Western Port Fishery Assessment 2015

Technical Report (PDF Available) · December 2016with 15 Reads
DOI: 10.13140/RG.2.2.31667.48164
Abstract
Fisheries Victoria conducts periodic assessments of the status of key fish species and the fisheries they support. These assessments compile relevant data from recreational fishery monitoring programs, commercial fishery catch and effort reporting where available, scientific surveys and other data such as age and length composition, to support a ‘weight of evidence’ approach to assessing stock or fishery status. The information delivered through the stock and fishery assessment process is used by fisheries managers to consider the need for review of current management arrangements. This assessment relies largely on data collected from the recreational fishery from 1998 to 2014 as a buy-out of commercial licences and removal of all net fishing in 2007 removed most commercial fishing from Western Port. Therefore commercial data is limited and cannot be relied upon to inform stock status of species in Western Port. Formal assessment meetings are held to present and discuss the data with stakeholders. A formal assessment workshop on the Western Port fishery was conducted at Hastings, Victoria on 31 August 2015 and was attended by recreational fishers; representatives of the recreational fishing sector; Fisheries Victoria managers, scientists and compliance officers; external scientists; and a catchment management representative from Melbourne Water. Workshop participants supported maintaining the current management regime. The Western Port recreational fishery is the second largest marine recreational fishery in Victoria. Fishing is mainly boat-based but there is also a small amount of shore-based angling and some spearfishing. The main recreational species include: King George whiting, snapper, gummy shark, flathead, southern calamari and elephant fish. The fishery data presented at the August 2015 stock assessment workshop along with stakeholder input did not indicate the need for a review of fishery management arrangements, and participants supported maintaining the current management regime. The King George whiting fishery, while highly variable over time, is healthy. Although catch rates declined in the most recent year, they are predicted to improve again during 2016 due to above average abundances of pre-recruits (small juveniles) detected by fishery independent surveys in Port Phillip Bay in 2013. Snapper catch rates peaked in the mid-to-late 2000s but have declined to levels around the long-term average since, although the 2014/15 year was below average. Pre-recruit surveys in Port Phillip Bay have shown above average abundances of 0+ age snapper in 2012/13 and 2013/14 which should support increasing catch rates of smaller pinkie and adult snapper in Western Port over the coming years as the fish disperse away from Port Phillip Bay and into Western Port. Flathead catch rates (dominated by sand flathead) have been highly variable but an abundance of small fish is expected to support an increase in the fishery in coming years. Overall, based on catch rate and size-frequency indicators, the Gummy Shark fishery in Western Port is considered to be in good condition. Workshop participants were concerned that using ‘partial length’ to measure Gummy Shark was leading to inaccurate measurements and the retention of undersize fish and that total length is the better method. The weight of evidence supports a significant decline in the Elephant Fish fishery both in terms of catch rates and fishing popularity. Prior to the 1980s there were also very low abundances of Elephant Fish in Western Port which could be linked to environmental/habitat changes that influence the egg laying grounds in the eastern region of the embayment. Fishing effort based on standardised trailer counts at ramps shows relatively stable effort in recent years with above average trailer numbers in 2014/15. Trailer counts in recent years have been lower than in the early to mid-2000s, particularly for key western ramps. Survey of satisfaction and perception of Western Port anglers in 2014/15 indicated that the primary motivations for fishing were ‘enjoyment of the sport’ and ‘fish for food’. Over 80% of anglers were either ‘very satisfied’ or ‘somewhat satisfied’.
Western Port Fishery
Assessment 2015
Recreational Fishing Grants Program
Research Report
Western Port Fishery
Assessment 2015
December 2016
Recreational Fishing Grants Program Research Report
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
ii
Published by the Victorian Government, Department of Economic Development, Jobs, Transport and Resources
December 2016
© The State of Victoria, Department of Economic Development, Jobs, Transport and Resources, Melbourne 2016
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Preferred way to cite this publication:
Conron S, Hamer P and Jenkins G (2016) Western Port Fishery Assessment 2015. Recreational Fishing Grants Program
Research Report, Fisheries Victoria, Department of Economic Development, Jobs, Transport and Resources.
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Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Contents
Executive summary____________________________________________________________________ 1
Background __________________________________________________________________________ 2
Overview of Western Port 2
Recreational fishery 2
Commercial fishery 2
Previous assessments 2
Western Port fishery assessment 2015 ____________________________________________________ 3
Stock Assessment Process 3
Main Features of the Western Port Fishery and Current Situation 4
Data and Methods 5
Fishery status classifications 7
Recreational data collection summary 8
Status of the Western Port fishery _______________________________________________________ 8
King George Whiting 8
Snapper 9
Flathead (all species) 9
Gummy Shark 9
Elephant fish 9
Satisfaction and Perception 10
Fishing Effort 10
Management 10
Areas of concern 10
Acknowledgements___________________________________________________________________ 30
References __________________________________________________________________________ 31
Appendix 1 __________________________________________________________________________ 32
Western Port Fishery Species Stock Structure 32
Western Port Fishery Species Life Histories 33
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Executive summary
Fisheries Victoria conducts periodic assessments of the status of key fish species and the fisheries they support. These
assessments compile relevant data from recreational fishery monitoring programs, commercial fishery catch and effort
reporting where available, scientific surveys and other data such as age and length composition, to support a ‘weight of
evidence’ approach to assessing stock or fishery status. The information delivered through the stock and fishery
assessment process is used by fisheries managers to consider the need for review of current management
arrangements. This assessment relies largely on data collected from the recreational fishery from 1998 to 2014 as a buy-
out of commercial licences and removal of all net fishing in 2007 removed most commercial fishing from Western Port.
Therefore commercial data is limited and cannot be relied upon to inform stock status of species in Western Port.
Formal assessment meetings are held to present and discuss the data with stakeholders. A formal assessment
workshop on the Western Port fishery was conducted at Hastings, Victoria on 31 August 2015 and was attended by
recreational fishers; representatives of the recreational fishing sector; Fisheries Victoria managers, scientists and
compliance officers; external scientists; and a catchment management representative from Melbourne Water. Workshop
participants supported maintaining the current management regime.
