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Final Report: The Shrimp Breeding Program, Selective Breeding of Penaeus vannamei
... The selection response for growth and TSV survival were measured periodically, but not for every generation. Selection response estimates for growth have ranged from 3.1% to 25.0% per generation (Fjalestad et al., 1997; Alcivar-Warren, 2000, Argue et al., 2002) and selection S31 D.R. Moss et al. / Aquaculture 272S1 (2007) S30–S37 response estimates for TSV survival have ranged from 12.4% to 18.4% (Fjalestad et al., 1997; Argue et al., 2002). For a more detailed description of the founder stocks and the breeding program see Wyban et al. (1993, and Argue et al. (2002). ...
... The selection response for growth and TSV survival were measured periodically, but not for every generation. Selection response estimates for growth have ranged from 3.1% to 25.0% per generation (Fjalestad et al., 1997; Alcivar-Warren, 2000, Argue et al., 2002) and selection S31 D.R. Moss et al. / Aquaculture 272S1 (2007) S30–S37 response estimates for TSV survival have ranged from 12.4% to 18.4% (Fjalestad et al., 1997; Argue et al., 2002). For a more detailed description of the founder stocks and the breeding program see Wyban et al. (1993, and Argue et al. (2002). ...
... However, selection responses (per generation) of 3.1%–25.0% for growth (Fjalestad et al., 1997; Alcivar-Warren, 2000, Argue et al., 2002) and 12.4%–18.4% for TSV survival (Fjalestad et al., 1997; Argue et al., 2002) have been reported for this breeding population. ...
The objective of this study was to investigate the effects of inbreeding on the performance of Pacific white shrimp, Penaeus (Litopenaeus) vannamei, under various culture conditions through a retrospective analysis of family performance data. Fourteen years of pedigree and eight years of performance data from Oceanic Institute's selective breeding program were used in the analysis. During this period, shrimp performance was evaluated in growout trials (in pond and raceway systems), laboratory challenges to three isolates of Taura syndrome virus (TSV), and a laboratory challenge to White spot syndrome virus (WSSV). The effects of inbreeding on growth and survival were estimated by regressing family phenotypic means (adjusted for contemporary group effects) on inbreeding coefficients. During growout, inbreeding had a small but significant effect on growth (2.6 to 3.9% reduction per 10% inbreeding) but had no effect on survival. The effects of inbreeding on survival after exposure to viral pathogens ranged from moderate (8.3% reduction per 10% inbreeding) to severe (38.7% reduction), although not all effects were significant. Furthermore, the effects of inbreeding on survival appeared to be sensitive to environmental quality, as inbreeding depression was more severe in more stressful environments (smallest effect during growout trials and largest effect during exposure to WSSV). These results suggest that moderate to high levels of inbreeding (> 10%) should be avoided in shrimp breeding programs, especially when shrimp are reared under stressful conditions. In addition, the effects of inbreeding on survival appear to be significant enough to justify the use of inbreeding as a germplasm protection strategy (under certain scenarios) for genetic improvement programs.
... Overall, genetic parameter estimates for penaeid TSV resistance are moderate (0.2 ≤ h 2 ≤ 0.3) (Argue et al., 2002;Cock et al., 2009;Fjalestad et al., 1997). Despite only relatively moderate heritability for TSV resistance, TSV resistant strains have been developed. ...
... Studies of G×E interactions in penaeid shrimp species have focussed on correlations between specific growth traits and different culture environments, in particular, effects of stocking density, location and temperature (Caballero-Zamora et al., 2015b;Campos-Montes et al., 2009;Castillo-Juárez et al., 2007;Coman et al., 2004;Fjalestad et al., 1997;Gitterle et al., 2005a;Ibarra and Famula, 2008a;Jerry et al., 2006b;Li et al., 2015;Pérez-Rostro and Ibarra, 2003a;Suarez et al., 1999;Sui et al., 2016c). ...
Pacific white shrimp (Penaeus vannamei) is currently in trade value terms, the most important food commodity in global aquaculture. Long term sustainability of farmed marine shrimp is crucial, not only because of its socioeconomic importance, but also because this product makes a significant contribution to world food security.
Results of the current project will assist the design of future breeding programs for marine shrimp that seek to develop locally adapted strains that target specific farming and market conditions in China.
The first step in the current project applied seven microsatellite markers to assess genetic resources for Pacific white shrimp that were available in China by documenting relative levels of genetic variation, extent of stock differentiation and genetic relatedness as an initial step towards producing a base population for a longterm
family-selection breeding program. Based on the genotypic information that identified 4 distinct groups, a complete 4 × 4 diallel cross was conducted to develop a base population for the family selection breeding program. Quantitative genetic analysis of growth traits in the base population confirmed that a substantial component of additive genetic variance (BW1: h2 = 0.52 ± 0.09; BW2: h2 = 0.44 ±
0.07) was available that could be used to improve relative stock productivity.
The next component of the project focused on optimising reproductive
performance of females in the base population by trialling two different rearing conditions for broodstock: recirculating tanks (RT) vs earthen ponds (EP). Results of the trial indicated that no significant differences were present for the majority of reproductive performance traits examined between broodstock reared in RT vs EPenvironments. Females exposed to the EP treatment however, were observed to show
significantly higher mean spawning frequency than their counterparts in the RT treatment. No evidence was detected however, for reproductive exhaustion in females that spawned multiple times vs those that spawned only once.
The final study undertook a quantitative genetic analysis of heritability for reproductive traits in the base population and results showed that there was potential to improve a number of key reproductive traits in mature females (notably, number of eggs per spawn (NE), number of nauplii per spawn (NN), and spawn frequency(SF)) via genetic selection, but that egg hatching rate per spawn (HR) and number of
eggs produced relative to individual female weight (FE) traits, were unlikely to be improved via this approach. Results of genetic correlations between body weight at spawning and reproductive traits also provided no evidence to suggest that improving mean body weight will produce potentially negative effects on female broodstock
reproductive quality. Results from the current study clearly demonstrate that, selecting for a broodstock strain with fast growth and better reproductive performance can be achieved successfully at the same time.
