phosphorylase plays a key role in the metabolism of glycogen, a molecule critical for the growth and development of oysters. We evaluated the effect of polymorphisms in the glycogen phosphorylase) on growth and glycogen content. We tested the association between single nucleotide polymorphisms (SNPs) in coding regions of the gene and growth performance (shell height, shell length, shell depth, total weight and soft-tissue weight) and glycogen content using 322 oysters from five full-sib families. We identified 82 SNPs in the 1 940 bp gene, including 63 SNPs in the exon region, one SNP locus located in the 5′-UTR, and 18 SNPs in the 3′-UTR. The average density of SNPs in the coding region was one per 25 bp. Five SNPs were significantly associated with growth performance (<0.05), but there was no association between the SNPs and glycogen content. Furthermore, among the six SNP haplotypes constructed using the five SNPs above, the total weight of the individuals with haplotype H6 ( was significantly higher than those with the other five haplotypes(, suggesting this haplotype may be the most advantageous in terms of weight gain in . Our results provide basic information for future genetic improvement of growth performance in