On the economic optimality of marine reserves when fishing damages habitat

Submitted in partial fulfillment of the requirements for the degree of Master of Science at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010In this thesis, I expand a spatially-explicit bioeconomic fishery model to include the negative effects of fishing effort on habitat quality. I consider two forms of effort driven habitat damage: First, fishing effort may directly increase individual mortality rates. Second, fishing effort may increase competition between individuals, thereby increasing density-dependent mortality rates. I then optimize effort distribution and fish stock density according to three management cases: (1) a sole owner, with jurisdiction over the entire fishery, who seeks to maximize profit by optimizing effort distribution; (2) a manager with limited control of effort and stock distributions, who seeks to maximize tax revenue by setting the length of a single, central reserve and a uniform tax per unit effort outside it; and (3) a manager with even more limited enforcement power, who can only set a tax per unit effort everywhere in the habitat space. I demonstrate that the economic efficiency of reserves depends upon model parameterization. In particular, reserves are most likely to increase profit (or tax revenue) when density-dependent fish mortality rates are affected. Interestingly, for large habitats that are sufficiently sensitive to density-dependent fish mortality effects, reserve networks (alternating fished and unfished areas of fixed periodicity) emerge. These results suggest that spatial forms of management which include marine reserves may enable significant economic gains over nonspatial management strategies, in addition to the well-established conservation benefits provided by closed areas.MIT Linden Fellowship, funding from the WHOI Academic Programs Office, and an NSF Graduate Research Fellowship

Economically optimal marine reserves without spatial heterogeneity in a simple two-patch model

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Natural Resource Modeling 28 (2015): 244-255, doi:10.1111/nrm.12066.Bioeconomic analyses of spatial fishery models have established that marine reserves can be economically optimal (i.e., maximize sustainable profit) when there is some type of spatial heterogeneity in the system. Analyses of spatially continuous models and models with more than two discrete patches have also demonstrated that marine reserves can be economically optimal even when the system is spatially homogeneous. In this note we analyze a spatially homogeneous two-patch model and show that marine reserves can be economically optimal in this case as well. The model we study includes the possibility that fishing can damage habitat. In this model, marine reserves are necessary to maximize sustainable profit when dispersal between the patches is sufficiently high and habitat is especially vulnerable to damage.Graduate Research Fellowship and a Postdoctoral Research Fellowship in Biology Grant Number: DBI-1401332; US National Science Foundation Grant Numbers: OCE-1031256, DEB-1257545, DEB-11450172016-06-2

Habitat damage, marine reserves, and the value of spatial management

Author Posting. © Ecological Society of America, 2013. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Applications 23 (2013): 959–971, doi:10.1890/12-0447.1.The biological benefits of marine reserves have garnered favor in the conservation community, but “no-take” reserve implementation is complicated by the economic interests of fishery stakeholders. There are now a number of studies examining the conditions under which marine reserves can provide both economic and ecological benefits. A potentially important reality of fishing that these studies overlook is that fishing can damage the habitat of the target stock. Here, we construct an equilibrium bioeconomic model that incorporates this habitat damage and show that the designation of marine reserves, coupled with the implementation of a tax on fishing effort, becomes both biologically and economically favorable as habitat sensitivity increases. We also study the effects of varied degrees of spatial control on fisheries management. Together, our results provide further evidence for the potential monetary and biological value of spatial management, and the possibility of a mutually beneficial resolution to the fisherman–conservationist marine reserve designation dilemma.M. G. Neubert acknowledges the support of the National Science Foundation (DMS-0532378, OCE-1031256) and a Thomas B. Wheeler Award for Ocean Science and Society. H. V. Moeller acknowledges support from a National Science Foundation Graduate Research Fellowship. This research is based in part on work supported by Award No. USA 00002 made by King Abdullah University of Science and Technology (KAUST)

'Hedge Funds: Stock Pickers or Managers?

For decades, corporate managers have criticised analysts, fund managers, hedge fund managers and private equity professionals for telling them how to run their business, wihout having had the necessary experience. Now hedge fund activists are regularly suggesting operational decisions, and in some cases even in areas traditionally reserved for management. ‘Activism has gone from being frowned upon, something that marks you out as a rogue or maverick, to almost socially responsible.’1 These hedge funds may have become an accepted part of the governance universe but are they actually adding value? Recent studies have answered this question in the affirmative, but what if those companies picked out by hedge funds for their attention were already on their way to outperformance? The observed outperformance may not be due to a hedge fund’s ability to contribute to value creation but a mere reflection of their stock picking abilities. The difficulty is in identifying those companies that would have made typical hedge fund targets but which were not actually targeted, i.e. build an appropriate group of comparable companies. We have developed a statistical model to identify just these companies

