Quantifying recovery rates and resilience of seabed habitats impacted by bottom fishing

Summary The Ecosystem Approach to Fisheries requires that managers take account of the environmental impacts of fishing. Towed bottom-fishing gears disturb seabed habitats and cause mortality of benthic invertebrates. Measurements of recovery rates of marine habitats after fishing disturbance can provide insight into spatial variations in resilience and may be used to assess the sustainability of these fishing impacts and inform the development of appropriate management strategies. To measure recovery on real fishing grounds at fishery- and management-relevant scales, we estimated the post-disturbance recovery rates of epifaunal marine benthic communities on coarse and hard substrata across >4000 km² of seabed where the patchy distribution of bottom fishing in space and time creates a mosaic of habitat patches at different stages of recovery. The history of fishing events at each location was described using satellite vessel monitoring system (VMS) data. Recovery rates were extrapolated from the relationship between time since the last fishing event and abundance of epifaunal benthic invertebrates with life-history traits that are expected to make them sensitive to fishing. Recovery of abundance of all species and functional groups (medium to medium-large size, medium to long life span, suspension feeding, high body flexibility and low mobility species) was estimated to take 10 years, depending on the group, with faster recovery in areas with faster tidal currents. The recovery of large species was faster when conspecifics were abundant within a radius of 6 km, suggesting an important role for maintaining local sources of recruits to repopulate impacted areas. Synthesis and applications. We used a new method to estimate the recovery rate of benthic communities and to describe spatial differences in sensitivity to fishing. Bottom fishing in areas that recover quickly will minimize overall impacts, while leaving unfished patches of seabed will enhance recovery rates in fished areas. We conclude that management plans which limit bottom trawls and dredge fisheries to more resilient areas and maintain unfished patches within these areas will minimize the collective impacts of a given amount of fishing effort on seabed habitats.

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