Bycatch trend and its fate of the Spanish-owned tuna purse seiners fleet from the Atlantic and Indian oceans: Impacts of the implementation of good practices

This study examines the fate of species caught as bycatch in the tropical tuna purse seine fishery across the Atlantic and Indian Oceans from 2003 to 2022, focusing on the impact of the industry-implemented Code of Good Practices (CGP) and bycatch mitigation measures from Tuna Regional Fisheries Management Organisations (t-RFMOs). Data were sourced from scientific observers under both Spain’s National Data Collection Framework (DCF, Regulation (EU) No 2017/1004) and the OPAGAC-AGAC observer program, which covers other flags as well. Following the adoption of CGP and t-RFMO regulations, statistical tests reveal significant improvements in the live-release rates of sharks and rays after 2014 in both oceans, but no significant differences in live-release rates for marine turtles, which were already high. Despite these positive trends, interactions with certain species, such as billfish, experiences an increase in discard rates during the last years of the study period. The study identifies coastal regions near Gabon and Angola in the Atlantic, and northern Indian Ocean fishing areas as potential hotspots for some sensitive species, which may be confirmed as information from other fisheries come to light. • t-RFMO regulations and the CGP have reduced interactions with cetaceans and whale sharks. • These measures have increased live release rates for sharks and rays. • The CGP adoption has improved bycatch management and anticipated some t-RFMO measures. • Low billfish survival and few mitigation options suggest discard bans may be ineffective. • Spatial analyses highlight high interaction areas, aiding future management measures.