The Western Port recreational fishery is the second largest marine recreational fishery in Victoria. Fishing is mainly boat-
based but there is also a small amount of shore-based angling and some spearfishing. The main recreational species
include: King George whiting, snapper, gummy shark, flathead, southern calamari and elephant fish. The fishery data
presented at the August 2015 stock assessment workshop along with stakeholder input did not indicate the need for a
review of fishery management arrangements, and participants supported maintaining the current management regime.
The King George whiting fishery, while highly variable over time, is healthy. Although catch rates declined in the most
recent year, they are predicted to improve again during 2016 due to above average abundances of pre-recruits (small
juveniles) detected by fishery independent surveys in Port Phillip Bay in 2013.
Snapper catch rates peaked in the mid-to-late 2000s but have declined to levels around the long-term average since,
although the 2014/15 year was below average. Pre-recruit surveys in Port Phillip Bay have shown above average
abundances of 0+ age snapper in 2012/13 and 2013/14 which should support increasing catch rates of smaller pinkie
and adult snapper in Western Port over the coming years as the fish disperse away from Port Phillip Bay and into
Western Port.
Flathead catch rates (dominated by sand flathead) have been highly variable but an abundance of small fish is expected
to support an increase in the fishery in coming years.
Overall, based on catch rate and size-frequency indicators, the Gummy Shark fishery in Western Port is considered to be
in good condition. Workshop participants were concerned that using ‘partial length’ to measure Gummy Shark was
leading to inaccurate measurements and the retention of undersize fish and that total length is the better method.
The weight of evidence supports a significant decline in the Elephant Fish fishery both in terms of catch rates and fishing
popularity. Prior to the 1980s there were also very low abundances of Elephant Fish in Western Port which could be
linked to environmental/habitat changes that influence the egg laying grounds in the eastern region of the embayment.
Fishing effort based on standardised trailer counts at ramps shows relatively stable effort in recent years with above
average trailer numbers in 2014/15. Trailer counts in recent years have been lower than in the early to mid-2000s,
particularly for key western ramps. Survey of satisfaction and perception of Western Port anglers in 2014/15 indicated
that the primary motivations for fishing were ‘enjoyment of the sport’ and ‘fish for food’. Over 80% of anglers were either
‘very satisfied’ or ‘somewhat satisfied’.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Background
Overview of Western Port
Western Port (Figure 1) is a marine embayment that supports diverse habitats such as seagrass, mangroves, reef/algae
and estuaries. In turn, these habitats support a high diversity and abundance of fish species, many of which form the
basis of important fisheries.
.
Figure 1: Map of Western Port, Victoria.
Recreational fishery
The recreational fishery in Western Port represents the second largest marine recreational fishery in Victoria.
Recreational fishing is mainly boat-based but there is also a small amount of shore-based angling and some
spearfishing. The recreational fishery is a multi-species, multi-method fishery that is primarily managed by size and bag
limits. The main recreational target species are: King George Whiting, snapper, gummy shark, flathead, southern
calamari and elephant fish, with additional species including Australian salmon and southern sea garfish.
Commercial fishery
There has been a commercial fishery in Western Port since the early 1900s but the license buy-back scheme and gear
restrictions to hook methods implemented in 2007 removed the majority of commercial fishery effort. Today, only a few
fishers use long lines and hand lines to mainly target gummy shark with minor catches of snapper, elephant fish,
Southern calamari and King George whiting. In recent years, the total commercial harvest from Western Port has
dropped to less than 1 tonne. Western Port commercial catch and effort data, therefore, no longer provides reliable
information on fish population trends in Western Port.
Previous assessments
The previous formal Western Port fishery assessment was in 2009. Participants at that workshop did not identify the
need for the fishery management arrangements to be reviewed but flagged several issues:
Increases in recreational fishing pressure on breeding elephant fish in Western Port was of concern, as Western
Port is the main nursery area for this species in Victorian waters. Elephant fish are slow growing and take
approximately five years to reach maturity, making them vulnerable to overfishing.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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The estimated retained catch of elephant fish by recreational anglers in Western Port from March–May 2008,
based on trailer counts, interviews, and reporting from charter vessels, was 45 tonnes, the majority being
mature females. Added to the commercial harvest from Bass Strait, there was a high risk that the current
harvest levels were not sustainable (Braccini et al. 2008).
Long-line fishers predominantly targeted snapper and gummy shark in Western Port. With the closure of
Western Port to commercial netting, it is important to ensure that recreational monitoring is adequate for
assessing the future status of fish stocks.
Western Port fishery assessment 2015
Stock Assessment Process
Fisheries Victoria has developed a process to conduct periodic formal assessments of the status of key marine and
estuarine finfish stocks and the fisheries they support.
The assessment process involves:
The synthesis of all relevant fisheries data,
Evaluation of available fisheries-independent monitoring and research data,
Convening a workshop for scientists, resource users and resource managers to assess the status of the stock/fishery
in question, and
Producing an assessment report which presents the scientific information and advice to facilitate fishery management
decision making.
The assessment process:
Provides scientific evidence on the status of the fish stocks and the environmental factors and harvest pressures that
influence stock abundance,
Provides opportunity to draw on the knowledge of stakeholder groups,
Underpins evidence-based decisions in an ecologically sustainable development management context,
Complements Victorian fisheries management planning processes, and
Ensures the fishery assessment process is accountable and transparent.
The assessment workshop held on 31 August 2015 was attended by:
Recreational fishers,
Representatives of the charter fishing sectors,
Fisheries Victoria managers, scientists and compliance officers, and
Catchment management and university representatives.
This report provides a summary of the outcomes of this assessment.
Aims of this assessment:
Review available data on recent trends in key fish species and the fisheries in Western Port,
Obtain views and information from local experts and compliance officers,
Identify issues requiring management and research consideration,
Discuss and raise other issues relevant to the performance of the Western Port fishery (i.e. habitat and environmental
issues),
Produce a report summarising the recent status of the Western Port finfish fishery, and
For the first time, conduct an assessment relying largely on recreational fishery sourced data.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Main Features of the Western Port Fishery and Current Situation
Characteristics of the Recreational Fishery
Based on boat ramp survey results from 1998-2015, fishers in Western Port are mostly licensed with 15% exempt (Table
1). Most fishers in Western Port fished more than 5 days per year, primarily by line fishing from boats (Table 1). The
majority of fishers lived in the greater Melbourne area but targeted most of their fishing efforts on Western Port (Table 1).
