Insights into mixing and movement of South Pacific albacore Thunnus alalunga derived from trace elements in otoliths

Macdonald, Jed I., Farley, Jessica H., Clear, Naomi P., Williams, Ashley J., Carter, Thor I., Davies, Campbell R., and Nicol, Simon J. (2013) Insights into mixing and movement of South Pacific albacore Thunnus alalunga derived from trace elements in otoliths. Fisheries Research, 148. pp. 56-63.

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Abstract

Information on the movement and stock structure of commercially important tunas underpins the effective management of exploited populations. In the case of the South Pacific albacore (Thunnus alalunga) stock, longstanding questions remain regarding the degree of connectivity among larval pools, the migration routes of juveniles and adults and the biophysical factors influencing these processes. We measured trace elements (Li, Mg, Mn, Cu, Sr, Ba, Pb, Ca) in albacore otoliths collected across a broad geographical range in the South Pacific Ocean to address these knowledge gaps. Capture locations in French Polynesia, New Caledonia and New Zealand were discriminated with high accuracy (overall 85% of individuals correctly classified) based on analyses at the otolith edge (reflecting the final <1 month of life) using LA-ICPMS. Spatial comparisons of otolith core chemistry (reflecting the first ∼2 weeks of life post-hatch) from the 2005/06 cohort suggest some mixing of larval pools for fish sampled from New Caledonia and New Zealand, whereas French Polynesian fish may have originated from a chemically and/or geographically distinct larval source. Annual and/or sub-annual cycles in Sr:Ca and Ba:Ca were evident along ablation transects encompassing the full life history of individuals. These patterns may reflect seasonal north-south movements across ocean fronts; however, the vertical behaviours of albacore and the lack of opportunities for controlled experiments on temperature effects and time-lags in elemental incorporation complicates environmental reconstructions based on trace element data alone. Expanding the present analysis across multiple years and regions, and integrating data from several sources (e.g. commercial catch data, tag returns, otolith δ13C and δ18O, ocean circulation models) could help clarify the linkages between environmental factors and mixing and movement patterns in albacore.

Item ID: 31863
Item Type: Article (Research - C1)
ISSN: 1872-6763
Keywords: mobility, migration, ocean fronts, otolith chemistry, tuna
Funders: European Union 9th European Development Fund through SCIFISH (Scientific Support for OceanicFisheries Management in the Western and Central Pacific Ocean)
Date Deposited: 18 Mar 2014 06:44
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0704 Fisheries Sciences > 070405 Fish Physiology and Genetics @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8302 Fisheries - Wild Caught > 830207 Wild Caught Tuna @ 100%
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