Category Archives: IN THE NEWS

We need your help to understand the diet of Shy Albatross

21st June 2018

By Dr Rachael Aderman

Wildlife Management Branch – Marine Conservation Program DPIPWE

The shy albatross breeds nowhere else in the world apart from three tiny islands in Tasmania—Albatross Island in the north and Pedra Branca (pictured) and the Mewstone in the south. Unlike many of the other albatross species that travel widely across the Southern Oceans, most of the shy albatross population remains year-round within the south-east Australian shelf waters. They are truly Australia’s own.

The total population is estimated to be around 15, 000 annual breeding pairs. Like the other 21 albatross species around the world, the shy albatross is of high conservation concern. Albatross are very slow to mature and they have a very low reproductive rate. This means that even a slight increase in mortality or reduced chance of successful breeding, may have significant consequences for the persistence of a population.

Many of the threats to the shy albatross are encountered while the birds are foraging at sea and include marine pollution and plastics ingestion; fisheries interactions; competition with fisheries or reliance on discards; and a changing ocean environment driven by climate change which  is altering the type, distribution and availability of food sources.

Central to understanding the nature and consequence of these threats is knowing where shy albatross are foraging; what they are eating; and is their diet changing over time?

Researchers from the Tasmanian State Government have been monitoring the shy albatross populations for over thirty years; however, studies of their diet have been limited. Traditionally, the only way to sample their diet is to force the birds to vomit up their most recent meal. This method not only invasive but can also bias the data, as often only the hard parts—such as squid beaks— can be identified.

Now there is a powerful new tool available. DNA analysis of albatross scats (aka poo) allows researchers to identify all the food sources they have recently consumed and in what relative proportions.

Researchers have spent endless days watching shy albatross on their nests on Albatross Island in Bass Strait—waiting for the distinctive sound of an albatross relieving itself – before darting in to collect a tiny precious sample of poo in a vial. Thanks to funding from the Fisheries Research and Development Corporations (FRDC), the Australian Fisheries Management Authority (AFMA) and the Tasmanian Albatross Fund, researchers from the Marine Conservation Program of the Tasmanian State Government, in collaboration with CSIRO, are now analysing hundreds of diet samples collected over the past four years.

Key to the success of this project is ensuring that researchers have reference DNA sequences for all potential species the shy albatross could consume.

While we have managed to find samples from most of their likely food sources, DNA sequences from some key species of fish are still missing. SETFIA has kindly offered to help supply samples to fill these gaps. In coming weeks, we will be circulating to SETFIA fishers our ’most wanted’ list, complete with mug-shots and a how-to-guide. With your help, we hope to be able to create a complete picture of the diet of this incredible species.

[FRDC project 2016-118: Using scat DNA to inform sustainable fisheries management and Ecological Risk Assessments: a Shy Albatross case study]

Autonomous saildrones out and about

23rd May 2018

Through the GipNet Environmental Monitoring Research Initiative, CSIRO are trialing the use of a saildrone, a type of Unmanned Surface Vehicle (USV) to collect a range of oceanic data in Bass Strait.

The saildrones are controlled remotely through satellite communications and are powered by wind and solar. They are also equipped with navigation lights, radar reflectors and an Automated Identification System (AIS) beacon to help prevent collisions. The saildrones are approximately 7m in length and 4m in height and have an average speed of around 3 knots (max 8 knots).

They have been equipped with advanced monitoring technology, capable of measuring a range of parameters include carbon dioxide levels in the water. Data collected is being sent back CSIRO researchers in near real time.

The saildrones are designed to travel anywhere in the ocean. Vessel controllers simply plug in coordinates of the area to be monitored and the saildrone makes its way there using its ‘sail.’ Monitoring and communications are powered by an inbuilt solar unit. Each vessel can stay offshore for extended period of time (up to twelve months) without returning to land.

A saildrone is being trailed in Bass Strait to test a range of sensors that ensure this type of platform is reliable, durable and accurate for future monitoring of ocean properties and proposed carbon storage sites. If you see a saildrone, marine users are asked to stay 500m away from the system.

For further information  visit, call the GipNet team on 0467-003122 or watch the video below.