The majority (70%) of the catch is taken in summer and autumn (Table 1). The main recreational target species are: King
George whiting, elephant fish, snapper, flathead, Southern calamari, garfish, Australian salmon, and gummy shark
(Figure 2).
Table 1: Characteristics of Western Port fishers summarised from the recreational creel surveys, 1998-2015.
Characteristic Percentage of fishers Characteristic Percentage of fishers
Licenced-fishers >85% Licence-exempt
fishers
<15%
Avidity of
15+/5–14 days
per year
96% Avidity of
1–4 days per
year
4%
City dwellers 95% Country-
Inland-
Interstate-
dwellers
5%
0%
0%
Bay/Estuary
fishers
95% Inshore-
Offshore-fishers
5%
0%
Boat fishers 99% Shore fishers 1%
Line fishers 100% Non-line fishers 0%
Summer/Autumn
fishers
70% Winter/Spring
fishers
30%
Figure 2. Most common species retained by anglers with no specific target preference from recreational creel
surveys, 1998–2014.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Commercial Fishery
In 2015 there were 42 Western Port/Port Phillip Bay Fishery Access Licences but less than five operated in Western
Port. The commercial fishery catch had been gradually declining in Western Port until the netting buyout in 2007 after
which the catch was reduced by 99% (Figure 3). From 2000–2007 the annual commercial catch was between 25–73
tonnes (the latter in 2006/07), but from 2008 onwards the catch dropped significantly, and has been under one tonne
from 2010 onwards (Figure 3).
Before the buyout, eight key species made up 80% by weight and 96% by value of the catch. Unlike Port Phillip Bay,
garfish and mullet were important fishery species, reflecting the different (seagrass dominated) environment in Western
Port. The main fishing methods now are long and hand lines and the main target species is gummy shark with minor
catches of snapper, elephant fish, Southern calamari and King George whiting.
Figure 3. Total commercial catch in tonnes by fiscal year from 1978/79 to 2014/15.
Environment and habitat
Melbourne Water is the agency responsible for managing the waterways entering Western Port. In 2011, Melbourne
Water commissioned a science review of Western Port that identified research priorities to improve understanding of the
Western Port environment (Keough et al. 2011). Research priorities from this report have resulted in projects that have
now largely been funded and completed or are underway. One of the projects that was funded investigated the
dependence of fish on various habitats in the bay, including seagrass (Zostera and Amphibolis), algae and reef (Jenkins
et al. 2015). A further priority project has investigated the fish habitat and biodiversity information that is available from
the Western Port recreational creel survey (Jenkins and Conron 2015). This information included preferred areas of the
bay, habitats and depth distributions of key recreational fish species for different seasons and life-stages.
Data and Methods
Unlike previous fishery assessments of Western Port, the 2015 assessment relied largely on data collected from the
recreational fishery only. This is a significant change from past assessments that relied heavily on commercial catch and
effort and compositional (age-length) data.
There were 3 types of recreational fishing data collected for the assessment:
Total Catch Surveys
Total recreational catch surveys use a random sub-sample of the population as the sample frame and scale the results
up to the entire population. There have been three major surveys of this type since 2000:
The National Recreational Fishing Survey (2000/01) ,
The Recreational fishing in Coastal Victoria survey (2006/07),
The Elephant Fish total catch survey (3 months; 2008).
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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On-site (boat ramp) surveys
On-site (boat ramp) surveys provide time series of estimated catch rates and size composition for key species. Data on
social and economic indicators, fishing effort, habitat and environment, and management effectiveness is also collected.
Surveys were conducted in Western Port annually between November and April from 1998 to 2015 at Stony Point, Blind
Bight, Warneet, Tooradin, Cowes, Rhyll, Newhaven and Corinella (Figure 4).
Figure 4: Boat ramps included in the on-site surveys. Arrows indicate the key ramps surveyed.
The western ramp waiting times ranged from 1 hour 30 minutes (Stony Point) to 30 minutes (Blind Bight). The eastern
ramp waiting times ranged from 1 hour 45 minutes (Corinella) to 45 minutes (Cowes). Surveys were done as morning
and afternoon shifts. The fortnightly surveys were focused on fine weather weekend days to maximise the number of
interviews.
Angler diary program
The angler diary program provides information on catch rate and size structure of key recreational fishing species. These
anglers contributed to either the ‘General’ Angler Diary (GAD) or ‘Research’ Angler Diary (RAD) program.
Both the GAD and RAD methods require fishers to record in diaries:
Time spent fishing
Fishing location
Species targeted and caught
Fish lengths
Number of rods
Bait and hook type/sizes used.
The general diary method allows anglers to choose and vary their target species. These anglers provided
information on catch, effort and fishing gear data, as well as targeting preferences and catch composition. A total of
90 general anglers fished in Western Port.
The research diary method uses prescribed gear to target key species identified for them and targeted the whole
size range including undersize fish. These anglers provided a time series of information on size and age structure
and year-class strength (recruitment). A total of 45 research anglers fished in Western Port.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Performance Indicators
A series of performance indicators were used to assess the Western Port fishery:
Scientific monitoring of small juveniles (pre-recruit surveys) provides an indicator of replenishment of the
population by young fish (i.e. spawning success). Signals from pre-recruit monitoring of snapper and King
George whiting in Port Phillip also strongly influence the fisheries for these species in Western Port, either
because stocks are linked or because the environmental processes driving recruitment are the same.
Fishery catch rates are calculated by dividing the catch by the nominal effort (e.g. fishing hour or days) to give
an index of stock abundance. The data is also standardised for factors that can influence effort and catch
independently of fish abundance (e.g. weather or target species).
Length and age composition provides information on growth and survival, and can also indicate new
recruitment and overfishing. Diary anglers are an important source of this information as they measure fish
caught.
Effort and targeting patterns shows changes in fishing pressure, fishing behaviour, species vulnerability and
socio-economic value.
Fisher satisfaction/perceptions measures social value and identifies management performance issues. This
indicator relates to the overall fishing experience.
Fishery status classifications
A qualitative classification framework has been developed as an indicative summary of status for individual indicators
(Table 2). This classification approach provides an assessment of the recent status of individual indicators (primarily
catch rate time series, or other abundance proxies) relative to the long-term averages. The classifications readily identify
the condition of fishery and stock performance indicators and in particular highlight areas of concern from a management
and fishery performance perspective.
