Thursday, June 19, 2008

ENV: Fish Tag Journey

Fish tag flies from Oregon to New Zealand
BirdLife, 16-06-2008

A small electronic tag that was implanted in a Steelhead Salmon Oncorhynchus mykiss at the USFWS Columbia River Hatchery (USA) has been discovered in New Zealand. Because Steelhead Salmon do not migrate across the equator, the best theories about the tag’s travels involves Sooty Shearwaters Pufinus griseus.

The tiny device was noticed by Maori hunter Dale Whaitiri on Mokonui Island, one of the Titi Islands (New Zealand). Shearwaters nest in burrows among tree roots on the island, and are known locally as Titi or Muttonbirds. The tag was recorded two years earlier as young steelhead smolts were passing the Bonneville Dam, on the Columbia River – 10,170 km from Mokonui!

Scientists think that the fish may have been eaten by a shearwater that was scavenging fishery wastes behind a processing vessel in the north pacific. Steelhead Salmon are not a commercial species, but they are sometimes accidentally taken as by-catch. Alternatively, the fish may have been predated as it passed below one of the large shearwater flocks that frequent the mouth of the Columbia River.

Sooty Shearwaters breed on islands off New Zealand, Australia, Chile and the Falkland Islands. They undertake annual journeys of up to 60,000 km during their migration period. Birds fly from their breeding colonies to northern wintering sites in Japan, Alaska or California. This brings the shearwaters into contact with Steelhead Salmon.

Sooty Shearwaters are classified as Near Threatened because they have undergone a moderately rapid decline owing to the impact of fisheries, the harvesting of its young and possibly climate change. In New Zealand, the number of burrows in the largest colony declined by 37% between 1969-1971 and 1996-2000.

Harvesting of young birds currently accounts for the loss a quarter of a million birds annually, but is unlikely to account for the full scale of the decline. Longline fishing is responsible for a large numbers of Sooty Shearwater deaths, along with many other seabird species such as albatrosses.

Ben Lascelles, BirdLife’s Marine IBA Research Officer, said “The epic journeys undertaken by Sooty Shearwaters illustrates how conserving seabirds is an international challenge. Seabirds don’t respect country borders!”

The IBAs Programme of BirdLife International seeks to identify and conserve sites that are critical for the long-term viability of bird populations. The Global Seabird Programme and a number of BirdLife Partners are taking the lead on identifying marine IBAs. “Marine IBAs will make a vital contribution to current global initiatives to gain greater protection and sustainable management of the oceans”, commented Ben.

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