Where do the guitarfish go? Scientists and fishers team up to find out

Where do the guitarfish go? Scientists and fishers team up to find out

  • In late March and early April of this year, a team of researchers and local fishers caught, sampled and released more than 50 sharks and rays in the Bijagós Archipelago of Guinea-Bissau, including several threatened species.
  • A first for conservation, researchers tagged members of a critically endangered ray species, the blackchin guitarfish (Glaucostegus cemiculus), with satellite transmitters.
  • Team leader Guido Leurs says the research will provide crucial information for policymakers to better protect sharks and rays in Guinea-Bissau.
  • Fisheries management within the archipelago, which spans 12,950 square kilometers (5,000 square miles) and 88 islands, is a challenge for the West African nation.

In late March and early April this year, researchers from the University of Groningen in the Netherlands teamed up with fishers, conservationists and scientists in Guinea-Bissau to catch, study, sample and release more than 50 sharks and rays off the coast of the West African country.

The team, which included experts from the Guinea-Bissau-based Institute of Biodiversity and Protected Areas (IBAP), took blood and other tissue samples from the animals for DNA analyses, determined their sex and maturity, and looked for signs they recently  gave birth. In all, the animals belonged to 10 different species, including the smalltooth stingray (Dasyatis rudis), scalloped hammerhead shark (Sphyrna lewini), tiger shark (Galeocerdo cuvier) and bull shark (Carcharhinus leucas).

The team conducted the research in the Bijagós Archipelago, a UNESCO Biosphere Reserve that covers 88 islands spread across 12,950 square kilometers (5,000 square miles). The region has struggled with fisheries management for decades: illegal fishing is pervasive among foreign-owned industrial vessels, according to a 2018 paper, and small-scale fishing continues to operate within marine protected areas.

“As taking the animal from the water is stressful, we want to make the effort as quick as possible, but at the same time make sure that we can learn as much from the animal as possible,” team leader Guido Leurs, from the University of Groningen, said in an email.

The second blackchin guitarfish to be tagged with a satellite transmitter in the Bijagós Archipelago. The guitarfish is released by fisher Igualdino Titi and Guido Leurs (researcher). In honor of the long collaboration between the research team and the fishers, this guitarfish was named after Igualdino’s family name, ‘Titi’. Photo: Maarten Zwarts/University of Groningen

One species received special treatment: the critically endangered blackchin guitarfish (Glaucostegus cemiculus), one of the most threatened ray species in West Africa. The team attached satellite transmitters to two blackchin guitarfish to track their movements, marking the first time this species has been tracked with this method.

Currently, no one knows where local blackchin guitarfish migrate to outside the archipelago, leaving questions about what could be impacting their survival unanswered. Leurs said he hopes this research will provide answers, giving Guinea-Bissauan policymakers more information to protect the species.

“In nine months from deployment (275 days to be exact) we will hopefully find out where these animals have been!” Leurs added.

The team is saving one satellite tracker to place on a scalloped hammerhead during their next expedition.

A critically endangered hammerhead shark is being measured by the research team. During this process of about four minutes the team inserts a tube in the mouth of the shark to pump seawater over its gills to ensure that the shark can ‘breathe’. Besides taking measurements and small tissue samples, the researchers also place a unique tag on the shark so that fishers can report if they catch this shark in the future. Photo: Maarten Zwarts/University of Groningen

Nearly one-third (32.6%) of shark and ray species are threatened with extinction due to overfishing, according to a study published in the journal Current Biology late last year. This is an increase from the first global assessment of chondrichthyes (sharks, rays and chimeras) conducted in 2014, which found roughly a quarter (24%) of species were threatened. In the tropics, the threat is disproportionately high.

Sharks and rays play an important cultural and spiritual role for the people of the Bijagós, inspiring dances, costumes and even buildings. While industrial and artisanal coastal fisheries target them within and outside the marine protected areas of the archipelago, Leurs said that because of their cultural significance, Bijagós fishers generally do not, nor do they want to catch them accidentally as bycatch. Leurs said the fishers on his team hope the research results will help them learn how to reduce rates of bycatch.

Igualdino Titi, a fisherman who has worked with Leurs’s team for four years, helped catch the two guitarfish. In his honor, they named one of the fish “Titi,” after his family name.

“I can still see his face when we told him,” Leurs said. “It was just such a moment of pride for him.”

Banner image: The first critically endangered blackchin guitarfish being released with a satellite transmitter. This adult female is named Aissa after IBAP conservationist Aissa Regalla, who works for improved protection of natural areas in Guinea-Bissau. Researchers can now follow this guitarfish and another of its kind to learn about the migration of the little-studied species within the region, with an eye to better protecting it. Image by Maarten Zwarts/University of Groningen.

Mike DiGirolamo is Mongabay’s audience engagement associate. Find him on Twitter @MikeDiGirolamo, Instagram, or TikTok via @midigirolamo.

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Citations:

Intchama, J. F., Belhabib, D., & Tomás Jumpe, R. J. (2018). Assessing Guinea Bissau’s legal and illegal unreported and unregulated fisheries and the surveillance efforts to tackle them. Frontiers in Marine Science, 5. doi:10.3389/fmars.2018.00079

Dulvy, N. K., Fowler, S. L., Musick, J. A., Cavanagh, R. D., Kyne, P. M., Harrison, L. R., … White, W. T. (2014). Extinction risk and conservation of the world’s sharks and rays. eLife, 3. doi:10.7554/elife.00590

Dulvy, N. K., Pacoureau, N., Rigby, C. L., Pollom, R. A., Jabado, R. W., Ebert, D. A., … Simpfendorfer, C. A. (2021). Overfishing drives over one-third of all sharks and rays toward a global extinction crisis. Current Biology31(22), 5118-5119. doi:10.1016/j.cub.2021.11.008

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