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Ecological and economic viability for the sustainable management of mixed fisheries


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Gourguet, S 2014 , 'Ecological and economic viability for the sustainable management of mixed fisheries', PhD thesis, University of Tasmania.

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Empirical evidence and the theoretical literature both point to stock sustainability and the protection
of marine biodiversity as important fisheries management issues. Decision-support tools
are increasingly required to operationalize the ecosystem-based approach to fisheries management.
These tools need to integrate (i) ecological and socio-economic drivers of changes in fisheries and
ecosystems; (ii) complex dynamics; (iii) deal with various sources of uncertainty; and (iv) incorporate
multiple, rather than single objectives.
The stochastic co-viability approach addresses the trade-os associated with balancing ecological,
economic and social objectives throughout time, and takes into account the complexity and
uncertainty of the dynamic interactions which characterize exploited ecosystems and biodiversity.
This thesis proposes an application of this co-viability approach to the sustainable management
of mixed fisheries, using two contrasting case studies: the French Bay of Biscay (BoB) demersal
mixed fishery and the Australian Northern Prawn Fishery (NPF). Both fisheries entail direct and indirect
impacts on mixed species communities while also generating large economic returns. Their
sustainability is therefore a major societal concern.
A dynamic bio-economic modelling approach is used to capture the key biological and economic
processes governing these fisheries, combining age- (BoB) or size- (NPF) structured models
of multiple species with recruitment uncertainty, and multiple fleets (BoB) or fishing strategies
(NPF). Economic uncertainties relating to input and output prices are also considered. The bioeconomic
models are used to investigate how the fisheries can operate within a set of constraints
relating to the preservation of Spawning Stock Biomasses (BoB) or Spawning Stock Size Indices
(NPF) of a set of key target species, maintenance of the economic profitability of various fleets
(BoB) or the fishery as a whole (NPF), and limitation of fishing impacts on the broader biodiversity
(NPF), under a range of alternative scenarios and management strategies.
Results suggest that under a status quo strategy both fisheries can be considered as biologically
sustainable, while socio-economically (and ecologically in the NPF case) at risk. Despite very different
management contexts and objectives, viable management strategies suggest a reduction in
the number of vessels in both cases. The BoB simulations allow comparison of the trade-os associated
with dierent allocations of this decrease across fleets. Notably, co-viability management
strategies entail a more equitable allocation of eort reductions compared to strategies aiming at
maximizing economic yield. In the NPF, species catch diversification strategies are shown to perform
well in controlling the levels of economic risk, by contrast with more specialized fishing
strategies. Furthermore analyses emphasize the importance to the fishing industry of balancing
global economic performance with inter-annual economic variability.
Promising future developments based on this research involve the incorporation of a broader
set of objectives including social dimensions, as well as the integration of ecological interactions,
to better address the needs of ecosystem-based approaches to the sustainable harvesting of marine

Item Type: Thesis - PhD
Authors/Creators:Gourguet, S
Keywords: bioeconomic modelling, uncertainty, viability approach mixed fisheries, sustainable management
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