Reproductive ecology of Otocinclus vittatus (Regan, 1904) in the Pantanal floodplain, upper Paraguay River basin

Abstract We studied the reproductive biology of Otocinclus vittatus in the southern Pantanal, Brazil. A total of 1066 fishes were analyzed (490 males, 488 females and 88 individuals of undetermined sex), sampled with a rectangular sieve and a seine net from February/2009 to January/2011. Variations in the sex ratio, seasonality in reproduction, fecundity, and size at first maturity were estimated. No variations were detected in the total sex ratio for the study period as a whole; although ratio has varied over time. The gonadosomatic index varied according to the river level, but not according to water temperature and rainfall. The mean fecundity was estimated at 84.1 oocytes, with a positive correlation with standard length. The size at first maturity (L50) estimated was 18.7 mm for females and 20.1 mm for males.

摘要：本研究于巴西南部潘塔纳尔湿地（Pantanal）开展，针对条纹吸口鲶（Otocinclus vittatus）的繁殖生物学进行系统调查。本次研究共分析1066尾鱼类样本，其中雄性490尾、雌性488尾、性别未确定个体88尾；样本采集时间为2009年2月至2011年1月，采集工具为矩形筛网与围网（seine net）。研究对性别比例变化、繁殖季节性、繁殖力以及初次性成熟体长（L50）等指标进行了估算。尽管研究周期内性别比例存在阶段性波动，但整体而言，整个研究周期的总性别比例未检测到显著变化。性腺指数（gonadosomatic index）随河流水位发生变化，但与水温及降雨量无显著关联。本次研究估算的平均繁殖力为84.1枚卵母细胞（oocytes），且繁殖力与鱼体标准体长（standard length）呈正相关。研究得到的雌性初次性成熟体长为18.7毫米，雄性为20.1毫米。