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. 当前学界对鲨鱼及其他高度洄游海洋物种的生态学认知，往往依赖渔业依赖型数据，或是采用具有可捕性偏差与体型选择性偏差的破坏性渔业独立采样技术。远洋诱饵式远程水下立体视频系统（pelagic stereo-BRUVs）提供了一种标准化、非破坏性且无需依赖渔业的方法，可用于估算水体层中鱼类群落的生物多样性指标。然而，该新型方法的采样性能尚未与其他标准采样技术进行对比评估。2. 本研究对比了采用远洋诱饵式远程水下立体视频系统与常规科学延绳钓调查所采样的鱼类群落的渔获组成、相对丰度与体长分布。特别地，本研究以西澳大利亚州沿岸的纬度梯度为研究范围，以真鲨科（Carcharhinidae）物种为研究对象，评估该新型采样技术的有效性。我们对两种技术所需的采样投入进行了校准，以获取目标物种的等效样本，并探讨了这两种方法用于研究高度洄游物种的优势、局限与潜在应用场景。3. 在整个纬度梯度范围内，远洋诱饵式远程水下立体视频系统与科学延绳钓调查所采样的鲨鱼占比并无显著差异。两种采样技术所获样本中，铅灰真鲨（Carcharhinus plumbeus）均为丰度最高的物种。与远洋诱饵式远程水下立体视频系统得到的体长分布数据相比，延绳钓调查所采样的真鲨科个体体型更大。不过，远洋诱饵式远程水下立体视频系统的相对丰度估算值（单位努力渔获量，catch per unit of effort）与使用5至30枚延绳钓钩的采样结果相当。4. 远洋诱饵式远程水下立体视频系统可与标准采样技术进行校准，从而在大空间与时间尺度上开展高度洄游鱼类群落的物种组成、行为、相对丰度与体长分布研究。该技术属于非破坏性的渔业独立采样方法，可在禁渔区域开展采样，适用于珍稀或濒危物种的相关研究。