Abstract:Female specimens of the dwarf form of Sthenoteuthis oualaniensis, the purple flying squid, were collected from light-falling fishery catches from the South China Sea in 2017. The fecundity of this species was investigated and characterized. The results showed that the potential fecundity of female individuals ranged from 1218 to 32843 oocytes. The number of ovarian oocytes ranged from 1178 to 30397 cells, and the number of ripe eggs in the oviducts ranged from 113 to 2904 cells. In addition, the relative fecundity ranged from 48.93 to 842.12 cell/g of a female’s total weight, and the overall potential reproductive investment index varied from 0.005 to 0.213. The potential fecundity showed a significant power regression relationship to mantle length and linear relation to body weight. Relative fecundity showed a significant exponential relation to mantle length and linear correlation with body weight. Potential individual reproductive investment index increased linearly with increasing mantle length as well as body weight. Batch fecundity had an estimated range from 1895 to 2904 cells based on the number of ripe oocytes in the oviducts of late-maturing individuals (stage Ⅵ), and the number of spawn per batch was estimated to range from 6 to 15 with an average of 9.87±4.36. Major axis length of ovarian oocytes was measured and ranged from 0.17 to 0.99 mm with an average of (0.51±0.14) mm. There were significant differences in major axis length of ovarian oocytes among different maturity stages (P<0.05). The frequency of major axis length of oocytes in the ovary showed a unimodal distribution for specimens at stages Ⅲ to Ⅵ. Moreover, the frequency distribution peak showed a forward increase with maturation when the mode was between 0.35 and 0.60 mm for stages Ⅲ and Ⅳ, while it showed a forward increase when the mode was between 0.40 and 0.75 mm for stages Ⅴ and Ⅵ. The major axis length of ripe eggs in the oviducts ranged from 0.50 to 1.08 mm. Cumulatively, these findings indicate that fecundity of the dwarf form of female S. oualaniensis tends to increase as body size increases and as maturation progresses. Furthermore, the ovarian oocytes develop in a pattern of group-synchrony, and ovulation occurs multiple times.