... Selective breeding of P. vannamei for TSV resistance began in the mid-1990s and several research and commercial breeding programs have developed lines of shrimp which exhibit varying degrees of TSV resistance (Argue et al., 2002; Bienfang and Sweeney, 1999; Clifford and Preston, 2006; Wyban, 1999); note: the terms " resistant " and " resistance " have been adopted by many stakeholders in the shrimp farming industry to refer to a shrimp's ability to survive viral exposure. Although heritability for TSV resistance is considered low to moderate, significant improvements in TSV resistance have been made (Argue et al., 2002; Fjalestad et al., 1997; Gitterle, 1999; White et al., 2002), including the establishment of some selectively bred stocks which exhibit N80% survival to TSV in per os laboratory challenges (Moss et al., 2011; Srisuvan et al., 2006; Wyban, 2000). TSV has a single-stranded, positive-sense RNA genome comprised of two open reading frames (ORFs), with ORF1 coding for non-structural proteins (helicase, protease, and RNA polymerase) and ORF2 coding for structural proteins, including three capsid proteins (Bonami et al., 1997; Mari et al., 2002). ...
... Argue et al. (2002) reported paternal half-sib, full-sib, and realized h 2 estimates (±SE) of 0.19 ± 0.08, 0.14 ± 0.05 and 0.28 ± 0.14, respectively. Similarly, Fjalestad et al. (1997) reported a maternal half-sib h 2 estimate of 0.22 ± 0.9. Despite low to moderate h 2 , significant improvements in TSV survival have been made through selection (Argue et al., 2002; Cock et al., 2009; Gitterle, 1999). ...
... Argue et al., 2002; Bondary, 1983; Dunham, 2006; Gitterle et al., 2006; Hetzel et al., 2000; Hussain et al., 2002; Ilyassov, 1987; Kincaid et al., 1977; Kirpichnikov, 1987; Kuzema, 1971; Langdon et al., 2003; Moav and Wohlfarth, 1963, 1973, 1976 Nell and Hand, 2003; Newkirk and Haley, 1983; Schaperclaus, 1962). Large scale family based breeding programs, now established as the industry standard for genetic improvement of aquaculture species, were first introduced for salmonids in the 1970s (Gjedrem, 1985), for Nile tilapia in 1988 (Eknath et al., 1991) and for marine shrimp P. vannamei in 1993 (Fjalestad et al., 1997). Since then selection programs utilizing sib information have been implemented for a number of aquaculture species worldwide. ...
... In addition to the direct benefits from selection for disease resistance, four studies report a positive genetic correlation (averaging 0.29) between growth rate and disease resistance (Gjedrem et al., 1991; Jonasson, 1993; Rye et al., 1990; Standal and Gjerde, 1987) which means that as growth rate increases disease resistance also increases. In shrimp the relationship between growth rate and disease resistance seems to be different than fish because negative genetic correlations have been estimated (Fjalestad et al., 1997; Gitterle et al., 2005). Further, as the growth rate of fish and crustaceans increases, and time to market size becomes shorter, mortality will be reduced simply because the animals live a shorter time. ...
Aquaculture is the fastest growing food production industry, and the vast majority of aquaculture products are derived from Asia. The quantity of aquaculture products directly consumed is now greater than that resulting from conventional fisheries. The nutritional value of aquatic products compares favourably with meat from farm animals because they are rich in micronutrients and contain high levels of healthy omega-3 fatty acids. Compared with farm animals, fish are more efficient converters of energy and protein. If the aquaculture sector continues to expand at its current rate, production will reach 132 million tonnes of fish and shellfish and 43 million tonnes of seaweed in 2020. Future potential for marine aquaculture production can be estimated based on the length of coastline, and for freshwater aquaculture from available land area in different countries. The average marine production in 2005 was 103 tonnes per km coastline, varying from 0 to 1721 (China). Freshwater aquaculture production in 2005 averaged 0.17 tonnes/ha, varying from 0 to close to 6 tonnes per ha (Bangladesh), also indicating potential to dramatically increase freshwater aquaculture output. Simple estimations indicate potential for a 20-fold increase in world aquaculture production. Limits imposed by the availability of feed resources would be lessened by growing more herbivorous species and by using more of genetically improved stocks.
... These software tools can handle large amounts of pedigree and phenotypic data, allowing for more accurate estimation of breeding values and better-informed selection decisions. Massive family-centered breeding programs, currently developed as the industry standard for the genetic advancement of aquaculture species, were first introduced for salmonids in the 1970s [30], Nile tilapia in 1988 [31], and marine prawn P. vannamei in 1993 [32]. After that, selection programs based on sib data have been utilized for a variety of species of aquaculture throughout the globe. ...
Agriculture and Food Science Book series aims to bring together leading academic scientists, researchers and research scholars to publish their experiences and research results on all aspects of Agriculture and Food Science. It also provides a premier interdisciplinary platform for researchers, practitioners and educators to present and discuss the most recent innovations, trends, and concerns as well as practical challenges encountered and solutions adopted in the fields of Agriculture and Food Science. High quality research contributions describing original and unpublished results of conceptual, constructive, empirical, experimental, or theoretical work in all areas of Agriculture and Food Science are cordially invited for publication.
... The response was greater than the previous study on M. rosenbergii reported by Hung et al. (2013;, Luan et al. (2012) and Sui et al. (2019). It was also higher than the responses for marine shrimp (Argue et al., 2002;Fjalestad et al., 1997;Goyard et al., 2002;Hetzel et al., 2000;Preston et al., 2004;Sui et al., 2015) but it is in line with other aquaculture species as reviewed by Nguyen (2015), likely due to the large genetic variability and the strong selection pressure applied here. ...
A breeding programme of giant freshwater prawn Macrobrachium rosenbergii is conducted in Malaysia to improve growth performance. The harvest body weight (HBW) data of 6,159 individuals from 102 sires and 141 dams produced over three generations of selection was analysed using residual maximum-likelihood methodology. This enabled the estimation of variance components and genetic parameters of the studied trait in the population. The heritability (h 2) and common environmental effect (c 2) of HBW were 0.165 + 0.153 and 0.043 + 0.013 respectively. The selection response per generation estimated by comparing the difference in mean breeding value of HBW between generations was 18.01%. It was similar with the average selection response estimated by comparing least square mean (LSM) between generations (17.78%). These results indicated that improvement of the studied trait has been achieved in this population.
... In the later years AKVAFORSK was involved in other breeding projects for Pacific white shrimp in cooperation with CENIACUA in Columbia (Gitterle et al. 2005) and with Aquatec in Brazil. In one generation of joint selection, they obtained a genetic gain of 4.4% for harvest body weight and 12.4% for TSV survival (Fjalestad et al. 1997). At present, there are about four breeding programmes operating for Pacific white shrimp (Neira) and three for tiger shrimp (Penaeus monodon) (Rye et al. 2010). ...
