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Observations of the bowmouth guitarfish (Rhina ancylostoma) by-catches by the tropical tuna purse seine fleet in the Indian Ocean’s open waters

Published online by Cambridge University Press:  22 July 2025

Alex Salgado
Affiliation:
Marine Research, AZTI-Basque Research and Technology Alliance (BRTA) Txatxarramendi s/n Sukarrieta, BI, Spain
Iñigo Krug
Affiliation:
Marine Research, AZTI-Basque Research and Technology Alliance (BRTA) Txatxarramendi s/n Sukarrieta, BI, Spain
Jon Ruiz
Affiliation:
Marine Research, AZTI-Basque Research and Technology Alliance (BRTA) Txatxarramendi s/n Sukarrieta, BI, Spain
Guzman Diez*
Affiliation:
Marine Research, AZTI-Basque Research and Technology Alliance (BRTA) Txatxarramendi s/n Sukarrieta, BI, Spain
*
Corresponding author: Guzman Diez; Email: gdiez@azti.es

Abstract

Bowmouth guitarfish (Rhina ancylostoma) is typically described in the literature as a coastal ray species that inhabits nearshore waters up to 70 m deep on the continental shelf, dwelling on or near the seafloor, primarily over sandy or muddy substrates and around coral reefs. However, the scientific monitoring programme aboard the Spanish and Seychellois tropical tuna purse seine fleets has documented 37 incidental captures of this species in open waters of the Indian Ocean, through onboard observers and electronic monitoring systems. All these captures occurred within the first 200 m of the water column, at locations where the maximum depth exceeded 2000 m. The study was conducted based on at-sea observations onboard the Spanish and Seychellois tropical tuna purse seine fleets operating in the Indian Ocean from 2017 to 2023. The observation coverage varied throughout this time-series, with more than 85% of fishing activity monitored since 2017. The interactions recorded were predominantly between January and May, and more frequent in the years 2018 and 2021. The captured individuals ranged from 150 to 250 cm in total length, with females recorded more frequently than males. These observations provide valuable insights into the large-scale movements of this neritic species beyond its typical coastal and inshore habitats in the Indian Ocean.

Information

Type
Research Article
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Marine Biological Association of the United Kingdom.

