The relationship between the magnitude of reproduction and adult density of pelagically spawning carp (PSC) species (bigheaded carp Hypophthalmichthys spp., Grass Carp Ctenopharyngodon idella, and Black Carp Mylopharyngodon piceus) and the influence of environmental factors on this relationship are valuable information for management and control of these highly invasive cyprinids. Six years of standardized monitoring for PSC reproduction and adult density in navigation pools of the Illinois Waterway (IWW; the Illinois River and its connection to Lake Michigan through the Des Plaines River and Chicago Area Waterway System), in conjunction with removal efforts in the upper IWW, where there is limited fish movement between pools, provided an opportunity to deepen our understanding of factors affecting the reproductive productivity of this invasive assemblage. Reproductive activity most commonly occurred in May and June, with the magnitude of reproduction in June far exceeding that occurring in other months. The highest egg counts were found within a 72-km zone containing the hydromorphological transition between the upper and lower Illinois River, with the majority of PSC larval drift occurring below this zone in the lower Illinois River. Magnitude of reproduction increased nonlinearly with adult PSC density, declining at high adult densities. Annual egg counts were also higher in years that combined more variable spring discharge with higher accumulated degree-days through June. The density-dependent reproduction exhibited by PSC implies that any stock–recruitment variation observed for these species needs to be interpreted cautiously before being ascribed to environmental factors affecting survival from hatching to juvenile stages. An increased understanding of which life stages of PSC are subject to density dependence can refine projections of how these species respond to harvest and other control measures.

中文翻译：

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伊利诺伊水道入侵远洋产卵鲤鱼繁殖规模的时空变化

远洋产卵鲤鱼 (PSC) 物种（鳙鱼Hypophthalmichthys spp.、草鱼Ctenopharyngodon idella和黑鲤鱼Mylopharyngodon piceus）的繁殖规模与成体密度之间的关系) 以及环境因素对这种关系的影响对于管理和控制这些高度入侵的鲤鱼来说是有价值的信息。六年来对伊利诺伊水道（IWW；伊利诺伊河及其通过德斯普兰斯河和芝加哥地区水道系统与密歇根湖的连接）导航池中 PSC 繁殖和成虫密度的标准化监测，以及上游的清除工作IWW 池之间的鱼类活动有限，这为我们提供了加深对影响这种侵入性组合繁殖生产力的因素的理解的机会。繁殖活动最常发生在5月和6月，6月的繁殖量远远超过其他月份。在包含伊利诺伊河上游和下游之间的水文形态过渡的 72 公里区域内发现了最高的卵数，大部分 PSC 幼虫漂移发生在伊利诺伊河下游的该区域下方。繁殖幅度随成年 PSC 密度呈非线性增加，在高成年密度时下降。在 6 月之前结合了更多变化的春季排放和更高的累积度日数的年份中，年产卵数也更高。PSC 表现出的密度依赖性繁殖意味着，在将这些物种观察到的任何种群-补充变化归因于影响从孵化到幼体阶段生存的环境因素之前，都需要谨慎解释。