Langtímabreytileiki í erfðasamsetningu þorsks (Gadus morhua L.) við Ísland

• Main Author: Klara Björg Jakobsdóttir 1968-
• Other Authors: Háskóli Íslands
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2013
• Subjects: Doktorsritgerðir; Líffræði; Þorskur; atlantic cod; Gadus morhua
• Online Access: http://hdl.handle.net/1946/13858

The population genetics, such as population structure, of Atlantic cod have been unravelled in the last two decades, at an ever finer scale. Yet, much is still unknown about the evolutionary genetics of cod and the possible impact of fisheries on the genetic structure, both temporal and spatial. The objectives of this thesis were to investigate the extent of temporal genetic differentiation in Icelandic cod over the latter half of last century and to correlate historical changes of genetic variation with known factors such as the potential impact of fisheries. A prerequisite for such a study is access to historical genetic material and development of the appropriate genetic markers. DNA was obtained from dried tissue on stored cod otoliths, previously used for age determination. These were retrieved from the archives of the Icelandic Marine Research Institute. In the first part of the thesis, specific set of microsatellites markers were developed, suitable for the degraded cod DNA, usually obtained from dried tissue remains. Secondly the connection between important behavioral phenotypes and genotypes at non-neutral marker Pan I was determined, using current-day genetic material. This analysis showed that the Pan IAA homozygotes could be assigned to a “coastal” type that appeared to follow seasonal trend in temperature, foraging in relatively shallow waters. On the other hand, most Pan IBB homozygotes were assigned to “frontal” type that is characterized by migrating to colder and deeper waters during feeding migration. For the main part of the thesis historical data set of archived otoliths collected between 1948 and 2002 was used to jointly examine phenotypic and genetic data with the goal to examine historical trends in the genetic composition of the Icelandic cod stock. This analysis showed that there have been major changes in the genetic variation at the Pan I locus of Icelandic cod during the latter part of last century. These have occurred alongside changes in fishing patterns and pressure, and age ...