Fishing Sea-bed Habitat Risk Assessment (A framework towards the quantitative assessment of trawling impact on the sea-bed and benthic ecosystem)

A framework to assess the impact of mobile fishing gear on the seabed and benthic ecosystem is presented. The framework that can be used at regional and local scales considers the physical effects of trawl gears on the seabed, on marine taxa and the functioning of the benthic ecosystem. A reductionist approach is applied that breaks down a fishing gear in its components and distinguishes a number of biological traits that are chosen to determine the vulnerability of benthos for the impact of a gear component or to provide a proxy for their ecological role. The approach considers a wide variety of gear elements, such as otter boards, twin trawl clump and ground-rope, and, sweeps that herd the fish. The physical impact of these elements on the seabed, comprising scraping of the seabed, sediment mobilisation and penetration, are a function of the mass, size and speed of the individual component. The impact of the elements on the benthic community are quantified using a biological-trait approach, that considers the vulnerability of the benthic community to trawl impact (e.g. sediment position, morphology), the recovery rate (e.g. longevity, maturation age, reproductive characteristics) and the ecological role. The framework is explored to compare the indicators for pressure and ecological impact of bottom trawling in three main seabed habitat types in the North Sea. Preliminary results show that the sublittoral mud habitat is impacted most due to the combined effect of an intensive fishing and high proportions of long-lived taxa.

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Rijnsdorp A.D., Bastardie Francois, Bolam S.G., Buhl-Mortensen Lene, Eigaard O.R., Hamon Katell G., Hiddink Jan Geert, Hintzen N.T., Ivanovic Ana, Kenny Andrew, Laffargue Pascal, Nielsen R.N., O’neill F.G., Piet G.J., Polet Hans, Sala Antonello, Smith Chris, Van Denderen P.D., Van Kooten Tobias, Zengin Mustafa (2015). Fishing Sea-bed Habitat Risk Assessment (A framework towards the quantitative assessment of trawling impact on the sea-bed and benthic ecosystem). Ref. BENTHIS Deliverable 3.6. https://archimer.ifremer.fr/doc/00425/53642/

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