Rare Aggregations: Seasonal Variations and Abundance of the Critically Endangered Widenose Guitarfish ( Glaucostegus obtusus )

Journal article

The widenose guitarfish (Glaucostegus obtusus) is a Critically Endangered shark‐like ray in the Northern Indian Ocean. They aggregate in shallow waters where they may be threatened by nearshore fisheries, tourism and coastal development, yet their use of these spaces is not well documented. Understanding their population sizes and seasonal use of these nearshore waters is crucial in developing effective conservation strategies. We estimated the abundance of juvenile widenose guitarfish across 10 beaches in South Goa, India, and their variation with seasonal, environmental and anthropogenic factors. We walked transects along the wave line (< 30 cm deep) from September 2023 to March 2024 to record guitarfish counts, sizes and distribution. The total juvenile guitarfish abundance was estimated through N‐mixture modelling as 538 individuals over 25 km of coastline. Galgibaga Beach had significantly higher juvenile abundances (205 individuals, 95% CI: 191–217), indicating the presence of a nursery ground, and has been identified as an Important Shark and Ray Area (ISRA) based on our work. November showed the highest relative abundance of juveniles (35.14 ± 38.47), suggesting that this month is a potential pupping season. We provide first estimates for the population of this species in India and new insights into their ecology, highlighting critical habitats and seasons where conservation efforts, like spatiotemporal restrictions or live release measures, could be directed.

Authors: Miranda, B; Gupta, T; Das, D; Suryawanshi, K; Nazareth, E

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Aquatic Conservation: Marine and Freshwater Ecosystems
• Volume: 35
• Issue: 11
• Article number: e70259
• Publication date: 2025-11-19
• Acceptance date: 2025-10-23
• DOI: 10.1002/aqc.70259
• EISSN: 1099-0755
• ISSN: 1052-7613
• Language: English
• Keywords: elasmobranch; nursery grounds; N‐mixture model; rhino ray; coastal aggregations; walking transects