We tested a novel approach for fish abundance and size estimates along a 3.6-km reach in the main stem of a free-flowing section of the Danube River east of Vienna. We deployed an adaptive resolution imaging sonar (ARIS) with horizontal beam orientation from a moving boat in order to assess spatial and temporal fish abundance distributions in different mesohabitats. To validate the results obtained from imaging sonar, hydroacoustic abundance and fish length estimates were compared with those received from boat electrofishing surveys conducted at the same time and place. Furthermore, fish occurrence was related to hydraulic conditions based on a three-dimensional hydrodynamic model in order to reveal patterns of habitat use. Hydroacoustic abundance expressed as catch per unit effort estimates deviated significantly from fish abundances assessed by boat electrofishing, but when comparing relative abundances both methods yielded a similar spatial and temporal pattern. Total fish length estimates obtained from the two methods did not differ significantly. The mobile application of the non-invasive ARIS technology offers the opportunity to quickly gain detailed information on fish abundance and position of individuals. This yields more specific information on temporal and spatial distribution patterns, habitat use and fish size distributions in large rivers.

中文翻译：

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一条大河（奥地利多瑙河）中鱼的丰度，分布和栖息地利用：流动，水平水声调查与标准捕鱼方法

我们在维也纳东部多瑙河自由流段主干沿3.6公里处测试了鱼类丰度和大小估计的新方法。为了评估不同中生境中鱼类的时空丰度分布，我们从移动的船上部署了具有水平波束方向的自适应分辨率成像声纳（ARIS）。为了验证从声纳成像获得的结果，将水声丰度和鱼长估计值与在同一时间和地点进行的船用电钓鱼调查得到的值进行了比较。此外，鱼的发生与基于三维水动力模型的水力条件相关，以揭示栖息地利用的模式。水声丰度表示为每单位工作量估计的捕获量，与船用电捕鱼法所评估的鱼丰度有显着差异，但是当比较相对丰度时，两种方法产生的空间和时间格局相似。通过两种方法获得的总鱼长估计值没有显着差异。非侵入性ARIS技术的移动应用程序提供了机会，可以快速获取有关鱼类丰度和个体位置的详细信息。这产生了关于大河流中时空分布格局，栖息地利用和鱼类大小分布的更具体的信息。非侵入性ARIS技术的移动应用提供了机会，可以快速获取有关鱼类丰度和个体位置的详细信息。这产生了关于大河流中的时空分布格局，栖息地利用和鱼类大小分布的更具体的信息。非侵入性ARIS技术的移动应用提供了机会，可以快速获取有关鱼类丰度和个体位置的详细信息。这产生了关于大河流中的时空分布格局，栖息地利用和鱼类大小分布的更具体的信息。