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Gjerde B.,NOFIMA | Gjerde B.,Norwegian University of Life Sciences | Mengistu S.B.,Norwegian University of Life Sciences | Mengistu S.B.,Hawassa University | And 4 more authors.
Aquaculture | Year: 2012

With the objective of how to best improve fillet weight in Nile tilapia (Oreochromis niloticus) through selection round and gutted body weight and fillet weight were recorded at harvest over four generations (G0, G1, G2 and G3) and from which the following traits were derived: Fillet yield (fillet weight×100/round weight), non-edible part of the fish (NEP=round weight-fillet weight), and non-meat part of the gutted weight (NMP=gutted weight-fillet weight). The round weight was recorded on 42,795 offspring of 327 sires and 422 dams, and the other traits on a random sample of 3361 of the offspring of 277 sires and 359 dams. The fish were reared in net-cages in a lake or in earthen ponds. Selection was performed for harvest weight and fillet yield with an equal relative economic weight (50%) on each trait. The heritabilities for round, gutted and fillet weight, NEP and NMP were all moderate (0.16-0.19) and lower for fillet yield (0.06). The effect common to full-sibs (c 2) accounted for a large proportion of the phenotypic variance for all traits (0.11-0.19). The genetic correlation between round weight of fish reared in cages and in ponds was unity (1.00), indicating no genotype by environment interaction for this trait. The genetic correlations between round, gutted and fillet weights were all close to unity, as were the genetic correlations of round and fillet weight with the calculated traits NEP and NMP. The close to unity genetic correlation between round body weight and fillet weight indicates that genetic improvement of one of the traits without achieving a proportional genetic change in the other is difficult or even impossible. This implies that improvement of fillet yield through direct selection is difficult to achieve. Still, based on the current results, fillet yield is expected to increase with increasing body weight, both genetically and phenotypically. However, if increased growth leads to harvest at a younger age rather than higher weight, response in fillet yield may not be observed. Improvement of fillet weight can be obtained through selection for increased round body weight, a more efficient strategy as the trait can be recorded on live breeding candidates and as higher economic weight can be put on this trait instead of on fillet yield. © 2012 Elsevier B.V. Source

It has been exciting to follow the rapid development of aquaculture production in Norway, and internationally, since 1971. As an animal breeder I am particularly impressed with the genetic gain obtained for growth rate, and also for disease resistance in several aquatic species, which is five to six times higher than what has been achieved in terrestrial farm animals. This is illustrated in five selected projects I have been involved in. The sad story is, however, that only less than 10% of the world's aquaculture production is based on genetically improved stocks. The big challenge for the future is to develop more selective breeding programs for existing and new emerging aquaculture species in order to increase the production of this nutritious food source and to improve the efficiency of the use of feed, water, land and labor resources. © 2012 Elsevier B.V.. Source

Gjerde B.,Nofima Marin | Odegard J.,Nofima Marin | Thorland I.,Akvaforsk
Aquaculture | Year: 2011

The magnitude of the genetic variation in the susceptibility of Atlantic salmon to Lepeophtheirus salmonis was estimated through a controlled infestation test of 2206 individually tagged post-smolts of 154 full-sib families, i.e. the offspring of 78 sires and 154 dams. The infestation test took place in two replicated tanks with seawater. On average 74 and 36 copepodids per fish were added to tanks 1 and 2, respectively. The number of sessile lice (chalimus II-II stage) per fish (LC) was counted ten days after infestation at which the average body weight of the fish was 260g in each of the two tanks. The average LC per fish was 27.1 (SD=16.4) and 13.9 (SD=13.2) in tanks 1 and 2, respectively while the lice density per fish, calculated as LD=LC/Body weight2/3, was 0.66 (SD=0.38) and 0.34 (SD=0.29). Observed LC was found to increase with increasing body weight, while LD was seemingly independent of body weight. These relationships explain the lower heritability for LD (0.26±0.05) than for LC (0.33±0.05), and a genetic correlation between LC and LD (rg=0.89±0.03) different from unity. The magnitude of the heritability estimate for LD together with the large phenotypic variation of the trait, and a genetic correlation close to unity between LD in the two replicated tanks, shows that there is substantial additive genetic variation in resistance to L. salmonis in Atlantic salmon, and thus a great potential for increasing the resistance through selective breeding. The genetic correlation between LD and harvest body weight recorded on two subsamples of sibs of the lice infected fish reared at two farms was close to and not significantly different from zero (0.06±0.12 and -0.13±0.11). Hence, the increasing lice problem in the salmon industry during the last years is most likely caused by other factors than the selection that has been practised for increased growth rate over the last 3-4 decades. © 2011. Source