Hilsa: Status of Fishery and Potential for Aquaculture is a proceedings book, which is edited by an international team of experts and authored by 10 international expert teams working on different disciplines of the hilsa shad. Hilsa is a widely distributed fish within the Bay of Bengal region and harvested in the waters of Bangladesh, India and Myanmar. It is famous worldwide for its delicious taste and superb texture, which persist for a long time. Hilsa is unique in that it contains high amounts of both proteins and lipids. The fish is also rich in amino acids, minerals, micronutrients, vitamins, fatty acids and good quantity of omega-3 that has made the fish ideal for health-conscious people, especially women and children. There has been a growing interest in understanding the status of hilsa stock within the region and exploring its potential for aquaculture with hatchery produced seeds. Several attempts have been made on domestication, breeding and raising of juveniles in brackish water ponds in both India and Bangladesh, but success has been very limited, indicating that coordinated extensive research and development initiatives are needed to establish aquaculture of this species. This book presents 10 review chapters that include biology and ecology of hilsa; status of the hilsa fishery in India and Bangladesh; hilsa fishery management; seed production and rearing; food, feeding and nutritional requirements; status of aquaculture; population genetics; market trends; nutritional values; consumption and utilization as well as hilsa’s social, cultural and religious importance.
... However, there are thousands of selection candidates and test individuals in aquaculture breeding, which make genotyping costly even though the cost of individual-based genotyping has dramatically decreased. Selective breeding of penaeid shrimp over the last 20 years has guaranteed a sustainable shrimp aquaculture industry globally, which was worth over US 800 million dollars in 2017 [3,7,8]. The Pacific white shrimp Litopenaeus vannamei is the most important cultured shrimp worldwide, accounting for~80% of total cultured penaeid shrimp production. ...
Using pooled DNA genotyping to estimate the proportional contributions from multiple families in a pooled sample is of particular interest for selective breeding in aquaculture. We compared different pooled libraries with separate 2b-RAD sequencing of Litopenaeus vannamei individuals to assess the effect of different population structures (different numbers of individuals and families) on pooled DNA sequencing, the accuracy of parent sequencing of the DNA pools and the effect of SNP numbers on pooled DNA sequencing. We demonstrated that small pooled DNA genotyping of up to 53 individuals by 2b-RAD sequencing could provide a highly accurate assessment of population allele frequencies. The accuracy increased as the number of individuals and families increased. The allele frequencies of the parents from each pool were highly correlated with those of the pools or the corresponding individuals in the pool. We chose 500–28,000 SNPs to test the effect of SNP number on the accuracy of pooled sequencing, and no linear relationship was found between them. When the SNP number was fixed, increasing the number of individuals in the mixed pool resulted in higher accuracy of each pooled genotyping. Our data confirmed that pooled DNA genotyping by 2b-RAD sequencing could achieve higher accuracy than that of individual-based genotyping. The results will provide important information for shrimp breeding programs.
... Over the past few decades, several breeding programs have been carried out to improve the growth traits of L. vannamei worldwide (Neira 2010;Rye et al. 2010). In general, the growth rate of L. vannamei has been significantly improved, and the genetic gain for harvest body weight improved from 4.4 to 21% after one generation of selection (Fjalestad et al. 1997;Argue et al. 2002;Andriantahina et al. 2013). However, it is widely accepted that the growth of shrimp needs to be further improved. ...
The Pacific white shrimp Litopenaeus vannamei is one of the major economic aquaculture species. The growth trait is considered as the most important trait in L. vannamei aquaculture. Identification of the genetic components underlying growth-related traits in L. vannamei could be useful for the selective breeding of growth trait. Our previous work identified several growth-related SNPs by genome-wide association study (GWAS). Based on the assembled genome, we identified a new candidate gene (LvMMD2) beside the associated marker. This gene encodes the progestin and AdipoQ receptor 10 (PAQR10) protein. We further investigate the polymorphisms of LvMMD2 and their association with body weight of L. vannamei. By resequencing the coding region of LvMMD2, a total of 8 SNPs were identified, including 6 synonymous mutations and 2 nonsynonymous mutations. Association analyses based on a population of 322 individuals revealed that several SNPs located in the coding region of LvMMD2 were significantly associated with the body weight, especially the nonsynonymous mutation named as MMD_5 contributed the most association to the trait and it could explain 10.5% of phenotypic variance. In addition, several genes involved in growth and development have been identified as LvMMD2-interacting genes. These findings strongly suggested that LvMMD2 might be an important gene regulating the shrimp growth. More importantly, the MMD_5 could be a promising candidate locus for marker-assisted selection (MAS) of the body weight in L. vannamei.
... Although disease resistance traits showed a low to moderate heritability, genetic improvements have been achieved through traditional selection breeding. Selection response for shrimp survival from TSV infection ranged from 12.4% to 18.4% (Argue et al., 2002;Fjalestad et al., 1997), and selection response estimated for shrimp survival from WSSV infection reached 22.7% after selection for three generations in L. vannamei (Huang et al., 2011). In the current study, approximate moderate heritability was estimated for the resistance of shrimp against V. parahaemolyticus. ...
Vibrio parahaemolyticus (V. parahaemolyticus) carrying the toxic plasmid of pirA and pirB has been identified as the causative agent of acute hepatopancreatic necrosis disease (AHPND), which has caused serious economic loss to the aquaculture industry of penaeid shrimp Litopenaeus vannamei (L. vannamei) in recent years. To effectively control the outbreak of this disease, breeding of Vibrio resistant broodstocks of L. vannamei was regarded as an important approach. Due to the advantages in selection accuracy and efficiency, genomic selection (GS) was expected to be a feasible alternative to accelerate the genetic improvement of disease resistance traits. In the present study, the heritability of shrimp resistance to V. parahaemolyticus was estimated and the feasibility of GS was evaluated in L. vannamei based on the real and simulation data. The heritability of shrimp resistance against V. parahaemolyticus was around 0.15–0.24, which indicated that the genetic improvement can be achieved by selective breeding. Subsequent analysis for GS based on real data showed that the genomic best linear unbiased prediction (GBLUP) can result in more accurate prediction than the traditional pedigree-based best linear unbiased prediction (PBLUP), with a 6.8% increase in the prediction accuracy for the survival time, and a 3.5% increase for binary survival. Similarly, for the simulated data, a relative increase (3.0% and 5.0%) in the prediction accuracy was obtained for survival time and binary survival when comparing the PBLUP to GBLUP. Overall results suggest that GS could be an alternative approach to improve the genetic gains in L. vannamei for the resistance to V. parahaemolyticus.
