Abstract Bottom trawling is a common fisheries method and also a widespread scientific sampling method for benthic and demersal species. Selectivity and catchability are usually estimated using different meshes and studies with alternative methods are rare. In this study, to improve the estimation of trawl selectivity, we compare bottom trawl catches and recordings made by a camera fitted on the top of the net. Scientific trawling was conducted along the Northeast Brazilian shelf, a typical carbonate shelf with presence of sponges, coralline bottoms and a high water visibility. In total, 23 taxa (19 species and four genera) were identified in the videos and 30 taxa (25 species and five genera) in the trawls, indicating a higher potential of trawling to record species richness. Overall, no significant differences were observed in the assemblage structure identified by trawling and underwater footages. However, divergences were observed in fish catchability between trawls and videos. Net sampling was more selective for fish with low swimming capacity, while species with shelter and fast swimming capacity seemed to be underestimated. Furthermore, underwater footages allowed for an assessment of the trawling impacts on erect sponges with the observation of the damage on large branching and tubular sponges. The vulnerability of those habitats that concentrate higher fish diversity to mechanical impact raise the need for creation of preventive measures to protect these sensitive areas from commercial fishing operations. The use of less destructive methods is an important survey alternative under special conditions, particularly in conservation areas. In this study the videos could not be used as a complete alternative for the trawls, which presented higher efficiency, however, videos had shown to be a useful complement. Possibly, the speed and height determined by the trawling operation affected the performance of video sampling, being performed in suboptimal conditions. Using dedicated video sampling, such as towed video, could significantly improve its efficiency and compensate the disadvantages observed from the videos.

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在碳酸盐架上进行底拖网捕捞：你能看到你所看到的吗？

摘要 底拖网捕捞是一种常见的渔业方法，也是一种广泛用于底栖和底栖物种的科学取样方法。通常使用不同的网格来估计选择性和可捕获性，并且很少使用替代方法进行研究。在这项研究中，为了提高对拖网选择性的估计，我们比较了底部拖网捕获量和安装在网顶部的摄像头拍摄的记录。沿着巴西东北部陆架进行了科学拖网捕捞，这是一个典型的碳酸盐陆架，存在海绵、珊瑚底部和高水能见度。在视频中总共确定了 23 个类群（19 种和 4 个属），在拖网中确定了 30 个类群（25 种和 5 个属），表明拖网捕捞记录物种丰富度的潜力更大。全面的，通过拖网和水下镜头确定的组合结构没有观察到显着差异。然而，在拖网和视频之间的鱼类可捕获性方面观察到了差异。净采样对游泳能力低的鱼类更具选择性，而具有庇护所和快速游泳能力的物种似乎被低估了。此外，水下镜头允许评估拖网对直立海绵的影响，并观察对大分枝和管状海绵的损害。那些集中了较高鱼类多样性的栖息地对机械影响的脆弱性提出了制定预防措施以保护这些敏感区域免受商业捕鱼活动影响的需求。使用破坏性较小的方法是特殊条件下的重要调查替代方法，特别是在保护区。在这项研究中，视频不能用作拖网的完整替代品，拖网效率更高，但是，视频已被证明是一种有用的补充。可能是拖网作业决定的速度和高度影响了视频采样的性能，在次优条件下进行。使用专用视频采样（例如拖曳视频）可以显着提高其效率并弥补从视频中观察到的缺点。在次优条件下进行。使用专用视频采样（例如拖曳视频）可以显着提高其效率并弥补从视频中观察到的缺点。在次优条件下进行。使用专用视频采样（例如拖曳视频）可以显着提高其效率并弥补从视频中观察到的缺点。