University of Iceland

Collapse in cod population prior to industrialised fishing

Collapse in cod population prior to industrialised fishing

Results of an extensive study by Guðbjörg Ásta Ólafsdóttir, Director of Research Centre of the Westfjords, University of Iceland, show a collapse in the Icelandic Atlantic cod population at the beginning of the 16th century and a continuing decrease till the current day. Atlantic cod (Gadus morhua) vertebrae from archaeological sites were used to study the history of the Icelandic Atlantic cod population in the time period of 1500–1990.
 
These results were published last week in the Scientific journal Royal Society's Proceedings B; one of the most prestigious journals in the field of biology. Dr. Ólafsdóttir’s research has great academic value as she one of the first scientists to research directly changes in animal species over an extended period and connect them with environmental change. The results show that the population size crash coincides with a period of known cooling in the North Atlantic, and the authors conclude that the collapse may be related to climate or climate-induced ecosystem change. Furthermore, the results are valuable to fisheries control as they reveal that great fluctuations can occur in cod population during short periods, even without the influence of industrialised fishing.
 
The study was extremely extensive and a collaboration of Guðbjörg Ásta Ólafsdóttir, Kristen M. Westfall, VÖR Marine Research Centre, Ragnar Edvardsson, Research Centre of the Westfjords, University of Iceland, and Snæbjörn Pálsson, Faculty of Environmental and Life Science, University of Iceland. 
 
Abstract:
Atlantic cod (Gadus morhua) vertebrae from archaeological sites were used to study the history of the Icelandic Atlantic cod population in the time period of 1500–1990. Specifically, we used coalescence modelling to estimate population size and fluctuations from the sequence diversity at the cytochrome b (cytb) and Pantophysin I (PanI) loci. The models are consistent with an expanding population during the warm medieval period, large historical effective population size (NE), a marked bottleneck event at 1400–1500 and a decrease in NE in early modern times. The model results are corroborated by the reduction of haplotype and nucleotide variation over time and pairwise population distance as a significant portion of nucleotide variation partitioned across the 1550 time mark. The mean age of the historical fished stock is high in medieval times with a truncation in age in early modern times. The population size crash coincides with a period of known cooling in the North Atlantic, and we conclude that the collapse may be related to climate or climate-induced ecosystem change.
 
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