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 and individuals used in this study. This is most likely an effect of the extreme relatedness and relatively high variance in individual inbreeding coefficients in the population. There is a significant relationship between inbreeding (f) and the occurrence of hip dysplasia. However, the molecular measures did not detect hip dysplasia as an inbreeding effect.

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 estimated heritability (h 2 AE SE) for body weight, gutted weight and the condition factor (CF) were 0.31 AE 0.06, 0.34 AE 0.04 and 0.24 AE 0.06 respectively. Genetic correlation (r G ) in body weight between the two rearing locations was estimated as 0.95, which reflects a low G 9 E interaction. The estimated heritability for hepatosomatic index (HSI) and fillet yields was 0.061 AE 0.04 and 0.04 AE 0.04 respectively. The HSI and fillet yields were highly genetically correlated with body weight or 0.67 and 0.82 respectively. The genetic correlation between the CF and body weight was estimated as 0.31. There appears to be substantial amount of additive genetic variation for body weight suggesting that selection is likely to be successful. Low heritability for fillet yields and the HSI indicates less promise of genetic improvement. Assigning of parentage to individuals with DNA profiling was 80% successful.

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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 of 40 dams and 20 sires. The estimate for heritability of body weight was h2 = 0.34 at the average weight of 630 g, and heritability for proportion of maturity was h2 = 0.17 given the same weight. The relationship between body weight and the proportion of mature individuals at first winter revealed a strong genetic correlation of rG = 0.90. The phenotypic relationship between body weight and proportion of maturity was estimated with a Bayesian logistic regression as P(yi = 1(mature)) = Φ(β0 + β1weight + β2sex). The best fit yielded β0 = −2.9320 with a 95% interval between −3.2807 and −2.5394, β1weight = 0.0041 with a 95% interval ranging from 0.0035 to 0.0046 and β1sex = −0.0201 with a 95% interval from −0.2003 to 0.1445. The gender had no notable effect. This strong phenotypic and genetic correlation in body weight and maturation suggests that an increased growth rate will consequently lead to a higher proportion of mature individuals in the population. As a consequence, genetic manipulations to simultaneously increase growth and delay maturation may present a challenge.