Selectivity and Bycatch Reduction in Trawl Fisheries

Trawl fisheries play a pivotal role in global seafood supply but often capture non-target species and juveniles, undermining ecosystem health and economic sustainability. Advances in gear design and behavioural understanding have driven a shift from indiscriminate capture towards selective harvesting. Key strategies include optimised mesh geometry, compartmentalised codends and mechanical or visual sorting devices that allow smaller or unintended species to escape. These measures reduce discards, enhance the vitality of escaping individuals and support compliance with conservation thresholds. Integrating biological insights, such as species-specific swimming responses and light sensitivity, with engineering innovations has led to more flexible trawl systems. Overall, the field has moved from single-species management towards ecosystem-based approaches, balancing catch efficiency with environmental stewardship.

Research from Nature Portfolio

Recent work has evaluated a two-section juvenile sorting grid fitted within a bottom trawl operating in a Mediterranean restricted area. Underwater footage analysis revealed that escapees from the sorting grid exhibited high survival probabilities, exceeding 65% on average and reaching over 90% for certain species. Comparative catch assessments demonstrated that the grid effectively reduced the retention of undersized European hake without significantly altering overall catch composition. Although some legal-sized individuals were lost through escapement, the device markedly decreased juvenile bycatch across several commercial species. This study underlines the potential of sorting grids to reconcile fisheries yield with conservation aims by enhancing the post-escape vitality of non-target organisms.

Selectivity and Bycatch Reduction in Trawl Fisheries publication trend

The graph below shows the total number of articles in selectivity and bycatch reduction in trawl fisheries across all publications each year (not limited to Nature Index journals).

Technical terms

Bycatch: Unintended species captured alongside target catch during fishing operations.

Selectivity: The capacity of fishing gear to preferentially retain desired species or sizes while allowing others to escape.

Codend: The terminal section of a trawl net where the catch accumulates before retrieval.

Sorting grid: A rigid device installed within a trawl to guide non-target or undersized organisms through escape openings.

Minimum Conservation Reference Size (MCRS): The smallest allowable size for retained specimens intended to safeguard juvenile cohorts and promote stock sustainability.

References

1. Vitality insights of fish escaping from a sorting grid installed on a bottom trawl net. Scientific Reports (2025).
2. One mesh does not fit all: A dual compartment codend provides flexible selectivity opportunities to manage mixed fisheries. Ocean & Coastal Management (2024).
3. Observing fish behavior in towed fishing gear—is there an influence of artificial light?. Reviews in Fish Biology and Fisheries (2024).
4. Inferring Fish Escape Behaviour in Trawls Based on Catch Comparison Data: Model Development and Evaluation Based on Data from Skagerrak, Denmark. PLOS ONE (2014).