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In the present work, we studied ten new productive traits in meagre (Argyrosomus regius), comprising three related to the carcass (cNiT) and seven related to morphometric (mNiT) characteristics. We harnessed non-invasive technology (NiT) by means of the IMAFISH_ML software. This tool's potential was leveraged on an industrial scale, encompassing the evaluation of 612 fish from two distinct rearing systems (marine cages and indoor tanks) at the time of harvest. Each fish underwent digital photography for morphometric measurements, manual weighing, and was manually eviscerated and filleted to calculate the carcass and fillet yield. Subsequently, the principal genetic parameters were estimated. The heritabilities for the growth traits were moderate (0.34 and 0.39 for TL and BW), whilst those for the cNiT traits ranged from medium to low (0.32–0.27). For the mNiT, they demonstrated a medium to low range (0.15–0.37), whereas the carcass and fillet yield heritabilities were considered to be medium to high (0.32 and 0.31). Most of the genetic correlations between the growth, NiT, and yield traits were not estimated accurately due to the limited data. As was expected, we observed predominantly high and positive correlations between the growth and mNiT. A genetic correlation to highlight was the fillet yield with the fish maximum height (0.87 ± 0.23) and with the head height (0.87 ± 0.24). This suggests that indirect selection using NiT could improve the growth and yield traits. Employing a multi-trait selection approach enables us to capture a broader spectrum of genetic variability and to potentially identify individuals with superior genetic potential. The use of image analysis software ensures objective and precise measurements, thereby reducing the potential for human error or bias during the selection process. Further studies should be carried out to improve the accuracy of the estimates, especially those of the genetic correlations. [ABSTRACT FROM AUTHOR]

In the present work, we studied ten new productive traits in meagre (Argyrosomus regius), comprising three related to the carcass (cNiT) and seven related to morphometric (mNiT) characteristics. We harnessed non-invasive technology (NiT) by means of the IMAFISH_ML software. This tool’s potential was leveraged on an industrial scale, encompassing the evaluation of 612 fish from two distinct rearing systems (marine cages and indoor tanks) at the time of harvest. Each fish underwent digital photography for morphometric measurements, manual weighing, and was manually eviscerated and filleted to calculate the carcass and fillet yield. Subsequently, the principal genetic parameters were estimated. The heritabilities for the growth traits were moderate (0.34 and 0.39 for TL and BW), whilst those for the cNiT traits ranged from medium to low (0.32–0.27). For the mNiT, they demonstrated a medium to low range (0.15–0.37), whereas the carcass and fillet yield heritabilities were considered to be medium to high (0.32 and 0.31). Most of the genetic correlations between the growth, NiT, and yield traits were not estimated accurately due to the limited data. As was expected, we observed predominantly high and positive correlations between the growth and mNiT. A genetic correlation to highlight was the fillet yield with the fish maximum height (0.87 ± 0.23) and with the head height (0.87 ± 0.24). This suggests that indirect selection using NiT could improve the growth and yield traits. Employing a multi-trait selection approach enables us to capture a broader spectrum of genetic variability and to potentially identify individuals with superior genetic potential. The use of image analysis software ensures objective and precise measurements, thereby reducing the potential for human error or bias during the selection process. Further studies should be carried out to improve the accuracy of the estimates, especially those of the genetic correlations.

Fillet yield, the proportion of edible fillet relative to body weight, is a major trait to improve in fish sold processed, as it has a direct impact on profitability and can simultaneously decrease the environmental impact of producing a given amount of fillet. However, it is difficult to improve by selective breeding, because it cannot be measured on live breeding candidates, its phenotypic variation is low, and, as a ratio, it is not normally distributed and a same change in fillet yield can be the result of different changes in fillet weight and body weight. Residual headless gutted carcass weight (rHGCW) is heritable and highly genetically correlated to Fillet% in rainbow trout, and can be predicted by the ratio of abdominal wall thickness to depth of the peritoneal cavity (E8/E23), measured on live fish by ultrasound tomography. We selected broodstock based on rHGCW, measured on sibs of the selection candidates, on ultrasound measurements (E8/E23) measured on the selection candidates, or a combination of both. Seven broodstock groups were selected: fish with 15% highest (rHGCW+) or lowest (rHGCW−) EBV for rHGCW, with 15% highest (E8/E23+) or lowest (E8/E23−) EBV for E8/E23, with both rHGCW+ and E8/E23+ (Both+) or rHGCW− and E8/E23− (Both−), or with close to zero EBVs for both traits (Mid). Seven corresponding groups of offspring were produced and reared communally. At harvest size (1.5 kg mean weight), 1,561 trout were slaughtered, measured for the traits of interest, and pedigreed with DNA fingerprinting. Offspring from groups Both+, rHGCW+ and E8/E23+ had a higher EBV for rHGCW than the control group, while down-selected groups had a lower EBV. Looking at the phenotypic mean for Fillet% (correlated response), up-selected fish had more fillet than down-selected fish. The highest difference was between Both+ (69.36%) and Both− (68.20%), a 1.16% units difference in fillet percentage. The change in Fillet% was explained by an opposite change in Viscera%, while Head% remained stable. Selection using sib information on rHGCW was on average more efficient than selection using the candidates’ own E8/E23 phenotypes, and downward selection (decreasing Fillet%) was more efficient than upward selection.

