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Northern Prawn Fishery (NPF) Harvest Strategy under Input Controls

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					                                              R2006/1128




                           Northern Prawn Fishery
                           (NPF) Harvest Strategy
                              under Input Controls
                                            AUGUST 2007




Principal Investigator: Cathy Dichmont
CSIRO Marine & Atmospheric Research
PO Box 120
Cleveland QLD 4163




Co-Investigator: Annie Jarrett
Pro-Fish Pty Ltd
PO Box 756
Caloundra QLD 4551
   Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007



Table of Contents

OVERVIEW ..................................................................................................................... 3
BACKGROUND .............................................................................................................. 3
SECTION 1 - LEGISLATIVE OBJECTIVES OF THE FISHERY ................................ 7
  OBJECTIVES OF THE FISHERY .............................................................................. 7
SECTION 2 - FISHERY OVERVIEW ............................................................................ 8
  GEOGRAPHICAL CONTEXT.................................................................................... 8
  FISHING SEASONS.................................................................................................... 9
  TARGET SPECIES ...................................................................................................... 9
  VALUE OF THE FISHERY ...................................................................................... 11
  MANAGEMENT REGIME ....................................................................................... 11
  CLOSURES ................................................................................................................ 12
  FISHERY INDICATORS........................................................................................... 12
    Data......................................................................................................................... 12
    Data Reliability ....................................................................................................... 14
  FISHERY MONITORING ......................................................................................... 14
SECTION 3 - THE TIGER PRAWN FISHERY .......................................................... 15
  OPERATIONAL OBJECTIVE .................................................................................. 15
  INDICATORS ............................................................................................................ 16
  FISHERY MONITORING ......................................................................................... 16
  FISHERY REFERENCE POINTS ............................................................................. 17
  METHOD OF ASSESSMENT................................................................................... 18
    Tiger Prawns ........................................................................................................... 18
    Endeavour Prawns: ................................................................................................. 19
    Decision Rules for the Tiger Prawn Fishery........................................................... 20
    Adjustment.............................................................................................................. 20
    Closures .................................................................................................................. 22
    Tiger Prawn Trigger Limit...................................................................................... 22
    King Prawns............................................................................................................ 23
    Decision Rules for King Prawns:............................................................................ 23
SECTION 4 - THE BANANA PRAWN FISHERY ...................................................... 23
  OPERATIONAL OBJECTIVES ................................................................................ 23
  INDICATORS ............................................................................................................ 23
  FISHERY MONITORING ......................................................................................... 24
  FISHERY REFERENCE POINTS (ABUNDANCE INDICATORS)....................... 24
  METHOD OF ASSESSMENT:.................................................................................. 24
  DECISION RULES .................................................................................................... 25
SECTION 5 - OTHER TARGET SPECIES & BYPRODUCT ..................................... 27
  SCAMPI...................................................................................................................... 27
  Decision Rules for Scampi ......................................................................................... 28
  SQUID ........................................................................................................................ 28
  BYPRODUCT ............................................................................................................ 28




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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007




OVERVIEW
The “Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls 2007” has
been developed in conjunction with the Northern Prawn Fishery Management Advisory
Committee (NORMAC) and the Northern Prawn Fishery Resource Assessment Group
in accordance with the Ministerial Direction to AFMA that requires all Commonwealth
fisheries to implement a Harvest Strategy by January 2008.
The Ministerial Direction states that, consistent with the United Nations Fish Stocks
Agreement, and based on advice from CSIRO and other relevant scientists, the initial
setting of the Commonwealth Harvest Strategy Policy for domestic fisheries, should be:
   I.      in all Commonwealth fisheries the exploitation rate of target stocks in any
           fishing year will not exceed that giving the Maximum Sustainable Yield. The
           catch of target stocks in all Commonwealth fisheries will not exceed the
           Maximum Sustainable Yield in any fishing year unless otherwise consistent
           with a scientifically robust harvest strategy designed to achieve a
           sustainable target level and that does not result in overfishing or overfished
           stock;
   II.     for the initial and default harvest strategy, reductions in exploitation rate
           and catch are to be implemented immediately when breeding stocks are
           assessed to have been reduced below 40% of pre-fished levels, and targeted
           fishing to cease when breeding stocks are assessed to have been reduced
           below 20% of pre-fished levels (known as a '20/40' harvest strategy).
           Alternative harvest strategies may be developed in specific cases where they
           meet the sustainability objectives and do not result in overfishing or
           overfished stocks;
   III.    the harvest strategy must achieve the objective of avoiding overfishing and
           avoiding overfished stocks with at least 80% probability (where lack of
           knowledge about a fish stock precludes decision making with this level of
           certainty, decisions on catch/units should reflect the application of the
           precautionary principle).

Because of the high variability in annual recruitment of prawns, particularly banana
prawns, the probability that, in any one year stock in the NPF falls below virgin stock
size, or even below 20% of virgin stock size, is high relative to longer lived, less
variable species. Accordingly it is not possible to ensure with 80% probability that the
stock will not exceed the above overfishing limit or fall below the above overfished
limit in any single year. The NPF harvest strategy is intended to ensure with 80%
probability that, on average, the stock will be maintained in accordance with these
limits.

BACKGROUND
In the past, the management objective for the NPF tiger prawn fishery was Maximum
Sustainable Yields (MSY). For management purposes this was broken down into the
levels of spawning stock which should produce the maximum sustainable yields (SMSY),
and the level of fishing effort which should produce maximum sustainable yields
(EMSY). Until 2001, the target reference point was Smsy. Emsy was essentially treated
as a limit below which serious remedial action would be implemented.


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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


In 2000, the tiger prawn stock assessment indicated that biomass of brown tiger prawns
was conclusively below Smsy. The biomass of grooved tiger prawns was also assessed
as below Smsy, but not as depleted as the brown tiger prawn population. In response to
this assessment, NORMAC agreed to rebuild brown and grooved tiger prawn stocks to
Smsy within 5 years (by the end of 2006). NORMAC agreed to adopt a new, more
conservative target reference point being: ‘there is a 70+% chance that the spawner
population at the end of 2006 will be above or at spawner level targets (Smsy).’ A stock
rebuilding strategy to pursue this reference point for tiger prawns was implemented at
that time. The stock rebuilding strategy was successful and the 2006 stock assessment
indicated that recovery has occurred and that both species of tiger prawns are no longer
overfished.

NORMAC subsequently agreed in 2003 to adopt Maximum Economic Yield (MEY) as
the target reference point for the tiger prawn fishery. Smsy was set as the point at which
overfishing occurs and treated as the overfishing limit reference point, once recovery
has been achieved. MEY has subsequently been adopted as the aspirational target
reference point in the Commonwealth’s draft harvest strategy.

The harvest strategy described in this document addresses the biological elements of
achieving the MEY objective. Strategies to improve cost efficiencies (i.e. economic
efficiency) which will be required to pursue MEY will be addressed as the results of
further analysis become available.

