Fillet Traits Research Articles

Genomic predictions for daily gain and fillet weight using correlated size and body area measurements in Asian seabass (Lates calarifer, Bloch 1790)

Genomic prediction models have proven efficient for increasing genetic gains of growth and fillet traits in aquaculture. However, measurement of these traits is expensive, time-consuming, or cannot be performed on live animals. This study investigated the potential of using correlated body traits as an alternative basis for supporting genomic prediction of average daily gain (ADG) and fillet weight (FW) in Asian seabass. A total of 954 fish were genotyped for 20,430 single nucleotide polymorphisms (SNPs). Phenotypic data at 390 days, including body weight, fillet weight, 16 size and four body-part-area measurements were used. Heritability estimates were high for ADG (0.47) and FW (0.44), low to moderate (0.12–0.39) for body sizes and body areas. Genetic correlations among pairs of traits were all high and positive (0.65–0.99). Five prediction models (1, 2, 3, 4 and 5) were evaluated using the GBLUP method and were compared using five-fold cross validation. Results indicated that model 4, which fitted the secondary traits derived from correlated body sizes and body areas as the phenotypes, was the best model, showing prediction accuracy of 0.47 with small prediction bias (0.95). The results demonstrated the advantage of using correlated traits for practical genomic prediction in Asian seabass, particularly for growth and fillet traits that are difficult to measure.

In Vivo Ultrasound Prediction of the Fillet Volume in Senegalese Sole (Solea senegalensis).

Simple SummaryThe ability to obtain in vivo information on characteristics related to fish composition is necessary for aquaculture. In addition, there is growing interest in production traits, such as growth, feed efficiency or fillet weight, but it remains difficult to precisely record in vivo individual fish traits that report to these production traits, which can increase edible fish meat production and decrease the environmental impact. In the present study, we performed an ultrasound approach for the in vivo prediction of fillet volume of the Senegalese sole (Solea senegalensis), a species considered a promising flatfish species for marine fish farming. The results show that models based on ultrasound fillet volume measurements explain above 95% of the variation observed in fillet volume. However, for fillet yield estimation, the results were modest. Therefore, further studies are necessary to better understand the potential of the ultrasound approach to this trait. Nevertheless, this work allows us to conclude that the approach with ultrasound is promising for measuring in vivo fish composition traits.Senegalese sole (Solea senegalensis) has been considered a promising new flatfish species for Mediterranean marine fish farming. Accurate prediction of fillet traits in live animals may allow for more efficient control of muscle deposition in fish. In this sense, this study was undertaken to develop a non-invasive method to predict in vivo fish fillet volume and yield using real-time ultrasonography (RTU). The trial was conducted with 44 market weight Senegalese sole (298.54 ± 87.30 g). Fish were scanned with an Aloka SSD 500V with a 7.5 MHz probe. Ten RTU cross-sectional images were taken from the operculum to the caudal fin at regular intervals. These images were analyzed using Fiji software. These data were then used to estimate the partial volumes of the fillet. Actual fillet volume was determined using Archimedes’ principle. Simple and stepwise multiple regression analyses were then used to develop prediction models of fillet volume and yield. The most cranial RTU sections of the fish fillet were the best single predictors of both fillet volume and fillet yield and were the ones included in the best stepwise models. The best RTU slice area explained 82% of the variation observed in fillet volume, but the other RTU slice areas used as predictors of fillet volume showed poor to moderate accuracy (0.035 ≤ R2 ≤ 0.615). Single RTU partial volumes showed poor to very high accuracy (0.395 ≤ R2 ≤ 0.970) as predictors of fillet volume. The best stepwise model based on the RTU slice areas included three independent variables and explained 88.3% of the observed variation. The best stepwise models based on RTU partial volumes (single volumes and/or combinations of single volumes) explained about 97% of the variation observed in fillet volume. Two RTU volume traits, V1–5 + V6–9, and V1+()+9, showed to be practically direct predictors of the actual fillet volume, explaining, respectively, 97% and 96% of the variation observed in the actual fillet volume. The fillet yields show lower correlations with slice areas (r between 0.044 and 0.601) than with volumes (r between 0.288 and 0.637). While further studies are clearly necessary to better understand the potential of RTU for the estimation of fillet yield in fish in general and Senegalese sole in particular, the present results showed that RTU traits can be very good predictors of Senegalese sole’s fillet volume, either used in regression models or as direct predictors.

