Wobbegongs are benthic sharks that are commercially targeted in New South Wales (NSW), Australia. Given a dramatic reduction of more than 50% in landed catch in a decade, there is a clear need to ensure that basic ecological data such as distribution and abundance
are available for management use. Opportunistic sightings of wobbegongs
collected by recreational scuba-divers were used to assess the distribution
and relative abundance of wobbegongs in NSW. From July 2003 until January
2005, 304 dives were undertaken by recreational divers and 454 wobbegongs
were reported. Larger numbers of wobbegongs were sighted in northern
compared to southern NSW. Spotted and ornate wobbegongs were sighted in
similar numbers, but species composition was highly variable across
locations. Only a few juvenile and newborn spotted wobbegongs were sighted,
whereas small ornate wobbegongs were mostly sighted north of central NSW.
The latter were possibly the third, cryptic species, the dwarf ornate
wobbegong. The paucity of sightings of small wobbegongs suggests that
juveniles and newborns are inconspicuous to divers or that small wobbegongs
are found in areas not visited by divers. Potential species and size
segregation suggest that closing areas to fishing may enable populations to
sustain current levels of commercial exploitation. The cost-effectiveness of
using recreational scuba-divers to opportunistically collect distribution
and relative abundance data was apparent from this study. However, the lack
of spatial and temporal homogeneity in diving effort suggests that future
studies should consider incorporating organized surveys and a facilitator,
rather than using opportunistic records of sightings.