Trans-equatorial migration of tropical shearwaters – wintering with tuna

Trans-equatorial migration of tropical shearwaters – wintering with tuna

NERP researchers from James Cook University have undertaken the first study to track the migratory movements of non-breeding wedge-tailed shearwaters (Puffinus pacificus) from the Great Barrier Reef.

In April 2012 the team from Tropical Ecosystems Hub Project 6.3 deployed miniature ambient light sensitive geolocation devices and tracked 15 adult wedge-tailed shearwaters from the population that breeds on Heron Island in the southern GBR. Each bird was tracked for between 8-12 months.

Adults departed the breeding colony in mid to late May and migrated rapidly in a north-easterly direction, crossing the equator and travelling into the region around the Federated States of Micronesia. Individuals travelled up to 6,000 kilometres in about two weeks, at an average of speed of about 428km/day.

During the next 3-5 months, many individuals spent time foraging over and around the Mariana Trench, which is the deepest point in the world’s oceans. While there was variation among the foraging locations used by individuals, all birds spent the winter in an area spanning about 2,000 x 1,500kms with a high degree of overlap in core foraging locations.

Much of this region encompassed the Western Pacific Warm Pool, which is known globally for consistently exhibiting the warmest sea-surface temperatures. Other tube-nosed seabirds (Procellariiformes) such as Streaked shearwaters that breed in Japan also migrate to this area in their non-breeding season.

Importantly, both wedge-tailed shearwater migration routes and over-winter foraging grounds overlapped considerably with globally significant commercial purse-seine and long-line tuna fishing activity, as this region hosts part of the world’s largest tuna fishery (the Western and Central Pacific Tuna Fishery) and is an area providing some of the highest commercial catch rates.

Wedge-tailed shearwaters have strong associations with sub-surface predators such as tuna as these predators drive prey to the surface where they are accessible to foraging birds. This implies that the presence of high sub-surface predator numbers in these areas is important for over-winter survival. Therefore, the overlap of wedge-tailed shearwater migration and wintering grounds with this major global fishery raises previously unidentified conservation concerns for this GBR breeding species

Fiona McDuie & Dr. Brad Congdon, JCU

For more information, contact Brad Congdon at:

Project 6.3: Critical seabird foraging locations and trophic relationships for the Great Barrier Reef



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