Production performance, nutrient digestibility, serum biochemistry, fillet composition, intestinal microbiota and environmental impacts of European perch (Perca fluviatilis) fed defatted mealworm (Tenebrio molitor)

Yellow mealworm (Tenebrio molitor) larvae meal (TM), one of the seven insect species approved for use in aquafeed in Europe, is a frequently investigated candidate for fish diets. This study aimed to investigate the effects of dietary defatted TM on production performance, serum biochemistry, nutrient digestibility, fillet traits, intestinal microbiota, and environmental impacts of perch (Perca fluviatilis). Four experimental diets, characterized by defatted TM inclusion levels of 0, 6.8, 13.5 and 20.3%, respectively, or 0, 25, 50, and 75% replacement for fishmeal on a w/w basis (TM0, TM25, TM50, and TM75, respectively), were fed to juvenile perch (bodyweight 20.81 ± 3.36 g, total length 117.7 ± 7.2 mm) (quadruplicated per diet) for 105 days. Inclusion levels of 6.8% or 25% fishmeal replacement by defatted TM did not show a significant effect on specific growth rate and feed conversion ratio, while further levels of 13.5 and 20.3%, or 50 and 75% fishmeal replaced by defatted TM, respectively, displayed a significant delay in the former (P = 0.01), but increase in the latter indice (P = 0.04) compared to TM0 diet. The aspartate aminotransferase activities in perch's serum increased with increasing dietary TM (P = 0.02). Protein digestibility of perch exhibited a negative correlation with dietary TM (P = 0.03). Dietary defatted TM did not, alter fillet composition of perch (P > 0.05) and modify diversity of fish gut microbiota (Chao1 index, P = 0.742; Shannon index, P = 0.557; and observed species, P = 0.522), but significantly reduced abundance of Lactobacillus (P = 0.04) and Streptococcus (P = 0.01). Diets containing more than 6.8% TM generated a comparable amount of total solid waste and solid phosphorus waste as the TM0, whereas solid nitrogen waste significantly increased with elevated TM levels (P < 0.001). The estimated environmental impacts of perch fed TM25 were comparable to TM0 for global warming potential, acidification, and land use (P > 0.05), whereas TM50 and TM75 exerted heavier burdens on energy use, eutrophication, and water use than TM0 (P < 0.001). Fishmeal replacement by TM significantly reduced the economic fish-in fish-out ratio (P < 0.001). Results of this multidisciplinary study revealed important considerations for formulating diets with insect meals and their potential effects on fish performance and environmental impacts.

Performance and fillet traits of rainbow trout (Oncorhynchus mykiss) fed different levels of Hermetia illucens meal in a low-tech aquaponic system

In this study, we evaluated the effects of dietary substitution of fishmeal (FM) with partially defatted Hermetia illucens meal (HI) on the growth, feed digestibility, gut morphology, and fillet quality of rainbow trout reared in a low-tech aquaponic system. A total of 173 rainbow trout (initial body weight: 156 g ± 39.8 g) were distributed among nine experimental aquaponic units. Three diets were fed to fish (three aquaponic units per dietary treatment) over a period of 76 days, i.e. H0 diet (control), H6 diet, and H12 diet containing 0 g/kg, 62 g/kg, or 124 g/kg of HI and 200 g/kg, 150 g/kg, or 100 g/kg of FM, respectively. We found that the apparent digestibility coefficients of diets were unaffected by the inclusion level of dietary HI. At the end of the trial, trout mortality was low (2.9%) and unaffected by dietary treatment. The specific growth rate was, however, lower in fish fed the H12 diet than in those fed H0 and H6 diets after 26 days (1.07% d−1 vs. 1.22% d−1; P < 0.001) and at the end of the trial (0.81% d−1 vs. 0.88% d−1; P < 0.05). In contrast, dietary inclusion of HI appeared to have no appreciable effect on the feed conversion ratio (on average 1.53), final weight (303 g), fish condition factor (1.40), viscerosomatic index (10.9%), or hepatosomatic index (1.22%). The inclusion of HI was, nevertheless, found to promote a 10% increase in the density of goblet cells in the gut of fish fed the H12 diet compared with those receiving the H0 diet (P < 0.05). With regards to fillet traits, redness and yellowness indices were lower in fish fed the H12 diet than in those fed the H0 diet. Although dietary HI had little effect on the proximate composition and fatty acid profile of fish, the proportions of C12:0 and C14:0 increased with HI dietary inclusion. In conclusion, fish growth and fillet quality were essentially unaffected by a 25% fish meal replacement with HI in isonitrogenous and isoenergetic diets (control diet containing 200 g/kg of fish meal), whereas at a replacement rate of 50%, we detected certain effects on gut histology and fillet colour and nutritional characteristics, which warrant further investigation.