... Generally, in the long run, selection for growth rate is also expected to increase disease resistance. Gjedrem and Olesen (2005) report eight positive genetic correlations in the range 0.20-0.50 between growth rate and different diseases, but with important exceptions reported for P. vannamei; estimates of genetic correlations between growth and resistance to Taura virus and WSSV are negative À0.12 (Fjalestad et al. 1997) and À0.60 (Gitterle et al. 2005), respectively. ...
The aquaculture sector is significantly behind plant and farm animal production in applying selective breeding, in spite of the fact that it has been suggested that the world aquaculture production could be doubled in 13 years if breeding programmes were supplying stocks for the farmed species. It is estimated that as late as in 2010, only 8.2% of the world's total aquaculture production was based on material developed in selective breeding programmes. Reported estimates of genetic gain per generation for a key trait like growth rate average 13%, implying that the animal's potential for growth can be doubled in a time span of only six generations of selection, as demonstrated for major farmed species like Atlantic salmon and Nile tilapia. Likewise are reported genetic gains for improved disease resistance generally very high. This study offers an updated review of published estimates on genetic gains for a range of traits in aquaculture species. Results are highly encouraging and demonstrate a substantial potential for genetic improvement in aquatic productions, in particular for traits such as growth rate and resistance to diseases.
... The reason for the low genetic gain in White Spot Syndrome Virus (WSSV) resistance, varying from 1.7% [27] to 6.3% [32] is not obvious, it could partly be due to difficulty and inaccuracy of mortality recording. Multi trait selection for Taura syndrome in P. vannamei is also high [33,34] while it is of medium magnitude for M. Sydney parasite in oyster [35]. The amoebic gill disease in Atlantic salmon has been shown to have genetic variation (h 2 = 0.09-0.56) ...
Disease in fish and shellfish is one of the main problems facing aquaculture production. Therefore, all attempts should be made to increase the rate of survival and, thus, reduce economic losses. Much has been done to develop vaccines and medical treatments to reduce mortality; and however, farming of aquatic species has a long way to go to optimize the environmental conditions for the animals and, thus, reduce stress and improve animal welfare. However, the good news is that there is the potential to increase disease resistance by selective breeding. By challenge-testing fingerlings from a number of families per generation, and including the rate of survival in the breeding goal, the results so far are very promising. By focusing on one disease at a time it is possible to increase the rate of survival by at least 12.5% per generation for most diseases studied. Unfortunately, selective breeding is only used to a small degree in aquatic species. In 2010, it was estimated that only 8.2% of aquaculture production was based on genetically improved stocks.
... High selection responses for growth rate have also been reported in oysters (Haley et al. 1975;Newkirk 1980;Nell et al. 1999). In whiteleg shrimp, Penaeus vannamei, the estimated response after one generation of selection was 4.4% for growth rate and 12.4% for survival after challenge testing against the Taura Virus Syndrome (Fjalestad et al. 1997). Tave (1994) report a response to selection of 9.1% (unadjusted) and 5.3% (adjusted) for body length per generation for golden shiner, Notemigonus crysoleucas. ...
Definition of breeding goals for sustainable fish production is considered, with emphasis on non-market (e.g., ethical) as well as market values. The need for long-term biologically, ecologically, and sociologically sound breeding goals is emphasized, because animal breeding determined only by short-term market forces has lead to unwanted side effects. Farmed fish is at an early stage of domestication and breeding, but rapid selection responses for growth have already been documented for several species. Reports of selection responses for fish and shellfish in both temperature and tropical environments are reviewed. Growth-rate responses of 4-20% have been obtained per generation. Broad breeding goals, including health and functional traits, in addition to production traits, are required. More basic knowledge of, e.g., animal welfare and behavioral disorders of fish is also needed. Less than 1% of the aquaculture fish material in 1993 originated from selection programs. For most species under improvement, only one or very few programs are running, and the effective population sizes are often limited. Such populations may however easily gain sufficient advantage above non-improved populations to capture much of the market. This will also discourage further genetic introductions into the breeding nucleus. Long-term inbreeding and loss of genetic variability because of genetic drift may then affect performance and further genetic progress. A sufficiently large and genetically diverse breeding population with appropriate family structure is therefore fundamental when establishing and running a selection program. Important prerequisites for breeding programs for sustainable production are appropriate governmental policies and awareness of our way of thinking about aquaculture, nature and society. A more communal worldview informed by a subjective epistemology (how we learn about/analyze nature) and a holistic ontology (belief about what/how nature is) is also required.
... Nowadays we know that the heritability for resistance to TSV is rather high for a viral disease, with published estimates in the range 0.20-0.30 (Fjalestad et al., 1997;Argue et al., 2002;CENIACUA unpublished data). Argue et al. (2002) also found a negative relationship between growth and TSV resistance after a single round of selection and Moss et al. (2005) reported a weak but statistically significant negative correlation (r = −0.15) between mean family harvest weight and mean family survival in a TSV challenge test. ...
Diseases are a major constraint on the intensive production of shrimps. Conditions in production ponds favour disease development, and epidemics of several previously unreported diseases have occurred and caused severe losses. When elimination, eradication or cultural control is difficult, selective breeding for host resistance to the pathogen may be an attractive option for disease control. However, host resistance is not a panacea and should only be considered when (a) the disease causes severe damage (b) there are no other existing simple cost effective control measures and (c) there is demonstrable genetic variation in resistance and this is not coupled with an excessive level of negative associations with other desirable characteristics. Shrimp have only recently been domesticated and breeding for resistance only began in the mid 1990s; there is limited experience with shrimp breeding in particular and crustaceans in general. Consequently, the principles and concepts behind breeding programmes are based largely on experiences with other species in both the plant and animal kingdoms. Commercial growers now seed ponds with shrimp populations selected for resistance to Taura Syndrome Virus with excellent results, whilst up to now development of White Spot Syndrome Virus resistant populations has been an elusive goal. The original TSV resistant populations were developed using simple mass selection techniques (Colombia). In later generations family based selection has been applied on populations, which initially had survival rates of about 30%, with care taken to reduce inbreeding and loss of genetic variation. This suggests that when the original populations have a reasonable level of resistance, and straightforward, effective selection protocols exist, it is relatively simple to breed for resistance. With catastrophic diseases, such as WSSV, which cause mortalities of 98% or more the frequency of resistance is low and it is suggested that for theoretical reasons single gene, rather than polygenic, resistance is likely to develop. The low frequency of resistance genes in breeding populations may cause genetic bottlenecks which will greatly reduce the genetic variation in the populations. In order to maintain the genetic variation the genes from the small numbers of survivors should be introgressed into populations with broader genetic variability. Furthermore, in order to minimize the probability of breakdown of resistance pyramiding of resistant genes on different loci would be advantageous.Genetic variation in resistance may be encountered either in the initial base populations or may spontaneously arise due to mutations or new recombinants. With extremely prolific species such as shrimps, millions of animals can readily be screened for survival and hence resistant mutants or recombinants may be identified. Once genetic variation has been detected the most appropriate breeding methodology will depend on the nature of both the resistance and the disease or diseases that are of interest to the producers.
