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Habitat sensitivity to bottom trawling

Published on: May 14, 2018

The sensitivity of the benthic community to bottom trawling can be estimated from the biological traits of species in the community.

Longevity composition of the benthos in the four main seafloor habitats in the North Sea

Biological traits are characteristics of species, that can be used to analyse the benthic community. They include the lifestyle of a species (sedentary, mobile), body size (small, medium, large), the position in the sediment (on top, just below the surface, deeply buried), the longevity (lifespan <1 year, 5-10 years, > 10 years), the type of exoskeleton (soft, hard), the way of reproduction, etc.

Body size and longevity are the most important traits when considering the impacts of bottom fishing. The relevance of longevity is due to its relation with the recovery rate of the organism. Hence, once we know the longevity composition of the community, we can estimate its recovery rate. This was shown in an analysis of a broad spatial data set on the biological trait composition from a wide range of study areas representing different habitats and regions ranging from northern Norway to the Mediterranean Sea.

The longevity composition of the community differs across habitats. Hard grounds with gravel are characterised by a larger proportion of long-lived organisms. Therefore, the recovery rate after fishing is low and the sensitivity to bottom fishing is high. The proportion of long-lived taxa is also high in stable habitats with a low level of natural disturbance. Habitats exposed to a high natural disturbance due to tides or waves, are characterised by a low proportion of long-lived species. In these habitats, the sensitivity to bottom trawling is lower compared to hard substrates and naturally stable habitats.

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References:

Bolam SG, Garcia C, Eggleton J, Kenny AJ, Buhl-Mortensen L, Gonzalez-Mirelis G, van Kooten T, Dinesen G, Hansen J, Hiddink JG, Sciberras M, Smith C, Papadopoulou N, Gumus A, Van Hoey G, Eigaard OR, Bastardie F, Rijnsdorp AD, 2017. Differences in biological traits composition of benthic assemblages between unimpacted habitats. Marine Environmental Research 126: 1-13.

Relation between longevity and sensitivity : (Hiddink et al., in prep)

Longevity composition of the community: (Rijnsdorp et al., 2016b).