Data from: Calibration of pelagic stereo-BRUVs and scientific longline surveys for sampling sharks

1. Our understanding of the ecology of sharks and other highly mobile marine species often relies on fishery-dependent data or extractive fishery-independent techniques that can result in catchability and size-selectivity biases. Pelagic Baited Remote Underwater stereo-Video Systems (pelagic stereo-BRUVs) provide a standardized, non-destructive and fishery-independent approach to estimate biodiversity measures of fish assemblages in the water column. However, the performance of this novel method has not yet been assessed relative to other standard sampling techniques. 2. We compared the catch composition, relative abundance and length distribution of fish assemblages sampled using pelagic stereo-BRUVs and conventional scientific longline surveys. In particular, we focused on sharks of the family Carcharhinidae (requiem sharks) to assess the sampling effectiveness of this novel technique along a latitudinal gradient off the coast of Western Australia. We calibrated the sampling effort required for each technique to obtain equivalent samples of the target species and discuss the advantages, limitations and potential use of these methods to study highly mobile species. 3. The proportion of sharks sampled by pelagic stereo-BRUVs and scientific longline surveys was comparable across the latitudinal gradient. Carcharhinus plumbeus was the most abundant species sampled by both the techniques. Longline surveys selected larger individuals of the family Carcharhinidae in comparison with the length distribution data obtained from pelagic stereo-BRUVs. However, the relative abundance estimates (catch per unit of effort) from the pelagic stereo-BRUVs were comparable to those from 5 to 30 longline hooks. 4. Pelagic stereo-BRUVs can be calibrated to standard techniques in order to study the species composition, behaviour, relative abundance and size distribution of highly mobile fish assemblages at broad spatial and temporal scales. This technique offers a non-destructive fishery-independent approach that can be implemented in areas that may be closed to fishing and is suitable for studies on rare or threatened species.

1. 当前我们对鲨鱼及其他高度洄游海洋物种生态学的认知，往往依赖于渔业依赖型数据（fishery-dependent data）或抽取式渔业独立采样技术（extractive fishery-independent techniques），这类方法可能会引入捕获率偏差与体型选择性偏差。远洋诱饵式远程水下立体视频系统（Pelagic Baited Remote Underwater stereo-Video Systems，缩写为pelagic stereo-BRUVs）提供了一种标准化、非破坏性且无需依赖渔业的采样方案，可用于估算水体层中鱼类群落的生物多样性指标。但目前尚未针对其他标准采样技术，对该新型方法的采样性能开展对比评估。
2. 本研究对比了远洋立体BRUVs与传统科学延绳钓调查所采集的鱼类群落的渔获组成、相对丰度及体长分布。其中，我们以真鲨科（Carcharhinidae，俗称白眼鲨）物种为研究对象，评估了该新型方法在澳大利亚西部沿岸纬度梯度上的采样有效性。我们对两种技术所需的采样工作量进行了校准，以获取目标物种的等效样本，并讨论了这两种方法用于研究高度洄游海洋物种的优势、局限与潜在应用场景。
3. 在整条纬度梯度上，远洋立体BRUVs与科学延绳钓调查所采样得到的鲨鱼占比均无显著差异。两种采样技术采集到的丰度最高的物种均为高鳍真鲨（Carcharhinus plumbeus）。相较于远洋立体BRUVs得到的体长分布数据，延绳钓调查所采样的真鲨科个体体型更大。不过，远洋立体BRUVs的相对丰度估算值（单位努力渔获量，catch per unit of effort）与使用5~30枚延绳钓钩的采样结果相当。
4. 远洋立体BRUVs可与标准采样技术进行校准，从而在大时空尺度上开展高度洄游鱼类群落的物种组成、行为、相对丰度及体长分布研究。该技术属于非破坏性的渔业独立采样方案，可在禁渔区域开展采样，适用于稀有或受威胁物种的相关研究。