1. No category

SouthgEastgAustraliangProgram
Preparinggfisheriesgforgclimategchange
BLUEgGRENADIER
fact sheet
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andghighlightghowgfisherygassessmentgandgmanagementgframeworksgcouldgbegadjustedgtogbettergconsiderg
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classesgovergtheglastgFjgyearsgareg
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About the case study
))))The)Blue)grenadier)fishery)depends)on)infrequent)large)recruitment)
pulses)that)produce)strong)year9classes)that)support)fishery)
production)for)many)years%)These)recruitment)pulses)are)driven)by)
inter9annual)variation)in)spawning)success)that)is)thought)to)be)related)
to)variation)in)the)survival)rates)of)the)early)life)stages)Si%e%)larvae)or)
small)juveniles5)in)their)first)few)weeks)to)months)of)lifeI%
)
Little)is)known)about)the)processes)influencing)variable)survival)of)
larvae)and)small)juveniles)in)Australian)blue)grenadier)stocks5)but)
earlier)studies)suggest)that)climatic)factors)are)likely)important%)
Changes)to)either)the)average)magnitude)and3or)frequency)of)these)
strong)year)classes)would)have)a)major)impact)on)the)fishery)and)is)
seen)as)a)key)vulnerability)of)this)fishery)to)climate)change%)
This)case)study)explored)the)relationship)between)blue)grenadier)
year–class)strength)SYCSI)and)climatic)variables)that)could)be)
influenced)by)climate)change%)It)also)conducted)a)preliminary)analysis)
of)how)variation)in)larval)dispersal)trajectories)may)influence)year9
class)strength%)
Finally5)given)that)any)potential)climate)change)impacts)on)
recruitment)are)likely)to)be)difficult)to)forecast)with)high)confidence5)it)
is)important)that)the)harvest)strategy)for)this)fishery)can)deal)with)a)
variety)of)possible)recruitment)scenarios)and)continue)to)recommend)
appropriate)catch)levels%)This)case)study)therefore)also)looked)at)the)
performance)of)the)current)harvest)strategy)framework)in)protecting)
the)stock)from)collapse)under)various)recruitment)regimes%
Key effects of climate change
))))We)found)that)blue)grenadier)YCS)was)related)to)winds)and)sea)
surface)temperatures%)Wind)strength)during)the)autumn)period)just)
prior)to)the)blue)grenadier)spawning)season)and)mean)annual)sea)
surface)temperature)together)explained)89x)of)the)variation)in)the)
YCS)estimates)for)the)24)years)from)19P29766H5)and)P0x)for)the)
74)years)from)19H29766H)when)recruitment)estimates)are)more)
confident%)Strong)autumn)winds)may)be)more)conducive)to)retention)of)
larval)stages)in)the)spawning)region5)as)preliminary)analysis)of)larval)
dispersal)modelling)indicated)that)years)with)greater)retention)of)
larval)stages)along)the)west)Tasmanian)shelf)region)had)higher)YCS%
Together)with)analysis)of)a)range)of)other)climatic)variables5)our)
results)suggest)that)windy)autumns5)where)there)is)greater)vertical)
mixing)of)the)water)column)and)more)nutrient)supply)to)surface)
waters)just)prior)to)spawning5)and)colder)winter)to)spring)periods5)are)
conducive)to)higher)YCS)of)blue)grenadier)off)western)Tasmania%
)
Projections)of)future)wind)conditions)for)western)Tasmania)under)
climate)change)scenarios)suggest)that)changes)to)winds)will)have)only)
a)minor)effect)on)average)YCS%)However5)sea)surface)temperatures)
are)predicted)to)increase)by)792)˚C)by)7686%)The)predicted)increase)
in)temperature)may)have)a)major)negative)impact)on)blue)grenadier)
spawning)and)recruitment)success)off)western)Tasmania)if)the)water)
temperatures)experienced)by)the)egg)and)larval)stages)are)beyond)
their)tolerance)levels%))
Key unknowns in regard to
climate change
Key unknown is the upper temperature tolerances of
the eggs and larvae. There also remains high uncertainty
around how climate change will influence changes in sea
temperatures at depths below 400 m where blue
grenadier spend a large portion of their lives. This hinders
our ability to predict if there will be changes in migratory
patterns or distribution.
Poor understanding of the juvenile (first year of life)
ecology and distribution is a key knowledge gap limiting
understanding of how climate change may influence blue
grenadier fishery production.
Improving the capabilities of our models to conduct
modelling of larval dispersal under future climate
scenarios will be important for assessing implications of
climate change.
