For the first time, researchers have documented a round-trip migration of a tiger shark between Hawaiʻi and Mexico. This discovery was made by the University of Hawaiʻi at Mānoa’s Hawaiʻi Institute of Marine Biology (HIMB) Shark Lab and the Pacific Islands Ocean Observing System (PacIOOS). The finding helps advance the understanding of the species and highlights the importance of international data-sharing initiatives.
The female tiger shark was originally tagged in Kāneʻohe Bay, Oʻahu, in November 2016. Less than a year later, she was detected at the Revillagigedo Islands and Cabo Pulmo in Mexico by equipment maintained by Mauricio Hoyos and James Ketchum from the non-profit Pelagios Kakunjá in Mexico. After three years, the shark returned to Hawaiʻi, where she was consistently detected until early 2024.
“We had previously documented a shark swimming from Hawaiʻi to Mexico,” said Carl Meyer, a researcher at the HIMB Shark Lab. “However, that shark was caught by fishermen and not released, leaving uncertainty about whether these transoceanic travelers return to Hawaiʻi. This latest discovery resolves that question, providing the first direct evidence that individual tiger sharks are capable of completing round-trip migrations between Hawaiʻi and Mexico.”
Sharing data, active collaboration
This transoceanic connection was realized because both the UH and research teams from Mexico shared their data with the PacIOOS-led PIRAT Network and its partner organization Migramar. Identifying such long-range movements is extremely difficult without active collaboration. The PIRAT Network provides a data-sharing platform for researchers that automatically checks for cross-matches like this every four months, paving the way for future discoveries.
“Most detections of our tagged sharks occur within the Hawaiian Islands,” said Meyer. “This individual, for instance, was tagged off O‘ahu but later detected near Maui and Hawaiʻi Island, in addition to making a remarkable journey to Mexico and back.”
“Identifying long-range movements like these are often difficult, unless the researchers involved happen to collaborate directly and actively share data,” said Tom Tinhan, PIRAT Network lead. “Not only is this a valuable piece of evidence that advances our understanding of this highly migratory species, but it illustrates the importance of data sharing initiatives like these.”
While the finding confirms a round-trip migration, HIMB shark researcher Kim Holland noted that many details about the journey remain unknown. “We don’t know the route by which the shark crossed the ocean (in both directions) so it’s a little misleading, although tempting, to draw straight lines between Hawaiʻi and Mexico,” said Holland. “This event is in line with other sharks we have tracked that show offshore movements of several hundred miles before returning to Hawaiʻi.”
