Quantifying vulnerability of sharks and rays species in Indonesia: Is biological knowledge sufficient enough for the assessment?

Abstract

Sharks and rays are vulnerable species, which are highly exploited in Indonesian waters but lacked of detailed information on their ecology and fisheries status. This research aims to assess the level of vulnerability of sharks and rays to overfishing using the maximum intrinsic rate of population increase (rmax), derived from the Euler-Lotka equation, as a proxy of extinction risk. It is calculated based on several biological parameters including fecundity, maximum age, age at maturity, and the number of offspring. Using rmax calculation adapted to shark and ray life history traits by accounting for survival to maturity, we were able to calculate rmax values for 26 out of 208 sharks and rays species present in Indonesia. This includes vulnerable species such as Mobula alfredi, Prionace glauca, and Pristis zijsron. This result showed that rmax is a valuable tool which can be used to quantify extinction risk with some level of precision, but it also highlights the necessity to collect important biological information of the most vulnerable species to further estimate their status. This approach requires complementary information related to external threats such as habitat degradation, species economic value and threat level from local fishing effort and related fishing gears.

Universal closed-tube barcoding for monitoring the shark and ray trade in megadiverse conservation hotspots

“…As a result of substantial bycatch, Indonesian fisheries hold the world’s largest volume of elasmobranch landings (Fahmi and Dharmadi, 2015; FAO, 2022). This exploitation contributes to the high vulnerability rate of elasmobranch populations in Indonesian waters (Mardhiah et al, 2019), including the populations in its coral reef ecosystems (MacNeil et al, 2020). This is particularly concerning as Indonesia harbours almost a quarter of the world’s elasmobranch diversity (Ali et al, 2018; Ali et al, 2014).…”

Shark-dust: High-throughput DNA sequencing of processing residues unveils widespread trade in threatened sharks and rays

“…Continued and increasing anthropogenic stressors have devastated habitats and wildlife across the globe, including the dramatic depletion of sharks and rays (hereafter referred to as ‘elasmobranchs’) (Dulvy et al 2021). Conservative life-histories (Mardhiah et al 2019) make elasmobranchs vulnerable to fisheries overexploitation, and their extirpation can destabilise functional diversity and ecosystem structure (Dulvy et al 2021). Although some elasmobranch fisheries can be sustainably managed (Simpfendorfer and Dulvy 2017), the market demand for high value products, such as fins, liver oil and gill plates, typically leads to overexploitation of elasmobranch resources (Dulvy et al 2021), which is then further fuelled by illegal and unreported catches.…”

Universal Closed-Tube Barcoding for Monitoring the Shark and Ray Trade in Megadiverse Conservation Hotspots

“…As a result of substantial bycatch, Indonesian fisheries hold the world's largest volume of elasmobranch landings (Fahmi and Dharmadi, 2015;FAO, 2022). This exploitation contributes to the high vulnerability rate of elasmobranch populations in Indonesian waters (Mardhiah et al, 2019), including the populations in its coral reef ecosystems (MacNeil et al, 2020). This is particularly concerning as Indonesia harbours almost a quarter of the world's elasmobranch diversity (Ali et al, 2018;Ali et al, 2014).…”