Manta and Devil Ray Fisheries and Landings in Semporna Sabah, Malaysia

26 August 2026

Nidhi G. D'Costa, Scarlett R. Taylor , Alison Hochstetter, Shefali Bhatt, Betty J.L. Laglbauer, Daniel Fernando & Guy M. W. Stevens

Summary: Manta and devil rays are globally threatened and highly vulnerable to overfishing, yet Malaysian mobulid fisheries remain poorly documented. This study analysed landings in Semporna, Sabah (2011-2014). Spinetail devil rays (Mobula mobular) and bentfin devil rays (M. thurstoni) made up over 75% of landings, and most individuals were below size-at-maturity (77.8% of M. mobular, 55.8% of M. thurstoni), raising concerns about growth overfishing. Year-round artisanal gillnetting, weak legal protection and the gill plate trade sustain high fishing mortality, threatening slow-growing, low-fecundity populations. The authors urge legal protection for all mobulids, species-specific monitoring, bycatch mitigation, stronger trade enforcement, community engagement, and coordinated action under CITES and CMS.

Abstract

“Manta and devil rays are globally threatened and highly vulnerable to overfishing. This study presents one of the first species-level analyses of mobulid landings, providing valuable baseline information for a fishery that remains poorly documented in Malaysian waters. The study analyzed catch composition, size structure, and demographic characteristics of mobulids landed in Semporna, Sabah (May 2011 to November 2014), combining fishery-dependent sampling and morphometric measurements. Over 75% of landings comprised Mobula mobular and M. thurstoni, with most individuals (n = 95) below size-at-maturity; specifically, 77.8% of M. mobular and 55.8% of M. thurstoni were immature. This composition raises concerns about growth overfishing, though spatial and temporal segregation may explain the demographic pattern.  Chronic year-round artisanal gillnet fishing, combined with weak legal protections and socio-economic pressures, including international gill plate trade, sustains high fishing mortality. These pressures threaten population viability, especially given mobulids’ slow growth and low fecundity. The study emphasizes the urgent need to expand legal protections to all mobulid species in Malaysia, improve species-specific monitoring and management, implement bycatch mitigation, strengthen trade enforcement, and engage fishery communities in alternatives. Coordinated regional conservation efforts under CITES and CMS, integrated with local actions, are critical to safeguard mobulid populations in Malaysian waters.”

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Author Affiliations

  • Proyecto Manta Pacific Mexico

  • Tecnológico Nacional de Mexico / IT Bahía de Banderas

  • The Manta Trust

  • Oregon State University

Contribution towards the Manta Trust's Strategic Plan

Goal 1: Strategic Objective 1.1 – More protective policies exist to support manta and devil ray conservation for geographical focus areas.

Goal 1: Strategic Objective 1.2 – There is improved enforcement of existing protective policies.

Goal 2: Strategic Objective 2.1 – Fishers within focus areas are working towards measures to reduce capture and bycatch mortality.

Goal 2: Strategic Objective 2.2 – Regulations and effective enforcement exist to reduce manta and devil ray capture and bycatch mortality.

Goal 3: Strategic Objective 3.1 – All manta and devil ray species in the regions where we work are fully protected and conserved through species management plans.

Download the manta trust five-year plan