Abstract:To explore the effects of dissolved oxygen on the reproductive characteristics and embryo quality of female Chinese mitten crab (Eriocheir sinensis), the reproductive and oviposition experiment of broodstock under different dissolved oxygen levels (5 mg/L, 6.5 mg/L, 8 mg/L, 9.5 mg/L, 11 mg/L, 12.5 mg/L) was carried out. The reproductive characteristics of female crabs, including mating rate, spawning rate, egg production, and fecundity, as well as the egg diameter, biochemical composition, and fatty acid composition of the produced embryos under each dissolved oxygen level were analyzed. The results showed that with the increase of dissolved oxygen, the mating rate of broodstock gradually increased, and the spawning rate, egg production, fecundity, and reproductive index showed a trend of first increasing and then decreasing. When the dissolved oxygen was 11 mg/L, the above four indicators were the highest and had significant differences from other groups (P＜0.05). When the dissolved oxygen was 9.5 mg/L, the embryo diameter was the largest, with an average of (418.81±5.72) μm, which was significantly higher than other groups. When the dissolved oxygen was 11 mg/L, the wet weight of a single embryo was the heaviest, with an average of (48.70±5.08) μg, but there was no significant difference from the 9.5 mg/L group (P＞0.05). With the increase of dissolved oxygen, the phospholipids in the embryos gradually increased, while the total fat gradually decreased, and the changes in ash and moisture were not obvious. The crude protein, total cholesterol, and triglycerides showed a trend of first increasing and then decreasing, and they were the highest when the dissolved oxygen was 9.5 mg/L. A total of 21 fatty acids were detected in the embryos of Chinese mitten crab. Among them, the total amounts of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), C20:5n3 (EPA), and C22:6n3 (DHA) were the highest when the dissolved oxygen was 5 mg/L, with average contents of (1.9734±0.3037)%, (3.2140±0.7934)%, (2.8823±1.0818)%, (0.5429±0.0789)%, and (0.9299±0.2878)%, respectively. The study indicates that dissolved oxygen has a certain impact on the reproductive characteristics and embryo quality of Chinese mitten crab. When the dissolved oxygen is 11 mg/L, the reproductive characteristics of Chinese mitten crab is the best, and when the dissolved oxygen is 9.5 mg/L, the embryo quality is relatively better. The research results can not only enrich the knowledge of breeding biology of Chinese mitten crab, but also provide scientific support for the conservation of fishery resources of Chinese mitten crab in the Yangtze River Estuary.