... Fish have certainly received the greatest attention; genetic improvement programs have been developed for tilapia, Oreochromis niloticus (Longalong et al., 1999), in Atlantic salmon, Salmo salar (Gjerde, 1986;Gjerde and Korsvoll, 1999), in Coho salmon, Oncorhynchus kisutch (Hershberger et al., 1990;present study), in rainbow trout, Oncorhynchus mykiss (Kincaid et al., 1977;Gjerde, 1986), in channel catfish, Ictalurus punctutatus (Rezk et al., 2003) and in common carp, Cyprinus carpio (Tran and Nguyen, 1993), among others. In contrast, only a few genetic improvement programs have been described in other aquatic organisms such as shrimp, Panaeus vannamei (Fjalestad et al., 1997;Hetzel et al., 2000), freshwater crayfish, Cherax destructor (Jerry et al. 2005) and in the Pacific oyster, Crasostrea gigas (Ward et al., 2000). One of the principal drawbacks of BLUP selection is the high level of inbreeding which results from the tendency of the procedure to select relatives as future parents (Quinton et al., 1992;Sonesson et al., 2005), especially when the heritability of the character is low. ...
In this study the genetic response to selection and the effects of inbreeding on harvest weight in two populations (which spawned as even and odd years classes) of Coho salmon are described. Artificial selection was performed using the best linear unbiased prediction (BLUP) of breeding values obtained from an animal model. Both populations were also selected for early spawning date using independent culling levels; these results are presented in a companion paper. The estimation of genetic parameters was based on the phenotypic records of 12,208 animals randomly sampled at harvest time (random group). These fish represented a mean of 64% and 48% of all animals with phenotypic records in the even and odd year classes, respectively. The narrow sense heritability estimated for harvest weight was high and very similar in the two populations, 0.39 ± 0.03 in the even year class and 0.40 ± 0.04 in the odd year class. Due to the mating design, the genetic selection differentials were 2.3 times greater in males than in females. The mean genetic selection response obtained was high in both populations, 383.2 g or + 1.26 σ and 302.4 g or + 1.23 σ per generation in the even and odd year classes, respectively. This is equivalent, on the average, to an increase in weight of 13.9% per generation compared to the base population, or 10.2% per generation with respect to the difference between successive generations. After the 4th generation of selection the mean inbreeding level was 9.5% in the even year class and 4.4% in the odd year class, which are close to preliminary estimates based on the records of the random group plus a group of animals with high harvest weight (Gallardo, J.A., García, X., Lhorente, J.P., Neira, R., 2004b. Effects of nonrandom mating schemes to delay the inbreeding accumulation in cultured populations of Coho salmon (Oncorhynchus kisutch). Can. J. Fish. Aqua. Sci. 61, 547-553.). The estimated effects of inbreeding depression on harvest weight were negative, but not significantly different from 0 in either the even year class (bf = − 7.04 g/ΔF, s.e. = 3.9; Mean = 4118 g; inbreeding depression per 10% of ΔF was − 1.7%; P = 0.06) or the odd year class (bf = − 4.8 g/ΔF, s.e. = 0.33; Mean = 3243 g; inbreeding depression per 10% of ΔF was − 1.5%; P = 0.33). Other programs in salmon have selected for more than one character, however, there are still no estimates of economic weights published in salmon breeding programs, which are necessary to calculate the total genetic merit for these animals.
... Despite low to moderate heritability (h 2 ) estimates for TSV resistance (0.2-0.3, Fjalestad et al., 1997;Argue et al., 2002;Cock et al., 2009), significant improvements in this trait have been made through selection. Argue et al. (2002) reported that selected families of L. vannamei exhibited an 18.4% increase in survival to TSV after one generation of selection, compared with unselected control families. ...
About 3.5 million metric tons of farmed shrimp were produced globally in 2009 with an estimated value greater than USD$14.6 billion. Despite the economic importance of farmed shrimp, the global shrimp farming industry continues to be plagued by disease. There are a number of strategies a shrimp farmer can employ to mitigate crop loss from disease, including the use of Specific Pathogen Free (SPF), selectively bred shrimp and the adoption of on-farm biosecurity practices. Selective breeding for disease resistance began in the mid 1990s in response to outbreaks of Taura syndrome, caused by Taura syndrome virus (TSV), which devastated populations of farmed shrimp (Litopenaeus vannamei) throughout the Americas. Breeding programs designed to enhance TSV survival have generated valuable information about the quantitative genetics of disease resistance in shrimp and have produced shrimp families which exhibit high survival after TSV exposure. The commercial availability of these selected shrimp has benefitted the shrimp farming industry and TSV is no longer considered a major threat in many shrimp farming regions. Although selective breeding has been valuable in combating TSV, this approach has not been effective for other viral pathogens and selective breeding may not be the most effective strategy for the long-term viability of the industry. Cost-effective, on-farm biosecurity protocols can be more practical and less expensive than breeding programs designed to enhance disease resistance. Of particular importance is the use of SPF shrimp stocked in biosecure environments where physical barriers are in place to mitigate the introduction and spread of virulent pathogens.
... An alternative approach is to develop strains of carp that are resistant to the disease by selective breeding for increased disease resistance (Fjalestad, Gjedrem & Gjerde 1993). The prospect for significant improvements in disease resistance has been confirmed in Atlantic salmon, Salmo salar L. (Standal & Gjerde 1987;Gjedrem & Gjoen 1995;Ødegård, Olesen, Gjerde & Klemetsdal 2007), rainbow trout, Oncorhynchus mykiss (Walbaum) (Henryon, Jokumsen, Berg, Lund, Olesen & Slierendrecht 2002;Henryon, Berg, Olesen, Kjaer, Slierendrecht, Jokumsen & Lund 2005), Atlantic cod, Gadus morhua L. (Kettunen & Fjalestad 2006), rohu carp, Labeo rohita Hamilton (Mahapatra, Gjerde, Sahoo, Saha, Barat, Sahoo, Mohanty, Ødegård, Rye & Salte 2008) and shrimp, Penaeus vannamei Boone (Fjalestad, Gjedrem, Carr & Sweeney 1997;Argue, Arce, Lotz & Moss 2002;Gitterle, Salte, Gjerde, Cock, Johansen, Salazar, Lozano & Rye 2005). Common carp crossbreeds often show heterosis for growth rate (Wohlfarth 1993), and other production traits (Hulata 1995). ...