Table 2. Qualitative classification ratings and descriptions applied to individual fishery status indicators.
Indicator status
classification Description
Above average The indicator is 20% higher than the long-term average.
Average The indicator is within 20% of the long-term average.
Below average The indicator is 20% lower than the long-term average.
Limited Data A limited amount of information has been collected, or, the available data is
inappropriate/insufficient to confidently assess stock/fishery status, or, there are
inconsistent or contradictory signals in the data that preclude determination of stock/fishery
status.
Red flags identify specific concerns/issues or uncertainties regarding an indicator’s status.
* Long-term refers to the duration of the time-series.
The primary indicators used to determine fishery status are catch rates from the recreational fishery but other indicators
also contributed to the ‘weight of evidence’ approach.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Recreational data collection summary
For the 17 years from 1998 to 2014, 13,595 fishing trips in Western Port were surveyed by the boat ramp surveys, for a
total of 30,887 anglers and total trip hours of 69,523 (average of 5 hours per trip). Approximately two-thirds of fishing trips
were targeting either King George whiting or snapper, while very few trips were targeting flathead (Table 3). 4,539 fishing
trips in Western Port were undertaken by 97 diary anglers during the same period (Table 3).
Table 3: Sampling effort (number of fishing trips) for targeted species in the boat ramp and Anger Fishing Diary
Program survey of Western Port, 1998–2014.
Survey method King
George
Whiting
Snapper Flathead Gummy
Shark Elephant
Fish
Boat based fishers 5,386 4,319 185 1,909 1,347
Fishing Diary Program 2,882 855 62 432 131*
Note: Diary anglers did not undertake fishing trips targeting elephant fish after 2003 .
Status of the Western Port fishery
King George Whiting
The Western Port King George whiting fishery has historically shown cycles in catches with peaks at about 10-year
intervals similar to Port Phillip Bay and Corner Inlet (Figure 5). This is consistent with the influence of climatic variation,
primarily variation in the westerly winds over winter/spring on the supply of larval stages from coastal spawning areas
well to the west and the subsequent recruitment of juveniles into Western Port (Jenkins 2005).
Recreational catch rates (nominal) declined from the most recent peak in 2011/12, to be at the long-term average in
2014/15, the most recent year included in this assessment (Figure. 6). However, similar to Port Phillip Bay and Corner
Inlet, shortly after this assessment, catch rates began to increase again during 2016 (see Conron et al. 2016, Hamer and
Giri 2016). The reports of recent higher catch rates are consistent with the strong recruitment of post-larvae recorded in
the Port Phillip Bay pre-recruit (post-larval) survey in 2013 (Figure 7). The increased catch rates are expected to occur
through 2016 and into 2017, after which they are predicted to drop as fish from the strong 2013 cohort emigrate from
Western Port to coastal waters during 2017/18.
Recreational King George whiting catches in Western Port in better performing years were characterised by bags of at
least 5 fish per boat for about 50% of trips and at least 10 fish per boat for about 30% of trips (Figure 8). Average catch
rates by anglers participating in the diary program have been sustained at a higher level due to the influence of a few
highly effective expert anglers targeting larger fish in southern Western Port (Figure 9). However, when these anglers are
excluded from the analysis, the historical catch rate variation and recent decline from 2011/12 is consistent with the boat
ramp survey (Figure 9).
Length-frequency data from the diary angler program also shows a group of larger whiting (40-50 cm TL, total length)
moving through the fishery (predominantly taken by the expert anglers in southern Western Port), a distinct shift in the
modal size from 33 cm TL in 2012/13 to 37-38 cm in 2013/14 and 2014/15, and some new recruitment at 23-30 cm TL in
2014/15 (Figure 10). The shift in size to larger fish was supported by the opinions of anglers that size had increased over
the several years prior to this assessment (Table 5).
Overall, while the most recent catch rate indicators are at around the long-term average level, based on the expected
new recruitment into the fishery, the productivity of the Western Port King George Whiting fishery is expected to improve
over the next 1-2 years (Table 4).
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Snapper
The recent trend for the recreational snapper fishery, as seen in boat ramp surveys and angler diaries, has been a
decline in catch rates since the peak in 2012–2013 (Figures 11and 12). The most recent catch rate data in 2014/15 is
now just below the long-term average and well below the highest catch rates since the data collection began in 1998/99
(Figures. 11and 12).
Pre-recruit surveys in Port Phillip Bay (the main nursery area that supplies larger snapper to Western Port, Hamer et al.
2011) showed above average abundances of 0+ age snapper in 2012/13 and 2013/14, and prior to that, average to
above average numbers from 2007/08 to 2009/10 (Figure 13). These cohorts should support increasing catch rates of
smaller pinkie and adult snapper in Western Port over the coming years. The adult snapper fishery in Western Port (fish
>40 cm TL) in 2014 was still dominated by the two historically large cohorts emanating from spawning in 2000/01 and
2003/4 (Figures. 13 and14).
Catches of adult snapper in better performing years were characterised by catches of at least 3 fish per boat by
about 30% of trips surveyed and catches of at least 5 fish for about 20% of trips (
Figure 15). Catches of “pinkie” snapper in better performing years were characterised by catches of at least 3
fish per boat for about 50% of trips and at least 5 fish by about 40% of trips (
Figure 15).
Length-frequency data from the diary anglers in 2012/13 shows modes at 33, 37, and 45 cm TL; (Figure. 16) that mostly
likely correspond to the three average to above average cohorts from the Port Phillip Bay pre-recruit survey (i.e. 2009/10,
2008/09 and 2007/08; Figure. 13). The overall length ranges and composition for 2013/14 and 2014/15 show new
recruitment of small snapper between 18-25 cm and a broad range of lengths to a maximum of 95 cm (Figure. 16).
Overall, based on pre-recruit and catch rate indicators, the Western Port snapper fishery is considered to be at around
average levels but with an increase in catch rates, particularly of smaller fish, expected over the coming 1-3 years (Table
4).
Flathead (all species)
Recreational catch rates for flathead (all species, but dominated by sand flathead) in Western Port have been below the
long-term average from 2012/13 to 2014/15 but since 1998 have been highly variable, with four peaks periods: 1998,
2001-2002, 2006, 2010-2011 (Figure 17). The recent drop in catch rates is therefore not unusual or likely to be indicative
of ongoing decline.
