STUDY ON THE EFFECTS OF SEX RATIO AND SALINITY ON FERTILIZATION RATE AND LARVAL DEVELOPMENT OF THE RAGWORM (Tylorrhynchus heterochaetus)

Abstract

Ragworm (Tylorrhynchus heterochaetus Quatrefages, 1865) is a nutrient-rich aquatic species with high economic value and a favorable consumer market, it is also listed among aquatic species permitted for commercial use in Vietnam. This study consisted of two independent experiments to evaluate the effects of sex ratio and salinity on fertilization rate and larval development of ragworm. The first experiment examined the effect of sex ratio with four treatments: 1 male/2 females, 1 male/3 females, 1 male/4 females, and 1 male/5 females. The second experiment assessed the effect of salinity at four levels: 5, 10, 15, and 20‰. The experiments were conducted at the aquatic seed production facility of Kim Son Aquaculture Service Cooperative, Kim Dong Commune, Ninh Binh Province (from March 2025 to April 2025). Each treatment was replicated three times. The results showed that both sex ratio and salinity significantly affected fertilization rate and larval development of ragworm. In particular, a salinity of 10‰ combined with a sex ratio of 1 male/5 females or 1 male/4 females yielded the optimal results in terms of fertilization rate and larval development rate, with statistically significant differences (p < 0.05). These findings provide important information and contribute to improving the artificial seed production process for ragworm.