MEPS prepress abstract  -  DOI: https://doi.org/10.3354/meps12326

Combination of underwater video methods is more effective at surveying demersal fish assemblages across habitats

Jordan M. Logan, Mary A. Young, Euan S. Harvey, Alexandre C. G. Schimel*Daniel Ierodiaconou

*Email: daniel.ierodiaconou@deakin.edu.au

ABSTRACT: Knowledge of methods biases and advantages can inform and create more efficient sampling of either whole fish assemblages or targeted species. Comparisons of stereo baited remote underwater video (stereo-BRUV) and towed video, a new and relatively uncommon methodology of assessing fish assemblages, are made for assessing fish assemblages beyond diveable depths (>30 m). Stereo-BRUV and towed video footage were analysed for species composition and feeding functional groups in structure-forming macroalgae and sponge-dominated benthic habitats in temperate waters off Warrnambool, Victoria, Australia. Multibeam echosounder (MBES) data, light attenuation and temperature recordings were gathered for each deployment in order to characterise the seafloor structure and oceanographic parameters at each stereo-BRUV location and towed transect. More abundant and diverse fish assemblage was observed in stereo-BRUV compared to towed video. The fish assemblage observed using the two methods was relatively similar in canopy forming algae habitat, but clearly distinct in sponge habitats. Power analysis has also shown stereo-BRUV to have greater statistical power when observing total individuals, species richness and functional group richness across both habitats, with the exception of functional group richness in the sponge habitat. Stereo-BRUVs observed higher abundances of elasmobranches, Meuschenia spp., snapper (Chrysophrys auratus), demersal invertivores and pelagic planktivores, whilst towed video observed more cryptic and territorial species such as Olisthops cyanomelas and Pempheris multiradiata. Using a combination of stereo baited and towed video sampling techniques records a more detailed description of the fish assemblage on temperate reefs.