NSW Southern Trawl Fishery to join the South-East Trawl

18th May 2018

The NSW and Australian Governments have been working on merging the NSW managed Southern Fish Trawl and the Commonwealth managed South East Trawl fisheries. The NSW trawl fishery operates inside 3 nautical miles and the Commonwealth trawl fishery between 3 and 200 nautical miles.

The push for the merger has come because the two fisheries often target the same species with the same trawl method and operate side by side but do so under different rules and restrictions.  The 2016 Productivity Commission report investigated management inefficiencies between Commonwealth and State fisheries and recommended that these fisheries merge.

An agreement between NSW and the Commonwealth sets down how the two fisheries operate and share the resource.

NSW operators have limits on “Commonwealth quota” stocks like tiger flathead. This frustrates NSW operators because they are often forced to discard commercially valuable fish that have little chance of survival.

Commonwealth operators are frustrated because NSW catches are debited to Commonwealth quotas.  This ensures that the sustainable limit, set by the Commonwealth, is not exceeded but means that Commonwealth operators are the last in the line and only receive what NSW don’t catch (noting NSW vessels can only catch limited volumes).  Commonwealth fisheries are also frustrated that the NSW fishery does not contribute to the cost of assessing stocks.

Often fishers hold both NSW and Commonwealth endorsements but cannot operate inside and outside the 3-mile line on a single trip.  This too is inefficient.

All this because a line was placed at 3 nautical miles in NSW based how far a cannon ball could be fired in the 17th century.

The truth is that both sectors have an equally strong right to operate and there must be a better way to organise a fishery.

The NSW and Australian Governments formed the Southern Fish Trawl Working Group made up of fishers, associations and managers from both fisheries, they have agreed how the NSW Southern Fish Trawl could become part of the Commonwealth South East Trawl.  NSW released a consultation document that captured these proposals.  The proposal is that rather than debit NSW catches to Commonwealth quotas, that NSW operators should become Commonwealth operators working on a special permit allowing them inside “the line” (3 miles) and be issued around 246 tonnes of Commonwealth quota.  A separate NSW allocation panel would divide up this quota across the 23 NSW operators.

Under this system there is no change to the sustainable catch and no quota is taken from existing owners to give to new NSW entrants to the Commonwealth system – the catch is already coming off Commonwealth quotas.

The Committee also made recommendations that NSW vessels entering the Commonwealth fishery should operate seabird bafflers, VMS (satellite monitoring) and be subject to normal conditions such as ongoing efforts to reduce discards and by-catch.

SETFIA supports the transition under these terms and believes it offers the many benefits:

* fish trawling in south-east Australia will be managed by a single jurisdiction and many fish species will have a cap on how much can be caught each year;

*better data collection and improved understanding of stock status;

*one jurisdiction removes duplication and administrative burden;

*where the required concessions are held, fishers will be able to complete a single trip inside and outside NSW waters;

*security of access for NSW fishers will be increased

*no more trip limits and less discarded fish from NSW vessels.

The Association is frustrated at some recreational fishing groups who have led with headlines like, “the trawlers are coming”.  This is clearly not the case, there has been a trawl fishery inside NSW waters for more than 100 years.  What is being proposed is just a better outcome for the fishing industry and the Australian community.

ABARES report South-East trawler profitability up

20th April 2018

Latest financial and economic survey results from operators in the Commonwealth Trawl Sector (South East Trawl) shows that the profitability of vessels operating in the fishery improved in 2014-15.

Generating a gross value of fishery production of almost $43 million in 2015-16, the South East Trawl is the major supplier of locally caught finfish to Melbourne and Sydney fish markets.

The survey undertaken by the Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) for the 2013-14 and 2014-15 financial year show that profit at full equity (a profit indicator that assumes all assets are fully owned by operators) increased for the average boat in the CTS from $131,000 in 2013–14 to nearly $154,000 in 2014–15. The improvement was primarily due to lower average costs on items like fuel.

The rise in average vessel performance is also reflected in an improvement in net economic returns (NERs) from the fishery in 2014-15.  ‘NER’ measures how well the fishery has performed as a whole and accounts for all revenue and costs of the fishery including all management costs, owner labour (even where there is no cash transaction) and capital employed in the fishery.  ABARES estimates that net economic returns continued to improve for the fishery in 2015-16 and 2016-17 reaching $4.2 million by 2016-17. Three years of consecutive growth in returns is great news for trawl operators, particularly as it comes following a three year period of decline.