Fillet yield, the proportion of edible fillet relative to body weight, is a major trait to improve in fish sold processed, as it has a direct impact on profitability and can simultaneously decrease the environmental impact of producing a given amount of fillet. However, it is difficult to improve by selective breeding, because it cannot be measured on live breeding candidates, its phenotypic variation is low, and, as a ratio, it is not normally distributed and a same change in fillet yield can be the result of different changes in fillet weight and body weight. Residual headless gutted carcass weight (rHGCW) is heritable and highly genetically correlated to Fillet% in rainbow trout, and can be predicted by the ratio of abdominal wall thickness to depth of the peritoneal cavity (E8/E23), measured on live fish by ultrasound tomography. We selected broodstock based on rHGCW, measured on sibs of the selection candidates, on ultrasound measurements (E8/E23) measured on the selection candidates, or a combination of both. Seven broodstock groups were selected: fish with 15% highest (rHGCW+) or lowest (rHGCW−) EBV for rHGCW, with 15% highest (E8/E23+) or lowest (E8/E23−) EBV for E8/E23, with both rHGCW+ and E8/E23+ (Both+) or rHGCW− and E8/E23− (Both−), or with close to zero EBVs for both traits (Mid). Seven corresponding groups of offspring were produced and reared communally. At harvest size (1.5 kg mean weight), 1,561 trout were slaughtered, measured for the traits of interest, and pedigreed with DNA fingerprinting. Offspring from groups Both+, rHGCW+ and E8/E23+ had a higher EBV for rHGCW than the control group, while down-selected groups had a lower EBV. Looking at the phenotypic mean for Fillet% (correlated response), up-selected fish had more fillet than down-selected fish. The highest difference was between Both+ (69.36%) and Both− (68.20%), a 1.16% units difference in fillet percentage. The change in Fillet% was explained by an opposite change in Viscera%, while Head% remained stable. Selection using sib information on rHGCW was on average more efficient than selection using the candidates' own E8/E23 phenotypes, and downward selection (decreasing Fillet%) was more efficient than upward selection. [ABSTRACT FROM AUTHOR]

Carcass and fillet yields are traits of great economic importance in aquaculture species, including rainbow trout. Headless gutted carcass percentage (HC) is a convenient selection criterion to improve carcass yield given that it is highly genetically correlated with the latter and also with fillet yield. However, HC is a sib trait that cannot be recorded on selection candidates. Consequently, the within-family component of the genetic variance cannot be exploited with traditional pedigree-based BLUP selection. Two alternatives to exploit this component would be to select directly on an indicator trait genetically correlated with HC that can be recorded on live candidates or to apply genomic selection. The objective of this simulation study was to predict the phenotypic gains for HC in rainbow trout breeding programs when four alternative selection strategies are used: i) sib selection for HC, ii) indirect selection for a morphological indicator recorded in vivo; iii) genomic selection for HC; and iv) genomic selection for the indicator. Also, the four strategies were compared in a multitrait selection scenario where body weight was also included in the breeding objective. The different scenarios were compared at the same selection intensity and number of records (2000) for HC (on sibs) and IHC (on candidates). Two different heritabilities for HC (0.55 and 0.25) were considered. For the highest heritability, the phenotypic gain for HC was higher with sib than with indirect selection for both BLUP (1.03 versus 0.98) and genomic selection (1.22 versus 1.04). However, for the lowest heritability, the phenotypic gain for HC was lower with sib than with indirect selection for both BLUP (0.60 versus 0.64) and genomic selection (0.70 versus 0.71). In any case, the differences in phenotypic gains for HC between sib and indirect selection were not large. Therefore, given that sib selection implies extra costs associated with maintaining and genotyping sibs and indirect selection allows higher selection intensity for a given number of fish, indirect selection appears to be a more cost-effective option. The patterns found for single trait selection were maintained when the yield trait (HC or indicator) was selected simultaneously with body weight. We conclude that the optimum approach to improve carcass yield is a combination of genomic and indirect selection in both single and multitrait selection scenarios. • Gains for headless carcass from indirect and sib selection are similar • The highest increase in the phenotypic mean of headless carcass was obtained with genomic selection. • Indirect genomic selection on an indicator of headless carcass is the most profitable option to improve carcass yield • The benefit-cost ratio of indirect genomic selection will increase when including growth in the breeding goal [ABSTRACT FROM AUTHOR]

