We quantified patterns of circannual reproductive breeding periodicity in a multi-species assemblage of the gymnotiform knifefish genus Brachyhypopomus from Amazonian floodplain and terra firme stream habitats. We applied linear mixed-effect models and model selection to a dataset of 3205 fish from the five most abundant species to identify environmental variables predictive of gonadosomatic index (GSI) – including rainfall, river level, water temperature, conductivity, dissolved oxygen (DO), and pH. A single common floodplain species exhibited a well-demarcated ca. 6-month breeding season corresponding to the rising-water and high-water period. In this species the strongest predictors of GSI in both sexes were river level and pH. Conductivity, temperature, and DO all exhibited substantial circannual variation in the floodplain but were uncorrelated to GSI. Four common terra firme stream-dwelling species exhibited longer (ca. 7–9-month) and less distinct breeding seasons that were approximately coincident with the late dry/early rainy season. The stream species exhibited a congruent species-wide response in which GSI was predicted in both sexes by rainfall, but not by physico-chemical water properties (all of which exhibited relatively minor circannual variation). Five of the most abundant species in this study have a semelparous one-year life history, but one ( B. beebei ) has an iteroparous two-year life history. Consistent with a pattern of terminal reproductive investment, we observed a more pronounced elevation of GSI (especially in females) in B. beebei ’s final second breeding season than in its first.

中文翻译：

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亚马逊电鱼多物种组合中循环繁殖周期的环境相关性

我们量化了来自亚马逊河泛滥平原和陆地河流栖息地的裸刀鱼属 Brachyhypopomus 的多物种组合中的年度生殖繁殖周期模式。我们将线性混合效应模型和模型选择应用于来自五个最丰富物种的 3205 条鱼的数据集，以确定预测性腺体指数 (GSI) 的环境变量——包括降雨量、河流水位、水温、电导率、溶解氧 (DO) , 和 pH 值。一个常见的洪泛区物种表现出明确的约。6个月的繁殖季节对应涨水期和高水期。在这个物种中，两性中 GSI 的最强预测因子是河流水位和 pH 值。电导率、温度、DO 和 DO 都在洪泛区表现出显着的年度变化，但与 GSI 无关。四种常见的陆地河流栖息物种表现出更长（约 7-9 个月）和不太明显的繁殖季节，几乎与晚旱/早雨季节重合。河流物种表现出一致的物种范围响应，其中 GSI 是通过降雨预测两性的，但不是通过物理化学水特性（所有这些都表现出相对较小的年度变化）。本研究中最丰富的物种中有五个具有半产一年的生活史，但一种（ B. beebei ）具有隔胎两年的生活史。与终端生殖投资模式一致，我们观察到 B 中 GSI（尤其是女性）的升高更为明显。