ABARES is currently undertaking the next survey of Commonwealth Trawl Operators of the fishery covering the 2015-16 and 2016-17 financial years.

The latest survey results can be found at:

Alec throws back $100,000 giant squid…

19th April 2018

Alec Harvey, skipper of the Empress Pearl could not believe his eyes when his vessel recently caught this enormous squid. It is the biggest he has ever seen. It was caught in 380m of water off the west coast of Tasmania. It was estimated at 2.5-3 metres long and weighing 80-100kgs.

Based mostly on its size Dr Julian Finn from the Melbourne Museum has tentatively identified the squid as being a ‘giant squid’ (Architeuthis dux).

There is some debate about whether different species of giant squid exist within the genus Architeuthis with some literature reporting eight species and some only a single specie. Some reports say that Alec’s squid was a tiddler with the maximum size reported at 14 metres long. Claims of 20 metre squid have not been scientifically documented.

Squid are a cephalopod and are propelled by pulling water into the mantle cavity, and pushing it through something called a siphon, in gentle, rhythmic pulses. They can also move quickly by expanding the cavity to fill it with water, then contracting muscles to jet water through the siphon.

Giant squid breathe using two large gills inside the mantle cavity. The circulatory system is closed, which is a distinct characteristic of cephalopods. Like other squid, they contain dark ink used to deter predators.

They have sophisticated nervous systems and a complex brain. The giant squid has the largest eyes of any living creature and can be up to 27cm in diameter.

Giant squid feed on deepsea fish and other squids. They catch prey using the two tentacles, gripping it with serrated sucker rings on the ends. Then they bring it toward the powerful beak, and shred it with the radula (a tongue with small, file-like teeth) before swallowing it. They are believed to be solitary hunters, as only individual giant squid have been caught in fishing nets.

Tales of giant squid have been common among mariners since ancient times, and may have led to the legend of the kraken a tentacled sea monster as large as an island capable of engulfing and sinking any ship. Eyewitness accounts of other sea monsters like the sea serpent are also thought to be mistaken interpretations of giant squid.






Whales are one of the giant squid’s few predators and much of the age data from giant squids come from giant squid mantle’s obtained from sperm whale stomachs.

In December 2005, the Melbourne Aquarium paid A$100,000 for the intact body of a 7 metre giant squid, preserved in a giant block of ice, which had been caught by fishermen off the coast of New Zealand’s South Island that year.


The video below is of a live giant squid filmed in a 2013 Discovery Channel documentary.



Seed bank protects food crop genetics

26th March 2018

Buried deep in the icy mountains of a remote island in Norway, is a seed storage facility that currently houses almost 1 million plant seeds from almost every country in the world.  Located 100 meters inside a mountain on the island of Spitsbergen, in the remote Arctic Svalbard archipelago, 1,300 kilometres from the North Pole its purpose is to be the ultimate insurance policy for the world’s food supply, offering options for future generations to overcome the challenges of climate change and population growth.  It will secure, for centuries, millions of seeds representing every important food crop variety available in the world today.

The location for the seed vault was chosen for various reasons; the area is geologically stable, has low humidity and is well above sea level so is unlikely to flood even if sea levels rise significantly.  A temperature of -18ºC is required for optimal storage of the seeds and the permafrost that the vault is built into provides a cost effective and fail safe method of keeping the seeds frozen naturally.  Although remote, Svalbard is still accessible on a commercial flight.

The vault has the maximum capacity to store 4.5 million varieties of crops which is equivalent to 2.5 billion seeds. It is currently the most diverse collection of food crop seeds in the world ranging from unique varieties of major African and Asian food staples such as maize, rice, wheat, cowpea, and sorghum to European and South American varieties of eggplant, lettuce, barley, and potato.

The global seed vault in Svalbard was established as the final backup to the 1,700 plus gene banks that exist around the world that hold crop seeds for safe keeping.