As a result of the current investigation of output controls for the fishery, NORMAC is
adopting a two stage approach to the development of harvest strategies for the NPF.
The first stage is to develop harvest strategies based on the current input control system,
using a single control measure (gear units) to be applied to the management of the main
target species, combined with other management measures (i.e. spatial and temporal
closures).

The second stage will be to develop harvest strategies for implementation under an
output control system1 however that cannot be done until such time as the research
required to set robust and effective TACs has been undertaken, and an appropriate
output control system has been designed for the fishery.

The purpose of this paper is to document the various harvest strategies which have been
developed for the NPF into a formal harvest strategy for target species under the current
input control system however it is noted that changes to the system may be
implemented as a result of a review of management approaches to commence in
November 2007.

A key output of this HS is to provide an operating framework which will deliver stock
sustainability and maximise the economic return of the fishery.

The harvest strategies in this paper have been tested using the NPF Management
Strategy Evaluation (MSE) model.

This Harvest Strategy comprises the following key elements:



1
    Subject to outcomes of discussions on optimal management arrangements for the fishery

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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


   •   Indicators (data from the fishery)
   •   Monitoring (agreed protocols to get data)
   •   Reference points (targets and limits)
   •   Method of assessment (e.g. stock assessment, cpue standardisation)
   •   Decision rules (agreed rules for setting catch levels)

The target and reference points and the confidence levels adopted in this strategy have
been developed to address the short-lived, multi-species nature of the target species in
the NPF.

Prawns grow rapidly and most reach commercial size and reproductive maturity at the
age of 6 months, although they take 9 to 12 months to reach the larger, more valuable,
sizes (Dall et al 1990). Given the short-lived nature of prawns, inter-annual variability
of recruitment can be extremely large and unpredictable. This is especially true for
common banana prawns (Penaeus merguiensis) where there is a link between high
rainfall and banana prawn catch, although this connection is moderated by the
interaction between rainfall and catchment size (Vance et al 1998). The key element to
the assessment of tiger prawns, a species much less influenced by environmental factors
and therefore displays less inter-annual variability in recruitment, is that there is a stock-
recruitment relationship (with surprisingly low steepness values) (Penn and Caputi
1986, Ye 2000, Wang and Die 1996, Dichmont et al 2003). Given the fact that the catch
in a year is dominated by a single year class, it is not surprising that, compared to more
long-lived species’ assessment, there are reasonably large confidence intervals in the
estimates of spawning stock and recruitment size whether using an age-based
assessment (Wang and Die 1996), a delay difference assessment (Dichmont et al 2003)
or a biomass dynamic model (Haddon 2001). These confidence intervals mean that,
when a stock median estimate is at MSY, the 90% confidence interval can range from
80 to 130% of Smsy in any single year. As previously noted this imprecision requires
that the harvest strategy for the fishery is effective in the longer term, rather than in any
particular year.

It is well-known that it is impossible to achieve MSY for all stocks when multiple
stocks are fished simultaneously. This is already recognized in the NPF through the
analyses being conducted to identify the effort levels corresponding to Maximum
Economic Yield (MEY). Similarly, attempts at developing management strategies that
achieve Smsy for both tiger prawns species have shown that only extremely complex
harvest strategies are likely to achieve this target for both species (Dichmont et. al.
2006). How multi-species technical impacts (the ability to account quantitatively for
biological interactions is not sufficiently well-developed for almost any fishery
worldwide) are handled depends in part on the objectives for the management system.
There are two general strategies: a) manage to maximize total returns (or benefits) from
the system and b) multi-species biological stock management. The former recognizes
that maximizing the net benefits from the system will lead to some species (stocks)
being over-harvested and other under-harvested; this outcome is considered satisfactory
(for a societal point of view) as long as no species (stock) is driven to very low levels –
this option is reflected in the Mixed Stock Exemption of the U.S. Sustainable Fisheries
Act. The second strategy involves developing management measures to avoid any
species (stock) dropping below conservation thresholds. These management measures
can range from lower catch limits for “healthy” species to area / seasonal closures in
addition to catch limits to protect “weak” stocks.


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For ease of reading, and to reflect the multi-species nature of the Fishery, this paper is
divided into harvest strategies for the tiger prawn fishery, (including the endeavour and
king prawn fisheries), harvest strategies for the banana prawn fishery, and harvest
strategies for Other Target Species and Byproducts.




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SECTION 1 - LEGISLATIVE OBJECTIVES OF THE FISHERY

OBJECTIVES OF THE FISHERY

The Fishery is managed under the NPF Management Plan 1995. The Objectives of the
Plan are:

Objective 1    Ensure the utilisation of the fishery resources within the Northern
               Prawn Fishery is consistent with the principles of ecologically
               sustainable development and the exercise of the precautionary
               principle.

Objective 2    Maximise economic efficiency in the utilisation of the fisheries
               resources within the Northern Prawn Fishery.

Objective 3    Implement efficient and cost effective management of the Fishery.

Objective 4    Effectively communicate and consult with AFMA, the fishing industry,
               other marine resource users and the broader community.

Objective 5    Ensure that the incidental catch of non-target commercial and other
               species in the NPF is reduced to a minimum.




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SECTION 2 - FISHERY OVERVIEW

GEOGRAPHICAL CONTEXT
The Northern Prawn Fishery (NPF) occupies an area of 771,000 square kilometres off
Australia’s northern coast. The Fishery extends from the low water mark to the outer
edge of the Australian Fishing Zone (AFZ) along approximately 6,000 kilometres of
coastline between Cape York in Queensland and Cape Londonderry in Western
Australia.




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Under an Offshore Constitutional Settlement (OCS) agreement between the
Commonwealth, Western Australia, Northern Territory and Queensland governments,
originally signed in 1988, prawn trawling in the area of the NPF to low water mark, is
the responsibility of the Commonwealth through AFMA.

Data from the AFMA logbook data base indicates that fishing effort was reported from
273 grids (6 minute x 6 minute) when the fishery opened in 1973. Effort reached a
maximum in 1989 when effort was reported in 1,407 grids and it has decreased since
then to be reported from 811 grids in 2000, the most recent figures available. It is
generally accepted that fishing effort was severely under-reported during the period
1970 to the early 1980's, when completion of logbooks was voluntary. Since the early
1980's logbook coverage of the fishery has been virtually 100%. There are an estimated
7281 grids in the area of the NPF.

The principle reasons that much of the area of the NPF managed area is not trawled are:

•      the permanent closure of areas such as all shallow water seagrass beds
•      the unsuitability of areas to trawling due to large reef outcrops
•      the low density of the target prawn species, (eg. central Gulf of Carpentaria).

There are also trawlable grounds closed to prawn trawling both seasonally (8.3% of
total area) and permanently (2.1% of the total area). These areas include all known
seagrass beds. The major trawl grounds are in the Gulf of Carpentaria and the area to
the north and south-west of Darwin.

