A rare shark species thought to be wiped out due to overfishing has been spotted for the first time after over five decades in Papua New Guinea, shedding more light on the region’s rich biodiversity.
The sailback houndshark, 𝐺𝑜𝑔𝑜𝑙𝑖𝑎 𝑓𝑖𝑙𝑒𝑤𝑜𝑜𝑑𝑖, is one of the world’s rarest sharks, described in the late 1970s based on a single specimen with no other records of the species found.
Now, scientists have documented six new individuals ofG. filewoodi, representing the first record of this species since its description 50 years ago.
“The five females and one male G. filewoodi recorded in 2020 and 2022 near the Gogol River mouth are the first verified records of this species since its description from a single specimen in the 1970s,” researchers write in a new study, published in the Journal of Fish Biology.
The latest report is based on specimens recorded in 2020 and 2022 during surveys of catch by artisanal and subsistence fishers at Madang in Papua New Guinea.
Researchers say the species, endemic to Papua New Guinea, has a unique evolutionary lineage not seen anywhere else in the world.
Very little is known about its biology other than a few physical traits, including the shark’s long first dorsal-fin base, which is unique among similar three-fanged sharks.
The global environmental network International Union for Conservation of Nature (IUCN) lists the species as “data deficient”, as the lack of records prevents any understanding of the shark.
Even previous deep-sea surveys for marine life conducted in PNG from 2010 to 2014 did not record this species, although these same expeditions identified six new species of sharks and rays.
In the latest study, market surveys conducted by the World Wildlife Fund (WWF) in PNG’s Madang Province between February and May 2020 recorded five female sailback houndshark in the same area where the type specimen was collected in 1970.
The five individuals were caught near the mouth of the Gogol River at a depth of 80 metres by a fisher from the Bilbil village who was targeting jewfish (Sciaenidae) using handlines, researchers said.
“Two individuals measuring 61 and 60 cm were caught on 18 March 2020, and three individuals measuring 75.5, 76.1 and 59 cm LT were caught on 19 March 2020,” they wrote.
One of the individuals is “the first male recorded for G. filewoodi”, scientists said.
The latest findings suggest that the geographic range of this rare species is likely restricted to a limited region around PNG’s Astrolabe Bay.
“This possible micro-endemism could make this species susceptible to population declines from increased fishing effort in the future,” scientists wrote.
“This study also highlights the importance of artisanal surveys in poorly studied regions,” they added.