But in a cruel twist of fate it seems that the seed vault my not be the all-withstanding fortress it was meant to be. The climate is changing and the northern polar region is warming twice as fast as the global average – and the permafrost that is currently preserving the seeds is melting!  Last year’s record soaring temperatures in the Arctic caused melting and heavy rain that that flooded the start of the tunnel that leads to the vault.  If Arctic winter temperatures continue to rise, the so called ‘Doomsday Vault’ itself may be doomed.

There is a growing acceptance that the world’s food production will need to grow by 50-100% by 2050.  Seafood is the largest contributor to the planet’s protein.   Good fisheries management is the ‘vault’ that must protect our fish stocks.

Global Fishing Watch; interesting but of limited value in Australia

15th March 2018

Global Fishing Watch (GFW) is an online tool with which users can view the tracks of some of the world’s fishing fleets.  The system uses ‘AIS’ data to do this.  AIS stands for “automatic identification system”.  It is an important safety tool used to avoid collisions between ships at sea.  Essentially a tracking system it allows ships to see information on other ships in the vicinity such as; name, call sign and position on their navigation systems, assign a ship’s name to a radar blip and even plot the path of nearby vessels.

Global Fishing Watch has created and made available free to the public a platform that allows anyone to view AIS equipped fishing vessels at sea and to try to understand their behaviour. GFW state that this allows research and innovation in areas that support ocean sustainability, including fisheries policy and compliance, seafood sourcing, and ocean conservation. GFW explain that their purpose is to protect the world’s fisheries because they are an important source of protein for almost half of the people on the planet.

However, the platform has very little value in Australia for many reasons:

Australian fisheries are more tightly managed than most international fisheries.  Many international fisheries are managed by simply limiting the number of vessels or placing some other inefficiency on vessels to limit their catches.  Countries do this because it is easier and cheaper than detailed counts of unloaded fish.  In contrast Australia’s larger fisheries are not managed by vessel number, instead they are managed by quotas which at set at sustainable levels based on stock assessments.  Australia’s larger fisheries use observers and cameras to quantify discards and have tight controls on counting landed catch so fisheries managers have an exact understanding of how much fish is being caught and can limit catches as required.

GFW explains that it tracks 65,000 vessels including 75% of fishing vessels larger than 36m in length using AIS.  However, the Australian Maritime Safety Authority (AMSA) only requires vessels of more than 300 tonnes on international voyages to operate an AIS system.  The reality of the Australian fishery is that there are very few vessels over this size fishing and hardly any fishing vessels are large enough to operate AIS so don’t appear on GFW’s map.

When SETFIA viewed the GFW site in south east Australia in April there were only four vessels (all less than 36m) appearing on the map. However, the reality is that there were likely more than 100 fishing in the region.

AIS can be turned off by fishing vessels.  GFW cite several case studies where they allege that they discovered illegal activities in international fisheries after the AIS was turned off.  GFW label the turning off of AIS data as, “going dark”.  This is a stretch given the rules in Australia that do not require AIS on small vessels.

The Australian Fisheries Management Authority (AFMA), who manage Australia’s deepwater fisheries, operate a system called the Vessel Monitoring System (VMS).  This pre-dates GFW’s map by more than a decade.  All Commonwealth vessels must have VMS on all of the time.  In comparison the GFW system only monitors some vessels some of the time and sometimes analyses some of this data.  AFMA’s VMS runs monthly reports that investigate all vessels to ensure that they have not fished in marine parks or fisheries closures.  VMS operating rates are monitored constantly and any vessel whose VMS fails must report their position manually and must not leave port again until the system is working.  VMS operating rates are in the high 90%s.

A recent article in alleges that one of SETFIA member Austral Fishery’s vessels had “gone dark” near a marine park.  eNGO Oceana allege that, “During the period from July 2015 through September 2016, the [Austral] vessel appeared to turn off its AIS before entering the protected area, and appeared to immediately turn it back on after exiting on 10 separate occasions”.

