<p>Triploid Pacific oysters (<i>Crassostrea gigas</i>) are highly valued due to their rapid growth and low fertility, making them commercially desirable. However, these reproductive characteristics also hinder their capability to produce subsequent generations. Large-scale triploid production relies on crossing female diploid and male tetraploid oysters. This study assessed the effects of shell morphology on body weight and fecundity in diploid and tetraploid oysters using multiple regression and path analysis. Substantial correlations were found between shell morphology and body weight traits, as well as between shell morphology and fecundity traits across diploid and tetraploid oysters. Path analysis revealed that shell morphology traits significantly impact body weight and fecundity in both diploids and tetraploids. Among these traits, shell height had the strongest direct effect on body weight and fecundity, while shell height and shell length notably contributed through indirect effects. These findings highlight the importance of shell height in shaping body weight and fecundity in diploid and tetraploid Pacific oysters, indicating that selective breeding, with a particular focus on enhancing shell height, could simultaneously promote increases in shell length.</p>