MEPS 218:275-282 (2001)  -  doi:10.3354/meps218275

Discrimination of northern bluefin tuna from nursery areas in the Pacific Ocean using otolith chemistry

Jay R. Rooker1,*, David H. Secor2, Vincent S. Zdanowicz3, Tomoyuki Itoh4

1Texas A&M University, Department of Marine Biology, 5007 Avenue U, Galveston, Texas 77551, USA
2Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, PO Box 38, Solomons, Maryland 20688, USA
3National Oceanic and Atmospheric Administration, National Marine Fisheries Service, James J. Howard Marine Sciences Laboratory, Highlands, New Jersey 07732, USA
4National Research Institute of the Far Seas Fisheries, 5-7-1 Orido, Shimizu 424, Japan

ABSTRACT: Otolith chemistry of juvenile Pacific bluefin tuna Thunnus orientalis was measured to assess differences in composition among 3 nursery areas in the North Pacific Ocean: East China Sea, Sea of Japan and the Pacific Ocean off Shikoku. Six elements (Li, Mg, Ca, Mn, Sr and Ba) were measured in whole otoliths using solution-based inductively coupled plasma mass spectrometry. Univariate contrasts of T. orientalis otoliths collected in 1994 and 1995 indicated that concentrations of 5 elements (Li, Mg, Ca, Mn, Sr) differed among nurseries. Concentrations of Ca and Sr were significantly higher in the Pacific Ocean than in either marginal sea (East China Sea or Sea of Japan) nursery, while concentrations of Li, Mg and Mn were higher in fishes inhabiting marginal seas. Discriminant analysis showed clear separation of elemental fingerprints between Pacific Ocean and marginal sea nurseries, and to a lesser degree separation between the 2 marginal sea groups. Temporal stability of the elemental fingerprint was examined over a 3 yr period (1995 to 1997) in the East China Sea. Significant interannual trends were observed for 3 elements (Mg, Mn and Ba); however, elemental fingerprints of T. orientalis from the Pacific Ocean nursery were markedly different from all year-classes in the East China Sea.

KEY WORDS: Otolith chemistry · Pacific bluefin tuna · North Pacific Ocean

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