The pop-up archival satellite tags (PSATs) recorded vast horizontal movements throughout the Pacific Ocean, challenging previously-held notions that striped marlin are highly localized in their regional, coastal aggregations.

The tagged marlin, which were tracked for up to one year, routinely crossed multiple fisheries management boundaries and ocean features like seamounts and fracture zones.

One tagged marlin, PG01, made a trans-Pacific journey not previously observed for its species. Having been tagged in the Eastern Pacific Ocean, PG01 eventually made its way thousands of miles to the central east coast of Australia.

“We didn’t expect a tag showing up off Australia,” Lam said. “I would say that was 50 percent luck and 100 percent hard work.

“Consulting with our captains and tagging partners docked at Pier 38 in Honolulu and providing first-hand training for scientific tagging paid off.”

The tags also showed the striped marlin spent 38 and 81 percent of their day and night, respectively, in the top five meters of the water column.

The papers’ horizontal and vertical movement data is important for fisheries managers and stock assessment scientists, who require timely, high-quality biological and habitat data to inform population modeling and stock status.

Such data also helps identify best practices to support sustainable harvest, which could include mandated live release and time-area restrictions.

“Longline fisheries targeting tuna and swordfish benefit from any scientific information that helps to reduce unintended interaction with non-targeted catch like marlin, while pursuing economic returns on targeted catch of tuna and swordfish,” Lutcavage said.

In addition to monitoring tagged fish, researchers collected fin clips from Hawaii-landed striped marlin. Genetic analyses of 55 striped marlin were assigned to two genetic groups: Australia, New Zealand and Hawaii (19 individuals) and Hawaii alone (36 individuals), suggesting the Hawaii-based longline fleet interacted with individuals from multiple populations.

“Information on stock structure is critical to inform stock assessments and develop appropriate management options, including options to rebuild the stock as needed,” emphasized Mark Fitchett, pelagic fisheries ecosystem scientists for the Western Pacific Regional Fishery Management Council.

Lam, Tam and Lutcavage believe more PSAT efforts and genetics analyses are called for, to fill in the scientific gaps underscored by their latest striped marlin research. Improved technology and knowledge of the species’ biology, physiology and life history will better inform management measures for the sustainable harvest of bigeye tuna and swordfish, and a reduction of incidental catch of non-target species like the striped marlin.