Multiple-trait genomic prediction of harvest and fillet traits in Asian seabass (Lates calcarifer, Bloch 1790)

Growth performance and fillet yield are considered economically important traits in Asian seabass farming. However, measurement of fillet traits is difficult, expensive and not possible on the selection candidates. The aim of this study was to assess the utilization of multi-trait genomic selection to improve breeding value prediction accuracy for these traits. A total of 1047 fish were genotyped for 29,521 single nucleotide polymorphisms. Pedigree based on eleven microsatellite loci was available. Phenotypic data at harvest, including body weight (BW), standard length (SL), fillet weight (FW) and fillet yield (FY) were used in the analysis. Traditional best linear unbiased prediction (BLUP) and genomic BLUP (GBLUP) were implemented via single- and two-trait models to predict estimated breeding values (EBV) and genomic (G)EBV. Prediction accuracies and bias were evaluated using five-fold cross-validation with five replications. Compared to BLUP, GBLUP increased the prediction accuracies by 25% for BW, SL, FW and 10% for FY. Within GBLUP, multi-trait prediction performed slightly better than single-trait analysis. Based on the standard errors and bias, GEBV predictions were more accurate for BW, SL and FW than for FY. Prediction accuracy for FY was substantially improved with inclusion of other correlated body size traits in the validation set, and ranged from 5 to 76% relative to multi-trait GBLUP. This strategy provided an alternative to improve fillet yield in Asian seabass.

Genetic parameters for growth and fillet traits in Asian seabass (Lates calcarifer, Bloch 1790) population from Thailand

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.

Mathematical models to predict growth, fillet traits, and composition of wild traíra, Hoplias malabaricus

ABSTRACT This study aimed to determine the length-weight relationship and mathematical models to predict dressed and fillet weight and yield and fillet composition of wild traira, Hoplias malabaricus (Bloch, 1794). A total of 80 marketable-sized fish from 292.28 to 2879.57 g and 32.06 to 61.19 cm were used. The length:weight ratio was estimated using the equation: , in which W is body weight (g) and L is length (cm). The models of dressed and fillet weight and yield and body [...]

Prediction of fillet yield in hatchery populations of Asian sea bass, Lates calcarifer (Bloch, 1790) using body weight and measurements

The purpose of this study was to develop and validate prediction equations for fillet traits in Asian sea bass. Ninety-day old fish (average weight = 9.48 ± 0.35 g; length = 8.78 ± 0.6 cm) from four hatchery stocks (Chachoengsao, Chon Buri, Chumphon, and Samut Songkram) were raised in earthen ponds. After 300 days, weight and body measurement data of live fish (n = 400) were collected. Mean individual weight was greatest for the Chacheongsao stock (1166.32 ± 23.42 g) and was similar for the other stocks, ranging from 982.96 ± 25.07 to 997.44 ± 24.71 g. Fillet percentage varied slightly from 47.33 to 49.88%. Positive high correlations were observed for weight and body measurements with fillet weight, whereas there were significant but weak correlations for body measurements with fillet yield. Prediction equations developed from body weight using simple linear regression models yielded R2 values of 0.97–0.98 for fillet weight for each stock. Correlations between values predicted from the body weight models and actual values were 0.98–0.99 for fillet weight. Stepwise regression was performed to develop prediction models for fillet yield from body measurements. The best fillet yield prediction models identified length and an additional 2–3 measurement as potential predictors depending on the population. Prediction biases were close to zero despite low to moderate (r values of 0.20–0.51) degrees of predictive power of the models. However, prediction models for fillet yield should be further developed to increase predictability and be applicable to new data.

