ASFB Home > 2003 > Biological Invasions: Consequences for Parasites, Pathogens, Emerging Diseases, and Fisheries in the Marine Environment.

Application of otolith microchemistry to investigate stock structure and movement patterns of snapper (Pagrus auratus) in South Australian waters.

Karina Hall^ab, Anthony Fowler^a and Bronwyn Gillanders^b

^aSARDI Aquatic Sciences, PO Box 120, Henley Beach, SA 5022
^bDepartment of Environmental Biology, University of Adelaide, SA 5005
Email: hall.karina@saugov.sa.gov.au

The stock structure and age-specific movement patterns of snapper in South Australian waters were investigated using two otolith microchemistry techniques based on inductively coupled plasma mass spectrometry (ICPMS). Solution-based ICPMS, which involves analysis of whole otoliths, was used to determine whether the microchemistry of otoliths differed amongst fish collected from six geographic regions in South Australia. Significant differences would suggest the existence of regional sub-populations. Up to 30 adults were sampled from a single year class from each region and the relative quantities of 24 different elemental isotopes were determined. Of these, only 12 could be reliably quantified for all otoliths. These were used to represent the “elemental fingerprint” of each individual and were compared between regions with multivariate statistics.

Laser ablation ICPMS was used to measure elemental concentrations along chronological transects of sectioned sagittae from up to 20 fish from each region. Elemental profiles were matched to the corresponding optical density data for each transect using digital image analysis software to provide a temporal reference according to the optical macrostructure of the otolith. This method was used to investigate age-specific differences in elemental concentrations that may relate to movement of the fish between different water bodies. The elemental profiles were also compared statistically between otoliths within a region and between regions to provide information on stock structure for comparison with the results from the solution based ICPMS.

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