1 research outputs found
Novel index for quantification of ecosystems effects of fishing as removal of secondary production
Exploited ecosystems are characterised by exports of secondary production from each
fished trophic level that reduce the energy available for upper levels at the ecosystem scale, thus
impinging on overall secondary production. Depletion in secondary production is proposed here as a
proxy for quantifying the ecosystem effects of fishing. Theoretical analysis of trophic web interactions
permits the quantification of the ‘loss in production’ and provides an ecological basis for defining a
new synthetic index (L index) that takes into account both ecosystem properties (primary production
and transfer efficiency) and features of fishing activities (trophic level of catches and primary production
required). Quantitative meta-analysis of ecological models, representing 51 exploited ecosystems
previously classified as overexploited or sustainably exploited, allows the association of a probability
of the ecosystem being sustainably fished with each index value. Moreover, by fixing the
reference level for this probability, the index provides a basis for estimating the maximum allowable
catches. The L index is applied here to several ecosystems worldwide using landings data and ecological
models, providing quantification of the disruption of energy flows for ecosystems subjected to
different types and levels of fishing pressure. Its application to outputs of calibrated dynamic models
enables the evaluation of sustainability of fisheries in past and future scenarios of alternative fisheries
management policies. Results highlight the usefulness of this index for quantifying the impacts of
fishing and providing directional advice for fisheries management. Thus, the L index may be used to
support ecosystem-based management of fisheries