Pike T.W.,University of Glasgow | Bjerkeng B.,Akvaforsk | Blount J.D.,University of Exeter | Lindstrom J.,University of Glasgow | Metcalfe N.B.,University of Glasgow
Functional Ecology | Year: 2011

1.Carotenoid-based signals typically vary in both the total concentration of carotenoids deposited and the relative quantities of different constituent carotenoids. As these constituents often have differing spectral properties, the relative and absolute concentrations of different carotenoids deposited in a signal can significantly affect the spectrum of light reflected. A critical but rarely tested assumption of hypotheses concerning the information content of carotenoid-based signals is that their colour directly reveals the concentration and composition of constituent carotenoids to intended recipients. Most previous studies have attempted to address this question using either photographic techniques or by analysing recorded reflectance spectra, neither of which take into account the specific properties of the receiver's visual system. 2.Here, we use psychophysical models of the visual system of three-spined sticklebacks (Gasterosteus aculeatus) to estimate their sensitivity to variation in the concentration and relative abundance of constituent carotenoids of males' carotenoid-based sexual signals. 3.We demonstrate that sticklebacks are acutely sensitive to variation in both the total concentration of carotenoids in the signal and the relative proportion of its constituents, and that the accuracy of these assessments is largely unaffected by the presence or absence of ultraviolet radiation in the illuminant. We discuss these findings in relation to the evolution, maintenance and information content of carotenoid-based sexual signals. © 2010 The Authors. Functional Ecology © 2010 British Ecological Society. Source

Skagemo V.,Nofima Marine | Skagemo V.,Norwegian University of Life Sciences | Sonesson A.K.,Nofima Marine | Meuwissen T.H.E.,Norwegian University of Life Sciences | Rye M.,Akvaforsk
Aquaculture | Year: 2010

We studied a typical breeding nucleus with dissemination of genetic material directly from the nucleus to the grow-out level by stochastic simulation. Profits could be increased through production and dissemination of specialised stocks suited for specific production environments or markets. Truncation selection of 50 sires and 200 dams (trunc ♂2.5% ♀10%) and of 5 sires and 25 dams (trunc ♂0.25% ♀1.25%) were compared to random selection of 50 sires and 200 dams (rand ♂2.5% ♀10%). Higher profit was obtained for all truncation selection schemes as compared to random selection, and increasing with decreasing proportion selected. By optimising the selection of parents, which are used for dissemination from the nucleus to the grow-out, instead of using randomly selected nucleus parents, an additional response corresponding of approximately 1.5 generations of selection in the nucleus was achieved. The effect of the correlation between the nucleus breeding goal and the breeding objective of the grow-out was that profit was highest when the correlation was high. With a negative genetic correlation between the traits, profit was still high if the trait with the highest heritability (i.e. the trait measured on candidate itself) had the highest economic value. The range of ΔF in the 7th generation in the nucleus was [- 0.0075-0.0269] with SD equal to 0.0056. The average over all the replicates was 0.0095. This study showed that selection of specialised stocks for specific breeding objectives from the nucleus to the grow-out level will give the grow-out producers a direct and extra genetic improvement and that selecting breeders in the nucleus for dissemination gives also more flexibility for a final product, by adapting economic weights for each grow-out producer. © 2010 Elsevier B.V. All rights reserved. Source

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