Abstract: Selection to improve processing yields relies on sib selection, in which live candidates are ranked according to their family breeding value. This approach limits genetic progress, as it only exploits genetic variability between families and not within them. Indirect criteria measured on live candidates could overcome this limitation. The present study (1) proposes a procedure to identify indirect criteria to predict processing yields in rainbow trout (head, carcass and fillet yields), (2) estimates genetic parameters of these indirect criteria, and (3) predicts relative genetic gains in processing yields using full-sib selection or indirect individual selection on those indirect criteria. DNA-pedigreed all-female rainbow trout Oncorhynchus mykiss (n =2029, 1631.0±355.6g) from 600 families produced from 100 sires and 60 dams were characterized by external and internal non-lethal morphological measures using digital pictures and real time ultrasound tomography. Nineteen landmarks were recorded on the digital pictures to define the outline of the body, head and lateral line. Their coordinates were used to calculate different lengths, heights and areas. Five different internal thicknesses were measured by ultrasound tomography. In the first phase of this study, processing yields were predicted using multiple linear regressions including both external and internal morphometric variables. In a second phase, the heritability of the predicted values and their genetic correlations with real processing yields were estimated using animal models. Predicted yields exhibited intermediate heritabilities (0.25–0.28) that were half the value of heritabilities for real processing yields (0.47–0.55), but had high genetic correlations with these real yields (0.87–0.90). The relative efficiency of indirect selection (IS) on these indirect criteria was compared to theoretical mass selection (MS) or sib selection (FS) with different family sizes (10 or 100) and two different selection pressures (10% or 40%). At the same selection pressure (10%, with 100 sibs per family %), full-sib selection created genetic progress 49.6% to 60.5% higher than indirect selection according to the processing yield targeted. However, when sib-selection pressure was limited to a more realistic between family selection pressure (40% and 10 sibs per family), indirect selection with 10% selection pressure was 21.9% to 32.7% more efficient than sib selection. [Copyright &y& Elsevier]

Abstract: Genetic parameters of production traits (growth, carcass yield, fillet yield) and bony tissues (head and vertebral axis) were estimated for large all-female rainbow trout Oncorhynchus mykiss reared in freshwater. Genetic parameters were estimated using REML at 16months of age (1636g) on 1962 DNA-assigned progenies from a partial factorial mating design with 60 dams and 100 sex-reversed sires. Most traits presented medium to high heritability (0.37 to 0.54). A high genetic correlation (rA =0.97) was found between fillet yield and headless gutted carcass yield (or HGCarc%). Due to its higher heritability and high genetic correlation with fillet yield, selection on HGCarc% should result in a 50% increase in selection efficiency on fillet yield by reducing operator-linked variability at filleting. However, strong negative genetic correlations were estimated between body weight or fillet yield and bony tissue development as head yield or the head and vertebral column yield (−0.48 to −0.57). Ten generations of selection on body weight (or fillet yield) are, therefore, predicted to decrease the relative head development by 25 to 30% for slaughtering at constant age. As it is impossible to disentangle this result from a correlation that is only mathematically determined, this result needs further investigations. If yields are corrected according to their allometric relationship with body weight, only selection for fillet yield will decrease the proportion of bony tissues for a slaughtering at a constant body weight. Whatever the final objective of selection (to increase body weight or to shorten the production cycle at constant body weight), it is concluded that at least selection on fillet yield will affect the relative head and the vertebral axis development and that selection on growth may affect bony tissue development. These results are discussed in relation to the past results from livestock breeding, resource energy allocation theory and a future improvement of robustness by selection. [Copyright &y& Elsevier]

Abstract: 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 (c2) 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. [Copyright &y& Elsevier]

We assessed whether visceral lipid weight, fillet weight, and percentage fillet from BW, 3 traits laborious to record, could be genetically improved by indirect selection on more easily measured traits in farmed rainbow trout. Visceral lipid is discarded as waste during slaughter, influencing production efficiency and production costs. Fillet weight and fillet percentage directly influence economic returns in trout production. The study comprised 3 steps. First, we assessed the degree to which selection on percentage of visceral weight from BW indirectly changes visceral lipid weight and the size of intestines and internal organs. The phenotypic analysis of weights of viscera, intestines, visceral lipid, liver, and gonads measured from 40 fish revealed that phenotypic selection against visceral weight was most strongly directed to visceral lipid, and to a lesser degree to intestines and gonads. Because genetic relationships among these traits were not established, it is not known whether indirect selection leads to genetic responses. Second, we examined whether direct selection for the fillet traits could be replaced by indirect selection on BW, eviscerated BW, visceral weight, visceral percentage, head volume, and relative head volume (head volume relative to BW). The selection index calculations based on the quantitative genetic parameters obtained from multigenerational pedigree data showed that genetic improvement of fillet percentage through direct selection (selection accuracy, rTI = 0.54) was equally efficient compared with indirect selection on visceral percentage (rTI = 0.54). Genetic improvement of fillet weight through direct selection (rTI = 0.56) was always more efficient than indirect selection, yet indirect selection for eviscerated BW (rTI = 0.50) was almost as efficient as direct selection. Third, the expected genetic responses to alternative selection indices showed that improved fillet percentage was mainly a result of a moderate decrease in visceral weight rather than of a major increase in absolute fillet weight. Moreover, fillet percentage is challenging to improve, even if it exhibits moderate heritability (h2 = 0.29). This is because fillet percentage displays low phenotypic variation. In conclusion, fillet weight and fillet percentage can be increased by indirect selection against visceral percentage and for high eviscerated BW. [ABSTRACT FROM AUTHOR]

