Assessing size, abundance and habitat preferences of the Ocean Perch Helicolenus percoides using a AUV-borne stereo camera system
Seiler, J and Williams, A and Barrett, N, Assessing size, abundance and habitat preferences of the Ocean Perch Helicolenus percoides using a AUV-borne stereo camera system, Fisheries Research: An International Journal on Fishing Technology, Fisheries Science and Fisheries Management, 129-130 pp. 64-72. ISSN 0165-7836 (2012) [Refereed Article]
Traditional fishery resource assessment methods using trawl gear are unable to sample rocky substratum
and are prone to underestimating the biomass of species having partial or strong association with
rocky reefs. This study successfully used an Autonomous Underwater Vehicle (AUV) and image-yielding
methods to estimate size, abundance and habitat preference of an abundant and commercially important
'rockfish' – the Ocean Perch (Helicolenus percoides) – in rocky habitats on the continental shelf off
Tasmania, SE Australia. More than half (53%) of the Ocean Perch observed were photogrammetrically
measured with known accuracy using a stereo camera system yielding length-frequency distributions.
Observations of juvenile and adult H. percoides across a depth gradient showed that adults preferred rocky
substrates over soft substrates, whereas juveniles preferred soft substrate over hard substrate. We found
a positive relationship between rockfish abundance and increasing depth in most habitat types. These
results demonstrate the utility of image-based methods for determining size composition and habitat
preferences of some reef-associated species. However, there is scope to improve image-based methods
using length estimation procedures that enable higher proportions of individuals to be measured (compared
to the proportion achieved in this study), and by incorporating automated image annotation to
decrease image analysis times, particularly when examining species/habitat relationships. The importance
of analytical procedures that account for autocorrelation in non-independent image data on habitats
and associated species is discussed. We conclude that rapidly maturing image-based observational methods
have potential utility in complementing fishery stock assessments of some reef-associated species.
Image-based methods are also well-suited to simultaneously provide additional quantitative measures
of benthic habitats, invertebrate fauna and fishery environments.
size assessment, abundance assessment, stereo camera system, AUV, habitat preferences, ocean perch, fishery-independent data