Viability theory for an ecosystem approach to fisheries

Abstract

2005. Viability theory for an ecosystem approach to fisheries. e ICES Journal of Marine Science, 62: 577e584.Maintenance of overall ecosystem complexity is perceived as critical to the sustainability of ecosystem use. The development of an operational basis for an ecosystem approach to fisheries, however, faces many difficulties. On the research side, the challenge is in defining proper long-term, ecosystem-related objectives; determining meaningful reference values and indicators for desirable or undesirable states of the ecosystem; and developing appropriate data collection, analytical tools and models. The ''viability'' concept developed in economics by Jean-Pierre Aubin can be used to assist in the definition, selection of, and interaction among long-term objectives at an ecosystem level. It recognizes that ecosystems are complex assemblages of interacting and self-organizing natural and human components that cannot be predicted. Viability models define an ensemble of ''viable states'', in contrast to undesirable states defined as such by ecological, economic, and/or social constraints. These constraints can be derived from fisheries objectives, conservation principles, scientific results of modelling, or precautionary principles, and correspond to limit reference points to be avoided. Viability theory does not attempt to choose any ''optimal solution'' according to given criteria, but selects ''viable evolutions''. These evolutions are compatible with the constraints in the sense that they satisfy them at each time and can be delineated by the viability kernel. The southern Benguela marine ecosystem is presented as a first attempt for the application of this theory. In defining ecosystem-based objectives (and related issues such as target reference points), it seems more difficult to reach consensus among stakeholders on what is desirable than on what is undesirable (e.g. biological or economic collapse, species extinction, displacement of local rural communities). Expressed in the negative form or as limit reference points, ecosystembased constraints can be considered simultaneously with current target reference points, such as maximum sustainable yield, using viability models. The viability approach can help to progressively integrate ecosystem considerations, such as conservation, into fisheries management.

Conservation implications of the apparent mismatch between population dynamics and foraging effort in French northern gannets from the English Channel

“…In this context our study confirms the great importance of the tidal front zone between the western and eastern English Channel for marine wildlife, and stresses the need for special conservation measures within this zone. Such a management plan should not follow a classic single-species management strategy, but should rather consider the WEC ecosystem as an entity (ecosystem-based management, see Cury et al 2005).…”

Distinguishing benchmarks of biological status from management reference points: A case study on Pacific salmon in Canada

“…One, often paralysing challenge in making management decisions that account for the multi-dimensional nature of ecosystem dynamics is reaching consensus among diverse interests and conflicting objectives. Viability theory provides a promising solution by identifying management options that are 'viable' (namely above limit reference points) on all indicators, an option that is often easier to identify than optimization on indicators (or above target reference points) (Cury et al 2005). For example, in the Southern Benguela ecosystem, Mullon et al (2004) used an ecosystem model with interacting physical, biological and harvest components to identify a viable kernel containing all possible combinations of five ecosystem indicators that were above acceptable levels.…”

Safeguarding, Integrating and Disseminating Knowledge on Exploited Marine Ecosystems: the Ecoscope

“…Moreover, as the global scale of the large pelagic fishes distribution makes it necessary to collect data from all over the world (which means from heterogeneous data sources remaining on different technologies), the international context in IR management brings some generic solutions which have to be taken into account. The CRHMT thus set up the Ecoscope project 2 whose main idea, first formalized by Ulanow-2 www.ecoscope.org icz (UlAnOwICZ et al, 1993)and taken back by Cury (CURy, 2004), consists in enabling a reasoned management of knowledge related to these fisheries by using an ecosystemic approach. In practical terms, this project aims to sustain EAF by improving IR management (descriptions, searching, access, treatments) to support decision making process.…”