The objective of this study was to determine the differences in disease resistance against artificial infection with Aeromonas hydrophila between genetically different common carp families. Four strains differing in their origin and breeding history were selected from the live gene bank of common carp maintained at the Research Institute for Fisheries, Aquaculture and Irrigation (HAKI, Szarvas, Hungary) to establish families with wide genetic background: Szarvas 15 (15), an inbred mirror line; Tata (T) scaly noble carp; Duna (D), a Hungarian wild carp and Amur (A), an East Asian wild carp. A diallele mating structure was used to allow the assessment of genetic variation within and between the tested 96 families for a variety of traits. The existing technologies of fertilization and incubation of carp eggs, as well as larval and fingerling rearing had been modified because of the large number of baseline populations. Two challenge trials of the 96 families of carp with Aeromonas hydrophila were done. The 10 most resistant and 10 most susceptible families to A. hydrophila were identified from these two challenges. The crosses that produced the most resistant families were mainly those having parents from Tata and Szarvas 15 domesticated strains, while the most susceptible families were from the wild strains Duna and Amur.
Heritability estimates may be severely biased when a large common environmental effect on a family arises from a long-lasting separate rearing at early stages (SRES) in traditional selective breeding programs, especially when bred populations have weak genetic ties. Communal rearing at early stages (CRES) may reduce common environmental effect since all families are reared in the same environment immediately after hatching. Here, we compared the effects of CRES and SRES strategies on genetic parameter estimation for harvest body weight in a selective breeding population of Litopenaeus vannamei with a small number of half-sib families. Genetic parameters of each strategy were estimated by using animal models excluding and including the common environmental effect (Model 1 and Model 2, respectively). Heritability estimates for body weight were 0.21±0.06 (P <0.05) and 0.69±0.09 (P <0.05) for CRES and SRES, respectively, in Model 1, and 0.21 ±0.06 (P <0.05) and 0.52±0.27 (P >0.05) in Model 2. The ratio of common environmental variance to phenotypic variance was 0.002 ±0.000 and 0.071 ±0.112 for CRES and SRES, respectively. Neither strategy precisely partitioned the common environmental variance according to likelihood ratio test. Lower heritability for body weight in CRES than in SRES implied that a large common environmental variance was confounded with additive genetic variance and was not effectively partitioned in SRES. Moreover, genetic correlation of body weight between the two strategies was 0.75±0.15, indicating that family rankings truly changed. The CRES should be followed in the selective breeding program of shrimp, especially in a population with a shallow pedigree and weak genetic ties between families.
To investigate the genetic components of growth in the brine shrimp Artemia sinica, we estimated the genetic parameters of body length and the response to selection using a fully pedigreed population of A. sinica. The base population was generated from four wild founder populations. We tested 4160 offspring in 360 families over four generations for growth and survival performance. Across four generations, we produced full- and half-sib families with nested mating, where two dams were mated to the same sire. Individual body length was measured for each nauplius at day 20 post-hatching. Heritability of body length was estimated across four generations with the restricted maximum likelihood method. The heritability of body length in A. sinica was low (0.14 ± 0.05), and the common environmental effect was 0.14 ± 0.02. We estimated the response to selection for body length by calculating the difference in the mean breeding values between different generations. The accumulated genetic gain in body length was 278.94 μm after three generations of selection. This low response to selection was probably caused by the low heritability of body length, small sample size, and the low selection intensity (50%). The results suggest that A. sinica selective breeding programs must be changed to generate any substantial, sustainable genetic increases in body length. We suggest that optimal genetic gains could be achieved by introducing wild strains into the nuclear breeding population to increase genetic variation, and by increasing the size of the breeding population to allow for increased selection intensity.
The aim of the present study is to detect the potential of the base population from diallel crosses of eight introduced strains of the Pacific white shrimp (Litopenaeus vannamei) for improving the yield. Heterosis and heritability were estimated for pond survival at commercial farm conditions for the base population that included 207 full-sib families from a nested mating design by artificial insemination. Among all the hybrids, the heterosis ranged from–11.37% (UA1×UA2) to 20.53% (UA3×SIN) with an average of 0.953%. The results showed that more than half of the hybrids (51.85%) have negative heterosis for survival rate, but most of the hybrids with positive heterosis have high estimates. The high proportion of negative heterosis for survival rate reminders us that the survival trait also should be considered in the crossbreeding program to avoid yield decrease. However, high positive heterosis manifested in most of the hybrids for survival indicates the usefulness of these hybrids for improving the survival to obtain higher yield by crossbreeding in this breeding program. The heritability estimate for pond survival was 0.092±0.043 when genetic groups were included in the pedigree, and it was significantly different from zero (P<0.05). The results from this study also indicated that significant improvement for survival is possible through selection in L. vannamei.
The Huanghai No. 1 strain of Chinese shrimp Fenneropenaeus chinensis is an ecologically and economically important variety that is cultivated mainly in northern China. This strain has been subjected to multiple selective events in recent years. Conventional methods are insufficient to reveal the genetic background of Huanghai No. 1, especially with regard to a genome-wide transcription profile, and publicly available genomic resources for Huanghai No. 1 are limited. We obtained 907,945 original reads with an average length of 467.5 bp from muscle and haemocyte samples from Huanghai No. 1 using 454 pyrosequencing. After preprocessing, 867,245 high-quality reads were screened. Of the 64,830 assembled sequences, 34,633 of the unigenes had significant matches in the databases (similarity >30 %), including 14,138 isotigs and 20,495 singletons. A gene ontology analysis assigned 8,257 unigenes to 44 subcategories, with the majority of unigenes assigned to cellular component (28.2 %), biological process (20.5 %) and molecular function (5.0 %) categories. Pathway mapping based on information in the Kyoto Encyclopedia of Genes and Genomes database showed that 15,461 transcripts were associated with 223 pathways. A total of 14,981 putative SSRs, 72,370 SNPs, and candidate genes involved in growth, reproduction, and the immune response were identified. Our findings represent the most comprehensive transcriptomic resources currently available for Huanghai No. 1, and provide an important foundation for further genomic studies of F. chinensis.
