Category Archives: Fish Stocks

Fishing industry providing shark samples for assessments

16th April 2019

Four years ago, AFMA installed cameras on gillnet vessels targeting sharks in the south-east fishery to monitor dolphin and sea-lion interactions.

However, a consequence of doing this was that human observers were removed from these vessels.  These observers collected data on interactions with dolphins and seals but also collected lengths and vertebrae, which are used to age sharks.  These “biological” samples are used to understand the growth and the recruitment of young sharks both of which are critical in the assessment of the gummy and school shark stock.

SSIA* has now been engaged by AFMA to collect these biological samples.  Gillnet and hook vessels take a sample of sharks when directed by randomly tagging some of the sharks caught on a trip.  Each tag has a unique number and when entered into the database by SIDaC samplers each shark can be traced back to the depth, fishing method, vessel and area in which it was caught.

Vessels then deliver these tagged sharks to port samplers who measure the length of the sharks and take a vertebra from about half the sharks.  The vertebrae are cleaned, frozen and then encased in resin before being sawed in half.  A fish ageing specialist can then read growth rings in the vertebrae much like growth rings in a tree.

A very similar program to sample pink ling and blue eye trevalla has being simultaneously rolled out for the auto line sector of the fishery.

SSIA have engaged Ross Bromley, an ex-AFMA manager, to co-ordinate this work.  The project would like to thank port samplers Jeff North, Atlantis Fisheries Consulting Group , Ross Bennett, AFMA staff at Lakes Entrance, Nick and Chris Pitliangas, Kyri Toumazos, Toni Clarke, the Lakes Entrance Fisherman’s Co Operative, Heath Rogers and Bob Shaw from Mure’s Fishing.  Thanks too to the crews supplying samples: the skippers and crew of the sample vessels Cape Everard, Morrie D, Christine Claire, Candice K, Jean Bryant, Diana, Lutarna, Peter Crombie.



If you are a gillnet or hook vessel operating in the fishery and would like to be involved in the project or would like to become involved in the sampling of gummy or school sharks, or ling and blue eye trevalla please email Ross here.

* The Southern Shark Industry Alliance (SSIA) represents the interests of operators and quota owners in the gillnet, hook and trap sector of the south-east fishery.


What’s to become of Victoria’s Gippsland Lakes commercial fishery?

15th August 2018

By Ross Winstanley*

Not content with their exclusive fishing access to every Victorian estuary, recreational fishers are now pushing for the closure of commercial fishing in the Gippsland Lakes.

From the 1960s through the 1980s, Victoria’s annual 800 tonne Gippsland Lakes commercial fishery produced 80% of Australia’s black bream landings, averaging about 250 tonnes.

Today, the Gippsland Lakes commercial fishery is under extreme pressure from recreational fishers and related business interests.  Flushed with the success of the 2014 campaign to end commercial net fishing in Port Phillip Bay, these interest groups are pressing the major political parties to bring an end to commercial fishing in the Lakes.

Success for this campaign would mean the end of another 10 perfectly sustainable family fishing businesses and the end of Victorian consumers’ access to black bream.

So, in the lead-up to Victoria’s November election, what positions will the major parties adopt regarding the future of fishing in the Gippsland Lakes?

Victoria’s 23-year record of fisheries and stock assessments have consistently shown the sustainability of the black bream and overall Gippsland Lakes fisheries.  Together with environmental assessments of the lakes system, these studies have tracked changes to fish habitats and fish stocks which have been matched with fisheries management changes.

Commercial fishermen have been proactive in initiating some important changes: in 1996 they observed the apparent total loss of juvenile bream throughout the lakes.  When surveys drew similar observations, the Government introduced emergency controls including tight monthly commercial catch limits and reduced recreational catch limits.  Many years earlier, the closure of commercial fishing on weekends and public holidays had a marked effect in easing competition with anglers.

The 1996 event brought about lasting changes: an increase in the legal minimum length for bream and the continuation of reductions in the numbers of commercial fishing licences.  Since 1995 alone, the number has been reduced from 21 to 10, mainly as a result of voluntary licence buy-outs.

As the numbers of licences have decreased, the level of commercial fish production has fallen accordingly.  In 1995/96 the total catch was 721 tonnes, including 130 tonnes of bream: in 2016/17 the total catch was 316 tonnes including 42 tonnes of bream.

The most recent estimate of the recreational catch from the lakes was 203 tonnes of bream in 2000/01.

Two comparative studies of the economic values of commercial and recreational fishing in Victoria’s bays and inlets showed no grounds for re-allocating fish resources between the sectors.

