Pacific bluefin tuna satellite tagging

Image courtesy of Aziz Saltik on Flickr

Project Info:

The New Zealand Marine Research Foundation played a support role for a much larger project supported by universities and (at the time) the Ministry of Fisheries. For the first time in the southern hemisphere pop-up satellite tags were deployed on large Pacific bluefin tuna. These fish were tagged from recreational charter boats and one commercial hand line vessel fishing around the hoki trawlers working 50 milers off Hokitika and Greymouth. Over the three years 47 fish were tagged ranging in estimated size from 190 to 425 kg. Elapsed time from hookup to release ranged from 15 to 195 minutes (average 74 minutes). Tags remained attached for 13 to 180 days (average 104 days) before releasing and transmitting. Some tags were programmed to remain attached for up to 12 months but the anchor failed or the tags were pulled off by other fish in all cases. There were no clear cases of mortality after tagging, where the fish stopped moving and the tag released but 4 tags did failed to report (9%) some of which may have died.

Typically these tuna travel north in September to the Norfolk Ridge, Wanganella Banks or Lord Howe Rise then turned east or west to pass east of New Zealand or down the Tasman sea, moving south during spring. No tuna cross into the North Pacific, where the known spawning ground is. Some fish carrying convention plastic tags were caught a second time in the same West Coast area where they were tagged in following seasons.

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