Length-frequency data has been consistent since 2012/13 with the notable exception of the numbers of smaller flathead
(<25 cm L) appearing in the 2013/14 sample. This indicates some new recruitment into the fishery which should support
increased catch rates in coming years (Figure 18).
Overall, based on catch rate and size-frequency indicators, the stock is considered to be at around average levels with
an expected increase in catch rates of legal flathead over the next 1-3 years (Table 4).
Gummy Shark
Catch rates of gummy shark for the boat ramp and angler diary programs have increased since 2011 (Figure 19 and
Figure 20). However, while the boat ramp surveys indicate recent catch rates that are above the long-term average and a
notable peak in 2013, the diary angler catch rates were only just at the long-term average in 2014/15 and did not show a
peak above the long-term average in 2013 (Figure 19, 20). Both programs, however, show peaks in catch rates around
2009-2010. In the better catch rate years (2010, 2013) for the boat ramp surveys, anglers retained 1 or more gummy
shark per boat trip on 50-60% of targeted gummy shark trips (Figure. 21). Length-frequency data for gummy shark is
limited in terms of numbers of samples per year but has been consistent since 2010/11 (
Figure 22).
Interpretation of catch rates for gummy sharks in the boat ramp surveys is complicated by the low daily bag limit of two
fish (gummy shark/ school shark combined) per person. The two catch rate time series, however, indicate that the status
of gummy shark is consistent with the long-term average (Table 4).
Elephant fish
Elephant fish catch rates for the boat ramp surveys have declined continuously since 2007 and were at the lowest
recorded in 2014/15 (Figure 23). Interpreting this data is, however, challenging because the daily bag limit was reduced
from 3 to 1 in 2008. This effectively caps the catch and, based on comments made at the workshop, has been a
disincentive for targeted fishing as indicated by a reduction in targeted elephant fish trips since 2008, particularly in the
east of Western Port (Figure 24).
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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While there is consensus amongst fishers at the workshop that elephant fish abundance in Western Port has declined
greatly since the early-mid 2000s, the ongoing status of the population is difficult to gauge from the boat ramp survey
catch rate data under the current bag limit. Data on length-frequency was also limited by reduced targeting and low
catches but was consistent across the available time period (Figure 25). Other evidence, such as a contraction in the
area where elephant fish are caught to the Rhyll Basin (Jenkins and Conron 2015), and the opinion of expert fishers that
catches were already in sharp decline before the change to the bag limit, supports a significant decline in the elephant
fish population in Western Port.
Overall, the elephant fish assessment is limited by the data available but the weight of evidence supports a significant
decline in the fishery and elephant fish population. Prior to the 1980s, there were also very low abundances of elephant
fish population in Western Port and this long-term variation may be linked to environmental/habitat changes that
influence the egg laying grounds in the eastern region of the embayment (i.e. shifts from unvegetated to highly vegetated
bottom). Further studies are, however, required to better understand the cause of any long-term shifts in the Western
Port elephant fish fishery.
Satisfaction and Perception
A social survey of satisfaction and perception amongst Western Port anglers in 2014/15 identified a range of motivations
for anglers to fish there (Figure 26). The primary motivations were ‘enjoyment of the sport’ and ‘fishing for food’ (Figure
27).
Over 80% of anglers were ‘very satisfied’ or ‘quite satisfied’ with the general status of recreational fishing in Western Port
(Figure 29. Social survey reasons for non-satisfaction in the Western Port fishery.The main issue for those who were not
satisfied was ‘lack of fish’ (caused by ‘bad season/weather’) and, to a lesser extent, ‘boat ramp busy/no parking’ (caused
by ‘lack of facilities’ and ‘too many boats’) (Figure 29).
Fishing Effort
Fishing effort, based on standardised trailer counts at ramps, showed relatively stable effort in recent years with above
average trailer numbers in 2014/15 (Figure 30). Trailer counts in recent years have been lower than in the early to mid-
2000s, particularly for the western region ramps (Figure 31).
These trends tend to be correlated with catch rates, that is, higher catch rates lead to greater fishing effort. The
interpretation of the data is, however, limited by the fact that counts are only undertaken on weekends with fine weather.
Management
Fishery data presented at the August 2015 stock assessment workshop did not indicate the need for a review of fishery
management arrangements and participants supported maintaining the current management regime.
Areas of concern
Although data is limited; there is significant evidence of a continued decline in the elephant fish fishery. This issue
was raised at the last Western Port assessment in 2009 and it would be prudent to review the status of the larger
offshore stock for comparison, and encourage efforts to understanding how habitat and environmental factors
influence adult migrations, egg laying and reproductive success in eastern Western Port.
The use of ‘partial length’ to measure gummy sharks is a cause for concern by anglers as it can lead to confusion
as what is a legal-size shark and the retention of undersize sharks.
In species with very low bag limits, such as gummy shark and elephant fish, interpreting boat ramp survey catch
rate data in relation to population biomass trends is difficult. Collecting detailed data on discards and greater
participation of anglers who target these species in the diary angler program is recommended so that catch rate
data can be interpreted more confidently.
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Table 4: Stock status determination using recreational catch rate indicators for key species of the Western Port fishery. The following tables classify the status of key
species according to the ‘traffic light’ classification system using available indicators of stock status, most importantly boat ramp (creel) survey catch rates. Information
to support the assessment are presented in the ‘Assessment figures and tables’ section of this document.
Species King George Whiting Snapper Flathead Gummy Shark Elephant Fish
Indicator Recreational creel survey
standardised catch rate
(fish/angler hour) 17-year
time series (Figure 6)
Recreational creel survey
standardised catch rate
(fish/angler hour) 17-year
time series (Figure 11)
Recreational creel survey
standardised catch rate
(fish/angler hour) 17-year
time series (Figure 17)
Recreational creel survey
standardised catch rate
(fish/angler hour) 17-year
time series (Figure 19)
Recreational creel survey
standardised catch rate
(fish/angler hour) 17-year
time series (Figure 23)
Minimum 0.206 0.052 0.046 0.022 0.052
Maximum 0.519 0.381 0.145 0.088 0.210
Ten-year average 0.417 0.211 0.080 0.045 0.121
Five-year average 0.451 0.185 0.080 0.053 0.076
2014/15 0.324 0.137 0.067 0.049 0.052*
Trend in five year moving
average (standised)
Above long term average No No No Yes No
Status Average Average Average Above average Below average
Status classification notes While the most recent catch
rates are at around the
long-term average level,
based on the expected new
recruitment into the fishery,
the productivity of the
Western Port King George
whiting fishery is expected
to improve over the next 1-
2 years.
