Download Rock Lobster

South East Australian Program
Preparing fisheries for climate change
ROCK LOBSTER fact sheet
Adult rock lobsters tolerate a wide range of environmental
conditions and live across a wide range of different rockyreef communities. While this suggests the adults will have
resilience to climate change, the success of larval recruitment
is affected by oceanic current circulation and this stage of
development may be vulnerable to change in climate.
The ability to detect and respond to changes in recruitment
will be important for fishing industry and resource managers
to adapt to any future changes in productivity.
Southern rock lobster was one of four case-study fisheries selected to identify likely effects of climate
change and highlight how fishery assessment and management frameworks could be adjusted to better
consider climate change.
The fishery
The Southern Rock Lobster (Jasus
edwardsii) resource supports important
commercial and recreational fisheries
across Western Australia, South
Australia, Victoria and Tasmania. The
total annual catch is approximately
3000 tonnes with an estimated gross
commercial value of AUS$200 million.
Fishing has involved the use of baited
pots since the late 1800’s in most
jurisdictions.
All fisheries are managed under
management plans that have been
separately developed within each
jurisdiction. Management tools include
limited entry to the fishery, gear
limitations and spatial or temporal
closures, as well as minimum legal sizes
and total allowable commercial catches
(TACCs). Collectively these approaches
have been successful and harvests are
assessed as being sustainably managed.
About the case study
Patterns in production of other rock
lobster fisheries, and Southern Rock
Lobster in particular, show that the
fishery is primarily vulnerable to two
factors; (i) changes in the numbers of
young lobsters settling to the inshore
reefs each year (ie levels of recruitment
to the fishery); and (ii) the ability of
management decisions to respond to
changes in recruitment.
For this reason, analyses of the
relationship between environmental
processes and the rock lobster fishery
focused on the potential for climate
change to alter fishery recruitment and
the ability of management systems to
respond.
Links between environmental processes
and settlement was examined using
data on the numbers of the first bottomdwelling or benthic stage (called
puerulus) from monitoring programs
across all jurisdictions. This project was
the first attempt to examine
environmental drivers of Southern Rock
Lobster recruitment across the range of
the Australian fishery and across all
available environmental data including
wind, current and wave strength in
addition to oceanic indices such as the
Eastern Australian Current index (EACI)
and the Southern Oscillation Index
(SOI).
How changes in the physical environment may
affect lobster production
Southern rock lobster eggs are carried by female lobsters living
on reef on the continental shelf. After hatching, the larvae swim up
into the water and are pushed by currents from the continental shelf
into oceanic waters. It is thought that environmental factors such as
wind strength and directions affects their ability to make this
journey. Once in oceanic waters beyond the continental shelf they
drift for 12 to 24 months feeding and slowly growing larger.
Changes in oceanic current strength and direction are thought to
affect the dispersal of this larval stage.
After the oceanic stage, larvae are once again driven back across
the continental shelf towards inshore reef habitat. This movement is
also affected by environmental conditions. If they successfully find
coastal reef they settle and begin life as a benthic or bottomdwelling rock lobster. The number of these puerulus settling inshore
was below average for many parts of coast from roughly 2000 to
2010, depending on location. As a consequence, the total
allowable catch of all Southern Rock Lobster fisheries was reduced.
The decline in puerulus between 2000 and 2010 followed a period
of increase in stock abundance and egg production so this raised
the question of whether the decline in recruitment was caused by
some environmental or climate change related process.
This project identified that puerulus settlement followed broadscale
patterns across large areas of the fishery and in some areas these
trends correlated with wind strength and current strength. However,
these trends were not consistent from region to region and where
they were observed, the scale of effect was only weak. There is
clearly much more to learn about the processes driving recruitment
of lobsters and it may be that biological factors such as algal
blooms or abundance of predators of larvae in the open ocean are
critical.
While specific environmental factors that caused this pattern of
declines in recruitment were not clear, it does illustrate the type of
event that could occur with climate change through changes in
patterns of larval dispersal and survival. If climate change has an
effect on future recruitment we need to have management that is
effective when there is uncertainty.
Vulnerability of assessment and management
systems to climate change
22222The2greatest2concern2from2climate2change2for2lobster2fisheries2is2that2
settlement2and2future2recruitment2of2lobsters2to2the2fishery2will2reduce2
faster2than2management2responds.22All2Australian2rock2lobster2fisheries2
have2some2autonomous2capacity2to2respond2to2lower2recruitment2by2
reducing2the2total2allowable2catch.222This2process2has2protected2stocks2by2
lowering2catches2in2response2to2lower2settlement2between220002and2
2010.22
The2low2settlement2experienced2across2the2stocks2also2highlighted2areas2
within2management2that2could2be2improved.2These2included2the2speed2at2
which2management2responded2to2declines2in2recruitment2as2well2as2the2
need2to2revise2expectations2around2overall2fishery2productivity.2
Management2decisions2made2in2these2fisheries2from220002to220102
assumed2that2settlement2of2lobster2larvae2was2variable2from2year2to2
year2but2within2ranges2that2were2considered2plausible2from2past2
experience.22This2meant2that2management2systems2used2for2the2fishery2
were2not2well2prepared2for2declines2in2recruitment2that2remained2low2for2
a2longer2period2than2had2occurred2at2any2time2over2the2previous2302
years.22This2has2now2been2addressed2by2building2buffers2into2decision2
processes2for2the2fishery.2
Assessment and management suited to change
The2project2examined2the2process2of2quota2setting2in2the2presence2of2
uncertainty2about2future2recruitment2that2could2possibly2occur2with2
climate2change,2concluding:2
Biomass2targets2for2the2fishery2should2be2set2conservatively2and2that2
the2probability2of2reaching2these2targets2should2be2higher2than2
50B.2
2
Using2economic2targets2for2the2fishery2should2be2encouraged2and2
provides2good2protection2against2climate2change.22This2was2because2
high2economic2yield2occurred2when2lobsters2were2abundant2so2that2
cost2of2fishing2was2low.22
22
Much higher levels of biomass than occur in the fishery at present would
create much greater resilience to any future periods of low recruitment.
Rebuilding stocks to high levels of biomass would require setting low catch
limits although the economic impact of this was minor because cost of fishing
would also be reduced.
Knowledge requirements into the future
The ability of fishery management to respond to periods of low recruitment is
improved by having access to good data on recruitment to the fishery.
There are many ways to collect this information but one of the most effective and
lowest cost options are programs where commercial fishers measure some of the
undersize lobsters in their catch on a daily basis. These monitoring programs are
now underway across most of the fishery and will be increasing in value for
responding to changes in the fishery as the time series become longer.
Ensuring that the fisheries of south-east Australia adapt effectively to
climate change will require robust scientific understanding and the
development of management systems that will allow negative impacts to
be mitigated and opportunities that arise to be seized.
h�p://frdc.com.au/environment/climate_change/
Caleb Gardner, IMAS
[email protected]
+61 3 6227 7277
h�p://www.redmap.org.au/
Adrian Linnane, PIRSA-SARDI
[email protected]
+61 8 8207 5400
Gre�a Pecl, IMAS
Gre�[email protected]
+61 3 6227 7277
Photo credits:
Elsa Gärtner,
Adrian
Linnane,
Rick StuartSmith, IMAS
and SARDI