Sensitivity assessment as a tool for spatial and temporal gear-based fisheries management

Abstract

Assessment of ecosystem health is required in the ecosystem approach to fisheries management (EAFM). Mitigation measures that address impacts exceeding the acceptable level also require assessment. The various fishing métiers have different ecosystem impacts and this makes it difficult to assess them jointly. Sensitivity of the ecosystem to individual fishing métiers has been assessed previously, but to our knowledge, concurrent comparisons of different métiers on the same ecosystem have not been done. In this study, we combined the main characteristics of established approaches to sensitivity assessment into a single roadmap, called Sensitivity Assessment of Gear Effects (SAGE). SAGE is a widely applicable, three-step process to assess the ecological concerns of EAFM. The methodology used in the SAGE roadmap is built on a scoring system, which then results in a sensitivity index of the ecosystem components to the fishing métiers. The scoring system is based on a combination of expert judgement and data, both qualitative and quantitative. It allows for cross-evaluation of fishing métiers and ecosystem components. Sensitivity maps are created using the spatial and temporal distribution patterns of the ecosystem components in the index. The uncertainty of the sensitivity scores and maps are estimated through a pedigree index. The index is based on proxy representation, empirical basis, methodological rigour, theoretical understanding and degree of validation, all of which measure the strength of the research results. The proposed methodology is illustrated using a case study that compares the ecosystem effects of beam trawl and trammel net fisheries. The selected examples did not result in unexpected outcomes, but were rather chosen to evaluate the applicability of our methodology. They illustrate how a semi-quantitative framework, which includes the uncertainties associated with scientific assessments, can deliver holistic advice to fisheries managers in a fully transparent manner.