Offshore Net and Line Fishery
DoE Conditions and Recommendations for WTO
Northern Territory Department of Primary Industry and Fisheries
Report on Progress against Conditions and Recommendations
Conditions
Condition 1: Operation of the Northern Territory Offshore Net and Line Fishery will be
carried out in accordance with the management regime for the fishery in force under the
Northern Territory Fisheries Regulations and the Northern Territory Fisheries Act.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries report that the
Offshore Net and Line Fishery continues to be managed in accordance with the
management regime made under the Northern Territory Fisheries Regulations and
Northern Territory Fisheries Act.
Condition 2: The Northern Territory Department of Resources to advise the Department of
Sustainability, Environment, Water, Population and Communities of any intended change to
the Offshore Net and Line Fishery management arrangements that could affect the criteria on
which Environment Protection and Biodiversity Conservation Act 1999 decisions are based.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries (previously the
Northern Territory Department of Resources) report that there have been no
changes to the management arrangements that would negatively impact on resource
sustainability.
However, DPIF advises that the management arrangements for the fishery are
currently under review by the Offshore Net and Line Advisory Group (ONLAG). As a
result of this review, it is proposed to amend the management arrangements for the
fishery to better align its operating practices with the “National guidelines to develop
fishery harvest strategies” (Sloan et al., 2014).
Condition 3: The Northern Territory Department of Resources to produce and present
reports to the Department of Sustainability, Environment, Water, Population and
Communities annually as per Appendix B to the ‘Guidelines for the Ecologically Sustainable
Management of Fisheries — 2nd Edition’.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries (DPIF)
provided annual reports to the Commonwealth Department of Environment during
the period of the approved wildlife trade operation declaration.
The most significant new information available on the Offshore Net and Line Fishery
(ONLF) is the results of recent stock assessments conducted by Dr Carl Walters in
coordination with DPIF (Grubert et al., 2013). Stock assessments for Blacktip Shark
(Carcharhinus limbatus and C. tilstoni), Spot-tail Shark (C. sorrah) and Grey
Mackerel (Scomberomorus semifasciatus) were undertaken and the results
demonstrate at current harvest rates catches of these species are within sustainable
limits. The stock assessment results for Blacktip and Spot-tail Sharks correspond
with the results of a separate study which used tagging to determine harvest rates
and population trends. This study also concluded that current ONLF harvest rates
for the target shark species are sustainable (Bradshaw et al., 2013).
The Northern Territory Department of Primary Industry and Fisheries has actively
participated in the development of the 2014 report, “Status of key Australian fish
stocks”. In this report the stock status for Northern Territory stocks of the Blacktip
shark species complex (C. tilstoni, C. limbatus and C. sorrah) were determined to be
sustainable (Johnson et al., 2014).
Recommendations
Recommendation 1:
The Northern Territory Department of Resources to improve the species based management
of sharks in the Offshore Net and Line Fishery through:
a) in conjunction with other relevant jurisdictions, improving the
o identification
o knowledge of species biology and ecology, and
o knowledge of catch composition
of sharks in the Blacktip complex and hammerhead shark complex and developing and
implementing species specific performance indicators and trigger reference points, where
appropriate, to ensure that catch levels of individual shark species are ecologically
sustainable.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries (DPIF) are
committed to species specific management in the Offshore Net and Line Fishery
(ONLF). It should be noted that the fishery is currently undergoing a review and
specific performance indicators and trigger reference points will be implemented for
each species and will be based on the best knowledge available surrounding
appropriate harvest rates.
To support the implementation of species specific management the ONLF logbooks
require all species, apart from Blacktip Sharks (Carcharhinus tilstoni and C. limbatus)
to be reported in both numbers and kilograms for each shot. This includes specific
reporting for the three hammerhead species encountered in the fishery (Eusphyra
blochii, Sphyrna lewini and S. mokarran). The logbooks also require a high degree
of spatial and temporal data with mandatory reporting of date, time, amount of gear
and latitude and longitude of each shot. This detailed level of logbook reporting
gives a DPIF a good understanding of the spatial and temporal nature of catch
composition in the ONLF.