Longitudinal analyses of correlated response efficiencies of fillet traits in Nile tilapia

Recent studies with Nile tilapia have shown divergent results regarding the possibility of selecting on morphometric measurements to promote indirect genetic gains in fillet yield (FY). The use of indirect selection for fillet traits is important as these traits are only measurable after harvesting. Random regression models are a powerful tool in association studies to identify the best time point to measure and select animals. Random regression models can also be applied in a multiple trait approach to analyze indirect response to selection, which would avoid the need to sacrifice candidate fish. Therefore, the aim of this study was to investigate the genetic relationships between several body measurements, weight and fillet traits throughout the growth period and to evaluate the possibility of indirect selection for fillet traits in Nile tilapia. Data were collected from 2042 fish and was divided into two subsets. The first subset was used to estimate genetic parameters, including the permanent environmental effect for BW and body measurements (8758 records for each body measurement, as each fish was individually weighed and measured a maximum of six times). The second subset (2042 records for each trait) was used to estimate genetic correlations and heritabilities, which enabled the calculation of correlated response efficiencies between body measurements and the fillet traits. Heritability estimates across ages ranged from 0.05 to 0.5 for height, 0.02 to 0.48 for corrected length (CL), 0.05 to 0.68 for width, 0.08 to 0.57 for fillet weight (FW) and 0.12 to 0.42 for FY. All genetic correlation estimates between body measurements and FW were positive and strong (0.64 to 0.98). The estimates of genetic correlation between body measurements and FY were positive (except for CL at some ages), but weak to moderate (−0.08 to 0.68). These estimates resulted in strong and favorable correlated response efficiencies for FW and positive, but moderate for FY. These results indicate the possibility of achieving indirect genetic gains for FW and by selecting for morphometric traits, but low efficiency for FY when compared with direct selection.

Genetic parameters for growth performance, fillet traits, and fat percentage of male Nile tilapia (Oreochromis niloticus).

Improvement of fillet traits and flesh quality attributes are of great interest in farmed tilapia and other aquaculture species. The main objective of this study was to estimate genetic parameters for fillet traits (fillet weight and fillet yield) and the fat content of fillets from 1136 males combined with 2585 data records on growth traits (body weight at 290days, weight at slaughter, and daily weight gain) of 1485 males and 1100 females from a third generation of the Aquaamerica tilapia strain. Different models were tested for each trait, and the best models were used to estimate genetic parameters for the fat content, fillet, and growth traits. Genetic and phenotypic correlations were estimated using two-trait animal models. The heritability estimates were moderate for the fat content of fillets and fillet yield (0.2-0.32) and slightly higher for body weight at slaughter (0.41). The genetic correlation between fillet yield and fat was significant (0.6), but the genetic correlations were not significant between body weight and fillet yield, body weight and fat content, daily weight gain and fillet yield, and daily weight gain and fat content (-0.032, -0.1, -0.09, and -0.4, respectively). Based on the genetic correlation estimates, it is unlikely that changes in fillet yield and fat content will occur when using growth performance as a selection criterion, but indirect changes may be expected in fat content if selecting for higher fillet yield.

Verification of SNPs Associated with Growth Traits in Two Populations of Farmed Atlantic Salmon.

Understanding the relationship between genetic variants and traits of economic importance in aquaculture species is pertinent to selective breeding programmes. High-throughput sequencing technologies have enabled the discovery of large numbers of SNPs in Atlantic salmon, and high density SNP arrays now exist. A previous genome-wide association study (GWAS) using a high density SNP array (132K SNPs) has revealed the polygenic nature of early growth traits in salmon, but has also identified candidate SNPs showing suggestive associations with these traits. The aim of this study was to test the association of the candidate growth-associated SNPs in a separate population of farmed Atlantic salmon to verify their effects. Identifying SNP-trait associations in two populations provides evidence that the associations are true and robust. Using a large cohort (N = 1152), we successfully genotyped eight candidate SNPs from the previous GWAS, two of which were significantly associated with several growth and fillet traits measured at harvest. The genes proximal to these SNPs were identified by alignment to the salmon reference genome and are discussed in the context of their potential role in underpinning genetic variation in salmon growth.

The genetic architecture of growth and fillet traits in farmed Atlantic salmon (Salmo salar).

