Portfolio theory as a management tool to guide conservation and restoration of multi‐stock fish populations

DuFour, Mark R.; May, Cassandra J.; Roseman, Edward F.; Ludsin, Stuart A.; Vandergoot, Christopher S.; Pritt, Jeremy J.; Fraker, Michael E.; Davis, Jeremiah J.; Tyson, Jeffery T.; Miner, Jeffery G.; Marschall, Elizabeth A.; Mayer, Christine M.

doi:10.1890/es15-00237.1

Cited by 64 publications

(73 citation statements)

References 76 publications

(119 reference statements)

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“…Thus, fisheries portfolios need to be constructed with recognition of the constraints placed on multiple stock maximization that is set by ecosystem productivity. The proposal by Fogarty (2014) to embody these constraints as "ceilings and floors" in a fishery portfolio is certainly feasible, can help define the portfolio frontier, has been explored in a fisheries portfolio context (Edwards et al 2004;Sanchirico et al 2008;Rȃ dulescu et al 2010;Schindler et al 2010;Yang 2011;DuFour et al 2015;Jin et al 2016), has been proposed for ecological portfolios addressing biodiversity (Tilman et al 1998;Thibault and Connolly 2013;Schindler et al 2015;Brown et al 2016), and has actually been routinely adopted in financial portfolio approaches (Markowitz 1952;Brigham and Gapenski 1988;Gruber 1977, 1995;Choueifaty and Coignard 2008;Fabozzi and Markowitz 2011;Marston 2011). This portfolio cap constraint, coupled with the overfishing risk constraints, provides the useful trade space that is needed in many fisheries negotiations, helping to focus the debate on wise and equitable allocations among the stocks.…”

Section: Discussionmentioning

confidence: 99%

“…This concept is well represented in the ecological literature (e.g., Waltho and Kolasa 1994;Tilman et al 1998;Thibault and Connolly 2013;Schindler et al 2015;Brown et al 2016), particularly related to biodiversity. The concept has had some attention in the fisheries literature (Edwards et al 2004;Rȃ dulescu et al 2010;Schindler et al 2010;Yang 2011;DuFour et al 2015;Jin et al 2016), but the application has not been widely implemented. The theory and mathematics have been explored in a fisheries context, often with particular respect to EBFM (Sanchirico et al 2008;Jin et al 2016), such that the discipline is at the point where these academic examples could start moving into applied, operational management practice.…”

Section: The Portfolio Effectmentioning

confidence: 99%

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System-level optimal yield: increased value, less risk, improved stability, and better fisheries

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2018

Can. J. Fish. Aquat. Sci.

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Abstract:The discipline and practice of fisheries science and management have had an useful, successful, and interesting history. The discipline has developed over the past century and a half into a very reductionist, highly quantitative, socially impactful endeavor. Yet given our collective successes in this field, some notable challenges remain. To address these challenges, many have proposed ecosystem-based fisheries management that takes a more systematic approach to the management of these living marine resources. Here I describe systems theory and associated constructs underlying system dynamics, elucidate how aggregate properties of systems can and have been used, contextualize these aggregate features relative to optimal yield, and note how this approach can produce useful estimates and outcomes for fisheries management. I explore two contrasting examples where this approach has and has not been considered, highlighting the benefits of applying such an approach. I conclude by discussing ways in which we might move forward with a portfolio approach for both the discipline and practice of fisheries science and management.Résumé : La discipline et la pratique des sciences halieutiques et de la gestion des pêches ont une histoire utile, intéressante et couronnée de succès. La discipline est devenue, au cours du dernier siècle et demi, une entreprise très réductionniste, hautement quantitative et à forte incidence sociale. Malgré nos réussites collectives dans ce domaine, des défis notables demeurent. Pour relever ces défis, de nombreuses personnes ont proposé une gestion écosystémique des pêches qui adopte une approche plus systématique de gestion de ces ressources marines vivantes. Je décris la théorie des systèmes et les constructions associées qui sous-tendent la dynamique des systèmes, j'explique comment les propriétés groupées de systèmes peuvent être utilisées et l'ont été, je mets ces éléments groupés dans un contexte de rendement optimal et je souligne comment cette approche peut produire des estimations et des résultats utiles pour la gestion des pêches. J'explore deux exemples dans lesquels cette approche a, d'une part, été prise en considération et, d'autre part, ne l'a pas été, afin de souligner les avantages de son application. Je conclus en discutant d'avenues possibles pour l'avenir qui reposent sur une approche de portefeuille tant pour la discipline que pour la pratique des sciences halieutiques et de la gestion des pêches. [Traduit par la Rédaction]

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Section: Discussionmentioning

confidence: 99%

Section: The Portfolio Effectmentioning

confidence: 99%

System-level optimal yield: increased value, less risk, improved stability, and better fisheries

Link

2018

Can. J. Fish. Aquat. Sci.

