The use of otolith microstructure to estimate age in adult Atlantic cod Gadus morhua
Abstract:Transverse sections of otoliths from Atlantic cod Gadus morhua from the Baltic Sea revealed narrow growth increments. The widths of these increments corresponded to daily increments from fish with known otolith growth rates and were therefore assumed to be daily increments. They exhibited a distinct pattern with increasing distance from the primary primordium. A series of zones with clearly distinguishable increments, first with increasing then with decreasing widths in a dome-shaped pattern, were separated by zones where no regular increment structure was visible. Increment width seemed to be tightly coupled to the annual cycle in environmental temperature at a depth of 30–60 m, where G. morhua predominantly reside. Between 135 and 200 increments occurred within the different zones, with a non-significant trend towards lower increment numbers and widths with distance from the primary primordium of the otolith. Increment formation apparently ceased at temperatures < 5–6° C, but growth during the cold months corresponded closely with estimated growth rates. The increment patterns seemed to reflect annual cycles in environmental temperature, and the count of the increment cycles may thus be a promising tool for the determination of the true age of Baltic G. morhua.
Document Type: Regular Paper
Affiliations: 1: Department of Fishery Biology, Institute for Marine Research, University of Kiel, Düstenbrooker Weg 20, 24105 Kiel, Germany 2: Sea Fisheries Institute, ul. Kollataja 1, PL-81-332 Gdynia, Poland 3: Swedish Board of Fisheries, Institute of Marine Research, Utövägen 5, 371 37 Karlskrona, Sweden 4: Johann Heinrich von Thünen Institute, Federal Research Institute for Rural Areas, Forestry and Fisheries, Alter Hafen Süd 2, 18069 Rostock, Germany
Publication date: May 1, 2010