Cod otoliths used in the study of climate change

Cod otoliths used in the study of climate change

30 October 2016 news

Cod otoliths are taken into use in the study of age of fish and effects from climate change. The distance between the otolith rings are connected to climate effects as it reflects the growth of cod in "good" and "bad" years.

Otoliths are hard, calcium carbonate structures located directly behind the brain of bony fishes. These structures form annual growth increments which are employed to age fish and study their growth. The increments arise due to seasonal variations in growth rates that might be related to the environmental variability experienced by the fish in its lifetime. Similarly, the chemical composition of otoliths is used to characterize fish population, track their migrations, identify spawning grounds, etc. reflecting the environmental conditions in which the fish has lived (e.g. Black et al. 2013, Chang and Geffen 2013.

Hector Andrade from Akvaplan-niva presented a project applying otoliths studies at the 2016 ICES Annual Science Conference in Riga Latvia. The title of his presentation was "Effects of climate on cod life history and ecology along a temperate-arctic gradient". His presentation was part of theme session H: Looking backwards to move ahead: how the wider application of new technologies to interpret scale, otolith, statolith and other biomineralised age-registering structures could improve management of natural resources"

The presentation included some of the effects of climate upon cod life history and habitat use across a temperate-arctic gradient. Cod otoliths collected in Porsanger, Lofoten islands,  Isfjord and Kongsfjorden on Svalbad. were employed to develop short-term chronologies and perform trace element analyses. Preliminary results showed that there are no apparent differences in age‐specific growth rates for cod collected among the different sites. Trace element analyses revealed differences in microchemical composition of otoliths in relation to site and age, supporting the literature describing cod spawning and feeding migrations from the Barents Sea to the north of Norway. The differences in microelement composition of cod otoliths from Kongsfjord and Isfjorden might suggest that these fishes are not merely transient into the fjords.

The results presented by Andrade is from a project financed by the Fram Centre Flag Ship (Tromsø, Norway): "Effects of climate change on sea and coastal ecology in the north". Collaborative partners in the project are the Norwegian Institute of Marine Research, Texas University, BATES College, the University in Bergen (Norway), the University Centre in Svalbard and UiT The Arctic University of Norway. 

Photo: Hector Andrade, fieldwork at Svalbard.