Identifying gaps and establishing priorities in the protection and conservation of batoid elasmobranchs

Ciaran Hyde

doi:10.25907/01066

Rays (Elasmobranchii: Batoidea) comprise 661 species globally. Over one-third (38%) are threatened with extinction due to overexploitation, habitat degradation, and climate change. Despite their ecological importance as benthic predators, bioturbators, and key trophic links within marine ecosystems, rays remain systematically underrepresented in research priorities and spatial protections. Persistent knowledge gaps regarding their distribution, abundance and ecology, and life-history characteristics, impede effective conservation planning. Marine protected area (MPA) networks, a crucial tool in maintaining their persistence, often fail to adequately represent ray biodiversity or critical habitats. This thesis addresses these conservation shortfalls through integrated analyses of research effort, protected area coverage, and habitat prioritisation across global, regional and local scales.At the global scale, research effort across all 661 ray species was systematically quantified using 13,074 peer-reviewed and grey literature publications, assessed across taxonomy, IUCN Red List of Threatened Species (‘IUCN RED List’) extinction risk categories, and geographic distribution. This analysis revealed profound misalignment between conservation needs and research investment. Nearly half (47%, 314 species) were identified as under-researched relative to their extinction risk, with research effort disproportionately concentrated on just 24 species (4% of all rays). A Research Priority Index (RPI) integrating extinction risk with publication count identified systematic taxonomic biases. Rhino rays, comprising sawfishes, wedgefishes, guitarfishes and banjo rays, emerged as the most underrepresented group, with 75% of species threatened yet these accounting for only 2.4% of conservation relevant research effort. Geographic analyses revealed that species-rich Indo-Pacific biodiversity hotspots received eight times lower per-species research effort than less diverse temperate regions, indicating that research investment is driven more by accessibility and funding availability than by conservation urgency. At the regional scale, representation of Australian ray biodiversity within no-take MPAs was assessed across the mainland Exclusive Economic Zone (EEZ). Australia harbours 132 ray species (20% of global diversity), of which 73 (55%) are endemic. Spatial analyses using IUCN Red List range data identified 76 biodiversity hotspots across five categories: overall biodiversity, irreplaceability (endemism), global vulnerability (threatened), regional vulnerability, and irreplaceable and vulnerable species (threatened endemics). Quantification of overlap with existing no-take MPAs revealed systematic underrepresentation, with 60% of biodiversity hotspots lacking adequate protection. High Priority Areas where multiple biodiversity values converged were critically unprotected, with 85% having zero or inadequate (<10%) no-take coverage. Northern tropical waters supporting high overall biodiversity and globally threatened species exhibited systematic gaps, with 72% of overall biodiversity hotspots entirely unprotected. Southern temperate endemic-rich regions demonstrated similar deficiencies, with 67% of irreplaceable biodiversity hotspots lacking no-take protection. At the local scale, fine-resolution field surveys conducted across four annual cycles (2017–2020) in Moreton Bay, Australia, a globally significant subtropical embayment, documented ray habitat associations, species richness, abundance and community composition, and conservation value. Visual Observational Transect (VOT) and Baited Remote Underwater Video (BRUV) surveys spanning 169 survey hours recorded 1,195 observations of rays representing 13 ray species. Highest species richness and abundance were concentrated in interconnected intertidal mangrove and diverse sand habitats of the central eastern bay. Multi-criteria evaluation integrating abundance, species richness, threatened species occurrence, and alignment with Important Shark and Ray Area (ISRA) Criteria identified key sites supporting vital life-history functions including reproduction, feeding, and seasonal aggregations. Despite sites ranking highest in conservation value, 90–100% of these high-value habitats lacked no-take protection within Moreton Bay Marine Park. To address taxonomic uncertainties and fragmented occurrence data within this system a comprehensive verification framework was applied to 128 elasmobranch species historically reported from Moreton Bay. Integration of specimen records, peer-reviewed publications, and verified citizen science observations confirmed 67 species (42 sharks, 25 rays) currently occur. Twenty ray species were reclassified as taxonomically invalid due to recent revisions, particularly within the family Dasyatidae, while others were attributed to historical misidentifications or vagrant occurrences. This updated inventory resolved ambiguities in species composition and established a transparent framework for ongoing monitoring and adaptive management. This thesis demonstrates that knowledge gaps, underrepresentation in spatial protections, and fragmented data operate synergistically across scales to constrain ray conservation effectiveness. By integrating species-level research priorities with habitat-specific assessments and spatial protection analyses, this work provides conservation practitioners and policymakers with evidence-based tools for directing limited resources toward areas and taxa where intervention will yield maximum benefit. The identification of 314 priority ray species requiring increased research investment, 76 unprotected Australian biodiversity hotspots, and key habitats within a globally significant embayment, establishes actionable priorities that translate across spatial scales. These findings inform policy development, protected area planning, research prioritisation, and targeted management interventions essential for reversing ray population declines and preventing extinctions in this ecologically vital but imperilled vertebrate group.

Identifying gaps and establishing priorities in the protection and conservation of batoid elasmobranchs

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