Reproductive data of Electrona risso, Melamphaes polylepis and Scopelogadus mizolepis from the Eastern Central Atlantic in March and April 2015

Knowledge on life history traits of mesopelagic fishes is still sparse. This dataset contains reproductive data of the myctophid Electrona risso (Cocco, 1829) and the melamphaids Melamphaes polylepis Ebeling, 1962 and Scopelogadus mizolepis (Günther, 1878). The specimens were collected in March and April 2015 during cruise 383 of the fishery research vessel \"FFS Walther Herwig III\" in the Eastern Central Atlantic. A pelagic midwater trawl (\"Aalnet\", Engel Netze, Bremerhaven Germany) with multiple opening-closing device with three net bags of 20 mm mesh size and 1.8 mm mesh size in the cod-end container was used for catching fish at three depth strata per station between 50 and 700 m depth. Fish was stored in phosphate buffered 4% formalin solution and later on land in laboratories, specimens were measured, weighed, and dissected to examine gonads and oocytes under a stereo microscope. Reproductive phases were assigned based on macroscopic inspection following the standardised terminology for reproductive development in fish by Brown-Peterson et al. (2011, doi:10.1080/19425120.2011.555724). Histological cross sections of selected individuals were used for validation. The Gonadosomatic Index was calculated as GSI = 100 x gonad mass / (total mass – gonad mass). Batch fecundities were determined with the gravimetric method, counting the most advanced eggs in weighed subsamples.中层鱼类（mesopelagic fishes）的生活史相关研究资料仍较为匮乏。本数据集涵盖灯笼鱼科（Myctophidae）安氏电灯鱼（Electrona risso, Cocco, 1829），以及后肛鱼科（Melamphaidae）的多鳞后肛鱼（Melamphaes polylepis, Ebeling, 1962）和尖吻犀孔鲷（Scopelogadus mizolepis, Günther, 1878）的繁殖相关数据。样本采集于2015年3月至4月，搭载渔业研究船"FFS Walther Herwig III"执行383号航次，在东中大西洋海域完成。本次采样使用中层拖网（"Aalnet", 德国不来梅港Engel Netze出品），该拖网配备多网口启闭装置，网囊容器内设有3个网袋，网目尺寸分别为20 mm与1.8 mm，于每个站位的50~700 m水深范围内的3个深度层开展鱼类捕捞作业。采集的鱼类样本经磷酸盐缓冲的4%甲醛溶液固定，随后运回陆地实验室。实验人员对样本进行体长、体重测量，并通过解剖操作在体视显微镜下观察性腺与卵母细胞结构。繁殖分期的划分基于宏观形态观察，参考了Brown-Peterson等学者（2011, doi:10.1080/19425120.2011.555724）提出的鱼类繁殖发育标准化术语体系。选取部分个体的组织学切片对分期结果进行验证。性腺成熟指数（Gonadosomatic Index, GSI）的计算公式为：GSI = 100 × 性腺重量 /（总重量 - 性腺重量）。分批繁殖力采用重量法测定：通过称量子样本并计数其中发育最成熟的卵子完成统计。