Blacktip shark (C. tilstoni and C. limbatus) are reported as a species complex in the
ONLF logbooks. These two species are morphologically very similar, to the extent
that until recently, not even trained fisheries scientists could reliably distinguish
between the two species (Harry et al., 2012). Despite their morphological similarities
DPIF recognises that these two species are biologically very different and require
species specific management. In order to better understand the comparative
composition of these two species in the catch, DPIF has recently completed a project
that developed field methods to distinguish between C. limbatus and C. tilstoni. The
results of this project are summarised in the following abstract;
“Distinguishing between cryptic species is important for fisheries management and
also for conservation. This is especially true when setting catch limits where field
identification is important but challenging, as is the case for two carcharhinids in
Northern Australia. We collected 97 morphological measurements from 112
individuals of two species of cryptic Blacktip sharks to develop a model to identify
animals in the field. Species identity was confirmed by precaudal vertebrae (PCV)
counts revealing 95 Australian Blacktip Shark Carcharhinus tilstoni and 17 Common
Blacktip Sharks Carcharhinus limbatus. Identification was confirmed by molecular
analysis and we found 27 C. tilstoni x C. limbatus hybrids among the 112 individuals.
Of these 23 had C. tilstoni PCV counts and four had C. limbatus PCV counts. In the
absence of further information about hybrid phenotypes and for the purposes of this
study, hybrids were assigned to either C. limbatus or C. tilstoni based on PCV
counts. From the 97 morphological measurements, multivariate and machine
learning techniques were used to develop models to distinguish between the two
species. Discriminant analysis performed reasonably well (80% successful C. tilstoni
and C. limbatus identification), but, machine learning models performed better
discriminating between C. tilstoni and C. limbatus with 100% accuracy using six key
measurements (fork length, caudal-fin peduncle height, interdorsal space, second
dorsal-fin height, pelvic-fin length, pelvic-fin midpoint to first dorsal fin insertion).
Additionally, pelvic fin markings allowed us to distinguish reliably between the
species: C. limbatus had a distinct black mark greater than three percent of the total
pelvic fin area, while C. tilstoni had markings with diffuse edges, or had smaller or no
markings. The identification methods that showed most promise, i.e. machine
learning model and pelvic fin marking, were tested in the field achieving respectively
87% and 90% successful identification. The morphological differences identified here
are an important part of a multi-faceted approach to C. tilstoni and C. limbatus
identification and can inform the management and conservation of these
commercially important sharks. Similar identification issues exist in many fisheries
and the adoption of this approach can be applied broadly to improve the quality of
species identification in fisheries catches, monitoring, and the development of policy
for sustainable management of cryptic species by providing robust species
recognition.”
To facilitate the field application machine learning algorithm developed for Blacktip
Shark identification, DPIF designed a small computer program which can be installed
into any computer. This program will apply the algorithm and provide species
identification after the input of the six required measurements. Although this method
is suitable for observers and fisheries scientists, the time taken to collect six
measurements is probably not practical for professional fishers. However, the pelvic
fin black marking identification method described above, requires only a quick
inspection of the shark and could be used by fishers to distinguish between C. tilstoni
and C. limbatus with a reasonable degree of accuracy. Verification of both
identification methods are currently being trialled in the field by observers and initial
results are promising (Johnson, In Review). If these methods are successful an
education program will be rolled out to the ONLF fishers to assist with the
identification of these two cryptic species and to ensure that their logbooks are filled
out as accurately as possible. The results of this project indicated a ratio of five C.
tilstoni to every one C. limbatus in the ONLF catch. There were similar ratios
reported in (Ovenden et al., 2010), and this ratio was used in our recent stock
assessments (Bradshaw et al., 2013; Grubert et al., 2013) to determine the
comparative proportion of the catch of these two species.
The Department of Primary Industry and Fisheries continues to actively participate in
projects that provide greater information and assist with the sustainable
management of all species the ONLF interact with. A DPIF representative recently
participated in the International Union for Conservation of Nature’s (IUCN) Shark
Specialist Group workshop to update the Red List assessments for Australian
chondrichthyans. The Department of Primary Industry and Fisheries have authored,
co-authored or supported a number of recent projects that resulted in a peer review
papers / reports being published including (Salini et al., 2007; Welch et al., 2009;
Charters et al., 2010; Marshall, 2011; Tillett et al., 2011a; Tillett et al., 2011b; Field et
al., 2012; Tillett et al., 2012a; Tillett et al., 2012b; Tillett et al., 2012c; Bradshaw et
al., 2013; Field et al., 2013; Grubert et al., 2013; Geraghty et al., 2014; Johnson, In
Review). The Department of Primary Industry and Fisheries continue to actively
support and participate in work undertaken by universities, research organisations
and other jurisdictions which contribute to the knowledge that surrounds this fishery.
