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High mortality during grow out in the sea is a challenge for farmed Atlantic salmon production in Norway and globally, which is partly attributed to suboptimal smolt quality. In this study, two groups of pre-smolts were put on a standard light smoltification regime with alternating 12L:12D per day for 6 weeks (Phase I), followed by 24L:0D per day for 6 weeks (Phase II); one group was 0 + smolt (EXP1) and the other 1 + smolt (EXP2). To monitor the smoltification status of the fish, 100 (EXP1) and 60 (EXP2) fish were randomly sampled per week during Phase II. The following phenotypes for smoltification status were studied: RT-qPCR relative mRNA expression of values of two alpha catalytic subunits of the variants of the Na+K+ATPase (NKA) expressed in the sampled gill tissues of each fish. The first variant, alpha1a with increased expression in freshwater (FW) and the second variant alpha1b with increased expression in seawater variant (SW), as well as their ratio SW/FW. At the optimal time for seawater transfer based on the SW/FW trait, 1,000 (at sixth sampling of EXP1) and 1,500 (at fifth sampling of EXP2) fish were sampled for genetic parameter estimation. The individual variation in FW, SW, and SW/FW was very large at each of the seven samplings indicating a large variation among individuals in the optimum time of transfer to seawater. SW/FW showed significant genetic variation in both 0+ and 1+ smolts, which indicates the possibility for selection for improved synchronization of smoltification status of Atlantic salmon at the time where the largest proportion of the fish is considered to be smolt. However, the genetic correlation between SW/FW of 0+ and 1+ was not significantly different from zero indicating very little shared genetic variation in SW/FW in 0+ and 1+ fish. Smoltification phenotypes showed temporal progression over the smoltification period, and this progression varied between 0+ and 1+ smolt highlighting the importance of correctly timing the major sampling point, and when cohorts are transferred to seawater. This also highlighted the need for further research into noninvasive methods of objectively measuring individual smoltification through time and subsequent smolt survival and growth rate at sea. [ABSTRACT FROM AUTHOR]

Phenotypic and genetic parameters were estimated for three body traits (harvest weight, carapace length and standard length) and for adult male morphotypes of the giant freshwater prawn Macrobrachium rosenbergii in a fully pedigreed synthetic population in India. The data set included 9,173 progeny produced over four generations from 162 sires and 234 dams. Variance components and genetic parameters were estimated fitting an animal model using the residual maximum-likelihood methodology. The heritabilities for harvest body weight (HW), carapace length (CL) and standard length (SL) were moderate (0.22 ± 0.056, 0.22 ± 0.055 and 0.25 ± 0.059 respectively). The common environmental effects for HW, CL and SL were 0.10 ± 0.020, 0.08 ± 0.018 and 0.10 ± 0.021 respectively. As M. rosenbergii is sexually dimorphic, we estimated heritabilities within each sex. Heritability of HW in females (0.27 ± 0.068) was greater than that in males (0.15 ± 0.057). CL and SL followed the same pattern. The occurrence of male morphotypes is a unique characteristic of adult populations of M. rosenbergii. Populations from culture ponds exhibit a wide range of sizes. To examine whether there was a heritable component in male morphotype frequencies, we treated male morphotypes as traits. The additive genetic variance (and hence the heritability) was zero for male morphotype, indicating that selective breeding to increase the proportion of desirable male morphotypes would not be effective. The genetic correlations among body traits were all positive, high and approaching unity. The results are discussed in relation to selection plans for the giant freshwater prawn. [ABSTRACT FROM AUTHOR]

The aims of this study were the estimation of genetic parameters for survival rate from tagging until harvest and the evaluation of the correlated response in survival rate to selection for harvest weight in the genetically improved farmed tilapia ( GIFT) strain. The heritability for survival rate was low (0.038), and so was its genetic correlation with harvest weight (0.065), suggesting that selecting for the latter trait would have had no effect on survival. The calculation of the probability of survival by spawning season and line, fitting a model that included the random effects of individual animal and common environment, confirmed this prediction. There were very small and variable between line differences in the probability of survival, which generally favoured the selection line. We conclude that the focus of the GIFT programme on improving harvest weight was not detrimental to the survival of the fish during the grow-out phase. [ABSTRACT FROM AUTHOR]

Lumpfish (Cyclopterus lumpus) is the most widely use biological pest control agent to delouse sea lice on Atlantic salmon (Salmo salar). From 2012 to 2017, the production of lumpfish has increased from less than two million individuals to more than 30 million individuals in Norway alone. To meet the increasing market demand for lumpfish and to ensure sustainable production in the future, we need to domesticate the wild stocks and establish a breeding program for lumpfish. One of the most important traits in lumpfish, the genetic property for uniformity of body weight was investigated. In 2015, wild broodstock of lumpfish were collected from Southern and Northern coastal regions of Norway. A total of 68 full-sib families were produced and 7588 lumpfish juvenile were measured for body weight at tagging. A sire-dam double hierarchical generalized linear model was used to estimate the genetic parameters for body weight and its uniformity. Body weight was transformed by standardized and log scales. The heritabilities for uniformity of body weight in both scales, were low at 0.014 and 0.021 for the standardized and log scales, respectively. However, the genetic coefficient of variation for uniformity were relatively high, 45.8% and 63.5% (for standardized and log transformation), indicating that uniformity of body weight for lumpfish are substantially under genetic control. The genetic correlation between body weight and its uniformity was estimated. For the standardized transformation, the genetic correlation was −0.055 ± 0.252 (close to zero), and for the log transformation, the estimate was −0.813 ± 0.114. Both genetic correlations suggest that it is possible to simultaneously select for body weight and uniformity of body weight without a trade-off in genetic gain. In conclusion, there is substantial genetic variation for uniformity of body weight in lumpfish and the potential to select on this trait is promising. • Lumpfish is the third most valuable marine aquaculture species, after Atlantic salmon and rainbow trout in Norway. • Genetic coefficient of variation for uniformity of body weight in lumpfish were 45.8% and 63.5% indicating potential to improve this trait through selective breeding. • The close to zero and strongly negative genetic correlations between body weight and its uniformity suggest that these two traits could be improved simultaneously for lumpfish. [ABSTRACT FROM AUTHOR]

