The seasonal dynamics of the northern largemouth bass (Micropterus salmoides salmoides) reproductive cycle was investigated in a Midwestern United States population. Mature largemouth bass (n = five males and five females) were collected each month over a one‐year period. Environmental cues (water temperature and photoperiod) were recorded in situ using data loggers. Temporal changes in plasma sex steroid hormones (testosterone [T], 11‐ketotestosterone [11‐KT], and estradiol‐17β [E₂]) and vitellogenin (Vtg), gamete development (histology), and organosomatic indices were highly associated with temporal water temperature and photoperiod dynamics. Female plasma concentrations of T and E₂ and organosomatic indices exhibited similar temporal patterns, with peaks occurring in early summer. Gamete development in females was associated with increases in gonadosomatic index (GSI) and Vtg. In males, plasma concentrations of T and organosomatic indices exhibited bimodal peaks; high peaks occurred in the spring for T and GSI and in the fall for viscerosomatic and hepatosomatic indices. Male gamete development and GSI closely tracked temporal patterns in plasma T, with GSI lagging behind the T cycle by approximately one sampling period. Plasma concentrations of 11‐KT were elevated in late winter and spring and were considerably higher than T throughout the reproductive cycle. Unlike the Florida largemouth bass (M. salmoides floridanus) advanced gamete development was observed in both sexes before winter, which may reduce the immediate energy required for gamete development in the spring. Results from this study also provide baseline information necessary for off‐season spawning procedures and endocrine‐disruption studies in northern largemouth bass.

中文翻译：

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北方大嘴鲈鱼的繁殖周期salmoides salmoides。

在美国中西部人口中调查了北部大嘴鲈（Micropterus salmoides salmoides）繁殖周期的季节性动态。 在一年的时间内，每个月都会收集成熟的大嘴鲈鱼（n =五男五女）。使用数据记录器就地记录环境提示（水温和光周期）。血浆性类固醇激素（睾丸激素[T]，11-酮睾丸激素[11-KT]和雌二醇17β[E ₂ ]）和卵黄蛋白原（Vtg），配子发育（组织学）和有机体指数的时间变化与时间水温和光周期动力学。女性血浆中T和E _2的浓度有机体指数表现出相似的时间模式，峰值出现在初夏。女性的配子发育与性腺体指数（GSI）和Vtg升高有关。在男性中，血浆血浆T和有机体指数显示出双峰。T和GSI在春季出现高峰，而内脏和肝体指数在秋季下降。雄配子发育和GSI密切跟踪血浆T的时间模式，GSI落后于T周期约一个采样周期。在冬季和春季后期，血浆11-KT的浓度升高，并且在整个生殖周期中均显着高于T。不像佛罗里达大嘴鲈（M. salmoides floridanus）在冬季之前，男女双方都观察到高级配子发育，这可能会减少春季配子发育所需的即时能量。这项研究的结果还提供了北部大嘴鲈在淡季产卵程序和内分泌干扰研究所必需的基线信息。