Management of fisheries for sustainability requires dealing with multiple and often conflicting objectives. A stochastic viability approach is proposed to address the trade-offs associated with balancing ecological, economic and social objectives in regulating mixed fisheries, taking into account the complexity and uncertainty of the dynamic interactions which characterize such fisheries. We focus on the demersal fishery in the Bay of Biscay and more specifically on the fleets harvesting Norway Lobster (Nephrops norvegicus), Hake (Merluccius merluccius) and Sole (Solea solea). A bio-economic multi-species and multi-fleet model with technical interactions is developed to examine the trade-offs between preserving Spawning Stock Biomass (SSB) of every species and maintaining the economic profitability of the various fishing fleets. Different management strategies are tested and compared. Results suggest that ensuring viability of this demersal fishery requires a significant decrease in fishing capacity as compared to the reference year. The simulations allow comparing the trade-offs associated with different allocations of this decrease across fleets.

Managing mixed fisheries for bio-economic viability

A Survey of Applications of Viability Theory to the Sustainable Exploitation of Renewable Resources

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017EF000660

From Resistance to Transformation: A Generic Metric of Resilience Through Viability

n the last two decades resilience has emerged as a promising concept that can help societies and more generally social-ecological systems become less vulnerable to shocks and stressors. As such it has been adopted by a large number of disciplines—from psychology, physics, and ecology to disaster risk reduction, climate change adaption, and humanitarian and food security interventions. However, although numerous definitions or measures of resilience have been proposed, those were mainly discipline centered and, as such, failed to provide an adequate overarching framework. This paper explores the question of the formalization and measurement of resilience, with the objective to develop a generic metric that applies across the disciplines and to the different interpretations of resilience. Building on the definitions found in the literature, a continuum of five categories of resilience responses is identified: (i) resistance, (ii) coping strategies, (iii) adaptation, (iv) adaptive preference, and (v) transformation. Those categories are then reframed into a generic metric, using viability analysis—a mathematical formalism which builds on dynamic systems and control theory. Theoretical and empirical analyses are then conducted, looking in particular at how inertia and costs associated with the types of responses influence the level of resilience. To illustrate this new metric, we draw on two models widely discussed in the resilience literature: the exploitation of renewable resources and the case of lake eutrophication. Both theoretical and numerical analyses demonstrate the relevance of the typology as a generic framework for resilience but also highlight transformation as a particular case of resilience response. (This abstract was borrowed from another version of this item.)

How do fishing practices influence sperm whale (Physeter macrocephalus) depredation on demersal longline fisheries

Reconciling food security, economic development and biodiversity conservation is a key challenge, especially in the face of the demographic transition characterizing many countries in the world. Fisheries and marine ecosystems constitute a difficult application of this bio-economic challenge. Many experts and scientists advocate an ecosystem approach to manage marine socio-ecosystems for their sustainability and resilience. However, the ways by which to operationalize ecosystem-based fisheries management (EBFM) remain poorly specified. We propose a specific methodological framework—viability modelling—to do so. We show how viability modelling can be applied using four contrasted case-studies: two small-scale fisheries in South America and Pacific and two larger-scale fisheries in Europe and Australia. The four fisheries are analysed using the same modelling framework, structured around a set of common methods, indicators and scenarios. The calibrated models are dynamic, multispecies and multifleet and account for various sources of uncertainty. A multicriteria evaluation is used to assess the scenarios’ outcomes over a long time horizon with different constraints based on ecological, social and economic reference points. Results show to what extent the bio-economic and ecosystem risks associated with the adoption of status quo strategies are relatively high and challenge the implementation of EBFM. In contrast, strategies called ecoviability or co-viability strategies, that aim at satisfying the viability constraints, reduce significantly these ecological and economic risks and promote EBFM. The gains associated with those ecoviability strategies, however, decrease with the intensity of regulations imposed on these fisheries.

/pdf/ecoviability-for-ecosystem-based-fisheries-management-2nvwn8zfju.pdf

Luke Doyen

Papers

Ecoviability for ecosystem-based fisheries management