The thin edge of the wedge: Extremely high extinction risk in wedgefishes and giant guitarfishes

Abstract

1. The process of understanding the rapid global decline of sawfishes (Pristidae) has revealed great concern for their relatives, the wedgefishes (Rhinidae) and giant guitarfishes (Glaucostegidae), not least because all three families are targeted for their high-value and internationally-traded 'white' fins.2. The objective of this study was to assess the extinction risk of all 10 wedgefishes and 6 giant guitarfishes by applying the International Union for Conservation of Nature (IUCN) Red List Categories and Criteria, and to summarise their biogeography and habitat, life history, exploitation, use and trade, and population status.3. Wedgefishes and giant guitarfishes have overtaken sawfishes as the most imperilled marine fish families globally, with all but one of the 16 species facing an extremely high risk of extinction due to a combination of traits -limited biological productivity, presence in shallow waters overlapping with some of the most intense and increasing coastal fisheries in the world, and over-exploitation in target and bycatch fisheries driven by the need for animal protein and food security in coastal communities and trade in meat and high-value fins. 4. Two species with very restricted ranges, the Clown Wedgefish (Rhynchobatus cooki) of the Indo-Malay Archipelago and the False Shark Ray (Rhynchorhina mauritaniensis) of Mauritania may be very close to extinction. Only the Eyebrow Wedgefish (Rhynchobatus palpebratus) is not assessed as CriticallyEndangered, due to it occurring primarily in Australia where fishing pressure is low, and some management measures are in place. Australia represents a 'lifeboat' for the three wedgefish and one giant guitarfish species occurring there. 6. To conserve populations and permit recovery, a suite of measures will be required which will need to include species protection, spatial management, bycatch mitigation, and harvest and international trade management, all of which will be dependent on effective enforcement.

Catch composition and life history characteristics of sharks and rays (Elasmobranchii) landed in the Andaman and Nicobar Islands, India

“…While there exists a 45-day shark fishing ban, there are no regulations for ray fishing, despite them being predominantly threatened species. Rays are extremely susceptible to overexploitation, with wedgefishes and giant guitarfishes being the most imperiled marine taxa globally [ 1 , 70 ]. Susceptibility studies on the various shark and ray species in Papua New Guinea deemed P .…”

Monitoring Extinction Risk and Threats of the World’s Fishes based on the Sampled Red List Index

“…As in other assessment processes, Least Concern species may be fast-tracked more rapidly through the assessment process 67 . Thirdly, in the absence of a reassessment for 2020, application of retrospective assessments to assess past extinction risk status from a present perspective [68][69][70] should be considered to derive long-term trends in extinction risk over time.…”

Catch composition and life history characteristics of sharks and rays (Elasmobranchii) landed in the Andaman and Nicobar Islands, India

“…Most of the species listed in the WLPA are found in estuarine habitats and are not likely to occur around the islands, including Anoxypristis cuspidata , Glyphis gangeticus , and G. glyphis . Rhynchobatus djiddensis listed in the WLPA does not appear to occur in India and the species complex could include R. australiae and R. laevis [60]. However, the latter two species are not protected under the WLPA.…”

“…Of the 19 ray species identified, 15 species (85.17 %) are listed on the IUCN Red List of Threatened Species as threatened (Critically Endangered, Endangered, or Vulnerable), one species (0.4 %) as Near Threatened, one species (1.08 %) as Data Deficient, and two species (13.33 %) have not been evaluated. Rays are extremely susceptible to overexploitation, with wedgefishes and giant guitarfishes being the most imperiled marine taxa globally [1, 60]. Susceptibility studies on the various sharks and ray species in Papua New Guinea, deemed P. jenkinsii at the highest risk in trawl fisheries [61].…”