The New Normal: The Resurgence of Activist Investing Since the End of the Financial Crisis

ince 2010 there has been an incredible inflow of capital to hedge funds that focus specifically on activist investing. The aggressive and often hostile actions of activist funds have created negative publicity and an increased focus on the shortened holding period of these investors. But are activists a blessing or a curse? This report, produced by the M&A Research Centre (MARC) at Cass Business School provides an insight into the short- and long-term performance effects of activist campaigns in the United States, Germany, and the United Kingdom since the financial crisis. This report should not be considered as a guide for activist investors on what tactics to use or a guide for company executives on what they should be prepared for. It rather highlights important patterns in the outcomes of shareholder activism in the United States, Germany, and United Kingdom since the beginning of 2010, when the economies of these countries were emerging from the depths of the financial crisis. Activism tends to be concentrated largely in the United States, but the expectations for further expansion into Europe make it important to understand its existing environment and what activist methods have had success in the region. As equity markets reach new heights in Europe, there will be new opportunities for activist investors

Intraguild predation enables coexistence of competing phytoplankton in a well-mixed water column

Author Posting. © Ecological Society of America, 2019. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecology, (2019): e02874, doi: 10.1002/ecy.2874.Resource competition theory predicts that when two species compete for a single, finite resource, the better competitor should exclude the other. However, in some cases, weaker competitors can persist through intraguild predation, that is, by eating their stronger competitor. Mixotrophs, species that meet their carbon demand by combining photosynthesis and phagotrophic heterotrophy, may function as intraguild predators when they consume the phototrophs with which they compete for light. Thus, theory predicts that mixotrophy may allow for coexistence of two species on a single limiting resource. We tested this prediction by developing a new mathematical model for a unicellular mixotroph and phytoplankter that compete for light, and comparing the model's predictions with a laboratory experimental system. We find that, like other intraguild predators, mixotrophs can persist when an ecosystem is sufficiently productive (i.e., the supply of the limiting resource, light, is relatively high), or when species interactions are strong (i.e., attack rates and conversion efficiencies are high). Both our mathematical and laboratory models show that, depending upon the environment and species traits, a variety of equilibrium outcomes, ranging from competitive exclusion to coexistence, are possible.HVM and MGN designed the model. HVM and MDJ designed the experimental test system. HVM performed the model analysis, conducted the experiments, and analyzed the data. All authors wrote the paper. We thank Susanne Wilken for generously providing axenic CCMP 2951 and 1393 cultures for our use. R. Germain, S. Louca, G. Owens, N. Sharp, P. Thompson, and J. Yoder provided valuable feedback on figure design. We also thank J. Bronstein, S. Diehl, J. Huisman, C. Klausmeier, and four anonymous reviewers for comments on earlier versions of this manuscript. HVM was supported by a United States National Science Foundation Postdoctoral Research Fellowship in Biology (Grant DBI‐1401332) and a University of British Columbia Biodiversity Research Centre Postdoctoral Fellowship. This material is based upon work supported by the National Science Foundation under Grants OCE‐1655686 and OCE‐1436169, by a grant from the Simons Foundation/SFARI (561126, HMS), and by the Woods Hole Oceanographic Institution's Investment in Science Program. Research was also sponsored by the U.S. Army Research Office and was accomplished under Cooperative Agreement Number W911NF‐19‐2‐0026 for the Institute for Collaborative Biotechnologies

Formulation of the Spinor Field in the Presence of a Minimal Length Based on the Quesne-Tkachuk Algebra

In 2006 Quesne and Tkachuk (J. Phys. A: Math. Gen. {\bf 39}, 10909, 2006) introduced a (D+1)-dimensional $(\beta,\beta')$-two-parameter Lorentz-covariant deformed algebra which leads to a nonzero minimal length. In this work, the Lagrangian formulation of the spinor field in a (3+1)-dimensional space-time described by Quesne-Tkachuk Lorentz-covariant deformed algebra is studied in the case where $\beta'=2\beta$ up to first order over deformation parameter $\beta$. It is shown that the modified Dirac equation which contains higher order derivative of the wave function describes two massive particles with different masses. We show that physically acceptable mass states can only exist for $\beta<\frac{1}{8m^{2}c^{2}}$. Applying the condition $\beta<\frac{1}{8m^{2}c^{2}}$ to an electron, the upper bound for the isotropic minimal length becomes about $3 \times 10^{-13}m$. This value is near to the reduced Compton wavelength of the electron $(\lambda_c = \frac{\hbar}{m_{e}c} = 3.86\times 10^{-13} m)$ and is not incompatible with the results obtained for the minimal length in previous investigations.Comment: 11 pages, no figur