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    Can trace element signatures in the otoliths of Dissostichus eleginoides record capture size?

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    J.R. Ashford and C.M. Jones (USA)
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    The elemental structure of growth increments in the otoliths of fish reflects the composition of water passing across the gills: as a result, elemental signatures can potentially be used to reconstruct the environmental history experienced by fish. To test whether the otolith elemental signatures of Patagonian toothfish (Dissostichus eleginoides) can discriminate spatial differences, we compared signatures from the outer edges (which are laid down during the interval leading to capture) of otoliths taken from toothfish sampled from management areas off southern Chile, the Falkland Islands, South Georgia, Kerguelen and Macquarie Islands. Edge Ba/Ca values were higher for toothfish caught south of the Subantarctic Front (SAF) in 1996 and 1997 compared to those captured off the South American continent, whereas Mn/Ca values were lower. Edge signatures also showed differences between samples taken south of the SAF, both across the Polar Front and across ocean basins. A sample taken west of South Georgia in 1998 showed similarities to the samples taken in 1996 and 1997 off South America, but very different Mg/Ca concentrations from all other samples.With further development, otolith elemental signatures show promise for identifying the site of capture of sampled toothfish, and for use as retrospective spatial markers to trace toothfish population structure and movement.