Recommendation 2:
The Northern Territory Department of Resources to develop a program to review the
management objectives, performance measures and trigger reference points on a regular basis
to ensure that they are appropriately precautionary.
DPIF response:
The Northern Territory Department of Primary Industries and Fisheries (DPIF) are
currently undertaking a review of the Offshore Net and Line Fishery (ONLF). The
output of this review will be management frame work whose objective will be to
implement a management system that utilises total allowable commercial catch
(TACC) and individual transferable quotas (ITQ’s) to sustainably and profitably
manage the ONLF.
As part of this management framework, management objectives, performance
measures and trigger reference points are being developed, using a risk
management approach and will be formally contained in the framework document.
Performance measures will prescribe specific actions that will take place if a trigger
point is breached. Trigger points will be in place for all target, by-product, by catch
and threatened, endangered and protected (TEP) species caught in this fishery.
It is anticipated that the management framework will be under constant review to
ensure that the performance measures and trigger points outlined in the framework
remain contemporary and take into account the best available knowledge. Input into
this review process will be facilitated though periodic meetings of Offshore Net and
Line Management Advisory Group (ONLAG), which is a group comprised of
Government, Industry and other stakeholders groups to advise the Director of
Fisheries on management of the ONLF On a more formal basis the management
framework will be reviewed every three to five years to ensure that the performance
measures for this fishery are meeting the management objectives.
Recommendation 3:
The Northern Territory Department of Resources to:
a) initiate a program to review and update the ecological risk assessment for the Offshore
Net and Line Fishery on a regular basis, and
b) make public the results of future ecological risk assessments.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries (DPIF) are
committed to having regular ecological risk assessments (ERA) to review and update
the existing ERA for the Offshore Net and Line Fishery (ONLF). It is acknowledged
that significant time has elapsed since the last formal ERA for this fishery. However,
as part of the management review process being currently undertaken, the risk
posed by the ONLF to all target, by-product, by-catch and threatened endangered
and protected (TEP) species has been assessed. The ONLF management review
will produce a management framework which will implement specific management
measures addressing the relative risk the fishery poses to all species it interacts
with. This management framework is being developed by the Offshore Net and Line
Fishery Advisory Group (ONLAG) which is comprised of representatives from
government, business, non-government organisations and commercial, recreational
and traditional fishing sectors. As the ONLF is undergoing this comprehensive
review, its management structure and the risk parameters associated with harvesting
the species caught are likely to significantly change. As this is the case DPIF will
delay undertaking a formal ERA until the new management arrangements have been
implemented.
It is acknowledged that there are significant benefits for the public and Industry to
have the results of an ERA available as a publicly available document. The nature of
the ERA process means that there are commercially sensitive issues that surround
the release of some information which in the past has restricted its release.
However DPIF commit to working with Industry to produce an ERA document that is
publically available.
Recommendation 4:
The Northern Territory Department of Resources to ensure that the management
arrangements for the Offshore Net and Line Fishery take account of any future listings under
the EPBC Act of species harvested, or permitted to be harvested, in the fishery.
DPIF response:
The Offshore Net and Line Fishery (ONLF) does not target any EPBC Act
recognised threatened or near threatened species. The International Union for
Conservation of Nature’s (IUCN) listing is based on global concerns of unregulated
fishing for these species. Further, none of the target species in the ONLF are listed
under the threatened categories by IUCN (IUCN, 2013).
Recommendation 5:
The Northern Territory Department of Resources to continue to collaborate with relevant
jurisdictions to pursue increased knowledge and complementary management of shared
species and stocks across jurisdictions.
DPIF response:
The Northern Territory Department of Primary Industry and Fisheries (DPIF) conduct
ongoing collaboration with other jurisdictions and consider it necessary for the long
term sustainability of the stocks that this collaboration remains ongoing.
The Department of Primary Industry and Fisheries continue to actively participate in
cross-jurisdictional projects that provide greater information on the ONLF and the
species encountered in this fishery. The Department of Primary Industry and
Fisheries have authored, co-authored or supported a number of recent projects
which have resulted in a peer review papers / reports being published as described
in more detail at our response to Recommendation 1. The Department of Primary
Industry and Fisheries also continues to support and participate in work with
universities, research organisations and other jurisdictions which contribute to the
knowledge that surrounds this fishery.
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