Based on catch rate
indicators, the Western Port
snapper fishery is
considered to be at around
average levels. Pre-recruit
survey data from Port
Phillip Bay suggest an
increase in catch rates,
particularly of smaller fish
expected over the coming
1-3 years
Based on catch rate and
size-frequency indicators,
the stock is considered to
be at around average
levels. Abundant small fish
in the 2013/14 length
composition data suggest
an expected increase in
catch rates flathead over
the next 1-3 years.
Interpretation of catch rates
for gummy sharks in the
boat ramp surveys is
complicated by the low
daily bag limit of two sharks
per person. The data
indicates, however, that the
recent status of gummy
shark is consistent with the
long-term average following
a peak in 2013.
Overall, the assessment is
considered to be data
limited due to the recent
very low targeting of
elephant fish. The weight of
evidence, however,
supports a significant
decline in the fishery and
elephant fish population
since the mid-2000s.
*2013/14
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Figure 5. Time series of commercial catch in the three main Victorian King George whiting fisheries. Red lines
indicate peaks in catch occurring at approximately decadal intervals.
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Figure 6. Time series of catch rates of legal-sized King George whiting from the boat ramp survey in Western
Port, 1998/99 – 2014/15. Long-term and 5-year moving averages are for the standardised catch rate.
Figure 7. Time series of King George whiting pre-recruit (post-larval) abundances in Port Phillip Bay sampled by
fishery independent surveys at 8 seagrass sites in spring since 1998.
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Figure 8. Percentage of trips targeting King George whiting with at least 5 or 10 legal size fish from the boat
ramp survey in Western Port.
Figure 9. Time series of catch rate of King George whiting (all sizes) by diary anglers in Western Port.
0
1
2
3
4
5
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
Catch rate (No. fish/per angler hour)
Financialyear
Withoutexpertanglers
Allincluded
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Figure 10. Length-frequency distribution of King George whiting from the angler diary program (all sizes) in
Western Port. The vertical line at 27 cm indicates the legal minimum length.
Table 5. Expert opinion on trends in the King George whiting fishery from 18 Western Port diary anglers with
King George whiting as their target species.
Trend Increase Decrease Stable Unsure
Abundance of legal size
last 12 months
1 11 4 2
Abundance of under size
last 12 months
0 12 2 4
Average size last 12
months
13 1 3 1
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Figure 11. Time series of catch rates of legal-sized snapper from boat ramp surveys in Western Port. Long-term
and 5-year moving averages are for the standardised catch rate.
Figure 12. Time series of catch rate of snapper (all sizes) from diary anglers in Western Port.
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Figure 13. Time series of snapper recruitment from the Port Phillip Bay snapper pre-recruit survey.
Figure 14. Birth years of adult snapper captured in Western Port from the Tea-Tree fishing competitors in
November 2014 (sample length composition ranged from 40–85 cm total length).
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Figure 15. Percentage of trips targeting snapper with at least 3 or 5 legal size fish in Western Port from
recreational angler boat ramp surveys.
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Figure 16. Length-frequency distribution of snapper from the angler diary program (all sizes) in Western Port.
Vertical lines indicate the range of the slot size limit (i.e. 28 and 40 cm). There is a three fish bag limit for
snapper above 40 cm.
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Figure 17. Time series of catch rate of legal size flathead (all species) from boat ramp surveys in Western Port.
Long-term and 5-year moving averages are for the standardised catch rate.
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Figure 18. Length-frequency distribution of flathead from the angler diary program (all sizes) in Western Port.
Vertical line at 27 cm indicates legal minimum length.
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Figure 19. Time series of catch rate of legal-sized gummy shark from the boat ramp surveys in Western Port
(daily bag limit = 2 gummy shark/ school shark combined). Long-term and 5-year moving averages are for the
standardised catch rate.
Figure 20. Time series of catch rates of legal-sized gummy shark from diary anglers in Western Port.
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Figure 21. Percentage of trips catching at least 1 legal sized gummy shark, where gummy shark was the target
species, from boat ramp surveys in Western Port.
Figure 22. Length-frequency distribution of gummy shark from the boat ramp surveys in Western Port. The
vertical line at 45 cm partial length indicates the legal minimum length.
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Figure 23. Time series of catch rates of legal-sized elephant fish from the boat ramp surveys in Western Port.
There was insufficient data for 2012/13. Long-term and 5-year moving averages are for the standardised catch
rate.
Figure 24. Time series of the percentage of trips targeting elephant fish from western and eastern boat ramp
surveys in Western Port. Surveys were conducted from January to May in each financial year.
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Figure 25. Length-frequency distribution of elephant fish from the boat ramp surveys in Western Port. There is
no legal minimum length for elephant fish.
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Figure 26. Social survey responses to ‘Reasons for fishing in Western Port?’ (respondents could make multiple
choices).
Figure 27. Social survey responses to ‘Most important reason for fishing in Western Port’
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Figure 28. Social survey responses of ‘overall angler satisfaction’ in Western Port.
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Figure 29. Social survey reasons for non-satisfaction in the Western Port fishery.
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Figure 30. Time series of standardised trailer counts at boat ramps in Western Port (Western Ramps — Stony
Point, Hastings, Blind Bight, Warneet and Tooradin; Eastern Ramps — Cowes, Rhyll, Newhaven and Corinella).
Figure 31. Time series of standardised trailer counts at western and eastern boat ramps in Western Port
(Western ramps — Stony Point, Hastings, Blind Bight, Warneet and Tooradin, Eastern ramps - Cowes, Rhyll,
Newhaven and Corinella).
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Acknowledgements
This assessment was funded by Recreational Fishing Licence fees and Melbourne Water who supported this
assessment following recommendations of the Western Port Science Review.
The assessment could not have been undertaken without contributions from a large team of people.
Thanks to the field staff for their many hours spent interviewing anglers at Western Port boat ramps: Rod Barber, Andrew
Both, Colby Bowden, Peter Beddows, Sean Brodie, Jeremy Clifford, Barry Fraser, Dave Green, Daniel Grixti, Mike
Kirwin, Damien O’Mahony, Peter Oates, Pam Oliveiro, Harold Roeding, Trent Tobias and John Tornatora.
