Abstract

The seas around Sabah host the richest elasmobranch biodiversity in Malaysia. Currently, only 11 shark and ray species are protected under Malaysian legislation, while other species can be legally caught and sold in markets. Many of these species, including those with protected status, are captured as bycatch in commercial trawl fisheries. In Sabah, where trawling is a cornerstone of seafood production, indiscriminate fishing practices prioritize catch volume over gear selectivity. This study focuses on bycatch of Endangered, Threatened, and Protected (ETP) elasmobranchs, which represents an important ecological loss and is rarely retained for legal sale. To determine the spatiotemporal patterns of these captures, custom electronic monitoring (EM) cameras were deployed to capture time- and GPS-stamped imagery of all catch landed on fishing vessel decks. Over a 42-month period, more than 9400 individuals were recorded, of which 34% were identified as Endangered, Threatened, and Protected (ETP) species. The most common ETP shark species were Carcharhinus tjutjot, Rhizoprionodon acutus, and Sphyrna spp., while the most common ETP ray species were Telatrygon biasa, Maculabatis gerrardi/Maculabatis macrura, and Brevitrygon heterura. Spatial analysis and kernel density estimation were used to identify hotspot areas of high bycatch rates. We calculated bycatch per unit effort (BPUE) to quantify the density of ETP shark and ray bycatch across varying fishing intensities, based on the number of individuals caught per trawl towing hours in each district. Seasonal life-stage analyses indicated that neonate and immature individuals comprised a substantial proportion of the catch for several ETP species and occurred across multiple monsoon seasons, highlighting the vulnerability of early life stages to trawl fisheries. Potential mitigation measures, including spatial and temporal management strategies such as time–area closures, are recommended in areas with consistently high bycatch to reduce shark and ray bycatch and protect hotspot areas.

IPC Classification

Keywords