Although aquaculture as a biological production system has a long history, systematic and efficient breeding programs to improve economically important traits in the farmed species have rarely been utilized until recently, except for salmonid species. This means that the majority of aquaculture production (more than 90 %) is based on genetically unimproved stocks. In farm animals the situation is vastly different: practically no terrestrial farm production is based on genetically unimproved and undomesticated populations. This difference between aquaculture and livestock production is in spite of the fact that the basic elements of breeding theory are the same for fish and shellfish as for farm animals. One possible reason for the difference is the complexity of reproductive biology in aquatic species, and special consideration needs to be taken in the design of breeding plans for these species. Since 1971 AKVAFORSK, has continuously carried out large scale breeding research projects with salmonid species, and during the latest 15 years also with a number of fresh water and marine species. Results from this work and the results from other institutions around the world have brought forward considerable knowledge, which make the development of efficient breeding programs feasible. The genetic improvement obtained in selection programs for fish and shellfish is remarkable and much higher than what has been achieved in terrestrial farm animals.
Genetic parameters and predicted and realized selection responses were estimated for harvest body weight of Chinese shrimp (Fenneropenaeus chinensis) after five generations of multi-trait selection. The body weights of 15,201 tagged shrimp representing 460 full-sib families in 6 generations were recorded at harvest. Heritability estimates for body weight showed large variation in magnitude (0.00 ± 0.00-0.36 ± 0.07) when analyzing data from each generation separately. When data from all generations (G0-G5) were included in analysis, the heritability estimate for body weight was 0.18. While, G0 was more affected by environmental conditions than the other generation in this study, when data from G0 was excluded, the heritability was 0.21. The common environment effect estimate was 0.08 when all data included and 0.06 when G1-G5 included. The females were significantly larger than the males at harvest (P < 0.05). The genetic correlation of the harvest body weight between sexes was similar within and across generations, indicating that body weight in male and female shrimp is likely controlled by the same genes. Breeding candidates in the base population (G0) were selected according to their individual breeding values for growth. In later generations (G1-G5), candidates were selected according to a selection index including breeding values for growth, survival time after WSSV infection and pond survival. The response to selection for harvest body weight was estimated by two methods (the realized and predicted responses). The realized response was estimated from the differences in the least square means of body weight between the selection and control populations. The predicted response was obtained from the differences in the mean breeding values between generations. The accumulated realized response was 18.60% after performing five selections. The accumulated predicted responses estimated using two sets of genetic parameters obtained from within and across generation datasets were 6.43% and 6.50%, respectively. The results are discussed in a practical context of developing selective breeding programs for Chinese shrimp, and it is indicated that the selective breeding program has generated effective genetic improvement after five generations of selection. The future direction of the genetic improvement program is discussed.
Statement of relevance
Chinese shrimp, Fenneropenaeus chinensis, is one of the most valuable mariculture species in China. The Yellow Sea Fisheries Research Institute (Qingdao, China) initiated a multi-trait selective breeding program for Chinese shrimp in 2004, based on a combined family and within (inter) family selection scheme to improve growth, survival time after WSSV infection and pond survival. A new selected breed named “Huanghai No. 2” (registration no. GS01-002-2008) was approved in 2008. This program provided significant economic and social benefits. However, only limited results regarding this program have been reported, which involved genetic parameters of harvest body weight and genetic correlations among different traits using only one year data, a smaller subset of the current study.
Growth is one of the most desirable economic traits in aquaculture. Good growth is important for efficient production and contributes to more profitable and sustainable development. Currently, the selective breeding program for F. chinensis is ongoing and the breeding nucleus was divided into different lines after performing five selections. In this paper, we will focus on the results related to genetic evaluation for the harvest body weights from G0 to G5. We will present more reliable estimates of phenotypic and genetic parameters, calculate the response to selection after performing five selections and discuss the longer term implications of the findings from a genetic improvement viewpoint.
The growth of worldwide aquaculture has been sustained and rapid, and the explosion of research in genetic biotechnology has made significant impact on aquaculture and fisheries, although potential for much greater progress exists. Aquaculture and Fisheries Biotechnology: Genetic Approaches covers topics essential to the study of fish genetics, including qualitative and quantitative traits, crossbreeding, inbreeding, genetic drift, hybridization, selection programs, polyploidy, genomics and cloning. This fully updated second edition also addresses environmental risk, food safety and government regulation of transgenic aquatic organisms, commercial applications of fish biotechnology and future issues in fish genetics.
The aim of this study was to estimate heterosis and heritability for harvest body weight of the Pacific white shrimp (Litopenaeus vannamei) measured at commercial farm conditions. Heterosis and heritability were estimated using a base population from diallel crosses of eight introduced strains. The base population included 9936 shrimp from 207 families that were produced with 188 sires and 172 dams using a nested mating design by artificial insemination. Heterosis was calculated basing on the least squares means (LSM) of harvest body weight. The results showed that most of the hybrids (75%) have positive heterosis for harvest body weight, which ranged from −13.36% (UA2 × UA5) to 13.80% (UA6 × UA5) with a mean of 2.41%. The high amount of heterosis manifested in the hybrids indicated the usefulness of these hybrids for improving the growth. Variance components and heritability for harvest body weight were estimated using an animal model. The heritability estimate for harvest body weight was 0.092 ± 0.082 (h2) when genetic groups were excluded from the pedigree, but it was decreased when genetic groups were included in the pedigree ( = 0.066 ± 0.050), implying that there are strain additive genetic effect and heterosis in the base population. However, the heritability estimates for harvest body weight were significantly different from zero (P < 0.05) and there was no significant difference between h2 and (P > 0.05). The results from this study indicated that significant improvement for growth is possible through cross-breeding and selective breeding in L. vannamei.
An estimated 2.67 million metric tonnes of farmed shrimp were produced in 2005 with an estimated value greater than US$10.6 billion. Despite the economic importance of farmed shrimp, the global shrimp farming industry has been slow to adopt approaches to genetic improvement which are prevalent in more mature meat-producing industries. In the early 1990s, a number of research and commercial shrimp breeding programs emerged, and these programs generated basic information about the quantitative genetics of shrimp. Researchers quantified heritability estimates for commercially important traits, and generated information about phenotypic and genetic variation, phenotypic and genetic correlations, and genotype × environment interactions. Importantly, these programs provided evidence that selective breeding of shrimp can be effective in improving traits of commercial importance, such as growth and disease resistance. Currently, there are shrimp breeding programs in the Americas, Asia, Australia, New Caledonia, Madagascar, and the Middle East.