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“…Most conspicuous in the Great Lakes basin has been the inability of fisheries biologists to consistently discriminate and identify the relative contributions of Lake Erie's local spawning populations of Walleye Sander vitreus (DuFour et al. ; Chen et al. ).…”

mentioning

confidence: 99%

“…; DuFour et al. ). However, preserving this diversity can be difficult in fish populations that are supported by discrete local spawning populations (i.e., stocks) but are harvested from a combined (mixed) fishery elsewhere.…”

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confidence: 99%

RAD‐Seq Refines Previous Estimates of Genetic Structure in Lake Erie Walleye

et al. 2020

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Delineating population structure helps fishery managers to maintain a diverse “portfolio” of local spawning populations (stocks), as well as facilitate stock‐specific management. In Lake Erie, commercial and recreational fisheries for Walleye Sander vitreus exploit numerous local spawning populations, which cannot be easily differentiated using traditional genetic data (e.g., microsatellites). Here, we used genomic information (12,264 polymorphic loci) generated using restriction site‐associated DNA sequencing to investigate stock structure in Lake Erie Walleye. We found low genetic divergence (genetic differentiation index FST = 0.0006–0.0019) among the four Lake Erie western basin stocks examined, which resulted in low classification accuracies for individual samples (40–60%). However, more structure existed between western and eastern Lake Erie basin stocks (FST = 0.0042–0.0064), resulting in greater than 95% classification accuracy of samples to a lake basin. Thus, our success in using genomics to identify stock structure varied with spatial scale. Based on our results, we offer suggestions to improve the efficacy of this new genetic tool for refining stock structure and eventually determining relative stock contributions in Lake Erie Walleye and other Great Lakes populations.

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“…In marine fisheries, portfolio theory provides a framework for multi‐stock fisheries management (DuFour et al., ): when unique fish populations (i.e. portfolios) each comprised of distinct stocks (subpopulations) are uncorrelated in their dynamics, portfolio effects arise, whereby increased portfolio diversity helps stabilize population‐level productivity, buffer against recruitment failure and improve resilience to ever‐changing environmental conditions (e.g., Schindler and Hilborn, ).…”

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confidence: 99%

Fishing in hot waters threatens phenotypic diversity

Aubry

2019

Journal of Animal Ecology

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In Focus: Forces of unnatural selection, such as climate change and harvest, are rarely studied in concert, yet hold the great potential to act synergistically on individual performance, susceptibility to harvest, tolerance to warming temperatures, and ultimately population persistence and resilience. In this paper, Morrongiello et al. (2019) used long‐term monitoring of a site‐attached temperate reef fish, the purple wrasse (Notolabrus fucicola), to test novel predictions about how fisheries management and climate variability could alter individual growth rates and thermal reaction norms within and across stocks. Otolith growth increments were collected from three south‐east Australian populations between 1980 and 1999, pre‐ and post‐harvest, throughout an intensive warming spell. Using hierarchical models to partition variation in growth within and between individuals and populations, Morrongiello et al. detected increased average growth rate with warming, a release from density dependence post‐harvest, and a fishing‐by‐warming interaction that decreased diversity in thermal growth reaction norms because large individuals that tend to better tolerate warm temperatures were effectively culled from the population. This study outlines the importance of determining which phenotypes are more resilient to increasing temperatures, how fisheries should manage for them, and how such collective knowledge could help preserve and even promote resilience of managed populations to increasing temperatures in ecosystems threatened by climate change.

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Portfolio theory as a management tool to guide conservation and restoration of multi‐stock fish populations

Cited by 64 publications

References 76 publications

System-level optimal yield: increased value, less risk, improved stability, and better fisheries

System-level optimal yield: increased value, less risk, improved stability, and better fisheries

RAD‐Seq Refines Previous Estimates of Genetic Structure in Lake Erie Walleye

Fishing in hot waters threatens phenotypic diversity

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