FISHING SEASONS
The NPF has two open seasons when fishing is permitted. The current fishing seasons
are:

♦      15 April - 27 May (Banana Prawn Season2)
♦      1 August - 15 November (Tiger Prawn Season)

TARGET SPECIES
Target species are the most highly sought component of the catch taken in a fishery.

The NPF is a multi-species fishery with nine species of prawns being targeted:

•      White banana prawn Penaeus merguiensis
•      Red-legged banana prawn Penaeus indicus
•      Grooved tiger prawn Penaeus semisulcatus
•      Brown tiger prawn Penaeus esculentus
•      Blue endeavour prawn Metapenaeus endeavouri
•      Red endeavour prawn Metapenaeus ensis
•      Western king prawn Metapenaeus latisulcatus
•      Red spot king prawn Penaeus longistylus
•      Giant tiger prawn Penaeus monodon



2
 Decision rules are in place which provide for the extension of the banana prawn season in highly
productive years

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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


The prawn species fall into four general categories of banana, tiger, endeavour and king
prawns however individual species are not distinguished within those groups in the
commercial catch.       Extensive studies by CSIRO Marine Research, including
commercial catch sampling and analysis of substrate composition, have shown that the
adults of the two commercial species of tiger prawns have different spatial distributions.
These are related to type of substrate and water depth. This has allowed the commercial
catch category of tiger prawns to be approximately split between the two species
according to the six minute square grids. Dichmont et al 2001 updated the species split
methodology in 2001and included the potential for species split shifts over time and
area. This was further updated in 2006 to incorporate the results of the Venables et al
2005 species distribution project.

Banana prawns are split into the two component species. Red-legged banana prawns
are caught almost exclusively in deep water (>45 metres) in JBG and white banana
prawns elsewhere (Dichmont et al 2001).

White banana prawns, brown tiger prawns and grooved tiger prawns account for almost
80% of the total annual catch from the fishery. The remainder is made up mostly of
endeavour prawns and red-legged banana prawns.

Prawn species reach a commercial size at six months, and can live for up to two years.
Larger sizes bring the highest price. Growth rates vary considerably between species
and sexes, with females generally growing faster and to a larger size than males. Most
species are sexually mature at six months, but fecundity increases with age. A twelve-
month-old female can produce hundreds of thousands of eggs at a single spawning and
may spawn more than once in a season. The eggs sink to the bottom after release,
where they hatch into larvae within about 24 hours. Less than 1% of these offspring
survive the two to four week planktonic larval phase to reach suitable coastal nursery
habitats where they may settle. After one to three months on the nursery grounds, the
young prawns move offshore onto the fishing grounds.

During 2006 the catch of prawns was 5310 tonnes, comprised of 3117 tonnes of banana
prawns, 1802 tonnes of tiger prawns, 363 tonnes of endeavour prawns and 28 tonnes of
other prawn species . This level of prawn catch was significantly lower than the highest
catch recorded in 2000-01 of 9278 tonnes.

It is worth noting that there have been a number of gear reductions implemented in the
fishery over time. The most recent was a 25% reduction in headrope length that came
into effect at the start of the first season in 2005. As a result “catch rate”, measured in
terms of catch per unit effort (CPUE) being tonnes per day may be affected. Decreases
in CPUE, therefore, may not necessarily reflect poor catch rates or low abundances. The
banana fishery catch rate increased slightly from 0.88 t per day in 2005 to 0.96 t per day
in 2006. The nominal catch rate for the tiger fishery increased to 0.31 t per day for 2006
from 0.25 t per day in 2005, while the effective catch rate increased to 0.21 t per day in
2006 from 0.12 t per day in 2005.

The other target species listed in the NPF Management Plan are squid and scampi
however given the low volume and the low value of squid taken by NPF trawlers, squid
is treated as a byproduct in this Harvest Strategy. Numerous other byproduct species
including bugs, scallops and various fish species are also taken during trawling


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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


operations. Approximately 40 tonnes of non-prawn bycatch was also landed in 2004-
05.

VALUE OF THE FISHERY
The NPF is the most valuable Commonwealth managed fishery and is one of the most
valuable fisheries in Australia. The annual gross value of production (GVP) of the
fishery has varied between $65 million and $168 million AUD. This can be attributed to
the fluctuating annual catch, season lengths, market conditions and foreign exchange
rates.

The real gross value of production (GVP) of the fishery in 2005-06 was $73 million.
The majority of the catch from the fishery is exported, predominantly to Japan however,
exports to China and countries within the European Union are increasing.

MANAGEMENT REGIME
The NPF is managed through a series of input controls, including limited entry to the
fishery, gear restrictions, bycatch restrictions and system of seasonal, spatial and
temporal closures.

To fish in the NPF operators must hold Statutory Fishing Rights (SFRs), which control
fishing capacity by placing limits on the numbers of trawlers and the amount of gear
permitted in the fishery.

There are two types of SFRs:
   • − a Class B SFR, which permits a boat to fish in the NPF; and
   • − a gear SFR, which limits the amount of net a fisher can use.

There are currently 35,479 gear SFRs issued for the fishery. The total number of Class
B SFRs in the fishery is 52.

Operators must hold both Class B SFRs and the appropriate number of gear SFRs for
the length of headrope they wish to use to operate in the fishery. There is a minimum
holding of 100 gear SFRs for each Class B SFR.

A gear SFR currently represents 5.625 cm of operational headrope for operators towing
twin gear and 5.0625 cm of headrope for operators towing quad gear or tongue nets.

The fishery currently has assessments for brown and grooved tiger prawns.
Assessments are also being developed for the banana and endeavour species. The tiger
prawn fishery is the most valuable component of the Northern Prawn Fishery and
management of the NPF is primarily based around this part of the fishery. Endeavour
and king prawns are generally caught as incidental catch of tiger prawn fishing
activities.

Under input controls, it is possible to manage the target species according to the lowest
common denominator, which is currently brown tiger prawns. The endeavour and king
prawn resources are generally protected by the management measures adopted for the
tiger prawn resource, as well as through spatial and temporal closures.




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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


The banana prawn fishery is managed by a fixed length season, with some in-season
management aimed primarily at extending the length of the season to increase the
economic return to the fishery in highly productive years.

CLOSURES
A comprehensive system of spatial and temporal closures is in place in the NPF to
address biological and economic objectives of the fishery (see Jarrett et al 2005).

A total of 2.1% of the total managed zone of the fishery is subject to permanent
closures, while 8.3% is subject to seasonal closures.

Closures in the fishery include permanent closures of seagrass beds and other sensitive
habitats and seasonal closures of juvenile prawn stock habitat are designed to coincide
with recruitment phases, and also to protect pre-spawning prawns. Closures are also in
place to ensure prawns are at a commercial size for harvesting.

A daylight trawl closure is in place during the second (tiger prawn) fishing season to
reduce the capture of spawning tiger prawns.