Generating breeding programmes that effectively improve farmed fish performance across multiple environments and make fish more uniform within production environments would aid farmers to produce food under diverse environments. We review genotype-by-environment interaction leading to re-ranking of genotypes across environments, that is non-unity genetic correlation between traits measured in different environments, and micro-environmental sensitivity leading to a change in environmental variance of a trait. A quantitative review across 38 species showed that (i) genotype-by-environment interaction studies are lacking for many economically important traits. (ii) Re-ranking is moderate for growth (average genetic correlation = 0.72) and survival (average genetic correlation = 0.54). Significant re-ranking is of concern because selection in a nucleus leads to lower genetic responses in commercial environments compared to a case when re-ranking does not exist. (iii) Re-ranking is weak for age-at-sexual-maturity and fish appearance (average genetic correlation = 0.86), implying that genetic improvement in one environment is expected to be effective in the other environments. Future research should provide guidelines for how to account for genotype-by-environment interaction when collecting data, estimating breeding values and optimising the structure of the breeding programme. (iv) Coefficient of genetic variation for sensitivity against unknown micro-environmental factors within a single environment for body weight is high. Hence, genetic improvement towards less sensitive fish, resulting in more uniform production, is possible, but a large number of relatives with phenotypes is needed for obtaining moderate accuracy of selection. This review elucidates needs for further research on genotype-by-environment interaction and micro-environmental sensitivity in economically important traits and species.
Genetic parameters and response to selection were estimated for the harvest body weight of Litopenaeus vannamei. The data consisted of 24 072 progeny from 178 sires and 171 dams in two generations (G0 and G1) with a nested mating structure. All families were randomly divided into two groups and then cultured in two farms at different locations (Huanghua and Qingdao). The heritability estimates from G0 and G1 were 0.278 ± 0.136 and 0.423 ± 0.065 respectively. Over two generations, the heritability estimate was 0.335 ± 0.087, and the common environmental effect was 0.084 ± 0.031. A bivariate animal model was used to estimate variance and covariance components, whereby the body weight in the two farms was treated as a genetically distinct trait. Genetic correlation was close to unity (0.943 ± 0.066), indicating that a genotype by environmental interaction for harvest body weight was small. The response to selection in harvest body weight was estimated using two methods (the realized and predicted responses). The realized response was estimated from the difference in the least squares means of body weight for the selection and control populations. The predicted response was obtained from the difference in the mean estimated breeding values between generations. The realized response was 2.30%, while the predicted responses were 2.00% and 1.37% for within- and across-generation datasets using two sets of genetic parameters respectively. The results would provide crucial information in pacific white shrimp breeding programs in China.
From 1995 to 1998, the Oceanic Institute operated a breeding program for Pacific white shrimp, Litopenaeusvannamei, based on a selection index weighted equally for growth and resistance to Taura Syndrome Virus (TSV). In 1998, two separate breeding lines were established. One line was selected 100% for growth (Growth line) and a second line was selected on an index weighted 70% for TSV resistance and 30% for growth (TSV line). After one generation of selection, select shrimp from the Growth line were 21% larger than unselected control shrimp (24.2 vs. 20.0 g). The half-sib heritability (h2) estimate for growth was 0.84±0.43(s.e.) and realized h2 was 1.0±0.12. Females were 12.7% larger than males. Shrimp tails accounted for 65.1% of total body weight and males had a significantly higher percent tail than females (65.7% vs. 64.5%; P<0.001). Half-sib h2 for percent tail was 0.15±0.12. In the TSV line, there was an 18.4% increase in survival to TSV between select and control shrimp after one generation of selection (46.4% vs. 39.2%). Realized h2 for TSV resistance was 0.28±0.14 and h2 on the underlying scale was 0.30±0.13. However, select shrimp in the TSV line were 4.6% smaller than control shrimp (22.6 vs. 23.7 g) and there was a negative genetic correlation between mean family growth and mean family survival to TSV [−0.46±0.18(s.e.)]. Percent females per family ranged from 39.7% to 69.2% and averaged 51% female, but h2 for sex ratio was zero, indicating that it is not feasible to select for a higher percentage of females. Significant improvements in growth and TSV resistance can be made in L.vannamei through selective breeding; however, the negative genetic correlation between growth and TSV resistance must be considered when developing breeding plans.
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.
Penaeus (Litopenaeus) vannamei Boone, 1931 and Penaeus monodon Fabricius, 1798 provide 87% of the world’s farmed marine shrimp, and 99% with another five species, Penaeus (Fenneropenaeus) chinensis (Osbeck, 1765), Penaeus (Fenneropenaeus) indicus Milne-Edwards, 1837, Penaeus (Fenneropenaeus) merguiensis de Man, 1888, Penaeus (Litopenaeus) stylirostris Stimpson, 1874 and Penaeus (Marsupenaeus) japonicus Bate, 1888. Genetically improved strains have been traded for P. chinensis, P. stylirostris, P. vannamei and P. monodon, although closed populations have been developed for all seven species. To date, domesticated strains have played a dominant role in seed production for only P. vannamei and P. stylirostris. Extensive worldwide transfer of wild and/or domesticated stocks has occurred for these two species and for P. monodon, but the volume and extent of transfer of the other species is less. Genetic variation documented in wild stocks does not appear to be threatened, but variation within cultured stocks is often reduced relative to the wild and has affected performance in some (now mostly defunct) cultured populations. Hybridization is not effective in producing useful shrimp strains. There is no organized banking of penaeid shrimp genetic resources, either as live shrimp, frozen tissue, tissue or cell culture or DNA. Open access DNA sequences are available, although limited for most species. Significant expressed sequence tags and large insert libraries are available only for P. vannamei and P. monodon.
Penaeus monodon were reared in captivity in tanks over three generations with full pedigree information. Weights of animals were measured at six ages between 7 and 54 weeks along with survival in each period. Females were more variable in weight than males after week 16, and variances between each sex were standardised prior to estimation of heritability and genetic correlations. The phenotypic mean (standard deviation) of weights at week 40 were 35 (6) g for males and 44 (10) g for females. Heritability with standard errors at 16, 30, 40 and 54 weeks were 0.56 ± 0.04, 0.55 ± 0.07, 0.45 ± 0.11 and 0.53 ± 0.14 respectively. Heritability for family survival, determined from mean survival within each family, was 0.51 + 0.18, 0.36 ± 0.18 and 0.71 ± 0.17 over periods 4 to 10, 10 to 16 and 16 to 32 weeks respectively. The genetic correlations between weight and survival revealed no significant trend. The results from this study indicate significant concurrent improvements in both growth and survival are possible through selective breeding.
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