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.