New Zealand Journal of Marine and Freshwater Research abstracts
Modelling the effects of Marine Protected Areas (MPAs) on the southern
rock lobster (Jasus edwardsii) fishery of Victoria, Australia
David Hobday1
André E. Punt2,3
David C. Smith1
1Marine and Freshwater Systems Department of Primary Industries
P.O. Box 114, Queenscliff
VIC 3225, Australia
email: David.Hobday@dpi.vic.gov.au
email: David.C.Smith@dpi.vic.gov.au
2CSIRO Division of Marine Research
GPO Box 1538, Hobart
TAS 7053, Australia
email: Andre.Punt@csiro.au
3School of Aquatic and Fishery Sciences
Box 355020, University of Washington
Seattle, WA 98195-5020, United States
email: aepunt@u.washington.edu
Abstract Since 2002, 5.3% of the Victorian coastal waters
have been declared as Marine Protected Areas (MPAs). These are aimed at safeguarding
important marine habitats and species, significant natural features, and
areas of cultural heritage and aesthetic value. However, MPAs impact the
fishery for southern rock lobster (Jasus edwardsii), as total allowable
catches (TACs) were previously set to allow the biomass to recover to pre-specified
target levels. The model on which assessments and risk analyses are based
is extended to include the impact of MPAs. The MPAs and the area open to
fishing are modelled as subpopulations with different levels of mortality
and consequently different density and population size-structure. A range
for the probability of a lobster moving from a MPA to the fished area from
0 to 15% is considered, based on the results of tagging studies. The reduction
of biomass available to the commercial fishery because of the introduction
of MPAs is estimated to be 8% and 16% (Western and Eastern Zones) respectively.
The results of a risk assessment show that if the current TACs are maintained,
the time to increase the biomass available to the commercial fishery by 50%
would be delayed 5-9 years in the Western Zone and 1-4 years in the Eastern
Zone because of the impact of displaced effort. In contrast, spawning biomass
in the Eastern Zone is currently below the agreed limit reference point,
and the introduction of MPAs would enhance the rate of recovery, although
only marginally initially, faster than the absence of the MPAs.
Keywords spiny lobster; rock lobster; Marine Protected
Area; Marine Reserve; modelling; reference points; risk assessment
M04043; Online publication date 8 June 2005 Received 10 February 2004;
accepted 13 September 2004
New Zealand Journal of Marine and Freshwater Research, 2005, Vol. 39:
675-686
0028-8330/05/3903-0675 © The Royal Society of New Zealand 2005
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