Monitoring and assessment of elasmobranch bycatches in artisanal maritime fishing in southern Gabon, Central Africa

Abstract

Elasmobranchs (sharks and rays) are particularly vulnerable to fishing pressure owing to their life-history traits, making them a major conservation concern in coastal ecosystems. To assess the composition and temporal dynamics of elasmobranch captures in southern Gabon, this study analysed catches of sharks and rays at Mayumba from April 2022 to March 2023. Data from 260 pirogue landings recorded 2 499 individuals (9.8 tonnes) from two artisanal fishing practices: pêche côtière (coastal or inshore fishing practised mainly by Beninese fishing communities) and kango (offshore fishing practised mainly by Ghanaian fishing communities). Elasmobranchs represented ∼14% of the côtière and ∼17% of the kango catches, largely as bycatch. Although overall catch abundance did not differ significantly between practices, côtière fishing showed marked seasonality, with peaks in March and lows in June, while kango fishing exhibited no seasonal trend. A total of 92% of the recorded elasmobranch species in the bycatch assemblage are ones threatened with extinction, as categorised on the IUCN Red List. Three species dominated the elasmobranch catches: scalloped hammerheads Sphyrna lewini (n = 759, 30%), milk sharks Rhizoprionodon acutus (n = 565, 23%) and blacktip sharks Carcharhinus limbatus (n = 340, 14%). Sphyrna lewini and C. limbatus were most abundant between October and December, with the catch composition dominated by juveniles. The findings highlight an urgent need for reinforced conservation measures, including the protection of juvenile sharks and restrictions on catches of large adult sharks. Strengthening regional collaboration and involving local communities in management and monitoring efforts are essential to reduce fishing pressure on threatened shark and ray populations. Additional measures such as seasonal gillnet restrictions and the use of more-selective fishing gears (e.g. handlines and LED-illuminated nets) may further reduce the elasmobranch bycatch and support sustainable fisheries.