Phenology and North Sea cod Gadus morhua L.: has climate change affected otolith annulus formation and growth?
Article first published online: 2 FEB 2007
Journal of Fish Biology
Volume 70, Issue 2, pages 584–599, February 2007
How to Cite
Pilling, G. M., Millner, R. S., Easey, M. W., Maxwell, D. L. and Tidd, A. N. (2007), Phenology and North Sea cod Gadus morhua L.: has climate change affected otolith annulus formation and growth?. Journal of Fish Biology, 70: 584–599. doi: 10.1111/j.1095-8649.2007.01331.x
- Issue published online: 2 FEB 2007
- Article first published online: 2 FEB 2007
- (Received 27 February 2006, Accepted 9 October 2006)
- Atlantic cod;
- Gadus morhua;
- North Sea;
Timing and rate of seasonal zone formation in southern North Sea cod Gadus morhua otoliths was studied. Samples were taken from two time periods, representing low and high temperature regimes. Opaque zones were laid down between January and June, in contrast with the pattern described in other published studies. Translucent zone formation started earlier in the warmer period, corresponding to peak annual sea surface temperatures, and a period of slow body growth and low metabolic activity. Translucent zone formation, however, continued once temperatures decreased and growth rate increased. It is hypothesized that translucent zone formation is triggered at a threshold of metabolic stress, and that the combined energetic requirements of reproduction, growth and migration may maintain translucent zone formation even if feeding conditions improve. Higher temperatures had a significant negative effect on the rate of translucent zone deposition, but caused a slight increase in opaque zone formation rate. The findings of this study indicate that historical otolith collections could provide key inputs into future phenological studies to improve the understanding of climate change impacts and the dynamics of otolith structure.