Although species of Decapterus form important pelagic fisheries in the northern South China Sea, information on their spawning grounds is limited because identification of fish eggs based on their morphology is difficult. We identify eggs of four Decapterus species (D. macrosoma, D. maruadsi, D. macarellus, and D. tabl) with DNA barcodes from the fishery resources surveys in spring and autumn 2018 in Xisha islands, and spring and later summer–autumn 2019 along the continental shelf of the northern South China Sea, and describe egg morphology. Of 1405 fish eggs with obtained cytochrome c oxidase subunit I (COI) sequences, 81 were successfully attributed to four Decapterus species; eggs of each are spherical, have a smooth chorion and narrow perivitelline space, and can be partly differentiated by diameter, melanophore drops on the oil globule, and the notum of the embryo. Seasonal distributions of eggs reveal spawning grounds, with that of D. maruadsi located mainly off the Pearl River estuary in spring; eggs of D. maruadsi rarely co-occur with those of D. macrosoma. Spawning grounds of D. macrosoma are probably further south, where water temperature and salinity are higher. Spawning periods of these four Decapterus species overlap slightly. Spawning habitat of D. maruadsi has been lost, and the spawning season of D. macrosoma has extended. Identification of Decapterus eggs using DNA barcodes can assist with the identification of eggs using traditional morphological approaches. Spatial and temporal information on the distributions of Decapterus eggs can be used for improved conservation of spawning grounds and fisheries management in the northern South China Sea.

中文翻译：

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南海北部四种鲇鱼卵的分子形态学鉴定及季节分布：保护产卵场的关键

尽管鲎属物种在南海北部形成了重要的远洋渔业，但由于很难根据形态识别鱼卵，因此关于它们产卵场的信息是有限的。我们从 2018 年春秋西沙群岛渔业资源调查和 2019 年春末夏秋渔业资源调查中，利用 DNA 条形码识别了四种十鳍鱼（D. macrosoma、D. maruadsi、D. macarellus 和 D. tabl）的卵沿南海北部大陆架，并描述鸡蛋形态。在获得细胞色素 c 氧化酶亚基 I (COI) 序列的 1405 个鱼卵中，有 81 个成功归属于四种十角鱼属；每个卵都是球形的，具有光滑的绒毛膜和狭窄的卵周间隙，可以通过直径部分区分，油球上有黑色素细胞滴，和胚胎的notum。卵的季节性分布揭示了产卵地，D. maruadsi 春季主要分布在珠江口附近；D. maruadsi 的卵很少与 D. macrosoma 的卵同时出现。D. macrosoma 的产卵地可能更靠南，那里的水温和盐度更高。这四种 Decapterus 物种的产卵期略有重叠。D. maruadsi 产卵栖息地已丧失，D. macrosoma 产卵期延长。使用 DNA 条码识别十角菜蛋可以帮助使用传统形态学方法识别蛋。有关鲎卵分布的时空信息可用于改善南海北部产卵场的保护和渔业管理。卵的季节性分布揭示了产卵地，D. maruadsi 春季主要分布在珠江口附近；D. maruadsi 的卵很少与 D. macrosoma 的卵同时出现。D. macrosoma 的产卵地可能更靠南，那里的水温和盐度更高。这四种 Decapterus 物种的产卵期略有重叠。D. maruadsi 产卵栖息地已丧失，D. macrosoma 产卵期延长。使用 DNA 条码识别十角菜蛋可以帮助使用传统形态学方法识别蛋。有关鲎卵分布的时空信息可用于改善南海北部产卵场的保护和渔业管理。卵的季节性分布揭示了产卵地，D. maruadsi 春季主要分布在珠江口附近；D. maruadsi 的卵很少与 D. macrosoma 的卵同时出现。D. macrosoma 的产卵地可能更靠南，那里的水温和盐度更高。这四种 Decapterus 物种的产卵期略有重叠。D. maruadsi 产卵栖息地已丧失，D. macrosoma 产卵期延长。使用 DNA 条码识别十角菜蛋可以帮助使用传统形态学方法识别蛋。有关鲎卵分布的时空信息可用于改善南海北部产卵场的保护和渔业管理。