FISHERY INDICATORS

Data
A comprehensive data collection program has been established for the NPF to ensure
reliable information is available on which to base management decisions. Information
is maintained on all target prawn species taken in the NPF. The comprehensiveness of
the program is a product of the high value of the fishery, the management needs of the
fishery and the importance of stock assessment to determine the status of the target
species.

The data collection program is based on logbooks that provide for catch and effort data
to be recorded daily in logsheets. Processor records are obtained for landings data
which are used to verify the logbook catch.

Vessel gear details are also collected which tracks changes in gear and technology in the
fishery. This information assists in stock assessments and research being undertaken on
effort creep and fishing power studies.

This data forms the basis of the NPF’s fishery dependent research program. Targeted
fishery independent research, including annual fishery independent surveys for target
species and bycatch is undertaken in the NPF. Each year, a recruitment survey is
undertaken on the key fishing grounds of the Gulf of Carpentaria. A spawner survey is
undertaken during the mid-season break in winter on the western grounds of the Gulf.
These surveys started in 2003. These surveys have as yet, not been included in the tiger
prawn stock assessment as there are presently too few replicates to be meaningful. Since
the fishery is considering moving to ITQ by 2010, it is intended that these relative
indices will be incorporated into the TAC assessments.




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 Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007

Figure 2: Sources of data for Northern Prawn Fishery, and some routine data processing pathways

                                          Logbooks                            Processors               Owners (1988 to          Gear sheets in
      Annual Data                                                             (1969-92)                          Present)         logbooks
      Summary 1998-                                                                                   Landings
      present                                                                                                                         Vessel inspections
      Ad hoc management                               Annual validation/reconciliation/audit
      queries -not by species                                                                                      Gear audit
                                    GVP
                                                      1. Match geographical coverage of Logs &                                       Licensing information
                                                      Landings datasets                                             1992-99
                                                                                                                                     on vessel size etc
             AFMA                                     2. Compare catch totals boat by boat
                                                      3. Follow up discrepancies
                                                      4. Define audited "Landings"/boat on evidence
             CSIRO                                    5. Pro-rate all landings to currently defined NPF
                                                      boundaries




                                           Reconciled Landings         Time series of                 Logbooks time
                                            time series 1980-        adjustment factors                series 1970-
                                                 present               for imputation                    present                 Research survey data:
                                                                                                                                   vessel and gear
                                                                     Imputation -
                                                                     adjust for gaps in
                                                                     catch and effort
                                Banana prawn                         data
                                catch                                                                       Vessel and gear
                                predictions                                                                   time series
                                                                                                             1980-present
                                                                      Effort
                                                                      standardisation                                            Research data
 Annual Data                                                                                                                     species composition
 Summary
 to 1997
                          NORMAC/AFMA
  Update Fishery          Ad hoc queries for                             Link spatial
  Statistics tables       management                                     species data
  Pownall 1994

                          RESEARCH
                          Funded research projects under         NPFAG
                          NORMAC research priorities             Tiger prawn stock assessment
                                                                 Annual report on status of fishery




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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


Economic data is collected by ABARE on a regular basis to provide inputs to the NPF’s
bio-economic model.

Data Reliability
The CSIRO report ‘Accuracy of catch and effort data for the Northern Prawn Fishery’
concludes that annual landings in the NPF have been estimated reasonably accurately
since 1980 by combining information from logbooks to supplement landed weights
from prawn processing companies and trawler owners. There have been periods during
the early history of the fishery when not all operators provided logbook information. A
detailed augmentation process is used to estimate missing logbook information so that
the total logbook catch corresponds to the landings. This information is needed for
species specific stock assessments. A detailed investigation of possible errors in this
process has been undertaken by Dichmont et al (2001) and found to be small.

The NPF has a long time series of data available for scientific analysis. CSIRO holds a
copy of logbook data and annual reconciled landings since 1970. AFMA has had
primary responsibility for collecting, collating and verifying the logbook and vessel
register data and providing this data to CSIRO.

Economic data from the NPF has been collected by the Commonwealth government’s
economic research agency, the Australian Bureau of Agriculture and Resource
Economics (ABARE) since the 1980’s. Bi-annual economic surveys are carried out by
ABARE, aimed at capturing financial information from approximately 40% of the fleet.
The financial information is provided by NPF operators with small, medium and large
trawlers on a voluntary basis. The information collected in the surveys is used by
ABARE to calculate the economic performance of the fishery. ABARE survey
information is also used by the Department of Agriculture, Fisheries and Forestry to
assess the performance of AFMA in managing fisheries.

FISHERY MONITORING
The fishery has a number of monitoring processes in place which will continue under
this harvest strategy. These are:

 (a)   An annual Gulf of Carpentaria wide independent data collection program (at sea
       survey) which was implemented in the fishery in August 2002.

       The survey has two modules:
       • a January/February survey which provides data for a fishery independent
          recruitment index for banana, tiger and endeavour prawns; and

       •   a June/July survey which provides information to examine the spatial
           distribution in the fishery and attempt to quantify changes in fishing power,
           one of the key areas of contention with the current model.

       Scientific data is collected through these surveys for all target species and a
       range of bycatch species.

(b)    Scientific and crew member observer programs on commercial trawlers to
       collect data and to monitor bycatch.



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(c)       A fishery-wide Daily Catch & Effort logbook program for all target and
          byproduct species and to record interactions with protected species. Under this
          program, operators are required to record the location of fishing operations
          (latitude/longitude) for every day they fish and/or search, regardless of whether
          any catch is taken; the total number of shots for each fishing day; the
          species/product retained and size grade information.

(d)       Seasonal Landings Returns used to reconcile log book data (target and
          byproduct species) against commercial landings.

(e)       A gear monitoring program to monitor vessel fishing power and TED/BRD
          configurations. Mandatory data collected through the program includes vessel
          length; beam; depth; engine make and model; engine power; max. trawl RPM;
          Operating RPM; gear box reduction ratio; kort nozzle; propeller diameter and
          pitch; plotter make and model; sonar; max. speed; trawl speed (banana and tiger
          prawn fisheries); TED and BRD configurations.

(f)       Random comprehensive gear surveys to contribute to fishing power analyses
          and identification of new gear technologies.

(g)       VMS data to monitor position of vessels especially with respect to spatial and
          temporal closures.

(h)       Random enhanced VMS polling over a short period to monitor vessel speed.

(i)       ABARE surveys to collect economic data.


SECTION 3 - THE TIGER PRAWN FISHERY 3
Tiger prawns are caught predominantly in the second season. While tiger prawns remain
the target, endeavour and king prawns are predominantly caught incidentally. Bugs are
the main byproduct of this fishery. During this season and at specific moon phases,
some of the fleet also fish for red-leg banana prawns in the Joseph Bonaparte Gulf.

The operational gear (length of headrope/footrope) which is allowed to be towed in the
fishery each year is adjusted according to the annual tiger prawn stock assessment. In
the future, the output from the bio-economic model (which includes the biology of tiger
and endeavour prawns, and key economic variables) will be used to set the level of
standardised effort for the fishery.

