Digital video surveys of abalone (Haliotis sp.) stocks by commercial fishers in Western Australia

An evaluation of a digital video survey programme (DVI surveys) to provide cost-effective stock assessment information for Haliotid (abalone) fisheries was undertaken. Cost effectiveness was achieved by using commercial abalone industry divers to collect abundance and length–frequency data from remote locations using a custom designed video survey unit. Production of training DVD/video, training regimes, and a comprehensive suite of experimental tests on two abalone species (Haliotis laevigata; Haliotis roei) were utilised to achieve this outcome. Estimates of density and size–frequency of the populations of interest were achieved (0.5–1.0 m−2 for H. laevigata; 6–18 m−2 for H. roei), and appeared reasonable in comparison with existing studies. Although results were not be used as a basis for management decisions due to their preliminary nature, they provided evidence of the potential usefulness of the method for detecting change at the population level. Importantly, the DVI surveys performed favorably against a traditional area-based survey technique, providing the same level of precision in abundance estimation of recruited H. laevigata (greenlip abalone), for 40% of the sampling effort and costs. Overall, this work has expanded the role of DVI surveys as applied to fish and fish habitat assessment, however the abundance and size estimates generated by DVI surveys need to be primarily considered as relative indices, useful for detecting trends over time, provided that the selectivity and sampling issues have appropriately considered.