Thanks to the volunteer fishing diary anglers who generously return records of their fishing: Ray Airs, Ross Albiston,
Dale Amy, Graeme Anderson, Stuart Bate, Allan Beazly, Craig Beekhuizen, Andrew Both, Sean Brodie, Greg Cheetham,
Chris Christou, Steve Church, David Clark, John Close, Robert Colker, Don Collins, Eddie Coronado, John Dalla-Rosa,
Danny Divova, Michael Duke, Gerald Egan, Brian Fervolio, Colin Finkemeyer, Chris Garnar, Barry Geary, Neil Geraghty,
Martyn Gittens, Pat Gleeson, Phil Goodier, Ken Graves, Ricky Greensmith, Frank Harris, Richard Hawkins, Derek
Hichisson, Ernie Hill ,Stuart Irvine, Greg Jenner, Ian Jones, Dave Knight, Robert Krix, Richard Linossi, Andrew
Maguire, R. Mason, Sue McCracken, Ken Millican, Joe Montalti, John Morgan, David Oates, Bob O'Connell, Nick
Papadopoulos, Bob Pearce, Gavin Perkins, Craig Perrott, Rex Pitman, Mark Proctor, Lee Rayner, John Reid, Allan
Rogers, John Schmidt, Darryl Scott, Dave Scrase, Elliot Sims, Colin Sires, Michael Stephens, Russ Stewart, Alexander
Stone, John Teeuws, Alby Thomas, Max Thomas, David (Dave) Thomson, Trent Tobias, Matthew Urzia, John Whitford,
Peter Wilkinson and Ron Wilson.
Thanks to Pam Oliveiro, Katrina Halse, Pieta Lindberg and Tina Whillock for data editing and entry.
Thanks to James Morris and Natalie Bridge for managing the database and to Khageswor Giri for undertaking statistical
analyses.
Thanks to Bill Lussier and Allison Webb for comments on this report.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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References
Conron S, Green C, Hamer P, Giri K and Hall K (2016). Corner Inlet-Nooramunga Fishery Assessment 2016. Fisheries
Victoria Science Report Series No. 11.
Hamer, P., and Giri K. (2016) Port Phillip Bay Commercial Fishery Assessment 2016. Fisheries Victoria Science Report
Series No. 9.
Hamer, P.A., Acevedo, S., Jenkins, G.P. & Newman, A. (2011). Connectivity of a large embayment and coastal
fishery: spawning aggregations in one bay source local and broad-scale fishery replenishment. Journal of Fish
Biology, 78, 10901109.
Jenkins, G.P. and Conron S. (2015) . Characterising the status of the Western Port Recreational fishery in relation to
biodiversity value: Phase 1. Technical Report. School of Biosciences. Melbourne University.
Jenkins, G.P. (2005). The influence of climate on the fishery recruitment of a temperate, seagrass associated fish, the
King George whiting, Sillaginodes punctata. Marine Ecology-Progress Series 288, 263-271.
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Appendix 1
Western Port Fishery Species Stock Structure
Table 6. Stock structure of the major fishery species in Western Port.
Species Stock Structure
King George
Whiting
The stock structure of King George whiting in Victoria is uncertain but is thought to be
separate from stocks in central South Australia and Tasmania
King George whiting spawn and spend a substantial part of the life-cycle in coastal waters
Juvenile King George whiting remain in the same bay until approximately 4 years of age
when they move into coastal waters to compete their life cycle
King George whiting in Western Port are assumed to be part of a larger stock that includes
Victoria and south-eastern South Australia.
Snapper Two separate stocks of snapper occur in Victorian waters. The eastern stock is distributed up
the east coast of Australia through New South Wales into southern Queensland waters.
Fisheries to the west of Wilsons Promontory are based on the western snapper stock
Most of the adult snapper found west of Wilsons Promontory were spawned and raised in
Port Phillip Bay
Snapper in Western Port are assumed to be part of the western stock
Flathead
species
Two key species: sand flathead and Yank flathead. Also rock flathead but these are caught
less commonly (were important when commercial netting was allowed)
Sand and Yank flathead are likely to have local populations within bays
Gummy Shark The most recent research on the stock structure of gummy shark suggests that there is likely
one stock for southern Australia (extending from Bunbury in Western Australia to Jervis Bay
in New South Wales) and a second stock in eastern Australia (extending from Newcastle to
the Clarence River in New South Wales)
Gummy shark in Western Port are assumed to be part of the larger southern Australian stock
Local population structures are uncertain
Elephant Fish Western Port is the most important nursery area for elephant fish in south eastern Australia.
Aggregations of elephant fish move into Western Port to breed from February to May
This assessment assumes elephant fish in Western Port are part of a larger stock occurring in
southern Australian waters
Migrate between Bass Strait and bays
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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Western Port Fishery Species Life Histories
Table 7. Life history of the major fishery species in Western Port.
Species Life History
King George
Whiting
Spawning occurs in coastal waters in late autumn/winter
Long (90–150 days) larval drift period, influenced by westerly winds/currents on a decadal
cycle
Post larvae (2 cm long) enter bays and estuaries in spring and settle in shallow seagrass
Juveniles spend 3–4 years in bays/estuaries before migrating back to the ocean to complete
the adult life cycle
Adults may live up to 20 years of age in coastal waters
Seagrass is a critical habitat for juveniles
Fishery based on juveniles 2–4 years of age
Fishery highly variable at a 2–4 year time scale
Snapper Two separate stocks of snapper occur in Victorian waters. The eastern stock is distributed up
the east coast of Australia through New South Wales into southern Queensland waters.
Fisheries to the west of Wilsons Promontory are based on the western snapper stock
Snapper in Western Port are assumed to be part of the western stock
The main spawning and nursery area for the western stock is Port Phillip bay
Spawning occurs in lare spring/summer over sandy/muddy bottom at depths of 10–18 m.
