Bluefin Tuna CHART programme Tag Returned

A single spaghetti tag deployed on an Atlantic bluefin tuna last November as part of the English CatcH And Release Tagging programme (‘CHART’) has been recovered by a regional observer in the Mediterranean Sea from a bluefin harvested from a fish farm near Malta. More information on the regional observer programme is available here:

When tagged on 3rd November last year by Captain Dan Margetts, operating ‘Sowenna’ out of Looe, Cornwall, the fish was recorded at 165 cm (65”) Straight Fork Length. (The equivalent CURVED Fork Length would have been about 175 cm (69”) according to the most commonly used tables).

This fish was recaptured earlier this year and transferred to a fish farm to be further fattened. Upon harvesting from the farm cages in mid October the tag was discovered and reported to the ICCAT Atlantic-Wide Research Programme for Bluefin Tuna (GBYP – who have kindly shared this data. When harvested the fish was measured at 192cm CFL, (75.6”), indicating 17cm (6.6”) of growth over the 11 1/2 months since tagging. The round weight was recorded at 177kg (390lb) at harvesting.

Being a highly migratory species, the reality is that some of the fish tagged under various UK CHART style programmes will go on to be caught elsewhere. Previous electronic tagging of bluefin in UK waters has indicated some interesting examples of site fidelity, i.e. fish returning to the same location each autumn.

Multiple tags from the UK programmes have shown fish back within the locale they were tagged in around 1 year later.

In addition to the mass of point of capture data, the coming months and years may, via the large ‘spaghetti tag’ deployment under CHART, provide important information regarding site fidelity, growth rates etc., and highlight the potential significance of the UK’s Western waters in the life-history and migrations of Atlantic Bluefin tuna.