OPERATIONAL OBJECTIVE
The operational objective of this HS is to attain long term maximum economic yield
(MEY) from the tiger prawn fishery.

It is noted that MEY is not static. In this HS, MEY is calculated as the effort level in
each year over a 7 year projection period that creates the largest difference between the




3
 For the purpose of this HS, both species of tiger prawns and both species of endeavour prawns comprise the ‘tiger
prawn fishery’

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    Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


total revenue generated from tiger and endeavour prawns and the total costs of fishing
for the tiger prawn fishery as a whole4.

INDICATORS
(a)      Stock size

         The tiger prawn fishery performance indicators are spawning stock size in a year
         (Sy) relative to the estimated spawning stock size at maximum sustainable yield
         (Smsy) and at maximum economic yield (Smey), i.e. the indicators are Sy /Smsy
         and Sy/Smey.

         The data that input to the above indicators include:

              •    Catch and catch per unit effort data
              •    Economic cost and revenue data

         As the value of Sy/Smey must be estimated for each species from the available
         data, the uncertainty associated with the estimate produced by the assessment
         model must be taken into account. Accordingly, the assessment model is used to
         determine an estimate of the distribution of Sy/Smey (i.e. the probability that the
         model assigns to different values of this ratio). The median value5 of Sy/Smey
         from this distribution is then used as the value of this economic performance
         indicator. Similarly, the median value of the estimate of Sy/Smsy is taken as the
         value of the sustainability performance indicator.

(b)      Effort

         The tiger prawn fishery performance indicators for fishing mortality for each
         species are based on the estimates of the effort level within the year (Ey), the
         effort required to attain maximum economic yield from the tiger fishery (Emey)
         and the theoretical effort that would produce maximum sustainable yield for that
         species (Emsy). Each of these variables is derived from the stock assessment and
         bioeconomic models using logbook and, in the case of Emey, economic data.
         The economic performance measure for effort adopted for each species in the
         tiger prawn fishery is Ey/Emey, while the overfishing performance measure is
         Ey/Emsy.

FISHERY MONITORING
(a)      An annual fishery-independent data collection program based on two modules:

         •        a January/February survey which provides data for fishery-independent
                  recruitment indices for banana, tiger and endeavour prawns;

         •        a June/July survey which provides information to examine the spatial
                  distribution of the stock and to attempt to quantify changes in fishing
                  power, which is a key area of contention in the current model;
4
  Based on the definition of MEY in Grafton, Q.R., Kirkley, J., Komaps, T., Squires, D. 2006.Economics for
Fisheries Management. Ashgate Publishing, Hampshire.
5
  Previous modelling of the assessment results produced a skewed, rather than normal distribution thus requiring use
of a median (the midpoint of the values) rather than an average.


                                                                                                                16
  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007



        At present, these data are being used independently of the assessment as a check.

(b)     A fishery-wide Daily Catch & Effort logbook program for tiger, endeavour and
        king prawns, including vessel gear sheets.

(c)     Seasonal Landings Returns (data used to ground truth the logbook data).

(d)     Reported industry data on tiger prawn catches in the first (banana prawn) season.

(e)     Economic data collected by ABARE every second year.

FISHERY REFERENCE POINTS
(a)     Stock size

        In principle, a stock will be declared overfished if it falls below 0.5Smsy.
        However, prawn annual recruitment is highly variable compared to longer-lived
        species. This means that the reference point can not be applied using a single
        year’s statistic. For the tiger prawn fishery, the limit reference point for each of
        the two species of tiger prawns is the moving average of Sy/Smsy over 5 years.
        Thus, if the moving average falls below 0.5, the species is considered
        overfished.

        The appropriateness of the decision rule (described below) in light of the harvest
        strategy policy has been confirmed using the MSE.

        To assess whether the tiger prawn fishery has achieved the operational objective
        of attaining MEY, the tiger prawn fishery Target Reference Point is Smey. It is
        recognized, however, that the indicator Sy/Smey will vary considerably from
        year to year as a result of large inter-annual variability in recruitment and in the
        values of economic parameters.

        NORMAC 64 agreed to this reference point (Smey) as a point to be adopted
        for testing using the MSE.

  (b)   Effort

        The target reference point for the economic performance measure of effort is
        Ey/Emey = 1. A value greater than 1 indicates that effort for the year was in
        excess of that estimated to be required to produce MEY. Note, however, that
        because of natural inter-annual variability that Ey/Emey will exhibit
        considerable variability. Also, the yearly pathway to MEY is part of the bio-
        economic model calculation and therefore, unlike Bmsy-type reference points, a
        non-linear effort pathway.

        The limit reference point for fishing mortality is currently set as:

        Moving average of Ey/Emsy over 5 years = 0.5




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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


            That is, the fishery is considered to be experiencing overfishing if Ey is in
            excess of the effort that would be expected to result in a stock that is overfished,
            i.e. moving average of Sy/Smsy over 5 years ≤ 0.5.

METHOD OF ASSESSMENT
The Northern Prawn Resource Assessment Group (NPRAG) has responsibility for
assessing the dynamics and status of NPF species. NPRAG comprises fishery
scientists, industry members, fishery economists, and the AFMA NPF Manager. The
Group uses data from both logbooks and research in its stock assessment work.

Tiger Prawns
The NPRAG currently monitors trends in overall catch, catch per boat and catch per
unit of effective effort for tiger prawn species. Persistent downward trends over three or
more years in any of these parameters are investigated to determine whether there is a
biological problem with stocks.

The strength of NPF stock assessments is based in the NPRAG’s use of models,
particularly those used to assess tiger prawns. Most of the models have shown that tiger
prawns exhibit a strong stock-recruitment relationship. The models are peer reviewed
regularly and include:

•      Wang and Die model (1996)
•      Haddon Model (2000)
•      Modified Wang and Die model (2000)
•      Dichmont and Punt model (2001)
•      Kompas (2005) and Dichmont et al model (2003)
•      Kompas/ Dichmont et al combined bio-economic model (2007)
•      Kompas/Dichmont et al length based model (2007)

Research into improved stock assessment techniques is given a high priority in the NPF.
The drive for continuous improvement has resulted in a shift from providing results as
deterministic outcomes, to providing results of a stochastic nature that allows
NORMAC and AFMA to more realistically consider uncertainty in future management
decisions.

The fishery currently has separate biological and economic assessments for brown and
grooved tiger prawns. Assessments on these two species and endeavour prawns 6 will,
after 2007, be undertaken using an annual bio-economic model based on Kompas and
Dichmont to estimate Sy/Smsy for each species and the combined value of MEY over
all four species.

The status of the Northern Prawn Fishery tiger prawn stocks is assessed by considering
a number of management related quantities. These included estimates of the Smey,
Smsy (i.e. the spawning stock (S) that produces the MSY) the fishing effort (E) that
produces maximum sustainable yields (Emsy), the ratio of the spawning stock biomass
in the current year (Sy) to the Smsy (Sy/Smsy), and the ratio of the present effective
effort (Ey) to Emsy (Ey/Emsy).