David Carter, Austral’s CEO explained that “We generally keep AIS operating when in transit but once we’re fishing, its standard practice to turn it off”.  The crew switch off the AIS because “there are other commercial fisherman down there and exposing our location would compromise our commercial catch,” he said.  Mr Carter explained that in addition to VMS which was being constantly monitored by AFMA during the voyage in question they  also had two independent observers on board.   The fishery in which Austral’s vessel operates is Marine Stewarship Council accredited.  Mr Carter hit back at Oceana stating, “Any suggestion of wrong doing is hugely inappropriate and deeply offensive,”

In an open letter about the allegation against Austral AFMA stated, “While the report puts forward the case that turning off AIS means the vessel may be taking part in illegal activities, this is absolutely not the case for the Corinthian Bay referred to in your article. AFMA has checked on all of the data for the Corinthian Bay and we hold no concerns for their movements in the period in question.”

GFW claim that their system allows researchers access to data. However, CSIRO have completed a more detailed analysis of the impacts of trawling in South-East Australia using VMS data and the size of the net and this is available to Australian researchers.

A chart of North-West Australia shows the striking contrast in the scale of international and Australian fisheries with many more fishing vessels sitting outside the line (Australia’s EEZ) shown in yellow.

Although GFW has limited value in Australia it is an amazingly interesting and functional site and can be browsed here.

Fishing by electrocution

23rd February 2018

Electric pulse fishing (also known as electrofishing or electrical trawling) is a trawl fishing technique used in Europe to target flatfish (sole) and shrimp.  It involves the release of electric currents with a range of frequency, voltage, pulse polarity, pulse shape, and pulse duration combinations into the seabed to either immobilize fish so they do not try to escape the fishing net or to startle them to jump into the fishing net.  Traditional beam trawlers drag bobbin rope or tickler chains along the seabed to push finfish or shrimp up and into the path of the fishing net.

On ‘Electro-trawlers’, these gears are replaced with a number of electrodes, attached to the gear in the tow direction, that emit electric pulses. There are two basic types of pulses depending on the target species. Vessels targeting fish like Dover sole use a bipolar pulse of around 80Hz to induce cramping in the fish that immobilizes them and stops them from escaping the trawl net. While vessels that go after shrimp tend to produce unipolar pulses of around 5Hz that startle the shrimp and induce an involuntary tail-flip that causes it to jump up from the seabed into the net.

Watch the video below to learn more about how electric pulse trawling works.

On the surface, electrofishing might seem like the ideal, environmentally friendly fishing method.  The gear used islighter than some gear used in conventional beam trawling and consumes up to 50% less fuel to tow making it more economical. It also appears to be more selective. An average by-catch reduction of 35% in volume was observed during extensive commercial testing of the prototype. The trial also indicated that contact with the seabed was reduced by 75% while catch efficiency was maintained.

This method of fishing has been banned in the European Union (EU) since 1998 due to uncertainty about its impact on non-target marine organisms and ecosystems that may be exposed to its effects. However, since 2009 an exemption in the legislation has allowed EU member states to electrofish using 5% of their beam trawl fleet in the southern North Sea, and this was increased to 10% in 2014. In addition, some members states have increased their electrofishing capacity under the guise of conducting scientific trials to test fishing methods that avoid, minimise or eliminate fishery bycatch. In 2016 approximately 91, mainly Dutch and British, trawl boats were commercially electrofishing in this region.

However there is growing concern that electric pulse fishing may not be as sustainable as it is touted to be by some quarters. Studies on adult Dover sole and Atlantic cod have shown that the response of fish during and after exposure to electric pulses can range from a straightforward escape response at low electrical loads, to cramp reactions at medium electrical loads and tonic-clonic epileptic seizures, spinal injury and haemorrhaging in cod at high electrical loads.

Further, fishers in the southern North Sea have been reporting that since the industrial scale ramping up of electric pulse fishing in the area they have seen a drastic reduction in the key target species, sole, cod and seabass. They are also reportedly hauling large amounts of already dead fish and observing dead shellfish, starfish and small fish in areas fished by electro trawlers, so much so that they have started referring to the southern North Sea as the dead zone.

In January this year, French fishers blockaded the busy port of Calais to protest over the damaging impact that electric pulse fishing is having on fish numbers and their livelihood. Amid such heated protestation and controversy, on 16 January the EU parliament voted to ban electric pulse fishing in its waters. This ban is yet to be confirmed as decisions have to be negotiated with the European Commission and members states prior to being final but the EU parliament’s resolve has concerned the mostly Dutch fishers that have heavily invested in adopting the technology.

