Review of the statistical data available for Indian Ocean blue marlin

The document provides an overview of the consolidated knowledge about fisheries catching blue marlin (Makaira nigricans) in the Indian Ocean since the early 1950s based on a range of data sets collected by Contracting Parties and Cooperating Non-Contracting Parties (CPCs) of the IOTC and curated by the IOTC Secretariat. The available fisheries statistics indicate that the catches of blue marlin in industrial longline fisheries have substantially decreased over the last decade when the catches in coastal gillnet and line fisheries have increased, resulting in more than half of the total catch coming form artisanal fisheries in 2020. Information available on discarding practices of blue marlin in industrial fisheries indicates that discard levels are small in longline fisheries while blue marlins are more often discarded in large-scale purse seine fisheries, but in small quantities and with some variability between fleets. Discarding in coastal fisheries interacting with the species is poorly known but considered to be negligible. Information available on the spatial distribution of catch and effort has substantially improved over the last decade and shows that the longline fishing grounds for blue marlin are mainly located in the western Indian Ocean when catches from gillnet, ringnet, and line fisheries mostly occur along the coasts of Sri Lanka and India. The reporting of size-frequency data has also improved over the last decade but remains very limited for most coastal fisheries.