The mid-water rigs also allowed for similar rates of length measurements to be made in comparison
to rates of demersal stereo-BRUVS. We estimated lengths for 42% of the observed individuals and 78%
of the observed species. This level of efficiency is higher than that in a previous demersal fish survey
in Shark Bay using stereo-BRUVS, where length estimates were made for 30% of observed individuals
and 70% of the species (Liang et al., 2005). More generally, the mid-water rigs’ efficiency is similar
or slightly less than that of a range of demersal stereo-BRUV surveys undertaken in tropical Western
Australia, where on average 47% of individuals and 87% of species were measured (Meeuwig, unpubl.
data). The ability to measure lengths for a proportion of individuals and species comparable to those