6
    The endeavour assessment model is still under development and currently includes considerable uncertainty

                                                                                                                18
  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


Using the Dichmont et al. (2003) model, estimates of MSY, Smsy and Emsy are
calculated using the estimated recruitment and spawning structure derived from the
catch and within-year effort pattern, which is an improvement on the method used by
Wang and Die (1996).

Three fishing power series are currently used in the assessment. The first two are
constructed using one fishing power base model with optimistic (Base Case Low) or
precautionary (Base Case High) parameter values. The third (Spatial High) is a
sensitivity test and uses a different fishing power model that includes spatial aspects of
the fishery. In 2006, the NPRAG recommended that the Base Case High is the
appropriate model to be used. The 2007 NPRAG has recommended that the bio-
economic model only uses Base Case High as the Base Case. Two catchability values
are currently used in the assessment however the more precautionary of these is the
catchability parameter estimated in Wang 1999 (q) and this assessment will be used to
set the effort in the future.

The separate biological and economic models were used for the tiger prawn stock
assessment using data up to (and including) 2006 due to the significant changes in the
NPF fleet structure arising from the 2006 NPF Structural Adjustment Program. The
combined bio-economic model will be used for future assessments and the outputs will
be applied to the bio-economic assessments (including the 2007 assessment) undertaken
from 2008 and onwards. The inputs into the bio-economic model will include logbook
data and economic data.

The conclusions of the stock assessment are based on the new species split method
described in Venables et al. being used in the assessment (2006).

The abundance indices estimated from the surveys are not currently incorporated into
the assessment as the time series (four years) is too short. The survey data will be
included in future stock assessments subject to NPRAG endorsement.

The results of the NPRAG’s assessment process are published annually in NPF Fishery
Assessment Reports. These reports include analysis of previous and current stock
assessments, implications of prawn stock assessments for management, the economic
status of prawn stocks, environmental and ecological factors affecting prawn stocks and
current and future research within the NPF.

Endeavour Prawns:

Two species of endeavour prawns (blue and red endeavours) are caught in the NPF,
however blue endeavours are generally more predominant. No assessment of endeavour
prawns is available for the NPF beyond that of Park (1999), however an enhanced
model is currently being developed concurrently with the bio-economic model for the
NPF. Catches of endeavour prawns are considered along with tigers when assessing
MEY in the economic model. In this model, endeavour prawns are treated as being an
“incidental catch” of the tiger prawn fishery, i.e. their catches result from the effort that
is targeted towards tiger prawns. The presently-funded project of Dichmont and
Kompas will produce a combined MEY for endeavour and tiger prawns under input
controls during 2007.



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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


There is limited spatial separation between tigers and endeavours (with the exception of
the ‘spikes’ in redtailed endeavours which occur very occasionally) and the correlation
between tiger and endeavour prawn catches is quite high. As endeavour prawns are
generally taken as an incidental part of the tiger prawn catch, effort controls which
apply to tiger prawns also apply to endeavour prawns.

It is not possible at this time to accurately assess the state of either of the endeavour
prawn stocks or their limit reference points. The management strategy evaluation tests
have shown (using an early endeavour prawn assessment model) that controlling the
effort on tiger prawns is effective at sustaining endeavour prawn stock status.

The target reference point for the fishery is governed by the MEY target, which takes
into account all four species of tiger and endeavour prawns7.

It should be noted that the model of the endeavour prawns is at a very early stage of
development. Until its performance (i.e. the accuracy of its predictions) has been
validated by the NPRAG and the model has been sufficiently refined for its predictions
to be accepted as reliable, the endeavour assessment will not be used for decision
making beyond inclusion as an economic catch in the bio-economic model.

Decision Rules for the Tiger Prawn Fishery8
The following decision rules will be used in the management of the tiger prawn fishery
(2 species of tiger prawns and 2 species of endeavour prawns) to pursue the fishery
Target Reference Point (Smey):

Adjustment
The following method will be used to calculate the appropriate level of standardised
effort to be used in the fishery:

1.       A bio-economic assessment will be undertaken every alternate year, optimising
         the effort over a seven year moving window to maximise profits.
2.       Standarised effort for the fleet in any one year can not be less than half of the
         standardised effort targeted at brown tiger prawns in 2006.
3.       Provided the limit reference point for either species of tiger prawns is not
         triggered, the effort in standarised days for each fleet (brown and grooved) for
         the first 2 years from the bio-economic assessment will be be applied.
4.       Effort controls will be applied through the use of spatial and temporal closures,
         and gear; or any combination of these inputs.
5.       If the LRP is triggered, there will be no target fishing on the target species
         concerned. Spatial and/or temporal measures will be used to prevent target
         fishing on species below the limit reference point.
6.       If effort changes are to be implemented through gear, the change in effort versus
         the change in gear will be calculated empirically.



7
  Due to the lack of biological information on red endeavour prawns, endeavour prawns are assessed as a
group using blue endeavour prawn biology. The MSE tests showed this is precautionary towards both
species.
8
  For the purpose of this HS, both species of tiger prawns and both species of endeavour prawns comprise
the ‘tiger prawn fishery’ . In the context of the MEY target, endeavour prawns are treated as an economic
bycatch of the tiger prawn fishery

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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007



7.       The figure below will be used to calculate any required change in total gear.




      Figure 1: The relationship between relative increases and reductions in catch for a relative
      change in headrope length (Venables et al 2007).

As noted earlier, with the large interannual variability of recruitment that is experienced
in a short-lived species such as prawns, it is expected that, on occasions, stock size may
fall below 20% of the average level of virgin stock size. The above decision rule will be
tested using the MSE to ensure that, if the rule is applied, there is 80% or greater
probability that, for all four species, the value of the 5-year moving average of Sy/Smsy
does not fall below 0.5. However, should the monitored value of the moving average of
Sy/Smsy over 5 years actually fall below 0.5, the data will be examined critically by
fisheries scientists and the NPRAG will assess whether there is need for a more
precautionary management response than that which is called for by the application of
the above decision rule.



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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


Closures
   • Spatial and temporal closures will be used for biological/ecological protection
      (eg seagrass, habitat protection), for prawn size protection (eg juveniles, pre-
      spawning adults) and to maximize prawn growth/ increase economic return.

                  •       Closures will be introduced and/or amended by NORMAC according to the
                          protocols in the NPF Closures Review 2005 report, “Documenting the history of
                          and providing protocols and criteria for changing existing or establishing new
                          closures in the NPF”.

                  •       A daylight trawl ban will be used to protect spawning tiger prawns in the second
                          (tiger prawn) season.

