Fewer devil rays in the sea: Evidence of declining mobulid populations off India's coast

Abstract

Manta and devil rays (collectively, mobulids) are circumglobal, planktivorous pelagic rays. Mobulids are declining globally due to targeted and non‐targeted capture. However, limited and inaccurate data have hindered species‐specific fishery trend assessments, especially in data‐limited fisheries where unregulated bycatch and low monitoring make assessments challenging. Assessing mobulid fishery trends is becoming critical due to intensifying fishing pressure, to understand population declines and guide protective measures. We used a combination of morphometric, demographic, and fishery metrics to assess how the population status of mobulids has changed temporally in India, the largest fishing nation for these species globally. Our results suggest a decline in Mobula mobular , Mobula tarapacana , Mobula birostris , and Mobula thurstoni populations between 2013 and 2023, and age‐class truncation in M. mobular populations since 2013. These population declines have occurred alongside increasing fishing pressure, suggesting overfishing is responsible. This study is the first to use multiannual data to empirically assess changes in mobulid populations in India, reinforcing the need to include all mobulid species in India's no‐take national legislation. Our research approach can be applied to other data‐limited systems, demonstrating that alternative data can effectively assess population status even when reliable total catch data are unavailable, a common challenge worldwide.