## 2 Selective Breeding Strategies for Large Yellow Croaker Seedlings
### Growth Performance Selection  
The selective breeding of large yellow croaker (_Larinichthys crocea_) for growth performance primarily employs a combined strategy of individual selection and family-based selection. By establishing systematic family populations, key growth traits such as body weight, body length, and daily weight gain are quantitatively evaluated to identify and retain superior individuals with outstanding growth potential [16]. Particularly, using wild-caught populations as the base for breeding helps maintain genetic diversity while promoting the continuous accumulation and genetic improvement of favorable growth traits [17]. Several studies have systematically estimated the heritability of growth-related traits in the large yellow croaker, with findings indicating moderate to high heritability for these traits. This provides a solid theoretical and practical foundation for subsequent genetic improvement efforts [18]. In recent years, the rapid development of molecular biotechnology has led to the increasingly widespread application of molecular breeding techniques in the selection for growth performance, serving as a valuable supplement to traditional phenotypic selection. Genome editing (GE) technologies have also shown early promise in the large yellow croaker. Researchers have successfully induced targeted gene mutations by microinjecting Cas9 messenger RNA (mRNA) and its corresponding single-guide RNA (sgRNA) from the CRISPR/Cas9 system, demonstrating potential advantages in accelerating individual growth and enhancing disease resistance [19]. In practical breeding, \"Donghai No. 1,\" a representative strain derived from wild populations in the Daikuyang sea area, was developed through more than a decade of systematic selection. Experimental results confirm that under identical farming conditions, this strain exhibits significantly better growth performance compared to standard commercial seedlings [20]. In the field of marker-assisted selection (MAS), ZHANG et al. [21] identified significant correlations between mutations in the coding region of the FST gene and growth traits in large yellow croaker using single-nucleotide polymorphism (SNP) screening, providing molecular evidence for developing candidate markers. SUI [22] conducted genetic evaluations of growth traits using microsatellite markers. Although the estimated heritability was relatively low (0.09-0.19), high genetic correlations among traits were observed, and key markers such as LYC0088 and LYC0143, which are closely associated with growth traits, were identified--offering theoretical support for practical breeding efforts.  
Growth performance selection is of great significance for improving aquaculture profitability and promoting large-scale production. However, growth traits are highly affected by temperature, salinity, and density. Therefore, precise environmental control is essential during selection [23]. Moreover, due to the long breeding cycles and high financial and technical investments required, improving selection efficiency and achieving multi-technology integration remain key challenges to be addressed in future research and practice.