Age, growth, and intrinsic sensitivity of Endangered Spinetail Devil Ray (<em>Mobula mobular</em>) and Bentfin Devil Ray (<em>M. thurstoni</em>) in the Indian Ocean

Devil rays (Mobula spp.) are caught in fisheries across the Indian Ocean, with reports of significant recent declines in catch and sightings. Globally, the few populations studied have extremely low population growth rates due to low fecundity and long reproductive cycles, making them highly vulnerable to overfishing. To allow for assessment of the current sustainability of devil ray catch in the Indian Ocean, we provide estimates of age using the caudal vertebrae; somatic growth using a Bayesian, multi-model approach; maximum intrinsic rate of population increase (rmax); and fishing mortality for Endangered Spinetail Devil Ray (Mobula mobular) and Bentfin Devil Ray (M. thurstoni) sampled from small-scale fisheries catch in Indonesia, Kenya, and Pakistan. The oldest individuals of Spinetail Devil Ray (n = 79) and Bentfin Devil Ray (n = 59) were 17.5 and six years, respectively. Both species had relatively low growth coefficients (k = 0.05 and g = 0.19 year−1, respectively), with the von Bertalanffy and logistic models providing the best fitting growth models, and low rmax (0.109 and 0.107 year−1, respectively) indicating that they are highly sensitive to overexploitation. Fishing mortality F estimates (0.16 and 0.18 year−1, respectively) were higher than rmax and exploitation ratio E (0.77 and 0.80, respectively) were higher than an optimum value of 0.5 for biological sustainability for both species, suggesting that the fisheries catches of the species are unsustainable. We demonstrate an approach to assess data-poor species and apply this to two Indian Ocean devil ray species. The results highlight the urgent need for better management actions to reduce the catch of all devil rays to prevent species extinction and aid in population recovery

Satellite observed oceanographic drivers of Mobulidae fisheries catch in the Southeast Indian Ocean

\ua9 2024 The Authors. Indonesian coastal waters include several marine megafauna biodiversity hotspots. Several fish populations of ecological and socio-economic importance, such as elasmobranchs (sharks and rays), have experienced rapid decline due to unsustainable human activities, primarily overfishing. Small-scale fisheries (SSF) are currently exempt from governmental fisheries management measures despite contributing a significant proportion of a total catch. The Generalised Additive Models were used to investigate the effect of variations in oceanographic parameters of the Teluk Penyu fishing ground, south of central Java, on the magnitude of Mobulidae (Mobula spp.) catch based on its landings data over ten years (2009–2018) from one of Indonesia\u27s largest ports, Cilacap, Central Java, Indonesia. Mobulidae catch from Teluk Penyu fishing ground was generally higher from June to November when the water exhibited relatively high sea surface salinity (sal &gt;34.1 ‰), chlorophyll (0.32–0.45 mg/m3), and nitrate (nit &gt;0.0045 mg NO3/m3), water speed (&gt;0.29 m/s) and eddy kinetic energy (&gt;0.04 m3/s2) levels, and relatively low sea surface temperature (&lt;28 \ub0C), oxygen (&lt;0.182 mg O2/m3) and sea surface height (&lt;0.9 m) levels than the other months of the year. This study reveals that satellite Earth Observation (EO) data provided a preliminary relationship between oceanographic conditions and the amount of catch for developing more effective management and conservation measures for endangered species like Mobulidae. Utilizing EO data may also be applied to help inform much-needed ecosystem-based management measures, including habitat protection and bycatch reduction for conserving endangered Mobulidae species in the Southeast Indian Ocean. The in-situ onboard ocean observation and temporal species-specific catch data will greatly complement the current work

Global manta and devil ray population declines: Closing policy and management gaps to reduce fisheries mortality

\ua9 2025 The AuthorsSignificant progress has been made in advancing priority actions to conserve manta and devil rays, yet implementation and enforcement of protective measures often fall short, leaving most mobulid populations at risk of overfishing. Drawing on a literature review, fisheries databases, agency reports, and expert interviews, we assess global trends in mobulid catch and mortality. We examine both targeted and incidental catch, in small (&lt;15 m, ‘SV’) and large (&gt;15 m, ‘LV’) vessel fisheries to identify hotspots with the highest risk of fisheries-related mortality and population decline. We estimate global fisheries catch at 264,520 (184,407–344,987) mobulids per year, with SV fisheries accounting for 87 % of global mortality. The highest-risk hotspots, based on mortality and declines, are located in India, Indonesia, Sri Lanka, Peru, and Myanmar. Mobulid retention is driven by demand, with higher mortality rates observed in countries exporting gill plates, and to a lesser extent, in those trading meat domestically or internationally. We recommend urgent implementation and enforcement of mobulid listings under the Convention on International Trade in Endangered Wild Flora and Fauna (CITES), the Convention on the Conservation of Migratory Species of Wild Animals (CMS), and national protective measures, including (i) uplisting mobulids to CITES Appendix I, (ii) full legislative protection for all mobulid species in high-risk fishing nations to reduce demand, (iii) avoiding fishing in critical habitats through permanent or temporary targeted area closures, or management, (iv) limiting drift gillnet effort, and (v) involving fishers in management decisions and implementation