Theodor Kristjansson

Hafrannsóknastofnun · Aquaculture

The technical efficiency of the African catfish production in Nigeria was assessed. A total of 609 farms were sampled, and 1,118 operations were recorded covering both the pre-COVID and COVID periods. A translog stochastic frontier modeling approach was used to simultaneously assess the technical efficiencies and the determinants of technical ineff...

This study assesses the current economic performance of catfish production in Nigeria using profitability analysis taking the Federal Capital Territory as a case study. Aquaculture production in Nigeria has grown significantly in the last two decades. The farming of catfish accounts for more than half of the total national aquaculture production. H...

In 2013, Atlantic salmon juveniles were challenge tested for Piscirickettsia salmonis (SRS) in VESO in Norway. The juveniles belonged to year class 2012 (YC-2012) comprising of 100 full and half sib families. In 2016 a sib-group of YC-2012 (non-challenged) was selected as breeding candidates to create an offspring generation year class 2016 (YC-201...

The genetic variance for SRS resistance in Atlantic salmon was estimated based on the challenge test performed in VESO (Norway). Data was obtained from 1881 juveniles tested at average weight of 38.7 grams. The juveniles belong to full and half sib mating structure comprising 100 full sib and 100 and paternal half-sibs families. The challenge test,...

Background Genotyping-by-sequencing (GBS) is becoming an attractive alternative to array-based methods for genotyping individuals for a large number of single nucleotide polymorphisms (SNPs). Costs can be lowered by reducing the mean sequencing depth, but this results in genotype calls of lower quality. A common analysis strategy is to filter SNPs...

We present a method for estimating relatedness from genotyping-by-sequencing data. SNP depth affects the ability to correctly call genotypes, as only one of the parental alleles might be observed, with low depth. The estimation method accounts for sequencing depth, including cases with no reads (depth zero) for one of the individuals in the calcula...

Background Genotyping-by-sequencing (GBS) is becoming an attractive alternative to array-based methods for genotyping individuals for a large number of single nucleotide polymorphisms (SNPs). Costs can be lowered by reducing the mean sequencing depth, but this results in genotype calls of lower quality. A common analysis strategy is to filter SNPs...

Advances in next generation sequencing technology have increased the output/cost ratio to a level where cost effective genotyping-by-sequencing (GBS) in livestock, plants and aquaculture species is now a reality. High-throughput GBS methodology produces SNP genotypes that are supported by varying depth of sequence reads, dependent on the number of...

During the development of breeding programme for Atlantic cod Gadus morhua L., in Iceland, genetic parameters were estimated for 1402 individuals, which were assigned with DNA profiling to 140 dams and 70 sires. The cod was reared in cages on the eastern and western coasts of Iceland from 2004 to 2005. At the average body weight of 1.8 kg, the esti...

Three-year classes of Atlantic cod Gadus morhua were studied throughout their rearing in the eastern coast of Iceland from 2004 to 2011. The growth and status of maturity were recorded during the rearing. For one of the year classes, genetic parameters for body weight and maturity status were estimated from 757 individuals, which were the offspring...

Counter-gradient variation in growth has been documented for several commercial fish species. This phenomenon was tested for Atlantic cod (Gadus morhua) when forming the base population for a cod-breeding program in Iceland. In 2004, wild brood fish from five locations off the Icelandic coast were captured using gillnets from commercial fishing ves...

We examine the relationship of the inbreeding coefficient (f) and molecular estimates of inbreeding (IR, sMLH) in the Icelandic sheepdog. The breed experienced a severe genetic bottleneck and near extinction in the last century. Molecular estimates and the inbreeding coefficient are significantly correlated despite the moderate number of markers an...