Silky sharks can grow up to 2.5 metres in length by adulthood. Photo: Alan C. Egan
A New Zealand data science company is playing a critical role in protecting vulnerable shark species in the Pacific.
Dragonfly Data Science has been working with international development organisation Secretariat of the Pacific Community to assess the population of silky sharks in the western and central Pacific Ocean.
Dragonfly director and fisheries scientist Dr Philipp Neubauer said it was a rare success story for a shark species, and it showed protective measures were working.
Named for their smooth skin, the silky shark is typically found in tropical open ocean waters, and can grow up to 2.5 metres in length by adulthood.
But their numbers have depleted to critical levels, as they are often caught as bycatch by tuna fisheries, and before that, they were caught intentionally for their fins, meat, skin and jaws.
"In other words, close to levels that would have eventually led to a population collapse," Neubauer said.
Now, they have increased to levels which would allow the silky shark population to rebuild - "an astonishing turnaround for a shark species".
The analysts at Dragonfly used data recorded by observers on fishing vessels, submitted by various Pacific countries to the SPC.
Bycatch rules have decreased the number of silky sharks dying on fishing boats. Photo: Supplied / Secretariat of the Pacific Community
Recently, Neubauer said, fisheries had been reporting an increased number of catches, meaning the population was likely recovering.
A global ban on drift nets came into place from 1992, and bycatch rules had decreased the number of silky sharks dying on fishing boats.
But proving that numbers were on the rise was a challenging and complex task due to limited historical data and the general poor understanding of the biology of most oceanic sharks, according to SPC principal fisheries scientist Paul Hamer.
"We can't actually observe them, like counting trees in a forest," he said.
"We have to estimate their numbers using population models."
Those models needed to be based on data that was representative of the whole population.
"The actual size of the population is still very uncertain, and that comes back to the limitations of the data.
"We know the population's recovered, but we still don't know if the population's recovered to 30, 40, 50, 60 percent of its unfished level."
But he was confident the fishing mortality had reduced to a low enough point where the population could recover.
"Improving this knowledge about silky sharks is essential," he said, "not only for improving our advice to the WCPFC on their conservation efforts, but also for understanding more about their vulnerability to not only fishing but also climate change and related changes to oceanic ecosystems and food chains."
Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
