To GRaB or not to GRaB: a citizen science-based, decision-making index to assess the biological implications of lost fishing gears retrieval

Abandoned, lost, or otherwise discarded fishing gears (ALDFGs) represent a major threat to marine biodiversity, yet their removal remains controversial when entangled with sensitive benthic communities. This study presents a standardized marine citizen science (MCS) protocol and a novel decision-making index, the Gear Removal-Biological (GRaB) index, designed to assess the ecological risks of ALDFG removal. Experienced volunteer divers applied the “Reef Alert Network (RAN) - Assessment of lost fishing gear” protocol to survey ALDFGs at coralligenous sites between 29 and 51 m depth in the Portofino Marine Protected Area (Italy), recording site characteristics, gear type, colonization levels, and taxa affected. A total of 91 ALDFGs were documented across 350 m 2 , impacting nearly 1000 organisms, with the red gorgonian Paramuricea clavata being the most affected. The GRaB index integrates five indicators (Entangled Organisms, Surrounding Diversity, Biofouling Colonization, Habitat Complexity, and ALDFG Characteristics) to produce a simple traffic-light classification of low, medium, or high ecological risk. Tested on over 200 surveys, the index provided reliable estimates of potential harm, supporting informed decisions on whether removal should proceed and whether expert consultation is required. Beyond its scientific utility, the approach enhances MCS initiatives by empowering divers and stakeholders, raising awareness of fishing and ALDFG impacts, and providing managers with an adaptive tool transferable across Mediterranean habitats. Ultimately, this integrative framework promotes responsible retrieval practices while fostering collaborative governance, contributing to marine conservation, biodiversity restoration, and the sustainability goals of the UN Ocean Decade. • ⁠The Conservation Diver program provides a protocol to assess ALDFGs impacts • 91 ALDFGs were found impacting Portofino MPA's coralligenous assemblages • Up to 995 organisms were affected by gears, mainly represented by habitat-formers • GRaB index defines the potential harm to habitat formers during ALDFGs removal • The index uses 5 indicators to produce a user-friendly traffic-light classification