This study aimed to estimate genetic parameters for growth and fillet traits of Asian seabass using REML method and Bayesian approach via Gibbs sampling. Seabass fry were produced by mass spawning of 20 males and 24 females and reared as mixed families. At 120 days post hatch (dph) 3000 fish were measured, fin-clipped and marked with PIT tags in the body cavity and distributed equally into two earthen ponds. During grow-out, fish were measured at 270 dph. At 390 dph, fish were harvested, measured and filleted by skilled processors. Pedigrees were reconstructed using eleven microsatellite loci. A total of 1750 fish used in the analysis were progeny of 16 sires and 18 dams. A multivariate animal model with the fixed effect of earthen pond was used to estimate variance components. Heritability estimates for body weight (BW) were low to moderate and increased with age. The REML (and Gibbs sampling) estimates were 0.06 (0.26), 0.16 (0.31) and 0.45 (0.48) for BW120, BW270 and BW390, respectively. Heritability for total length (TL) followed the same trend, with REML (and Gibbs sampling) estimates of 0.07 (0.26), 0.11 (0.28) and 0.37 (0.40) for TL120, TL270 and TL390, respectively. The REML and Gibbs sampling estimates for fillet weight were high (0.50 and 0.52) and low to moderate for fillet yield (0.16 and 0.31). Genetic correlations were high and close to unity between BW at different ages and fillet weight (0.85–0.98). Results indicate a selection potential in this Asian seabass population and that use of weight at younger age (120 dph) as a selection criterion would result in increased body weight at harvest (390 dph) along with increased fillet weight. • Genetic parameters for growth and fillet traits were estimated from Asian seabass using REML and Gibbs sampling methods • Heritability estimates were moderate to high for harvest weight and fillet weight but low for fillet yield • Genetic correlations were high and close to unity between weight at different ages and fillet weight • REML and Gibbs sampling predicted similar EBV accuracy for body weight and fillet weight • Gibbs sampling outperformed REML for fillet yield [ABSTRACT FROM AUTHOR]

Selection to improve processing yields relies on sib selection, in which live candidates are ranked according to their family breeding value. This approach limits genetic progress, as it only exploits genetic variability between families and not within them. Indirect criteria measured on live candidates could overcome this limitation. The present study (1) proposes a procedure to identify indirect criteria to predict processing yields in rainbow trout (head, carcass and fillet yields), (2) estimates genetic parameters of these indirect criteria, and (3) predicts relative genetic gains in processing yields using full-sib selection or indirect individual selection on those indirect criteria. DNA-pedigreed all-female rainbow trout Oncorhynchus mykiss ( n = 2029, 1631.0 ± 355.6 g) from 600 families produced from 100 sires and 60 dams were characterized by external and internal non-lethal morphological measures using digital pictures and real time ultrasound tomography. Nineteen landmarks were recorded on the digital pictures to define the outline of the body, head and lateral line. Their coordinates were used to calculate different lengths, heights and areas. Five different internal thicknesses were measured by ultrasound tomography. In the first phase of this study, processing yields were predicted using multiple linear regressions including both external and internal morphometric variables. In a second phase, the heritability of the predicted values and their genetic correlations with real processing yields were estimated using animal models. Predicted yields exhibited intermediate heritabilities (0.25–0.28) that were half the value of heritabilities for real processing yields (0.47–0.55), but had high genetic correlations with these real yields (0.87–0.90). The relative efficiency of indirect selection (IS) on these indirect criteria was compared to theoretical mass selection (MS) or sib selection (FS) with different family sizes (10 or 100) and two different selection pressures (10% or 40%). At the same selection pressure (10%, with 100 sibs per family %), full-sib selection created genetic progress 49.6% to 60.5% higher than indirect selection according to the processing yield targeted. However, when sib-selection pressure was limited to a more realistic between family selection pressure (40% and 10 sibs per family), indirect selection with 10% selection pressure was 21.9% to 32.7% more efficient than sib selection. [ABSTRACT FROM AUTHOR]