While it is clearly difficult to predict changes to the
dynamics of YCS due to climate change, simulation testing
of the current assessment framework indicated that the
harvest strategy is capable of protecting the stock from
long-term decline under a range of potential recruitment
dynamics. However, the exercise clearly demonstrated
that changes to recruitment dynamics could have a major
impact on how the fishery operates under the current
harvest control rule, due in large part to a greater
uncertainty in the catch dynamics.
Responding to change
Existing capacity for the fishery to adapt
The most likely effects of climate change on the blue
grenadier fishery are changes in frequency and or
magnitude of the strong year classes that drive fishery
production. This may mean that the dynamics of fishery
production (catches) may change from the industries
contemporary experiences. Distribution and seasonal
migratory patterns, such as for spawning, may also be
influenced by climate change. The tractable adaptations
to such changes are limited but include changes in areas,
times or depths fished, and changes to fleet size or gear
used.
Options for improving assessment
frameworks
It is possible that blue grenadier growth, mortality or
other parameters might be affected by changes in
surrounding environmental conditions (e.g. water
temperature, prey availability). While this was not
considered specifically in this work, the key assumptions
used in the stock assessment model are reviewed and
agreed upon by fishery and biology experts prior to their
implementation. This allows frequent opportunity for
observed or inferred changes to a parameter to be
incorporated within the stock assessment model. In
addition, more episodic recruitment could lead to major
cycles in fishery production with intermittent periods of
low or even zero TAC (catches). Under such scenarios, a
review of control rules and fishery management plans/
objectives may be required to ensure the economic
performance of the fishery is maximised.
Possible planned adaptations to consider
in the future
Possible adaptation actions were elicited from
stakeholders in response to the potential climate change
impacts. The main impacts were listed as: changes in
location, timing and intensity of the spawning aggregation;
lower productivity through changes in recruitment
dynamics; increased interactions with protected species,
and reduced availability of the stock. Potential
adaptations included reducing catch quotas and/or effort,
moving fishing season dates, removal of restrictions on
fishing depths, changing target species and shifting areas
fished.
IIIII
Barriers to change
IIIIWeIfoundIveryIfewIpotentialIbarriersItoIadaptationIforItheIblueIgrenadierI
fishery.ITheIfisheryIcoversIaIsingleIjurisdiction,IandItheIgoalsIandIobjectivesIofI
fisheryImanagementIareIclearlyIdefined.ITheIfisheryIisIalsoIconfinedItoIaIsmallI
numberIofIlargeIoperatorsIsoItheIdemographicsIofItheIfisheryIareInotIasIdiverseI
asIsomeIlargerIfisheriesIandIthereforeIitIappearsItheIopinionsIregardingI
managementIchangeIareIquiteIsimilar.ITheImainIbarriersIhighlightedIincluded:I
costsIassociatedIwithIalteringIfishingIpractices,ItimingIorIquota,IlimitedIoptionsIforI
diversification,IimpactsIonIotherIstocksIifIchangesIinItargetIspecies.III
Knowledge/data requirements into the future
TheIkeyIknowledge/dataIrequirementsIidentifiedIwere:
IncreasedIcollectionIofIwaterItemperatureIdepthIprofilesItoIhelpIimproveI
forecastingImodels.
ImprovedImonitoringIofIreproductiveIaggregationIbehaviourIbyIcollectingI
timeIseriesIofIreproductiveIconditionIofIfishIinItrawlIshots,IwithIassociatedI
dataIonIdepthIofIcapture,IwaterItemperatureIatIdepthIofIcaptureIandIatI
theIsurface,IsexIratioIetc.
ImprovedImodellingIofIlarvalIdispersal,IparticularlyItheIspatialIresolutionI
andIabilityItoIinvestigateIrealisticIfutureIclimateIchangeIscenariosIofIlarvalI
dispersal.
UseIofIotolithsItoIstudyIhowIclimateIregimeIchangesImightIrelateIto/
influenceIgrowthIrateIvariationIandIimplicationsIforIassessmentImodelling.
http:33frdc0com0au3environment3climate_change3F
DataIonIjuvenileIabundanceIandIdistributionItoIvalidateImodelIYCSI
estimatesIandIimproveIunderstandingIofIjuvenileIecology.
ControlledIstudiesIofIeggIandIlarvalItemperatureItolerances.
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.
PaulFHamer5FFisheriesFVictoria
paul0hamer@ecodev0vic0gov0au
86_F8FwMw8F/M88
http:33www0redmap0org0au3
GeoffFTuck5FCSIRO
Geoff0Tuck@csiro0au
86_FAF6MAMFwMMM
GrettaFPecl5FIMAS
Gretta0Pecl@utas0edu0au
86_FAF6MM7F7M77
PhotoFcredits:F
BruceFBarker5F
ElsaFGärtner5F
RickFStuart2
Smith5FGeoffF
Tuck5FCSIROFandF
FisheriesFVictoria