Performance of triploid Haliotis discus hannai cultured in a subtropical area using sea-based suspended systems.

Considerable research has been conducted on the induction of triploids in Haliotis discus hannai. However, very few studies have focused on the performance of triploids. In this study, we present the first report of a comprehensive comparative field study on triploids of H. discus hannai and their diploid siblings cultivated for up to 30 months on a sea-based suspended system in a subtropical environment. Two types of triploids were created using cytochalasin-B (CB) and 6-dimethylaminopurine (6-DMAP). The triploid percentages were 89.10% (CB group) and 100.00% (6-DMAP group) at the larval stage, which fell to 28.58% (CB group) and 86.91% (6-DMAP group) at 30 months post-fertilization (mpf). The survival rates in both treatments were similar to that of the control group, except for the 6-DMAP group at 9 mpf and both treated groups during the first high-temperature period (Jun-Dec), when significant decreases in survival were observed (P < 0.05). Surprisingly, there was no difference in thermal tolerance between triploids and diploids through the assessment of heat adhesion duration (P > 0.05). The growth of the triploids differed across the two ploidy levels. The triploids within the CB group did not differ from control diploids throughout the observation period (P > 0.05), whereas triploids in the 6-DMAP group showed superior growth in body weight at 20 mpf (P < 0.05). After the end of the maturation season (30 mpf), a significant increase (19.57%) in foot muscle weight was found in the 6-DMAP group triploids, and a significant increase (7.22%) in the foot muscle-soft tissue index (FMSI) was found in the CB group triploids in comparison to diploid individuals (P < 0.05). The advantage of meat yield may be attributed to the hypothesis of the diversion of energy from gonadal to somatic growth. Despite the normal sex ratio (1:1) of triploids, their reproductive potential was significantly reduced, showing infertility in the females with highly reduced numbers of oocytes or abnormal oogonia and sterility in the males with an absence of spermatozoa. Our study confirms a definite advantage in the meat yield of triploid H. discus hannai and provides insights for the commercial promotion of triploid strains in the abalone aquaculture industry in southern China. • The first field study on the Pacific abalone triploids cultured in subtropical area by the sea-based suspended systems. • Triploids at 20 mpf in the 6-DMAP group exhibited greater body weight than diploids; the CB group was not. • Triploids had obvious advantages in meat yield after the end of the maturation season. [ABSTRACT FROM AUTHOR]