International Journal of Aquaculture, 2025, Vol.15, No.6, 298-307 http://www.aquapublisher.com/index.php/ija 304 and hatching rates; malnutrition will lead to a decrease in egg quality and affect reproductive efficiency. Water quality and nutrition often influence each other: good water quality allows broodstock to feed and metabolize smoothly, and nutrients can be fully utilized; while adequate nutrition enhances the stress resistance of broodstock and improves their reproductive adaptability under sub-ideal water quality conditions (Li et al., 2021). Therefore, in breeding management, it is necessary to simultaneously improve the water environment and strengthen the nutrition of broodstock. The coordinated optimization of the two can maximize the reproductive efficiency of yellow catfish. 7 Genetic Improvement and Prospects for Molecular Breeding 7.1 Genetic analysis and marker development of reproductive traits Genetic analysis and molecular marker development of reproductive traits of yellow catfish are the basis for To improve the genetic properties of the yellow catfish, one must first understand its reproductive characteristics. Researchers usually conduct reproductive experiments first to collect some specific data, such as the number of eggs laid, hatching rate, age of sexual maturity, etc. (Huang et al., 2022; Kim et al., 2024). These data may seem disorganized, but through family analysis and quantitative genetics methods, it is possible to calculate which traits are genetically controlled and how much they change. On this basis, they will further use molecular biological methods to look for genetic markers associated with these traits. For instance, screen microsatellite or SNP loci from the genome of yellow catfish to see which ones are associated with reproductive rate or early maturity. Then, construct a genetic linkage map and conduct QTL mapping to identify the key gene regions that control these traits. Once these markers are proven reliable, breeders can directly use them to screen juvenile fish. By simply testing the markers, they can roughly determine their reproductive potential and keep those individuals carrying superior genes as parents. In this way, the entire breeding process becomes faster and more accurate. 7.2 Molecular breeding and gene editing strategies Nowadays, yellow catfish breeding is increasingly advanced by molecular breeding and gene editing. Methods such as marker-assisted selection (MAS) or genome-wide selection have enabled breeders to identify potential fish in advance through DNA testing when they are still young. Compared with the traditional method that only relied on body shape and output in the past, this approach is more accurate in selection and can also significantly shorten the generation gap. Meanwhile, gene editing technologies (such as CRISPR/Cas9) are opening up new possibilities. Researchers envision that it is possible to make targeted modifications to key genes that affect growth and reproduction, such as knocking out genes that inhibit growth, to make individuals grow faster. Or adjust the genes related to gonadal development to make yellow catfish mature earlier (Huang et al., 2022). These ideas sound very attractive. After all, who wouldn't want to cultivate new strains that grow fast and are resistant to diseases. However, it should be noted that gene editing in aquaculture has not yet reached a mature stage. Safety and ethical issues remain unavoidable topics that require time and careful research to verify. 7.3 Case study: genomic selection for early-maturing yellow catfish strains An aquaculture breeding team successfully used genomic selection technology to breed a new strain of early-maturing yellow catfish. First, they screened out some precocious individuals from numerous broodstock families that would become sexually mature and spawn that year, and recorded the reproductive trait data of each broodstock in detail. Subsequently, genomic DNA sampling and high-density molecular marker detection were performed on these broodstock and their offspring to construct a genomic selection prediction model for yellow catfish (Figure 2) (Gong et al., 2018; Huang et al., 2022). By calculating the genomic breeding values carried by each juvenile fish (for traits such as age at sexual maturity), the researchers selected the fish with the highest predicted values as the next generation's parents. After several generations of genome-assisted breeding, the team finally obtained an early-maturing yellow catfish strain with stable genetics. This strain of yellow catfish can reach sexual maturity one breeding season earlier than the ordinary strain, shortening the seed production cycle and greatly improving reproductive efficiency. This case shows that genomic selection has significant results in improving the reproductive traits of yellow catfish, and provides an effective way to breed strains with special traits (Dong et al., 2011).
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