A Scientific Basis for Regulating Deep-Sea Fishing by Depth

Area of Science:

• Deep-sea ecology
• Fisheries management
• Marine conservation

Background:

• Deep-sea ecosystems harbor high biodiversity and vulnerable species, facing unsustainable exploitation.
• Northeast Atlantic fisheries show declining fish stocks since the 1970s, with challenges in compliance and bycatch.
• Current management strategies like effort restrictions and total allowable catch (TAC) are insufficient.

Purpose of the Study:

• To determine an appropriate depth limit for bottom trawling to inform new EU legislation.
• To identify depth-related changes in demersal fish biodiversity and biomass ratios.

Main Methods:

• Analysis of survey data on deep-sea demersal fish communities.
• Quantification of biodiversity, discarded biomass ratio, and Elasmobranchii to commercial biomass ratio.
• Assessment of commercial value in relation to depth.

Main Results:

• Biodiversity, discarded biomass, and Elasmobranchii ratios significantly increase between 600 and 800m.
• Commercial fish value decreases significantly below 600m.
• A depth of 600m appears to be a critical threshold for deep-sea ecosystems.

Conclusions:

• Limiting bottom trawling to a maximum depth of 600m is a viable management strategy.
• This strategy aligns with EU legislation, including the Common Fisheries Policy and Marine Strategy Framework Directive.
• Implementing a 600m depth limit can mitigate impacts on vulnerable deep-sea species and ecosystems.