Current assessment
In 2017, the Victorian Fisheries Authority conducted detailed assessments of the State’s key marine stocks.  To lend additional rigour to the process, interstate fisheries managers and scientists participated in the assessments.  Drawing on detailed long-term commercial and recreational fisheries data sets, they found that the combined pressures from fisheries for black bream in the Gippsland Lakes are sustainable, as were the recreational-only fisheries in other eastern and western Victorian inlets.

Their conclusion was that “Appropriate management is in place.”

In contrast, none of the current anti-netting campaigns offer any evidence that commercial fishing is unsustainable or incompatible with angling.  Referring to the state of fish stocks and to angling success, statements such as “the decline is attributed to commercial fishing” offer no supporting evidence of declines from fishing or other causes.

Current political pressure
Since 1994, VRFish and local anglers have participated in at least seven Gippsland Lakes black bream and fishery assessments, all of which found fishing to be sustainable.  When presented with the evidence they agreed with the conclusions and the management implications.

Today, against this solid background of evidence-based policy and fisheries management come spirited appeals to end commercial fishing in the lakes.  Recreational fishing peak body, VRFish’s, key push to ‘save our Gippsland Lakes’ is a compulsory buy-out of all 10 licences as part of their ‘fish recovery plan.’  A petition asserts that ‘it’s time to end commercial netting of fish in the Gippsland Lakes’ to ensure ‘the sustainability of the Gippsland Region.’  The Futurefish Foundation web page simply urges “Ban netting in the Gippsland Lakes.”

VFA creel surveys show that angling success in the lakes is comparable to success in other East Gippsland inlets where anglers face no ‘competition’ from commercial fishing.  The evidence simply confirms what we know about recreational fishing everywhere: the majority of anglers catch very few fish.  Removing commercial fishing pressure – spread across 20 fish species – would not alter that reality.

The economic importance of recreational fishing to the Gippsland Region, including tourism, is widely acknowledged.  While the anti-netting campaigns claim that these benefits are threatened by commercial fishing, the VFA’s 2017 assessment shows that this is plainly untrue.  In fact, the full social and economic value from fisheries in the Gippsland Lakes can only continue if the viable commercial fishery is retained.  This has to be good news for government, seafood consumers and the wider Victorian community.

Market demand
Victorian seafood consumers’ keenness for bream can be seen in the prices they’re prepared to pay: about $30/kg which is more than they’ll pay for snapper.

Anyone who has read reports of fishing offences in Victoria might recall the prevalence of illegal gill-netting in rivers and streams around the bays, inlets and coastline.  Whether in the Werribee, Paterson or Tambo rivers, the main target for these activities is black bream.  This is a reflection of high prices and an unmet market demand for the species.

Speaking of markets, there’s more at stake here than 300 tonnes of fresh fish annually.  The Lakes Entrance Fishermens Co-op is a major source of Victorian and inter-state fish supplies.  The Co-op operates on very thin financial margins and closure of the lakes fishery would seriously threaten its continued viability.  As a popular direct outlet for fresh fish, the Co-op shop depends on the lakes fishery.  Without that fishery the shop would be likely to close as trawl-caught fish can be unavailable for weeks at a time during unfavourable seasonal conditions offshore.

Political response?
In 2014, the major political parties bowed to pressure from recreational fishing interests and committed to banning the commercial net fishery in Port Phillip Bay.  They did so without any consideration of the proven sustainability of that fishery.

Faced with similar pressures in 2018, what will the major parties do?  Will they seek balanced evidence-based policy advice from the VFA?  If so, what advice will they receive and how will they balance this against pressure from recreational fishing interests?

The outcomes will be revealed in the next couple of months.

Ross Winstanley is a keen angler, fishing writer and fisheries consultant.  For 30 years he worked with Fisheries Victoria in policy, management and research.

Danish Seine Fishermen Act to Protect Juvenile Flathead Stocks

21st June 2018

The harvest strategy in the South-East aims to maintain tiger flathead stocks at a pre-determined % of the pre-fishing, or virgin, biomass.   This is called the target reference point.  The flathead stock has been above this target for many years so fishermen have enjoyed quotas (total allowable catches or TACs) designed to slightly reduce flathead stocks down to that reference point.  However, the last flathead assessment showed that flathead is almost at that reference point so the quota has declined.

Less quota means less revenue so fishermen within the Association began to think about how to increase the per kg value of flathead.  One way is to catch larger flathead because larger flathead have a higher per kg price.  The market pays more for larger flathead because they are easier to fillet and they returns a higher yield of fillets as a % of whole weight.

