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

How fast does the seafloor community recover after bottom fishing? Gwladys Lambert and her colleagues of BENTHIS’ partner Bangor University analysed thousands of pictures of the seabed around the Isle of Man (UK).

In this area, bottom fishing shows a patchy distribution in time and space. For each location Lambert knew the history of fishing events,  including when fishing had taken place for the last time, usually weeks to months earlier. The team counted all crabs, sea stars, tube worms, shellfish and other species on the photos and analysed the data. In the end, they obtained a database with the species composition of different habitats and locations in different stages of recovery.

Figure 1. Pictures of the seafloor showing different seafloor inhabitants, such as brittle stars, clams, dead men’s fingers and tube worms.
Figure 1. Pictures of the seafloor showing different seafloor inhabitants, such as brittle stars, clams, dead men’s fingers and tube worms.

Recovery of abundance was estimated to take less than 1 year to more than a decade, depending on the species group, with faster recovery rates in areas with faster tidal currents, north and south of the island. 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.

Lambert: “Our results show that if managers wants to minimize overall bottom fishing impacts in an area, trawling and dredging should be limited to more resilient areas that recover quickly, while unfished patches of seabed should be maintained to enhance recovery rates.”