The Lower Fox River is a modified tributary of Green Bay, Lake Michigan that hosts a remnant Lake Sturgeon (Acipenser fulvescens) population. Reproduction has been confirmed, although annual spawning events have been described as small and concerns regarding the long-term viability of the population remain. Contemporary and comprehensive surveys of spawning habitat, spawning stock, and production to the larval stage have not been conducted. The goal of this study was to describe spawning habitat, determine the size and demographic structure of the spawning stock, and quantify larval production (2017–2019) to identify impediments to population growth and recovery. Over 130 adults were present during annual spawning runs and spawning activity was consistently concentrated along the eastern riverbank. Adequate population structure exists to support reproductive success, but larval catch was low, ranging from 0 to 14 larvae captured annually. Evaluation of the riverbed below the De Pere Dam suggests the extent of the substrate available for spawning adult Lake Sturgeon is lower (~70% less) than previously described. Habitat deemed suitable for spawning exists offshore below the dam, but most habitat used for spawning is arranged along the eastern man-made shoreline. However, nearshore spawning is problematic at this location due to fluctuating discharge from dam operation and periodic seiche events. Possible impediments limiting the success of Lake Sturgeon reproduction include dewatering of eggs, retention of eggs and larvae, algae colonization, and egg predation. We discuss these issues in the context of previous Lake Sturgeon research, future monitoring of spawning adults/larval production, and the likelihood that river habitat improvement will foster increased reproductive success.

中文翻译：

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残余湖鲟（Acipenser fulvescens）种群的繁殖状况：威斯康星州福克斯河下游的产卵和幼虫漂流

下福克斯河是密歇根湖格林湾的一条经过改造的支流，这里栖息着一条残余的鲟鱼（Acipenser fulvescens） 人口。繁殖已得到确认，尽管每年的产卵事件被描述为很小，并且对种群长期生存能力的担忧仍然存在。尚未对产卵栖息地、产卵种群和幼虫阶段的生产进行当代综合调查。本研究的目标是描述产卵栖息地，确定产卵种群的大小和人口结构，并量化幼虫产量（2017 年至 2019 年）以确定种群增长和恢复的障碍。一年一度的产卵活动中有 130 多只成虫出现，产卵活动一直集中在东部河岸。存在足够的种群结构以支持繁殖成功，但幼虫捕获量很低，每年捕获的幼虫数量为 0 到 14 只。对 De Pere 大坝下方河床的评估表明，可用于产卵成年鲟鱼的底物范围比之前描述的要低（约少 70%）。被认为适合产卵的栖息地存在于大坝下方的近海，但大部分用于产卵的栖息地分布在东部人造海岸线。然而，由于大坝运行和周期性地震事件的流量波动，近岸产卵在该位置存在问题。限制鲟鱼繁殖成功的可能障碍包括卵的脱水、卵和幼虫的滞留、藻类定植和卵捕食。我们在之前的鲟鱼湖研究、对产卵成虫/幼虫生产的未来监测以及河流栖息地改善将促进繁殖成功的可能性的背景下讨论这些问题。