Using larger mesh in the last section of the net called the codend increases the average size of flathead caught.

However, using larger mesh and not catching medium sized fish means less catch which means that fishermen must shoot their net more often, spend more time at sea and potentially increase their operating costs.  There are also costs to change to new fishing gear.

The debate was not an easy one but SETFIA members have resolved through a formal vote to increase Danish seine mesh size.  Two non-SETFIA member seiners were contacted and both supported the idea.

SETFIA has written to AFMA stating that they would like AFMA to increase the minimum mesh size in Danish Seine codends to 75mm by 1 May 2019 (the start of the new fishing season).

SETFIA has contacted fishing gear suppliers and advised them of the likely change so that they can adjust their supply.

Sustainable fishing practices protect our future.



Eastern Orange Roughy 2016 Survey and Biomass Report

23rd February 2018

CSIRO have released the report on the biomass of orange roughy in the eastern zone.  Read the executive summary and download the full report below.



Based on the 2016 acoustic surveys the biomass of spawning orange roughy on the grounds at 38 kHz and 120 kHz ranges from 24 000 (CV 0.12) to 29 600 (CV 0.22) tonnes for observation or process error analysis respectively. There has been a significant 2 fold increase in spawning biomass at St Helens Hill since 2013.

The 38 kHz timeEastern Orange Roughy Survey and Biomass Report 2016 series estimate of spawning biomass in 2016 is now higher than that recorded in 2010 and the long term trend is consistent with a recovery of fish to the spawning sites. The 38 kHz snapshot survey biomass estimate in 2016 of 29 600 tonnes (CV 0.22) extends the index of survey observations since 1990. The 120 kHz biomass estimates were approximately 10% less than the 38 kHz estimates and this relationship is consistent with previous observations (Ryan and Kloser 2016).

The difference between 38 kHz and 120 kHz biomass estimates indicates a source of bias in one or both data sets. Until the source of bias is found the average of the 38 kHz and 120 kHz estimates is recommended. The averaged over frequency combined ground estimate is 27 700 tonnes (CV 0.18) assuming process error dominant and 24 000 tonnes (CV 0.12) assuming observational error dominant.

It is important to note that we an error in the 38 kHz transducer calibration data supplied by the manufacturer and have adjusted this and the 2013 data by 18% accordingly.

Eastern Orange Roughy Survey and Biomass Report 2016

Are There Several Blue-eye Stocks?

9th March 2017

By Dr Alan Williams CSIRO Oceans and Atmosphere, Hobart

Grilled with garlic, oven baked, or lightly pan fried with a hint of lemon, blue-eye trevalla is one of Australia’s premium fish, and an iconic fish species for commercial fishers and seafood lovers alike!  Given its popularity, it’s then surprising to realise the extent of the knowledge gaps for blue-eye in Australian waters, and how these create uncertainty for its stock assessment.  Some of this uncertainty has been addressed in a just-completed project funded by FRDC, CSIRO and VicDPIE which has shed new light on the ecology and spatial distribution of Blue-eye stocks in Australian waters.

Surprisingly, the blue-eye’s early life history remains something of a mystery.  Whilst it turns up on fishing grounds aged about two years old and measuring about 40 cm in length, only four juveniles have ever been seen in Australia (these were dip-netted by a commercial fisher off eastern Tasmania).  A good outcome from the project is a more complete picture of the biology and ecology (including early life history) for Australian blue-eye – a process helped considerably by the input of knowledgeable commercial fishers and SETFIA, and input by colleagues in New Zealand.

baby blue eyeSurface dives in open ocean off NZ discovered juvenile blue-eye (~ 5 cm in length) under kelp floating at the surface.

Other key knowledge gaps for the blue-eye assessment were uncertainties about the species distribution and the possibility of there being different stocks.  It was known that blue-eye ranges widely across southern Australia, lives on offshore seamounts, and extends to sub-tropical latitudes on both east and west coasts, but without detailed spatial mapping it could only be managed as a single stock. This meant it was difficult to identify the most appropriate total allowable catch (TAC) and determine a long term level of sustainable catch.