BackgroundPerformance and quality traits such as harvest weight, fillet weight and flesh color are of economic importance to the Atlantic salmon aquaculture industry. The genetic factors underlying these traits are of scientific and commercial interest. However, such traits are typically polygenic in nature, with the number and size of QTL likely to vary between studies and populations. The aim of this study was to investigate the genetic basis of several growth and fillet traits measured at harvest in a large farmed salmon population by using SNP markers. Due to the marked heterochiasmy in salmonids, an efficient two-stage mapping approach was applied whereby QTL were detected using a sire-based linkage analysis, a sparse SNP marker map and exploiting low rates of recombination, while a subsequent dam-based analysis focused on the significant chromosomes with a denser map to confirm QTL and estimate their position.ResultsThe harvest traits all showed significant heritability, ranging from 0.05 for fillet yield up to 0.53 for the weight traits. In the sire-based analysis, 1695 offspring with trait records and their 20 sires were successfully genotyped for the SNPs on the sparse map. Chromosomes 13, 18, 19 and 20 were shown to harbor genome-wide significant QTL affecting several growth-related traits. The QTL on chr. 13, 18 and 20 were detected in the dam-based analysis using 512 offspring from 10 dams and explained approximately 6–7 % of the within-family variation in these traits.ConclusionsWe have detected several QTL affecting economically important complex traits in a commercial salmon population. Overall, the results suggest that the traits are relatively polygenic and that QTL tend to be pleiotropic (affecting the weight of several components of the harvested fish). Comparison of QTL regions across studies suggests that harvest trait QTL tend to be relatively population-specific. Therefore, the application of marker or genomic selection for improvement in these traits is likely to be most effective when the discovery population is closely related to the selection candidates (e.g. within-family genomic selection).Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-015-0215-y) contains supplementary material, which is available to authorized users.

Flesh characteristics: estimation of genetic parameters and correlated responses to selection for growth rate in the GIFT strain

Flesh characteristics comprising chemical composition (protein, fat and moisture percentages and pH) as well as a sensory attribute (colour) were measured in 1951 fillet samples from two generations of two populations (a selection line, selected for increased harvest weight, and a control line, selected for average breeding values for harvest weight) of the genetically improved farmed tilapia (GIFT) strain of Nile tilapia. These data were jointly analysed with 5331 harvest weight records from three generations to estimate genetic parameters and correlated selection responses. Multiple trait animal models were used in the analyses. The potential for correlated responses was evaluated by estimating heritabilities and genetic correlations between body traits (weight, length, depth and width) and fillet traits (weight and yield) with the above mentioned flesh characteristics. The heritabilities for protein%, fat% and colour were low (0.06–0.11), whereas for moisture% and pH they were moderate (0.15–0.20). Genetic correlations among some flesh characteristics (moisture% with protein%, fat% and pH and with fat%) as well as between body and fillet traits with flesh characteristics, were significantly different from zero but low (−0.34 to 0.31). Correlated responses were evaluated by comparing the least squares means between the Selection and Control lines. Our results indicate that selection for high growth increased harvest weight in the Selection line relative to the Control line but it did not change the flesh characteristics of the GIFT strain.

Single nucleotide polymorphisms in the insulin-like growth factor 1 (IGF1) gene are associated with growth-related traits in farmed Atlantic salmon.

Understanding the genetic basis of variation in traits related to growth and fillet quality in Atlantic salmon is of importance to the aquaculture industry. Several growth-related QTL have been identified via the application of genetic markers. The IGF1 gene is considered a highly conserved and crucial growth-regulating gene in salmonid species. However, the association between polymorphisms in the IGF1 gene and growth-related traits in Atlantic salmon is unknown. Therefore, in this study, regions of the Atlantic salmon IGF1 gene were sequenced, aligned and compared across individuals. Three SNPs were identified in the putative promoter (SNP1, g.5763G>T; GenBank no. AGKD01012745), intron 1 (SNP2, g.7292C>T; GenBank no. AGKD01012745) and intron 3 (SNP3, g.4671A>C; GenBank no. AGKD01133398) regions respectively. These SNPs were genotyped in a population of 4800 commercial Atlantic salmon with data on several weight and fillet traits measured at harvest (at approximately 3 years of age). In a mixed model, association analysis of individual SNPs, SNP1 and SNP3 were both significantly associated with several weight traits (P < 0.05). The estimated additive effect on overall harvest weight was approximately 35 and 110 g for SNPs 1 and 3 respectively. A haplotype analysis confirmed the association between genetic variation in the IGF1 gene with overall body weight (P < 0.05) and fillet component traits (P < 0.05). Our findings suggest the identified nucleotide polymorphisms of the IGF1 gene may either affect farmed Atlantic salmon growth directly or be in population-wide linkage disequilibrium with causal variation, highlighting their possible utility as candidates for marker-assisted selection in the aquaculture industry.