Tiger Prawn Trigger Limit
A trigger limit of 39.6 tonnes of tiger prawns will apply in the first (banana prawn)
fishing season each year despite any chances in the length of the fishing season. If the
trigger limit of 39.6 tonnes is exceeded, fishing time will be subtracted from the start of
the second (tiger prawn) season based on the following graph using the total tiger line:
                  1800


                  1600


                  1400


                  1200


                  1000
  C a tc h (t )




                   800


                   600


                   400


                   200


                      0
                          1   2   3   4   5   6   7   8   9 10 11       1    2    3     4   5   6   7   8   9 10 11 12 13 14 15 16 17 18
                                                                                 Week

                                                                    Tigers       Grooved        Brown




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  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007




King Prawns
There is no formal stock assessment for king prawns.

King prawns are predominantly caught in August. Concerns were expressed in 2004-5
regarding reductions in king prawn catches however, it is possible that reductions in
catches have corresponded to the fishery being closed in August from 2002 to 2004.
The NPRAG was unable to resolve the reason, but since the fishery had been closed in
August for several years, this was seen as adequate protection. King prawn catches
increased when the fishery was re-opened in August in 2005.

Sustainability controls are currently in place to address fishing effort on king prawns
with several areas, where a large percentage of kings were historically caught, now
closed to fishing.

Effort on king prawns is controlled by the effort determined for the tiger prawn fishery.

Decision Rules for King Prawns:
   • King prawns will be monitored through both the fishery independent surveys
       and the fishery log book and seasonal landings programs to ascertain changes in
       catches and abundance. Changes in king prawn abundance will be evident from
       the survey data over a 4 to 5 year time series. (Need to include more information
       on the closures).
   • Appropriate management measures (including additional spatial closures), will
       be implemented to protect king prawns if a consistent decline in abundance is
       detected over a three year period.


SECTION 4 - THE BANANA PRAWN FISHERY

OPERATIONAL OBJECTIVES
To: (a)       allow sufficient escapement from the fishery to ensure an adequate
              spawning biomass of banana prawns (based on historical data).
       (b)    maximise the economic return from the fishery within the above
              parameter.
       (c)    minimize the take of tiger prawns in the banana prawn season.


INDICATORS
   •     Banana prawn catch and catch per unit effort data.
   •     Reported industry data on banana prawn catches during the 4th week of the
         season.
   •     Tiger Prawn incidental catch.




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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007




FISHERY MONITORING
1.      A fishery-wide Daily Catch & Effort logbook program for banana prawns.

2.      Reported industry data on banana prawn catches in the first (banana prawn)
        fishing season.

3.      Reported industry data on tiger prawn catches in the first (banana prawn) fishing
        season.

4.      An annual fishery independent data collection program based on two modules:

        •    a January/February survey which provides data for a fishery independent
             recruitment index for banana, tiger and endeavour prawns;

        •    a June/July survey which provides information on the spatial distribution of
             the fishery.

5.      Seasonal Landings Returns.

6.      Economic data collected by ABARE.


FISHERY REFERENCE POINTS (ABUNDANCE INDICATORS)
1.      An average catch rate across the fleet of no less than 500 kg per day per vessel at
        the end of the 4th week in the banana prawn fishing season.

2.      A trigger limit of 26.4 tonnes (6.6 t/week*4) of tiger prawns caught by the end of
        the 4th fishing week in the banana prawn season.

3.      An average catch rate across the fleet of no less than 500 kg per day per vessel at
        the end of the 6th week of the banana prawn fishing season.

4.      A trigger limit of 39.6 tonnes (6.6 t/week*6) of tiger prawns caught by the end of
        the 6th fishing week in the banana prawn season.

METHOD OF ASSESSMENT:
There is currently no formal stock assessment for banana prawns. The variability of this
resource means no clear stock-recruitment relationship can be determined and catch rate
data as an index of abundance is proving to be questionable. (Vance et al. 2003;
Rothlisberg et al. 2006). Analyses are complicated by the highly-variable catch per unit
of effort data which result from the schooling behaviour of the species. However,
recent work by Zhou et al 2007) in which the catches from the fishery were modelled as
outcomes of an overdispersed Bernoulli process, provides an approach that potentially
resolves the difficulty of relating cpue data to the abundance of the banana prawns and
thereby enables the development of a model that can be used for stock assessment of
this species. The results of a current modelling study, which will be completed in 2007,
will be reviewed by the NPRAG to assess the extent to which the approach should be
used in future stock assessments for banana prawns.

                                                                                        24
  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007



The fishery is currently controlled by a fixed season length of 6 weeks with in-season
management aimed at extending the length of the season to increase the economic
return to the fishery in highly productive years. Historical records indicate that the
banana prawn fishery is sustainable with an annual 6 week fishing season. The high
variability and environmental dependency of this species results in significant variations
in catch from year to year, and even in the years where there have been very poor
catches in some areas, the rebound in the stocks would indicate that the banana prawn
fishery is resilient. The recent reduction in fleet size is likely to reduce the ability of the
fleet to search for and catch banana prawns to the same extent they have done in the
past.

The 500 kg per day per boat catch indicator described in the decision rules below is the
criteria used to determine whether the season will be extended in highly productive
years. This catch indicator was derived by taking an average of the catches of the fourth
fishing week in the most productive banana prawn seasons over a 10 year period and
divided by the number of boats.

There is limited incidental catch of tiger, endeavour or king prawns during the banana
prawn season due to the extensive spatial closure in place to protect tiger prawns and
the industry agreement to minimize the targeting of tiger prawns during this season. A
catch limit for tiger prawns taken in the banana season is in place, based on advice from
the NPF RAG on the definition of acceptable levels of tiger prawn catches in the first
half and a sliding scale of trade-offs between catch to time during the banana prawn
season. NORMAC has adopted the definition of ‘an acceptable level’ of tiger prawn
catches as being 6.6 tonnes per week for 6 weeks (39.6 tonnes) as recommended by the
NPRAG. If incidental tiger prawn catches during the banana prawn season are above
that level, the penalty across the fleet is loss of fishing time in the second half (August).

AFMA Management analyses industry catch reports after the fourth fishing week to
determine which of the following decision rules are to be applied.

DECISION RULES
The Banana prawn fishery is managed by spatial and temporal closures. The fishing
season opens for six weeks at a starting date between 15th March and 15th May.

In-season Management:

1st Extension (4 to 6 weeks)

    (a)   If the average daily catch rate of banana prawns for the 4th week of the first
          season exceeds or equals 500 kg/boat/day;

    AND

    (b)   If the pro-rata total tiger prawn catch for the whole 4 weeks is less than 26.4
          tonnes (6.6 t/week*4);

    THEN

    (c)   The season is extended for a further 2 weeks;

                                                                                            25
     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007



      AND

      (d)     All existing spatial closures and other management measures will be extended.

To facilitate the assessment of whether an extension to the season is appropriate based
on the decision rule, a “representative sample” of the catch rates for the season across
the fleet is required. This decision rule is applied only if all catch data (kg/day, or total
catch and total days) for the whole fleet (or >95% of NORMAC members and advisors)
is supplied for the period of the 4th week of season by 3 days after the end of that
week.

