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This paper applies a stochastic viability approach to a tropical small-scale fishery, offering a theoretical and empirical example of ecosystem-based fishery management approach that accounts for food security. The model integrates multi-species, multi-fleet and uncertainty as well as profitability, food production, and demographic growth. It is calibrated over the period 2006–2010 using monthly catch and effort data from the French Guiana's coastal fishery, involving thirteen species and four fleets. Using projections at the horizon 2040, different management strategies and scenarios are compared from a viability viewpoint, thus accounting for biodiversity preservation, fleet profitability and food security. The analysis shows that under certain conditions, viable options can be identified which allow fishing intensity and production to be increased to respond to food security requirements but with minimum impacts on the marine resources.

Balancing bio-economic risks and high profit expectations is often a major concern in fisheries management. We examine this trade-off in the context of the Australian Northern Prawn Fishery (NPF). The fishery derives its revenue from different prawn species with different dynamics and recruitment processes. A multi-species bio-economic and stochastic model is used to examine the trade-offs between mean profitability of the fishery and its variance, under a range of economic scenarios, fishing capacities and distributions of fishing effort across the various sub-fisheries that comprise the NPF. Simulation results show that the current fishing strategy diversifying catch across sub-components of the fishery entails a compromise between expected performance and risk. Furthermore, given the current economic conditions, increases in fleet size would improve the expected economic performance of the fishery, but at the cost of increased variability of this performance.

This paper offers a theoritical and empirical model of ecosystem-based fishery management. A multi-species and multi-fleet integrating Lotka-Volterra trophic dynamics as well as production and profit assessments is developed and applied to the coastal fishery of French Guiana. This small-scale fishery constitutes a challenging example with high fish biodiversity, several non-selective fleets and a potentially increasing local food demand due to demographic growth. The dynamic model is calibrated with 13 species and four fleets using monthly catch and effort data from 2006 to 2009. Several contrasted fishing scenarios including status quo, total closure, economic and viable strategies are then simulated. They are compared from the viewpoints of both biodiversity preservation and socioeconomic performance, assuming fixed landing prices and fixed costs. We show that fishing outputs, including food supply and fleet profitability, can be sustained on average but a loss of species cannot be avoided.

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.

This paper develops a formal analysis of the recovery process for a fishery, from crisis situations to desired levels of sustainable exploitation, using the theoretical framework of viable control. We define sustainability as a combination of biological, economic and social constraints which need to be met for a viable fishery to exist. Biological constraints are based on the definition of a minimum resource stock to be preserved. Economic constraints relate to the existence of a guaranteed profit per vessel. Social constraints refer to the maintenance of a minimum size of the fleet, and to the maximum speed at which fleet adjustment can take place. Using fleet size adjustment and fishing effort per vessel as control variables, we first identify the states of this bioeconomic system for which sustainable exploitation is possible, i.e. for which all constraints can be dynamically met. Such favorable states are called viable states. We then examine possible transition phases, from non-viable to viable states. We characterize recovery paths with respect to the time of crisis of the trajectory, which is the number of periods during which the constraints are not respected. The approach is applied to the single stock of the bay of Biscay Nephrops fishery. The transition path identified through the viability approach is compared to the historical recovery process, and to both open-access and optimal harvesting scenarios. (C) 2007 Elsevier B.V. All rights reserved.

Overexploitation of marine resources remains a problem worldwide. Many works advocate for the use of marine reserves as a central element of future stock management in a sustainable perspective. In the present paper, we address the influence of protected areas upon fisheries sustainability within an eco-systemic framework through a dynamic bio-economic model integrating a trophic web, catches and environmental uncertainties. The model is spatially implicit. The evaluation of the ecosystem is designed through the respect along time of constraints of both conservation and guaranteed captures. Using the mathematical concept of invariance kernel in a stochastic context, we define different MPA effects according to biodiversity catches or mixed points of view. Numerical simulations inspired from data of Abore coral reef reserve in New Caledonia illustrate the main concepts. In this case, it is pointed out how MPA conservation effect is not necessarily conflicting with MPA catches effect. it is shown that such a co-viability requires medium exploitation rate. Moreover, the climatic changes represented by rise in cyclonic events seem to reinforce these assertions. (C) 2007 Elsevier B.V. All rights reserved.