Cone Bay proves reliable for acoustic recordings of humpback dolphins

Blog By: Josh Smith PhD, MUCRU

For what could be the last field trip in a project to determine the feasibility of conducting passive acoustic monitoring of snubfin and humpback dolphins, the research team headed to Cone Bay on the northeast tip of King Sound in the Kimberley to focus on recording humpback dolphins specifically.

I was fortunate enough to have the aid of fellow Murdoch University Cetacean Research Unit (MUCRU) researcher, Alex Brown, to help me in the field to focus on getting the recordings of the sounds that humpback and snubfin dolphins are making.

We were also fortunate to be joined and helped out by Dambimangari Rangers during several days of the fieldwork, who provided excellent dolphin spotting skills and assisted in photo-identification of the dolphins we encountered.

In September 2014, Alex and fellow MUCRU researcher Dr Simon Allen and Dr Stephanie King undertook a WAMSI trip to Cone Bay to determine the size of the dolphin populations there and reported consistent sightings of humpback dolphins around the Marine Produce Australia barramundi sea farm, in Cone Bay at Turtle Island.

Not only did Cone Bay provide consistent sightings of snubfin and humpback dolphins, it also provided an elevated land based platform that could provide information on the dolphins detection thresholds by comparing the dolphins location relative to the acoustic recorders.

The acoustic data that we are collecting will help to develop a better understanding of the acoustic repertoire of these species, whether there are geographical differences in the sounds they make within a species, and understand over what type of ranges these dolphins are using their sound.

The main objective is to determine the feasibility of conducting passive acoustic monitoring for these species, which is being conducted as a Bill Dawbin Fellowship and part of the Western Australian Marine Science Institution (WAMSI) Kimberley Marine Research Program dolphin project.

The trip to Cone Bay was a great success with encounters of humpback dolphins engaged often in very interesting social behaviour. The trip was divided up in effort with land based hilltop observations over the sea farm and boat-based recordings.

For the hilltop observations, we deployed several SoundTrap acoustic recorders around the farm and waited for humpback dolphins to come in around the sea farm. This did not always happen regularly and was difficult to determine exactly when during the day this would happen.

Hilltop observations using SLR camera and binoculars overlooking the barramundi sea farm
Hilltop observations using SLR camera and binoculars overlooking the barramundi sea farm

A humpback dolphin jumping not far from an acoustic recorder

A humpback dolphin jumping not far from an acoustic recorder

The hilltop observations (using a Canon SLR and mounted GPS unit along with Vadar software) allows information on the range that sounds can be detected by the acoustic recorders to determine detection thresholds. This is done by the SLR camera recording many attributes of the camera and lens settings and the GPS function being capable of determining the bearing the camera is pointed.

The software Vadar takes the elevation of the land based platform along with the camera settings and is capable of geo-referencing the dolphins’ location which is corrected for the tide. This is then related back to the known positions of the acoustic recorders.

Alex on the water as we pursure mobile acoustic recordings

Alex on the water as we pursue mobile acoustic recordings

It wasn’t long before Alex and I realised the humpback dolphins were not around the farm for the entire day and we needed to increase encounter rates. So, remaining within VHF radio contact of workers at the farm who could radio us if they saw dolphins, we went out on the six metre research boat to increase our dolphin encounters. Generally, we were quite successful, coming across either a group of snubfin or humpback dolphins.

The other objective of this trip to Cone Bay was to see whether we could increase the number of genetic samples of the dolphins from that obtained in September 2014 and from photo identification we could see whether many of the previously identified dolphins were still in Cone Bay. Almost straight away it became apparent that many of the same dorsal fins of the dolphins were being sighted from the photo ID, although there were also some new fins that Alex could not recognise.

Being on the boat meant that we could get close to the dolphins and use the mobile acoustic recorder, which was a SoundTrap attached to a rope on a float. When we had sighted a group of dolphins we would establish the type of behaviour they were exhibiting ie foraging, socialising or travelling, which would largely determine the possibility of getting acoustic recordings. When the dolphins are socialising, they are less worried about the boat and will often not travel as far, providing a better opportunity for good acoustic recordings.