This information can take the form of:

1.          Either

            (a)      Providing a copy of the logbooks from each of these boat which are
                     fishing for week 4 to AFMA, which shows the catch of banana and tiger
                     prawns per day fished;
            Or

            (b)      Providing company records indicating the total catch (broken down by
                     banana and tiger prawns) for week 4 and the number of days fished per
                     boat during that week.

            (c)      If the fishery is NOT extended, the banana prawn season will close at the
                     end of 6 weeks.

2nd Extension (6 to 8 weeks)

      (a)     If the average daily catch rate of banana prawns for the 6th week of the first
              season exceeds or equals 500 kg/boat/day;

      AND

      (b)     If the pro-rata total tiger prawn catch for the whole 6 weeks is less than 39.6
              tonnes (6.6 t/week*6);

      THEN

      (c)     The season is extended for a further 2 weeks;

      AND

      (d)     All existing spatial closures and other management measures will be extended.




                                                                                           26
     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


To facilitate the assessment of whether an extension to the season is appropriate based
on the decision rule, a “representative sample” of the catch rates for the season across
the fleet is required. This decision rule is applied only if all catch data (kg/day, or total
catch and total days) for the whole fleet (or >95% of NORMAC members and
advisors) is supplied for the period of the 6th week of season by 3 days after the end
of that week.

This information can take the form of:

2.         Either

           (a)      Providing a copy of the logbooks from each of these boat which are
                    fishing for week 6 to AFMA, which shows the catch of banana and tiger
                    prawns per day fished;
           Or
           (b)      Providing company records indicating the total catch (broken down by
                    banana and tiger prawns) for week 6 and the number of days fished per
                    boat during that week.

           (c)      If the fishery is NOT extended, the banana prawn season will close at the
                    end of 8 weeks.

The industry should note that the total tiger prawn catch trigger limit for the first
(banana prawn) season remains at 39.6 tons.


SECTION 5 - OTHER TARGET SPECIES & BYPRODUCT

SCAMPI
There is no current formal stock assessment for Scampi.

Scampi is taken from a deepwater area on the edge of the AFZ north of Melville Island
and is targeted during NPF prawn trawling closure periods. An average of only six NPF
trawlers (less than 5% of the total NPF fleet)9 has targeted scampi each year. This is a
result of the high cost associated with travel to and from the scampi grounds, and the
restricted market opportunities for sale of the catch. Average scampi catches from 2002
to 2004 were 27 tonnes per annum.

Historically, the total number of fishing days spent targeting scampi has been generally
static (within 10%). Given the low catches of scampi and the small number of boats
which take scampi the species is considered to be ecologically sustainable and it is
likely, given the recent NPF restructure, that even fewer boats will fish for scampi in the
foreseeable future.




9
    Fleet size at June 2006

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     Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007




DECISION RULES FOR SCAMPI

A total number of fishing days will be allocated for access to the scampi resource based
on an average number of fishing days per year for the last five years. The average
number of days fishing for 2002 to 2004 was 120.

Any operator with an NPF boat SFR and an applicable number of gear units will be
entitled to access the scampi resource.

Scampi catch & effort will continue to be monitored through the formal fishery log
book.

A review of scampi catch and effort data will be carried out every 3 years to ensure that
catch and effort levels on the resource are sustainable.

If catch rates fall below a minimum catch rate or exceed a maximum catch rate for
three years in a row, an analysis of CPUE will be undertaken, taking into account both
spatial and temporal trends, to ascertain catch and catch rates. 10


SQUID
Squid is a target species under the NPF Management Plan, however given the low
volume and the low value of squid taken by NPF trawlers, this resource is treated as a
byproduct in this Harvest Strategy. (Refer below)

BYPRODUCT
Byproduct refers to any part of the catch which is kept or sold by the fisher but which is
not the target species. Specific harvest strategies have not been incorporated in this
document for byproduct species. However, management controls (size/trigger limits)
are in place for a range of byproduct species. In addition, as a number of byproduct
species are taken as an incidental part of the tiger prawn catch, the effort controls which
apply to tiger prawns also apply to these species.

The byproduct species which are incidentally caught in trawling operations and which
are retained because of their commercial value include:

      •   two species of slipper lobster (bugs) (Thenus indicus and Thenus orientalis),
          also referred to as bay lobster are exploited in areas where prawns are targeted;
      •   one species of scallop (Amusium pleuronectes), or delicate saucer scallops –
          taken incidentally in the NPF in coastal waters off the Northern Territory, from
          around Melville Island to west of Karumba and an area around Weipa.
          Approximately 40% of NPF trawlers retain their catch of saucer scallops for sale
          (Pender and Willing 1990). Trawlers target resting (post-spawning) or pre-
          spawning adults when meat yield and scallop condition are at their best (Joll
          1989); and

10
  Note: existing scampi catch and effort data is being further analysed to ascertain appropriate minimum
and maximum catch rate limits for inclusion in this HS. The NPRAG will review and make
recommendations on the outputs of this analysis for inclusion in the HS.

                                                                                                      28
  Draft Northern Prawn Fishery (NPF) Harvest Strategy Under Input Controls - 2007


   •    some larger fish species.

Byproduct limits or other management measures are in place for a large range of species
(Refer Table 1). These bycatch limits are implemented through Directions made under
section 25 of the Northern Prawn Fishery Management Plan 1995 (as amended).

A FRDC funded research project “Biology, dynamics and management strategy
evaluation for byproduct species in the NPF” is currently developing harvest strategies
for byproduct species, including squid. This project commenced in August 2006 and is
due to report to the NPRAG in August 2008.

The NPF Harvest Strategy under Input Controls 2007 will be amended in consultation
with NORMAC to incorporate appropriate harvest strategies for byproduct species
when they become available.

TABLE 1.               BY PRODUCT LIMITS & MEASURES

Species                                             Catch Limit
All lethrinidae                                     10 whole fish per trip
Narrow       barred    Spanish   mackerel
(Scomberomorus commerson)
Gold band snapper (Pritipomoides multidens
and P. typus)
All serranidae
Longtail tuna (Thunnus tonggol)
broad       barred    Spanish    mackerel
(Scomberomorus semifasciatus

Mud crabs (Scylla species)                          10 per trip

ornate tropical rock      lobster (Panulirus        6 per trip
ornatus)

saddle tail snapper (Lutjanus malabaricus)          500 kgs in total from
red snapper (Lutjanus erythropterus)                1 January to 30 June;
red emperor (Lutjanus sebae)                        and 50 kgs in total from
                                                    1 July to 31 December

two species of bugs (Thenus species)                75 mm minimum carapace, no
                                                    female bugs; all bugs retained
                                                    whole; no removal by any method
                                                    (including chemical) of eggs from
                                                    egg-bearing females

Squid                                               500 tonne catch trigger limit.
                                                    Appropriate        management
                                                    measures to be developed and
                                                    implemented if catch trigger is
                                                    reached



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Description: Northern Prawn Fishery (NPF) Harvest Strategy under Input Controls ...