationality between the people of the North and South. In making this analysis, this article argues that much of the early impetus behind U.S. commercial penetration south of the Rio Grande after the Civil War was fueled by Americans’ deep anxieties regarding the integrity of their so-called exceptional republic

Total variation approximation for quasi-equilibrium distributions

Quasi-stationary distributions, as discussed by Darroch & Seneta (1965), have been used in biology to describe the steady state behaviour of population models which, while eventually certain to become extinct, nevertheless maintain an apparent stochastic equilibrium for long periods. These distributions have some drawbacks: they need not exist, nor be unique, and their calculation can present problems. In this paper, we give biologically plausible conditions under which the quasi-stationary distribution is unique, and can be closely approximated by distributions that are simple to compute.Comment: 16 page

A probabilistic analysis of a Beverton-Holt type discrete model: Theoretical and computing analysis

"This is the peer reviewed version of the following article: Cortés, J-C, Navarro-Quiles, A, Romero, J-V, Roselló, M-D. A probabilistic analysis of a Beverton-Holt type discrete model: Theoretical and computing analysis. Comp and Math Methods. 2019; 1:e1013, which has been published in final form at https://doi.org/10.1002/cmm4.1013. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] In this paper a randomized version of the Beverton-Holt type discrete model is proposed. Its solution stochastic process and the random steady state are determined. Its first probability density function and second probability density function are obtained by means of the random variable transformation method, providing a full probabilistic description of the solution. Finally, several numerical examples are shown.This work has been partially supported by the Ministerio de Economía, Industria y Competitividad under grant MTM2017-89664-P. The authors express their deepest thanks and respect to the editors and reviewers for their valuable comments.Cortés, J.; Navarro-Quiles, A.; Romero, J.; Roselló, M. (2019). A probabilistic analysis of a Beverton-Holt type discrete model: Theoretical and computing analysis. Computational and Mathematical Methods. 1(1):1-12. https://doi.org/10.1002/cmm4.1013S11211Kwasnicki, W. (2013). Logistic growth of the global economy and competitiveness of nations. Technological Forecasting and Social Change, 80(1), 50-76. doi:10.1016/j.techfore.2012.07.007De la Sen, M. (2008). The generalized Beverton–Holt equation and the control of populations. Applied Mathematical Modelling, 32(11), 2312-2328. doi:10.1016/j.apm.2007.09.007Cortés, J.-C., Navarro-Quiles, A., Romero, J.-V., & Roselló, M.-D. (2018). Computing the probability density function of non-autonomous first-order linear homogeneous differential equations with uncertainty. Journal of Computational and Applied Mathematics, 337, 190-208. doi:10.1016/j.cam.2018.01.015Casabán, M.-C., Cortés, J.-C., Navarro-Quiles, A., Romero, J.-V., Roselló, M.-D., & Villanueva, R.-J. (2017). Computing probabilistic solutions of the Bernoulli random differential equation. Journal of Computational and Applied Mathematics, 309, 396-407. doi:10.1016/j.cam.2016.02.034Cortés, J.-C., Navarro-Quiles, A., Romero, J.-V., & Roselló, M.-D. (2017). Randomizing the parameters of a Markov chain to model the stroke disease: A technical generalization of established computational methodologies towards improving real applications. Journal of Computational and Applied Mathematics, 324, 225-240. doi:10.1016/j.cam.2017.04.040Cortés, J.-C., Navarro-Quiles, A., Romero, J.-V., & Roselló, M.-D. (2017). Full solution of random autonomous first-order linear systems of difference equations. Application to construct random phase portrait for planar systems. Applied Mathematics Letters, 68, 150-156. doi:10.1016/j.aml.2016.12.01