The main objective of the mobile recordings was to increase our understanding of the different types of social sounds they were making to identify their acoustic repertoire. The boat recordings provided some interesting sound recordings, particularly from a mixed group of four humpback dolphins in what appeared to be attempted mating of a single snubfin dolphin.

A group of humpback dolphins socialising near the mobile acoustic recorder attached to the float

A group of humpback dolphins socialising near the mobile acoustic recorder attached to the float

Finally, after almost three weeks of what was pretty good weather and almost 12-hour days, we left Cone Bay for Cygnet Bay and eventually Perth, having collected as much data as the weather would allow.

In total, there is now approximately five hours of mobile recordings and 23 groups of humpback dolphin positional data to process to help with previous fieldwork to assess the feasibility of passive acoustic monitoring for humpback and snubfin dolphins.

Cone Bay definitely proved to be more reliable for acoustic recordings of humpback dolphins than previous Cygnet Bay fieldwork and provided a pretty amazing backdrop to this research.

This fieldtrip would not have been as successful or viable without the support of Marine Produce Australia and we are extremely grateful for their support.

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 


Kimberley Marine Research Program

Giant corals reveal WA’s heatwave history

WAMSI oceanographic research has contributed to new findings documenting historic weather maps contained within WA’s coral reefs.

The research, led by The University of Western Australia (UWA), which involved researchers from Australian Institute of Marine Science (AIMS), Curtin University, CSIRO, and the University of California Santa Barbara, drilled into giant porite coral cores from Ningaloo Reef, the Abrolhos Islands and Rowley Shoals to find the marine climate data.

Each of the cores contains seasonal growth bands, similar to tree rings, and provides information about past climate conditions.

The study concentrated on the relationship between the climate conditions in the central-western Pacific and the southeast Indian Ocean referred to as the Maritime Continent, which includes Indonesia, Borneo, New Guinea, the Phillipine Islands, the Malay peninsula and the surrounding areas.

WAMSI researcher CSIRO’s Dr Ming Feng said analysis of the coral core growth bands enabled the team to successfully reconstruct ocean conditions of the West Australian shelf for 215 years and determine what conditions cause marine heat waves among WA’s unique coral reefs.

 “What we found is that when the Maritime Continent is warmer than the central Pacific, a pattern amplified during strong La Niña events in the tropical Pacific, it creates an ocean temperature gradient which reinforces warming in the far western Pacific and south-eastern Indian Ocean,” Dr  Feng said.

Dr Jens Zinke, Senior Research Fellow at UWA and lead author of the research paper published in the journal Nature Communications, said the long coral records allowed the scientists to look at the occurrence of marine heatwaves as far back as 1795.

Dr Zinke said the marine heat waves happened through a series of ocean-atmosphere interactions that resulted in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off Western Australia.

“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” he said.

The international team found that the temperature gradient in the western Pacific was particularly strong after the late 1990s, which can be linked to the series of marine heatwaves off the WA coast in the recent decade. The coral cores also reveal that this temperature gradient was intensified in the early and late 1800s, yet against a much lower background ocean temperature off WA.

The authors concluded that strong warming over the past 215 years made it easier for natural climate events, such as La Niña and West Pacific temperature gradient events, to exceed the critical temperature threshold for marine heat waves and mass coral bleaching to occur off Western Australia.

Dr Feng, said it was likely that under a warming climate, future La Niña events coupled with a strong West Pacific temperature gradient would result in more extreme ocean warming and high sea-level events with potentially significant consequences for the maintenance of WA’s unique marine ecosystems.

This will likely reduce the future ability of the reefs of Western Australia to serve as a climatically stable area for coral under future ocean warming.

The research builds on previous work and contributes to more accurate thermal reconstructions necessary for better informed resource management.

Figure 1: Southeast Indian Ocean reefs and tropical Indo-Pacific SST variability.
From the paper, Coral record of southeast Indian Ocean marine heatwaves with intensified Western Pacific temperature gradient, by Jens Zinke, A. Hoell, J.M. Lough, M. Feng, A.J. Kuret, H. CLarke, V. Ricca, K. Rankenburg, & M.T. McCulloch, Nature Communications (DOI doi:10.1038/ncomms9562)

(a) Locations of the three reef areas (1–3) sampled for long coral cores, (b) rotated empirical orthogonal function 2 (REOF2) covariance of ERSSTv3b15 anomalies, and (c) REOF2 time series, 1960–2013, which explains 21% of the variance. The WPG11 is defined as the standardized difference between average SST over the Niño4 domain14 (black box) and the Western Pacific (WP; blue box), while the Western Australian region is highlighted in grey with coral sampling locations indicated, 1, Houtman Abrolhos, 2, Ningaloo Reef and 3, Rowley Shoals. The black-dashed box marks the Indonesian warm pool region (IWP06 (ref. 26)).