Resilience can be defined as the capacity of an animal to be minimally affected by perturbations or to quickly recover to the state it had before the perturbation. When applied to production animals, resilience is defined as consistency in production over time. This consistency can be quantified by the variance of deviations from the expected trait level measured at multiple time points. The objectives of this study were to estimate genetic parameters for resilience in Nile tilapia, measured as consistency in growth. We used log-transformed variance of deviations (LnVar) of body weight measured five times during grow-out in either an aerated or a non-aerated pond. The hypothesis was that fish grown in non-aerated ponds are more challenged by environmental conditions, such that heritable variation in LnVar of body weight is more expressed showing larger differences between more and less resilient fish. The heritability for LnVar was 0.10 in aerated pond and 0.12 in the non-aerated pond. In aerated ponds the genetic correlation (r g) of LnVar with harvest weight (HW) was 0.36 ± 0.26, and with thermal growth coefficient (TGC) it was 0.47 ± 0.21. In the non-aerated pond, the r g with HW and TGC were close to zero (−0.01 ± 0.29 and − 0.08 ± 0.22). The genetic correlation for LnVar between both environments was 0.80. These estimates suggest that selection for HW or TGC in aerated ponds will increase LnVar in both environments. Increased LnVar may decrease resilience and this will be detrimental to performance. Selecting for more resilient fish would lead to more constant growth rates, which makes biomass estimation more accurate and could therefore result in more optimal feeding regimes and less feed waste. This would have a favorable effect on the feed efficiency in production units and on the environmental impact of fish farming. To improve resilience together with growth we recommend that fish breeding programs collect repeated records on body weight, preferably in challenging environments. • Resilience based on variation of repeated bodyweight measurements is heritable, showing promise for genetic improvement. • With low to moderate genetic correlations the genetic improvement of both growth and resilience would be very well possible. • The high genetic correlation suggests that improved resilience will transfer between more and less challenging environments. [ABSTRACT FROM AUTHOR]

A major problem in smallholder Nile tilapia (Oreochromis niloticus) farms is that the achieved production is much lower than under optimal management. One of the main environmental factors contributing to lower production is dissolved oxygen (DO), because the majority of Nile tilapia production takes place under smallholder farms with no aeration of ponds which leads to large DO fluctuations. On the contrary, breeding programs select fish in aerated ponds. Aerating ponds is currently not an option for smallholder farmers because either it is too expensive or they lack access to cheap electricity supply. Therefore, it is crucial to know the genetic correlation between aerated and non-aerated ponds to optimize breeding programs to select fish that perform well in ponds with fluctuating DO levels. The objectives of this study were 1) to investigate the presence of genotype by environment (GxE) interaction between aerated and non-aerated earthen ponds using a design that minimized common environmental effects and 2) the impact of (non-)aeration on genetic parameters. The experimental fish were mass-produced using natural group spawning and nursed in four 30m2 hapas. A random sample of fingerlings from each hapa was tagged and randomly distributed to aerated and non-aerated ponds for a grow-out period of 217 and 218 days. Body weight and photographs were taken on five consecutive time points during grow-out. Of the stocked fish, 2063 were genotyped-by-sequencing. A genomic relationship matrix was built using 11,929 SNPs to estimate genetic parameters with ASReml. No-aeration significantly reduced mean harvest weight (HW), survival and thermal growth coefficient (TGC) compared to aeration. Substantial heritabilities (0.14–0.45) were found for HW, TGC, surface area (SA) and body shape, expressed as ellipticity, and low heritabilities (0.03–0.04) for survival in aerated and non-aerated ponds. In both ponds, the environmental effect common to full sibs was not significant. Genetic coefficients of variation were 20–23% lower and heritabilities were 19–25% lower in the non-aerated pond compared to the aerated pond, for HW, TGC and survival. Genetic correlations between ponds for HW, standard length, height, SA and TGC were 0.81, 0.80, 0.74, 0.78 and 0.78, respectively. In summary, some GxE interaction between aerated and non-aerated ponds was found and no-aeration decreased genetic coefficients of variation and heritabilities compared to aerated ponds. Breeding programs are recommended to use half sib information from non-aerated farms or to set up a reference population for genomic selection in a non-aerated environment either on-station or in farms. • No-aeration reduced mean harvest weight, survival and thermal growth coefficient compared to aeration of ponds. • No-aeration reduced genetic coefficients of variation and heritabilities compared to aeration of ponds. • Some genotype by environment interaction was found for harvest weight and growth between aerated and non-aerated ponds. [ABSTRACT FROM AUTHOR]