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References

Báez, J, Marta, G, María, A and Santiago, D (2020). Are sets on YFT not associated with floating objects really free schools sets? implications on fishing effort. IOTC-2020-WPTT22(AS)-14. 8.Google Scholar
Bonfil, R and Mohamed, A (2003) Field Identification Guide to the Sharks and Rays of the Red Sea and Gulf of Aden. FAO Species Identification Guide for Fishery Purposes. Rome, FAO. 2003. ISBN: 1020-6868, 71.Google Scholar
Borrell, A, Cardona, L, Kumarran, RP and Aguilar, A (2011) Trophic ecology of elasmobranchs caught off Gujarat, India, as inferred from stable isotopes. ICES Journal of Marine Science 68(3), 547554. doi: 10.1093/icesjms/fsq170CrossRefGoogle Scholar
Clavareau, L, Sabarros, PS, Escalle, L, Bach, P, Abascal, FJ, Lopez, J, Murua, H, Alayon, PJ, Ramos, ML, Ruiz, J, Mérigot, B (2020) Elasmobranch bycatch distributions and mortality: Insights from the European tropical tuna purse-seine fishery. Global Ecology and Conservation 24, e01211. doi: 10.1016/j.gecco.2020.e01211.CrossRefGoogle Scholar
Compagno, LJV and Last, PR (1999) Rhinidae (=Rhynchobatidae). wedgefishes the living marine resources of the western central pacific. In Carpenter, KE and Niem, V, FAO Identification Guide for Fishery Purposes. Rome: FAO. pp. 14181422.Google Scholar
Forget, F and Muir, J (2021) The critically endangered bowmouth guitarfish (Rhina ancylostoma) in the open ocean with an associated tuna school. Marine Biodiversity 51(4), 69 doi: 10.1007/s12526-021-01195-8CrossRefGoogle Scholar
IOTC (2025) Indian Ocean Tuna Commission. “Resolution 25/06 on a regional observer scheme.” iotc.org. Accessed 2 June 2025.Google Scholar
Jabado, R (2018) The fate of the most threatened order of elasmobranchs: Shark-like batoids (Rhinopristiformes) in the Arabian Sea and adjacent waters. Fisheries Research 204. doi: 10.1016/j.fishres.2018.03.022CrossRefGoogle Scholar
Jabado, R, Kyne, P, Pollom, R, Ebert, D, Simpfendorfer, C, Ralph, G and Dulvy, N (2017) The Conservation Status of Sharks, Rays, and Chimaeras in the Arabian Sea and Adjacent Waters. Environment Agency – Vancouver, Canada: Abu Dhabi. U.a.I.S.S.C.S.S.G. pp. 234.Google Scholar
Kipperman, M, Jabado, R, Haque, A, Fernando, D, Anjani, PADL, Spaet, J and Humble, E (2024) Population Structure and Genetic Diversity of the Critically Endangered Bowmouth Guitarfish (Rhina Ancylostomus) in the Northwest Indian Ocean. doi: 10.1101/2024.03.15.585225CrossRefGoogle Scholar
Last, PR, Naylor, G, Bernard, S, White, W, Stehmann, M and Carvalho, M (2016) Rays of the World CSIRO. 801. doi: 10.1071/9780643109148.CrossRefGoogle Scholar
Last, PR and Stevens, JD (2009) Sharks and Rays of Australia. Australia: CSIRO. ISBN 0643094571, 9780643094574, 656.Google Scholar
Mohamed, KS and Veena, S (2016) How long does it take for tropical marine fish stocks to recover after declines? Case studies from the Southwest coast of India. Current Science (Bangalore) 110(4), 584594. doi: 10.18520/cs/v110/i4/584-594CrossRefGoogle Scholar
Moore, ABM (2017) Are guitarfishes the next sawfishes? Extinction risk and an urgent call for conservation action. Endangered Species Research 34, 7588.10.3354/esr00830CrossRefGoogle Scholar
Moore, ABM, McCarthy, ID, Carvalho, GR and Peirce, R (2012) Species, sex, size and male maturity composition of previously unreported elasmobranch landings in Kuwait, Qatar and Abu Dhabi Emirate. Journal of Fish Biology 80(5), 16191642. doi: 10.1111/j.1095-8649.2011.03210.x.CrossRefGoogle ScholarPubMed
Murua, H, Ruiz, J, Justel-Rubio, A and Restrepo, V (2025) Minimum standards for electronic monitoring systems in tropical tuna purse seine and longline fisheries. ISSF Technical Report 2022-09.Rev. International Seafood Sustainability Foundation, Pittsburgh PA, USA. Accessed 20 February 2025.Google Scholar
Pierce, SJ, Trerup, M, Williams, C, Tilley, A, Marshall, AD and Raba, N (2008) Shark fishing in Mozambique: A preliminary assessment of artisanal fisheries. Eyes on the Horizon. Maputo 28.Google Scholar
Purushottama, GB, Sujitha, T, S.j, K and Zacharia, PU (2022) Catch composition, reproductive biology and diet of the bowmouth guitarfish Rhina ancylostomus Bloch and Shneider, 1801 (Batoidea: Rhinidae) in the eastern Arabian Sea, India. Indian Journal of Fisheries 69(3). doi: 10.21077/ijf.2022.69.3.117929-01CrossRefGoogle Scholar
Raje, SG, Sivakami, S, Mohan Raj, G, Manoj Kumar, PP, Raju, AA and Joshi, KK (2007) An atlas on the elasmobranch fishery resources of India. CMFRI Special Publication 95, 253.Google Scholar
Ruiz, J, Batty, A, Chavance, P, McElderry, H, Restrepo, V, Sharples, P, Santos, J and Urtizberea, A (2014) Electronic monitoring trials on in the tropical tuna purse-seine fishery. ICES Journal of Marine Science 72(4), 12011213. doi: 10.1093/icesjms/fsu224CrossRefGoogle Scholar
Ruiz, J, Martinez de Lagos, E, Canive, I, Grande, M, Krug, I and Santos, M (2021) Electronic monitoring programs conducted by AZTI and DATAFISH in the Spanish tuna fisheries. Indian Ocean Tuna Commission. IOTC-2021-WGEMS01-04_Rev1 . Available at: https://iotc.org/documents/WGEMS/01/04Google Scholar
Stobutzki, IC, Silvestre, GT, Abu Talib, A, Krongprom, A, Supongpan, M, Khemakorn, P, Armada, N and Garces, LR (2006) Decline of demersal coastal fisheries resources in three developing Asian countries. Fisheries Research 78(2), 130142. doi: 10.1016/j.fishres.2006.02.004CrossRefGoogle Scholar
White, W and Sommerville, E (2010) Elasmobranchs of tropical marine ecosystems. In Carrier, JC, Musick, JA and Heithaus, MR (eds), Sharks and Their Relatives II: biodiversity, Adaptive Physiology and Conservation. Boca Raton, FL: CRC, pp. 159239.10.1201/9781420080483-c4CrossRefGoogle Scholar