Otolith nucleus chemistry resolved the population structure of Patagonian toothfish (Dissostichus eleginoides), an exclusively marine species, along the Patagonian Shelf and North Scotia Ridge out to South Georgia in the Southern Ocean. Concentrations of 55Mn, 88Sr, and 137Ba, ratioed to 42Ca, showed a sharp population boundary in the vicinity of the Polar Front, between South Georgia and the North Scotia Ridge. These results validated otolith nucleus chemistry as a technique for examining population structure in Patagonian toothfish, demonstrating that otolith nucleus chemistry can discriminate between populations even in fully marine environments. Moreover, the nucleus chemistry indicated population heterogeneity not previously detected, suggesting the possibility of more than one South American population; and also suggested some South American-caught fish had moved from South Georgia.
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