Genetic improvement of tilapias in China: Genetic parameters and selection responses in fillet traits of Nile tilapia (Oreochromis niloticus) after six generations of multi-trait selection for growth and fillet yield

Genetic parameters and selection responses were obtained for fillet weight and fillet yield of Progift Nile tilapia (Oreochromis niloticus) in China after six generations of multi-trait selection for growth and fillet yield. A total of 9619 test fish representing 687 full-sib families in six generations (G1–G6) of Nile tilapia originating from the GIFT breed were sacrificed to record skin-on fillet weights. Some of these skin-on fillets were further processed by skinning (5971 test fish) and trimming (4633 test fish) to allow calculations of three estimates of fillet yield (based on skin-on, skinned and trimmed fillets). Recorded fillet weights were positively influenced by body weight and negatively influenced by age at recording. The heritability (h2) of skin-on fillet weight showed large variation in magnitude between generations (range of 0.00–0.45), but was of medium magnitude (0.30) when analyzing all data combined. The h2 of fillet yield, which varied between 0.08 and 0.30 in different generations, was relatively stable (0.17–0.23) for different estimates of fillet yield when analyzing across all generations. Including all data, the effects common to full-sibs (c2) accounted for 8% and 1–2% of the total phenotypic variance, respectively, for skin-on fillet weight and different estimates of fillet yield. The genetic correlations between different estimates of fillet yield were all very high (0.95–0.97 when analyzing all data) showing that it is sufficient to select based on skin-on fillet yield. The genetic correlation between skin-on fillet weight and body weight at harvest was also very high (0.97), while that between fillet yield and fillet weight was of moderate magnitude (0.33). The genetic correlation between fillet yield and body weight at harvest was not significantly different from zero. Genetic trend analysis based on all data predicted accumulated selection responses of 121g (1.87 phenotypic standard deviation units) larger skin-on fillet weight and 1.2%-units higher skin-on fillet yield after six generations of multi-trait selection. It is concluded that the ongoing program in China has resulted in considerable genetic improvement of fillet weight, and that genetic changes of fillet yield is a much slower process (0.2%-units per generation). Implications for commercial selective breeding programs are discussed.

Direct and indirect selection of visceral lipid weight, fillet weight, and fillet percentage in a rainbow trout breeding program1

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, r(TI) = 0.54) was equally efficient compared with indirect selection on visceral percentage ( r(TI) = 0.54). Genetic improvement of fillet weight through direct selection (r(TI) = 0.56) was always more efficient than indirect selection, yet indirect selection for eviscerated BW ( r(TI) = 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 (h(2) = 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.

Genetic parameters for fillet traits and body measurements in Nile tilapia ( Oreochromis niloticus L.)

Fillet weight is an economically important trait in Nile tilapia production for the European market which asks for fish with average body weights of at least 700 g. Genetic parameters to design or optimize breeding programs for these body weights are lacking. In an earlier study we showed that high phenotypic correlations exist between body measurements and fillet weight and low phenotypic correlations exist between body measurements and fillet yield. To evaluate the potential of mass selection for fillet traits, however, genetic parameters are required. The aim of the current study was to estimate genetic parameters for body weight, fillet weight, fillet yield and body measurements. Therefore, slaughter data was collected on 1884 pedigreed Nile tilapias. Measurements of body weight, length, width, corrected (=fillet) length and head length were taken on each fish. Filleting machines were used to fillet fish and measurements of fillet weight, fillet yield and head weight were collected. Subsequently, genetic parameters were estimated. Heritabilities were 0.26 for body weight, 0.24 for fillet weight and 0.12 for fillet yield. The genetic correlation between body weight and fillet weight was 0.99 and between body weight and fillet yield 0.74. The genetic correlation between fillet weight and fillet yield was 0.81. Genetic correlations between fillet weight and body measurements were 0.89 for length, 0.70 for head length, 0.94 for width and 0.91 for corrected length. Genetic correlations between fillet yield and body measurements were 0.62 for length, 0.47 for head length, 0.98 for width and 0.60 for corrected length. The potential of mass selection aiming to improve fillet weight was evaluated by a number of selection indexes. The accuracy of a selection index including only body weight indicated that in this way almost the same amount of the selection response could be achieved compared to what hypothetical direct selection for fillet weight would. The use of only width in the selection index would result in 8.5% lower selection response than the use of body weight. We conclude that body weight is the best predictor for fillet weight compared to body measurements.

