Marine Fisheries
Title:	Modern and Neolithic Baltic Sea cod otolith chemistry: potential to track juvenile habitat use and other life history parameters
Author(s):	Karin E. Limburg, SUNY College of Environmental Science & Forestry; Darren Dale, Cornell University; Hans I. Høie, University of Bergen, Norway; Carina Olson, University of Stockholm, Sweden; Yvonne Walther, Swedish Board of Fisheries
Date:	Tuesday, April 27, 2010
Time:	9:05 am 9:25 am
Room:	Lexington
Abstract: Baltic Sea cod Gadus morhua have been exploited since the Stone Age. Ajvide, a site on the island of Gotland rich in archaeological remains, yielded numerous Neolithic (ca. 4500 YBP) otolith. We used synchrotron-based X-ray fluorometry to map elemental concentrations in several of these otoliths as well as in modern Baltic Sea cod. As an out-group, we performed the same analysis on several otoliths of Norwegian cod whose rearing histories were known, as well as some cod from the North Sea. In modern Baltic cod, strong seasonal patterns in Sr and Mn were observed, and were generally asynchronous. Mn appeared to peak during summer growth, following redox dynamics, and Sr peaks were observed in winter. Mn is highest, and Sr lowest, in the first 1-3 years of life, typically reversing thereafter. The signature is also seen in Neolithic otoliths, although diagenetic effects on Mn are evident. We interpret the high Mn/low Sr as an inshore signature, representing rearing in nursery areas. The switch to low Mn/high Sr appears to be a directed migration into deeper, offshore waters. Norwegian cod show different patterns; strikingly, Br is incorporated along certain growth axes of the Norwegian otoliths, suggesting a genetic component to the incorporation of this element. We discuss the potential for using these and other markers to identify nursery areas and life history events such as migration to adult habitats.
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