Understanding the migration pathways of sharks and rays is key to conserving some of the world’s most endangered marine species, according to new research from the University of Queensland. 

Researchers from the School of the Environment analysed 30 years of satellite tracking, acoustic and mark-recapture studies to map how migratory shark species connect Australian waters with neighbouring countries.

“We shortlisted 29 species that occur within Australian waters, developed network models and built the first cross-boundary migratory connectivity baseline for Australian sharks and rays,” said PhD candidate, Diego Bezerra. “This allowed us to identify which species require international cooperation to support their recovery, and it exposed huge gaps in the available data.”

The research identified whale sharks, blue sharks, shortfin mako sharks, school sharks, and white sharks crossing international borders, with some travelling as far as South Africa, New Zealand, Indonesia, and Micronesia, as well as into offshore areas beyond national jurisdiction.

Bezerra said these long journeys can expose sharks and rays to threats across multiple jurisdictions and political boundaries. 

“Sharks are threatened by overfishing and being accidentally captured when another species is being targeted – blue sharks and school sharks are particularly susceptible to being bycatch,” he said. 

According to Associate Professor, Daniel Dunn, the study has also revealed significant gaps in scientific knowledge. Of the 20 shark and ray species in Australian waters listed under the Convention on the Conservation of Migratory Species, 18 species – some 62% – had no published movement information at all.

“You cannot manage migratory species by only looking at one part of their migration,” said Dr Dunn. “Two-thirds of the species we looked at had no information, and you cannot manage species or create policy when you have zero information.

“One of the big problems we have is that these animals don’t breathe air and don’t regularly come to the surface, making them much harder to tag and be detected. Other taxonomic groups, such as birds, are much easier to see and track and therefore have much more movement data available.

“We found eight species with sufficient data to build network models and identified five species crossing international borders, so there is a much larger effort required to understand the migration patterns of these animals.”

Overall, the findings underline the importance of understanding how shark and ray movements, and the threats they face, extend well beyond national borders. 

“Australia does a relatively good job of protection but other nations do not always have the same capacity to implement strong measures,” said Bezerra. “For example, whale sharks are protected here but they migrate to Indonesia where fishing could put them in danger, it is important to understand the different levels of protection between countries.

“It is also important that Australia supports neighbouring nations through collaboration and by sharing technology and information.”

The research has been published this week in Conservation Biology.

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