Overfishing threatens to wipe out bowmouth guitarfish in Indonesia

A study has found that uncontrolled fishing of wedgefish, a family of rays, in Indonesia threatens to push the bowmouth guitarfish to extinction.

White-spotted guitarfish at a fishing port in Central Java
White-spotted guitarfish at a fishing port in Central Java. Image: Mongabay Indonesia/ Khairul Abdi

The population of the nearly extinct bowmouth guitarfish in Indonesia is being depleted by overfishing, according to a recent study that calls for a reduction in its fishing and protection for juveniles of the species.

Marine researchers in Indonesia wrote that uncontrolled fishing for bowmouth guitarfish (Rhina ancylostoma) and other species of wedgefish in the Java Sea, the Karimata Strait and the southern Makassar Strait threatens to wipe out the bowmouth population within 20 years.

“This result is alarming,” reads the study that was published in the Journal of Ichthyology in June.

The scientists performed demographic analysis of two wedgefish species (the other was the white-spotted guitarfish, or Rhynchobatus australiae) involving scenarios with and without fishing. They used sampling programmes from 2017−2019 that recorded a total of 2,064 individuals of the white-spotted guitarfish and 334 of the bowmouth guitarfish. They found, however, that current fishing pressure didn’t negatively affect the white-spotted guitarfish.

These two species are the most commonly caught species in the wedgefish family, a type of ray, in Indonesian waters. Almost all their body parts are traded, particularly their fins, which supply the shark fin trade and thus command the highest prices on the international market.

The Indonesian fisheries ministry reported that fins larger than 15 centimeters (6 inches) sell for 350,000 rupiah per kilogram (about $11 per pound), with an additional 250,000 rupiah per kilo ($8 per pound) for every extra 5 cm (2 in).

The study noted that no stock assessment research has been conducted for these two wedgefish species, either in Indonesia or other regions, despite the globally threatened conservation status of both species. Neither is included in Indonesia’s protected species list.

The researchers called on the government to impose a strict catch quota for both bowmouth and white-spotted guitarfish and full protection of their juvenile populations to prevent them from going extinct in the wild. For the bowmouth guitarfish in particular, the authors strongly urged a substantial reduction in fishing to protect the population in Indonesia’s western waters.

“Wedgefish holds an important role in coastal and demersal ecosystems,” said co-author Benaya M. Simeon, a researcher from the Fisheries Resources Centre Indonesia (FRCI)-Rekam Nusantara Foundation.

This story was published with permission from Mongabay.com.

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