Building on life-history information, the project then mapped patterns in three different characteristics of blue-eye to look for evidence of stock structure.  Each of the three analyses showed there was some separation of stocks within Australian waters: spatial differences in age and growth and in fish ear bone (otolith) chemistry of the adult life stage implied there was local and regional residency by adults. Dispersal in ocean currents indicated that a broader scale connectivity amongst regional populations was likely during early life.

blue eye stocks

LEFT: Stock areas are defined by boundaries (green lines) within the geographical limits of the blue-eye’s Australian distribution (red lines), and the narrow depth range occupied by adult Blue-eye Trevalla (depth contours)





By overlaying these spatial patterns, we identified four broad Blue-eye ‘stock areas’ (see the map below): West, South, East and Seamounts-Lord Howe. Each of these stock areas represents an interconnected ‘meta-population’, i.e. a group of discrete adult sub-populations resident on the continental slope and seamounts without extensive migration between them. Stock areas do not reflect truly separated biological stocks because there is some exchange between them during pelagic early life history, and some of the adult sub-populations act as larger ‘sinks’ than others, i.e. benefiting more from recruitment derived from ‘upstream’ spawning areas.

These patterns, together with spatial patterns in catch and effort which have also been mapped up in detail by the project, will help AFMA and fishers to develop additional management options for the blue-eye fishery.  In turn, new options may provide a greater confidence in the stock assessment leading, potentially, to a less risk-averse setting of the blue-eye trevalla TAC.

Full report.

Research Industry Video “Sustainable catch: Blue’eye Trevalla”.


New Zealand Orange Roughy achieves MSC certification

14th December 2016

SETFIA congratulates New Zealand on the Marine Stewardship Council (MSC) certification of three of its largest orange roughy fisheries, following a lengthy and rigorous assessment process. This achievement is a testament to the New Zealand seafood industry and the Department of Primary Industry’s heavy investment in rebuilding the orange roughy stocks over the last 20 years.

To get to this stage, New Zealand reduced catches and set conservative harvest levels, and invested in world leading scientific techniques to measure and assess stock sizes. This included working with Australia’s Commonwealth Scientific and Industrial Research (CSIRO) over the last 18 years to continue the development of a multi-frequency Acoustic Optical System (AOS) that allows for the accurate and real time assessment of orange roughy stock sizes. This information is then used to set sustainable catch limits that ensure 95 per cent of the adults in the stocks are left in the water to continue to breed and to sustain and grow the population.

This development is particularly pertinent to the Australian South East Trawl Fishery (SETF) for various reasons. Commercial fishing of the eastern orange roughy stock recommenced almost two years ago, following a 10-year closure. The same CSIRO AOS technology used in New Zealand has also been applied to Australian orange roughy stocks off eastern Tasmania over the last 10 years to assess their status. This information is used to inform stock assessments and set sustainable total allowable catches.

The international gold standard sustainability tick of approval is the first of its kind globally for orange roughy fisheries. It is a great example of how investment in sound scientific innovation and strong fisheries management can lead to profitable and sustainable fisheries.

More on Orange Roughy:

The latest on the 2016 Acoustic Optical System Orange Roughy survey

Fact sheet on the re-opening of the eastern orange roughy zone in the SETF

New Zealand Orange Roughy gets top international sustainability tick

Underwater video of Orange Roughy at 800m on St Helen’s Hill off eastern Tasmania

2016 Roughy Survey Shows Continued Recovery

7th December 2016

Under contract to SETFIA, Tasmania’s CSIRO has completed another survey on two features known as St Patrick’s and St Helen’s off eastern Tasmania where roughy aggregate to spawn. St Helen’s Hill is typical of a roughy hill being a conical seamount rising from a depth of 1,100m to 600m.  This is the 5th acoustic survey in the Eastern Zone since 2006.

CSIRO use an acoustic optical system or AOS that they have designed in Hobart.  The AOS emits multiple frequency signals to accurately calculate the amount of fish present. The AOS is towed 200-300m above schools of aggregating roughy.  By using multiple frequencies it can distinguish between roughy and other gas bladdered fish.  AOS is particularly effective in assessing aggregations of deep-sea fish and has also been used in Australasia to assess blue grenadier (known as hoki in New Zealand).

The survey encountered the strongest and warmest surface currents to date with fish at St Patrick’s being very disrupted and not settling on the hill as it did in previous years.  As is normal the largest aggregations were found at St Helen’s hill.  The video below shows images of live orange roughy captured by the AOS on St Helen’s hill at 800m.

This year the survey team loaded the AOS onto a small vessel using a modified boat trailer before it was taken out to the trawler contracted to complete the survey.  This reduced costs to move CSIRO’s scientists and their equipment to the mainland where the survey vessel was domiciled.

The other change in the survey this year was that the cost of the survey will be charged directly to quota owners through their levies.   This meant that there was no need to catch and then sell fish to finance the survey which reduced sales risks to the project.

