Abstract Characterizing the structure of riverine fish populations that are patchily distributed and at low densities is often difficult. Due to the wide distribution but low abundance of Spotted Bass, Micropterus punctulatus, throughout the lower Wabash River (LWR), captures from fixed and random sampling designs were compared to assess their performance in determining relative abundance and size structure. The LWR is monitored using both sampling regimes—the Long Term Electrofishing Program monitors community assemblages uses a stratified-random sampling, whereas the Illinois Department of Natural Resources monitors the fish community using a fixed-sampling design. Mean CPUE was significantly higher for fixed site sampling compared to random sites. However, the size structure of Spotted Bass sampled by each design were similar. These results suggest random-sampling designs should be used when monitoring low density populations of fishes in large riverine systems because this method provides the greatest spatial coverage of habitats, evaluates heterogeneity in distribution, and provides a representative measure of abundance throughout an entire aquatic system. In situations where size distribution or temporal trends are the only goal, fixed site sampling would be sufficient.

中文翻译：

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大河中低密度斑点鲈鱼种群的固定采样与随机采样的比较

摘要 表征分布不均且密度低的河流鱼类种群的结构通常很困难。由于斑点鲈鱼分布广泛但丰度低，在整个瓦巴什河下游 (LWR) 中，我们比较了固定和随机抽样设计的捕获物，以评估它们在确定相对丰度和大小结构方面的性能。LWR 使用两种抽样制度进行监测——长期电子捕鱼计划监测社区组合使用分层随机抽样，而伊利诺伊州自然资源部使用固定抽样设计监测鱼类社区。与随机站点相比，固定站点抽样的平均 CPUE 显着更高。然而，每个设计采样的 Spotted Bass 的尺寸结构是相似的。这些结果表明，在监测大型河流系统中的低密度鱼类种群时，应使用随机抽样设计，因为这种方法提供了最大的栖息地空间覆盖范围，评估了分布的异质性，并提供了整个水生系统中丰度的代表性度量。在尺寸分布或时间趋势是唯一目标的情况下，固定站点采样就足够了。