Preliminary results on quality and quality changes in reared meagre (Argyrosomus regius): body and fillet traits and freshness changes in refrigerated commercial-size fish

Meagre (Argyrosomus regius) intensively reared in tank by a Tuscany farm and fed commercial diets, were examined to study a) marketable and flesh nutritional traits in commercial-size fish and b) loss of freshness under refrigerated storage condition. Eighty fish, sampled in May, July and November (at 24, 26, 30 months of age) were submitted to linear measurements and weight of the most important body components. Whole fillets were analysed for moisture, lipid and fatty acid composition. Data were analysed by ANOVA (sampling date). A sub sample of fifty-four meagre (902–1840 g b.w.) was stored at 1 °C with ice cover and evaluated every 24 h after death until spoilage for the EU freshness classes, dielectric properties, rigor index, muscular and eye liquor pH, K1% freshness index. Data were analysed by regression on time after death. A small sample of meagre (n = 6) and sea bass (Dicentrarchus labrax) (n = 6), reared in analogous rearing condition in the same farm were compared by ANCOVA on body weight (average b.w. 668 g). Meagre were characterised by 1.04 condition factor, 44% fillets, 6% viscera, negligible mesenteric fat (≅1%) and 94.5% dressing yield. The head incidence increased (P < 0.01) with b.w. increase. Moisture increased while lipid decreased (P < 0.01) in fillet from July to November (74.47 vs 75.96%; 2.93 vs 2.06%). An index of thrombogenicity calculated from the quantitative fatty acid composition was very low (0.10). In comparison with sea bass of the same body weight, meagre had greater length (41.2 vs 37.6 cm), head incidence (29.9 vs 20.7%) and dressing (94.8 vs 89.2%) and lower viscera (5.2 vs 10.9%), mesenteric fat (0.9 vs 7.9%) and intramuscular fat (2.24 vs 12.78%) incidences. Meagre had a 9-day shelf-life (E class from 1st to 3rdd and A class from 4th to 7thd). Rigor index and impedance remained higher than 90% and 66, respectively until the 3rdd after death. The quality traits found for this species indicated meagre as a promising candidate for Mediterranean aquaculture.

Relationships Among Total Weight, Body Shape, Visceral Components, and Fillet Traits in Palmetto Bass (Striped Bass Female Morone saxatilis× White Bass Male M. chrysops) and Paradise Bass (Striped Bass Female M. saxatilis× Yellow Bass Male M. mississippiensis)

Abstract.Relationships among total weight (W), and linear measures of body shape, visceral component weights, and fillet weight (Y) in market‐size (&gt;454 g) palmetto bass (Morone saxatilis female ×M. chrysops male, N= 138) and paradise bass (M. saxatilis female ×M. mississippiensis male, N= 134) were determined with the allometric equation: Y = aWb. Allometric analysis was used to compare traits of palmetto bass and paradise bass, and to identify factors influencing fillet yield. Paradise bass, an all female hybrid, had deeper, thicker, shorter bodies, and smaller heads than palmetto bass females. Male and female palmetto bass had similar body shapes. Values of growth coefficients (b) for body shape traits (range 0.21–0.48) indicated that shape was proportional across the weight range of fish used. Mean visceral fat and ovary weight were higher in paradise bass than in palmetto bass females suggesting the reproductive cycle was more advanced in paradise bass females. Whole fillet (skin and ribs intact) and skinless fillet (ribs intact) were larger for paradise bass than for palmetto bass, but trimmed fillet (skin and ribs removed) was not different between fish. Relative increases of whole and skinless fillet weights were greater than total weight in both groups indicating that the percentage of body mass attributed to fillet increases slightly as total weight increases. Therefore, small increases in fillet yield can be achieved by rearing fish to a larger size. Stepwise regression of whole, skinless, and trimmed fillet weight on body shape traits resulted in three parameter models with r2‐values of 0.27–0.29 in palmetto bass, and of 0.37–0.43 in paradise bass. Addition of visceral components as independent variables in the models increased r2‐values to 0.31–0.36 for palmetto bass and to 0.45–0.52 for paradise bass. Low phenotypic variation in fillet yield (CV = 3–5%) and poor predictability of yield from measures taken on live fish limit the potential for improving yield through individual selection. Identification of superior species or strain crosses or rearing fish to a larger size appear to be the best strategies for improving fillet yield of Morone hybrids.