SS1.02 Geochemical Tracers in Calcified Structures: Implications for Fisheries Research
Date: Tuesday, June 11, 2002
Time: 12:00:00 PM
Location: Carson A
RookerJR, Texas A&M University, Galveston, TX, USA,
Secor, D, H, University of Maryland Center for Environmental Science, Solomons, MD, USA,
Zdanowicz, V, S, National Marine Fisheries Service, Sandy Hook, NJ, USA, 
Chemistry of Atlantic bluefin tuna (Thunnus thynnus) otoliths was quantified to assess the feasibility of using these natural tags to discriminate juveniles (age-0 and age-1) from eastern and western nurseries. A suite of six elements (Li, Mg, Ca, Mn, Sr and Ba) was measured in whole otoliths using solution-based inductively coupled plasma mass spectrometry. Otolith chemistry of age-1 T. thynnus collected from the two primary nurseries in the Mediterranean Sea and western Atlantic Ocean differed significantly, with cross-validated classification accuracy at 85%. Spatial and temporal variation in otolith chemistry was evaluated for age-0 T. thynnus collected from three nurseries within the Mediterranean Sea: Alboran Sea (Spain), Ligurian Sea (northern Italy), and Tyrrhenian Sea (southern Italy). Distinct differences in otolith chemistry were detected among Mediterranean nurseries and classification accuracies ranged from 62 to 80%. Interannual trends in otolith chemistry were observed between year classes of age-0 T. thynnus in the Alboran Sea; however, no differences were detected between year classes in the Tyrrhenian Sea. Age-0 and age-1 T. thynnus collected from the same region (Ligurian Sea) were also compared and distinct differences in otolith chemistry were observed, indicating ontogenetic shifts in habitat or elemental discrimination. Findings suggest that otolith chemistry of juveniles from different nurseries and sub-nurseries are distinct and elemental signatures show some degree of temporal persistence, indicating the technique has considerable promise for future assessments of population connectivity and stock structure of T. thynnus.