Part 1 - Baited video surveys of the Pompey, Swain and
Capricorn-Bunker groups of reefs off Mackay and Gladstone
Research Report
Mike Cappo, Aaron MacNeil, Marcus Stowar and Peter Doherty
Australian Institute of Marine Science, Townsville
ISBN 9781921359361
Published October 2009
MTSRF Project 4.8.2 -
Influence of the GBR Zoning Plan on inshore habitats and
biodiversity, of which fish and corals are indicators: Reefs
and shoals
Executive Summary
This report presents the results of
a single survey (Summer 2009) of sixteen pairs of large, discrete,
deepwater reef bases in the southern Great Barrier Reef. Within
each pair, one reef was zoned 'green' (closed to fishing) and the
other 'blue' (open to all fishing).
The demersal habitats and vertebrate
communities were sampled using non-extractive baited remote
underwater video stations (BRUVS), which revealed a diverse (~360
species) fauna of fish, sharks, rays and sea snakes. This fauna
included species prized by fishers, taken as bycatch, or not
vulnerable to hook and line fishing.
Generalised linear models (GLM) and
generalised mixed-effects models were used to estimate the
influence of zoning on the maximum number of fish observed by each
BRUVS (MaxN) for specific components of the fish
community, showing that zoning had a significant effect on the
observed MaxN, but this was detectable mainly in habitats
dominated by corals. MaxN for aggregated groups of species
taken as bycatch were similar in both 'blue' and 'green' zones, but
the 'target' group MaxN was higher around green reefs in
coral dominated habitats. In this habitat type, 'target' species
were about 1.5 times, and unfished species about 1.9 times, as
abundant in the 'green' zones as the same groups in the 'blue'
zones.
Individual species showed distinct
reponses, with grey reef sharks (taken as bycatch) having higher
MaxN in a range of habitat types on green reefs, and the
Venus tuskfish having lower MaxN on green reefs. The
prized deep-water coral trout, red emperor and red-throat emperor
had higher MaxN values around the green reefs in coral
dominated habitats, but not by large margins. For every ten BRUVS
sets, there were about eleven coral trout, six red emperor and five
grey reef sharks more in green zones than in similar coral
dominated habitats of blue zones.
We lacked any data on spatial and
temporal variation in fishing effort in the deep habitats around
reef bases, and for this reason our results should not be
extrapolated regionally or throughout the Great Barrier Reef Marine
Park (GBRMP). It is plausible that fishing around the deep reef
bases in these remote southern reefs occurs (if at all) at such a
low level that the Representative Areas Program (RAP) 2004 zoning
has had little effect on local fish abundance in areas already
under little to no fishing pressure.
It is also possible that the deep, complex habitats around the
reef bases extended continuously between reefs within some pairs,
allowing fish unrestricted passage across zone boundaries. Our
sampling was the first exploration of these habitats, and we could
not stratify sampling by habitat type or extent. These results are
in contrast to previous surveys of the discrete tops and slopes of
the same reefs that have detected major impacts of the zoning plan
on shallow-water coral trout, which comprise the major target of
the long-range commercial fishery for the 'live reef fish'
trade.