The final outcomes of this saga may not be fully known for some time but if nothing else, this is a cautionary tale on the perils of unleashing on the environment technologies that may on the surface seem sustainability-friendly but are not sufficiently supported by rigorous scientific testing and evidence. What seems to have happened in the southern North Sea is that electric pulse fishing has resulted in the trawling and, potentially destruction, of benthic habitats that used to provide sanctuary to feeding and juvenile fish by virtue of their inaccessibility to conventional beam trawlers.

Electric pulse fishing is not an allowed method in the South East Trawl Fishery.    Conventional bottom trawling attracts criticism for its environmental impacts but Australian and international research has shown that its impact on the environment is less than many allege.  Bottom trawling in south east Australia is aggregated into small areas due to closures or due to grounds being unproductive or too rough for the fishing gear.  Research in the south east has found that only 6% of the seafloor is every touched by trawl gear and that bottom dwelling invertebrates populations are at  80-93% of their un-trawled abundance and continue t increase.

Read more.

*Featured image is by Wageningen UR.

Links to reports on electrofishing.

ICES working group report

IMARES research institute webpage on pulse fishing

an article in “The Conversation” by Mike Kaiser:

Science Mag article:


Offshore Fish Farming – Solution or Sci-Fi?

23rd February 2018

In January 2018 around 20,000 yellowtail kingfish escaped from the damaged sea pens of an offshore aquaculture research lease in Providence Bay, off Port Stephens, New South Wales.  The sea pen was part of a Marine Finfish Aquaculture Research Lease; a collaboration between Huon Aquaculture and the NSW Department of Primary Industries (DPI).  The projects aimed to evaluate the commercial viability of growing kingfish in sea cages, test the latest sea cage technologies and monitor the environment.  There are five sea pens in the lease, with each one able to hold 15,000-20,000 kingfish.  Severe weather and rough seas over a four day period was blamed for causing the damage that led to the fish escaping into the wild.  The so called ‘fortress pens’ were reportedly inundated by waves that were more than 11m high.

One man’s loss is another man’s gain and this incident was a 17,000-kingy windfall for the recreational fishers that happened to be at the right place at the right time, with Huon only able to recover 3,000 of the fish.  This disaster has set Huon Aquaculture back almost one million dollars.

However, this incident could just be one of many more to come as offshore or open ocean aquaculture starts to take off in Australia and globally.  Given estimates that by 2030 the world needs to produce 70% more food than it currently does to feed an ever increasing global population, the search for cutting edge innovation in food production has a lot of governments and companies looking at the oceans for a solution.

Norway has embarked on an ambitious project to set up the world’s first offshore fish farm – Ocean Farm 1.  They have built a fish farm in the middle of the ocean based on the same construction concept as submersible offshore installations such as oil and gas structures.  The fish farm is 68m high, 110m wide and 250,000m3 in volume. This is equivalent to 100 Olympic size swimming pools.  It is secured to the seabed by anchors and tethered at depths of between 100 and 300 metres.  It is large enough to fit an entire offshore platform inside that can stand up to 8-10 meters waves, with the capacity to raise 1.5 million fish annually.

The image below is Ocean Farm 1.  Its builders say it is a new and innovative design, developed to overcome the challenges of traditional inshore fish farming facilities by being located in deeper waters, further from the coast.

As well as feeding the world, proponents say that offshore fish farms have many benefits compared to inshore farms.  From a biological and an environmental standpoint, these structures will allow water to pass through the cages and wash away lice and other pollutants, giving the fish a habitat as close to natural as possible.  The risk of disease and infection is exacerbated by the stress of cramped conditions in fish farms will be a thing of the past as larger fish will be released into the larger.  The fish will also be fed 10 metres below sea level, forcing them to submerge to further reduce the risk of catching lice.

Oceanic fish farms could be established around retired offshore oil platforms.  This is particularly interesting given the aging of the 40 year old oil and gas infrastructure in eastern Bass Strait.

The jury is out as to whether offshore fish farming is going to solve world hunger with as little impact on the environment as possible. Inshore fish farms constantly struggle with disease, chemical runoff, damage to cages and fish escapes.  Is offshore or ocean fish farming the solution or will it just extend this issue out into the oceans – out of sight.

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