Comparison of growth and pearl production in males and females of the freshwater mussel, Hyriopsis cumingii, in China

Growth and pearl production were compared for males and females in the freshwater mussel, Hyriopis cumingii, from a full-sib family. The results indicated that there was no significant difference (p > 0.05) on individual weight between male and female mussels of 1- or 2-year-old, while significant difference (p < 0.01) lay among 3- or 4-year-old mussels with male greater than female. The average shell width of the male mussels was less than that of the female individual (p < 0.05). 1- and 2-year-old males and females did not differ significantly with respect to the total weights, grain weights, or grain sizes of the pearls they produced, but these three parameters were all significantly greater in 3- and 4-year-old males (p < 0.05). The round pearl percent were similar between male and females at ages 1, 2, 3 and 4 years. Male and female mussels were separately and mixed cultured in enclosures, respectively. The rates of growth in shell width and body weight of females separated from males were 3.42 and 4.16 %, respectively, higher than in females mixed with males (p < 0.05). The total pearl weight per mussel, the average weight per pearl, and the average pearl size of females separated from males were 6.61, 7.10, and 3.59 %, respectively, greater than in females mixed with males (p < 0.05). There was no significant difference in the growth rate or pearl yield of males cultured with or without females (p > 0.05). Under traditional culture methods, male mussels have a better pearl performance, and artificial separation of females from males can improve the growth and pearl production of female mussels.