Results are still being analysed but populations appear to be stronger than in previous years and provide more data about the recovery of Australia’s orange roughy stocks.  A stock assessment will consider this data in 2017 the Commission will use to set a total allowable catch from the 2018/19 fishing year.

Why is the East Australian Current Behaving so Badly?

18th October 2016

The East Australian Current (EAC) is a flow of water that is formed from the South Equatorial Current crossing the Coral Sea and reaching the eastern coast of Australia off Queensland. As the South Equatorial Current hits the Australian coast it divides forming the southward flow of the EAC. eacThe EAC is the largest ocean current close to the shores of Australia reaching a maximum velocity at about Coffs Harbour in NSW where its flow can reach a speed of 3 km per hour.

In the animated film Finding Nemo Marlin and Dory use the EAC as a superhighway travelling with fish and sea turtles to Sydney Harbour. The EAC is dominated by eddies which are circular currents of water that form whirlpools of up to 100km in diameter.

Their swirling motion is one of the forces that make nutrients found in cold, deep waters to come up to the surface of the ocean where phytoplankton (microscopic plants) feed on them.

Eddies do occur off the coast of Tasmania but a change in their behaviour over the last 24 years is concerning. These eddies are generated in the EAC and most of them do not go south of Bass Strait. When they do, they bring warm water with them and the bigger they are the more heat they can bring.


Scientists have noted a trend in eddies off Tasmania becoming larger, stronger and more frequent. Following the 1990s, eddy kinetic energy (EKE) increased gradually both north (red line in graph below) and south (blue line in graph below) of Bass Strait,  with a huge spike in eddy activity  off Tasmania (8 times the average EKE of the 1990s) in 2014 (see animation below). This trend is in agreement with climate modelling but there has been a dramatic increase over the last couple of years.

The presence of eddies south of Bass Strait is believed to be responsible for the atypically warm sea surface temperatures experienced off the east coast of Tasmania in 2015. If the eddy encountered off north east Tasmania in July this year is anything to go by (see image below), this heating trend is expected to continue into 2016.

A team of CSIRO scientists, AFMA observer and commercial fishermen from the South East Trawl Fishery came upon the eddy while conducting acoustic surveys of orange roughy off the north east coast of Tasmania in July 2016 as part of an ongoing monitoring program. eacIt was fast and hot and gave the team a bit of a hard time by making the deployment and retrieval of their sampling gear very challenging.

The eddy had current speeds of more than 2 knots and temperatures at its centre were more than 2 degrees warmer than the year round average between 100-400m depth and almost 1 degree warmer at 1200m depth. The eddy’s outer edge was close to the continental slope.

The implications of increased eddy activity on adult orange roughy spawning, orange roughy larvae, aquaculture, other fisheries and Tasmanian coastal waters in general are unknown. However, hot eddies warm up all the water around them and the bigger they are the deeper and wider their impact so if this trend continues there is no doubt that the Tasmanian offshore environment will change – the ‘how’ is anyone’s guess!

For up to date ocean information around Australia visit the IMOS Ocean Current website.


Searching for school shark pups in South Australia

20th July 2016

Matt McMillan is a PhD candidate working on school shark (Galeorhinus galeus) at the University of Adelaide. He needs your help to find school shark pupping grounds that may exist in South Australian waters.

School shark numbers declined in the 1990s and conservative total allowable catches (TACs) have been set to help them recover. School shark are no longer targeted by commercial fishers and are only caught incidentally while targeting gummy shark and other species. Anecdotal evidence suggests that school shark numbers are on the increase and their abundance is currently underestimated. However, before TACs can be raised science must support and increase in the school shark stock.

School shark are ovoviviparous meaning that they lay eggs which are hatched within the body of the parent. A lot of research has been done on the pupping grounds in Victoria and Tasmania but calculations have shown that the number of pups produced in these sites are too low to sustain the whole stock.

Matt’s hypothesis is that school shark may also be pupping in South Australia, and not just in Tasmania and Victoria. To test this theory, Matt plans to deploy underwater cameras at locations that school shark may use as nursery areas. He is calling on commercial fishers with knowledge and experience about school shark movements and behaviours to help him find locations in South Australia where sub 40 cm school shark have been caught.

Matt’s work will help address an important knowledge gap that the Commonwealth school shark stock rebuilding strategy (2008) acknowledges. Doing so could have strong benefits for the management of school shark.

If you have any information about school shark pupping grounds in South Australian waters or know someone who does call Matt on 0405-024344 or .