Snapper move extensively between Port Phillip and Western Port, and the ocean throughout
life
Mature at 30–40 cm, (most mature by > 40 cm, 6–7 years age)
May live up 40 years age
Use variety of habitats e.g. sediments, reefs
Spawning success is highly variable from year to year thought to be related to catchment
flows and nutrient inputs
Spawning success in Port Phillip Bay influences the Western Port fishery
Uncertain how much spawning occurs in Western Port
Adult snapper fisheries are variable at 7–10 year time scales
Pinky fishery variable at 2–5 year time scales
Flathead
species
Sand and Yank flathead spawn and recruit within Western Port, as well as other bays and
coastal areas
Bottom dwellers on sandy, muddy or shelly substrate
Female sand flathead mature at 3–5 years of age and 25 cm length, while males mature at 2–
4 years of age and 22 cm length
Sand flathead have a maximum age of at least 23 years, and reach a maximum length of
40–50 cm
Female Yank flathead mature at 2 years of age and 25+ cm length, while males mature at 1
year of age and 20+ cm length
Yank flathead have a maximum age of at least 12 years, and reach a maximum length of 70
cm
Spawning occurs from spring to autumn
Spawning and recruitment success is highly variable from year to year
Population dynamics is thought to be independent between bays, and between bays and
Western Port Fishery Assessment 2015 Recreational Fishing Grants Program
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coastal waters
Gummy Shark Maturity by approximately 6 -8 years of age, females mature by about 120 cm and males 110
cm total length
Females bear live young, up to 40+ pups per litter
Females give birth in summer after a 1 year gestation period
Bigger/older females generally have more pups
Pupping may occur in various areas of Port Phillip and Western Port, but pupping/nursery
areas are not well defined
Can migrate large distances (i.e. across southern Australia)
May live at least 16 years
Females grow larger than males; females grow up to 180 cm (20+ Kg) while males grow up to
150 cm total length
Number of adult females dictates recruitment – strong stock-recruitment relationship
Susceptible to overfishing
Less environmental influence on dynamics than finfish species
Elephant Fish Mature by about 60–70 cm length, and approximately 5–10 years of age
Western Port is the largest known egg laying aggregation in Australia, eggs are also
deposited in other bays, estuaries and sheltered inshore coastal bays
Annual breeding cycle with eggs deposited in late March to early May
Approximately 20 eggs are deposited per female per season
Egg cases are deposited in fine sediments in protected areas near seagrass beds
Egg survival sensitive to predation and habitat change (adults select certain substrates to lay)
Eggs take up to 8 months to hatch and young (neonates) may spend about 1 year in Western
Port before moving offshore
Neonates may use seagrass habitat as a nursery area but little information
May live more than 20 years
Seven gill sharks are a key predator of elephant fish
Females are larger than males, females up to 100 cm and males up to 80 cm
Number of adult females is a strong driver of recruitment
Fishery in Western Port depends on immigration from Bass Strait — seasonal ‘Feb–April
vic.gov.au/fisheries
This research hasn't been cited in any other publications.
  • Corner Inlet-Nooramunga Fishery Assessment
    • S Conron
    • C Green
    • P Hamer
    • Giri K Hall
    Conron S, Green C, Hamer P, Giri K and Hall K (2016). Corner Inlet-Nooramunga Fishery Assessment 2016. Fisheries Victoria Science Report Series No. 11.
  • Port Phillip Bay Commercial Fishery Assessment
    • P Hamer
    Hamer, P., and Giri K. (2016) Port Phillip Bay Commercial Fishery Assessment 2016. Fisheries Victoria Science Report Series No. 9.
  • Characterising the status of the Western Port Recreational fishery in relation to biodiversity value: Phase 1
    • G P Jenkins
    • S Conron
    Jenkins, G.P. and Conron S. (2015). Characterising the status of the Western Port Recreational fishery in relation to biodiversity value: Phase 1. Technical Report. School of Biosciences. Melbourne University.
  • Article
    Full-text available
    The King George whiting fishery in Victoria, Australia, is based on sub-adult fish of 3 to 5 yr old in bays and inlets. Previously, Zonal Westerly Winds (ZWW) and the El Nino southern oscillation index (ENSO) cycle have been found to influence the larval stages and subsequent catches of some fishery species in southeastern Australia. Offshore spawning and long larval life, together with a fishery based on a few year classes of sub-adult fish, led to the hypothesis that the fishery would be strongly influenced by climatic conditions in the larval stage. A significant positive correlation was found between the strength of ZWW in the region and the catch 3 to 5 yr later. These conditions may have influenced larval transport rates, or alternatively may have led to increased plankton productivity and therefore larval food supply. The ENSO cycle, however, was found to have a positive influence on catch at 0 lag. This positive correlation suggested that La Nina conditions may have led to increased catchability of King George whiting. Post-larval abundances at a seagrass site in Port Phillip Bay were strongly correlated with ZWW, confirming that the effect of these winds occurred in the larval to post-larval stages. Overall, results suggest that climatic conditions exert a strong influence on the larval to post-larval stages that subsequently affect the catch in the fishery.
  • Article
    Ichthyoplankton sampling and otolith chemistry were used to determine the importance of transient spawning aggregations of snapper Chrysophrys auratus (Sparidae) in a large embayment, Port Phillip Bay (PPB), Australia, as a source of local and broad-scale fishery replenishment. Ichthyoplankton sampling across five spawning seasons within PPB, across the narrow entrance to the bay and in adjacent coastal waters, indicated that although spawning may occur in coastal waters, the spawning aggregations within the bay were the primary source of larval recruitment to the bay. Otolith chemical signatures previously characterized for 0+ year C. auratus of two cohorts (2000 and 2001) were used as the baseline signatures to quantify the contribution that fish derived from reproduction in PPB make to fishery replenishment. Sampling of these cohorts over a 5 year period at various widely dispersed fishery regions, combined with maximum likelihood analyses of the chemistry of the 0+ year otolith portions of these older fish, indicated that C. auratus of 1 to 3+ years of age displayed both local residency and broad-scale emigration from PPB to populate coastal waters and an adjacent bay (Western Port). While the PPB fishery was consistently dominated (>70%) by locally derived fish irrespective of cohort or age, the contribution of fish that had originated from PPB to distant populations increased with age. At 4 to 5+ years of age, when C. auratus mature and fully recruit to the fishery, populations of both cohorts across the entire central and western Victorian fishery, including two major embayments and c. 800 km of coastal waters, were dominated (>70%) by fish that had originated from the spawning aggregations and nursery habitat within PPB. Dependence of this broadly dispersed fishery on replenishment from heavily targeted spawning aggregations within one embayment has significant implications for management and monitoring programmes.