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 


Kimberley Marine Research Program

Premier briefed on Kimberley marine research projects

WA Premier and Science Minister Colin Barnett released two AFL celebrity into waters off Broome as part of a broader program of marine research in the Kimberley.

The two green sea turtles Cyril and Sharrod, named after the AFL Hawkes forward Cyril Rioli and Eagles defender Sharrod Wellingham by the Yawuru Rangers, were caught in the waters off Roebuck Bay and tagged with a satellite tracking device. Premier Barnett released the turtles as part of the Yawuru Rangers marine turtle monitoring collaboration. The results will be updated daily on

Premier Barnett was also briefed on the Kimberley Marine Research Program by WAMSI program leader Stuart Field (DPaW); a $30million project under WA’s Kimberley Science and Conservation Strategy with 10 partner agencies and more than 100 scientists delivering 26 projects.

Researcher Scott Whiting prepares a turtle for release (Photo: Stuart Field, DPaW)
Tagged and ready for release
(Photo: Stuart Field, DPaW)


Premier Colin Barnett releasing Cyril the green sea turtle (@CollinBarnett: Twitter)
Monitor Cyril’s and Sharrod’s progress on

The Premier and Yawuru Rangers watch the sea turtles’ progress (DPaW)


WAMSI-DPaW Stuart Field briefs Premier Colin Barnett on WAMSI marine research in the Kimberley (DPaW)


DPaW Yawuru Rangers sea turtle monitoring:

  • Three species of marine turtle are common residents in Roebuck Bay (Green, hawksbill and flatback turtle), with other species (loggerhead, leatherback) less common.
  • Green turtles are abundant in Roebuck Bay and are ecologically and culturally significant.
  • Green turtles are a primary consumer of seagrass and algae and play a major role in the health of these systems.
  • Green turtles are highly significant in Yawuru culture and are important for food, ceremony, stories and songs.

Results from this study will provide information on:

  • Spatial (where) and temporal use (when) of habitats;
  • What habitats are important and how they use them;
  • How they use the proposed Roebuck Bay Marine Park and areas outside the park;
  • Identify any other spatial areas that are important (for example – are they frequently visiting areas 100 km away):
  • Identify areas where turtles and human pressures overlap (eg shipping lanes);
  • The results will be updated daily on

Kimberley Marine Research Program

Field report from research vessels in Camden Sound, Kimberley region

The initial ship-based expedition to Camden Sound was conducted under the auspices of WAMSI’s Kimberley Benthic Biodiversity Project, which aims to provide a better knowledge base about what occurs where in the Kimberley’s diverse marine environments, especially in areas of management priority such as the state government’s proposed marine parks and reserves.

Cruise leader on board the RV Solander, Dr Andrew Heyward from AIMS in Perth, said that the vessel operated 24/7 during its 18-day itinerary. “Scientists and staff worked in shifts, doing towed video and sediment sampling during daylight, and multibeam sonar surveys during the night,” he said.

Although the weather was generally very good, extreme tides, strong currents, turbid waters and some uncharted areas provided plenty of challenges for researchers. They successfully completed more than 200 km of towed video and thousands of km of multibeam seafloor mapping, in the first of two expeditions to the Camden Sound area.

“We’ve seen large areas of dynamic sand across the open Sound, including some patches with underwater sand dunes,” commented Andrew, “but also rocky ground covered in a large variety of marine invertebrates, in particular sponges and soft corals.”

The turbid waters of Camden Sound prevent sunlight from penetrating more than ~10 m in depth, so organisms that need light – such as corals and seaweeds – appear to be restricted to the shallowest parts of rocky ground and the upper edges of fringing reefs around islands. As depth increases and light fades the filter feeding sponges, soft corals, ascidians and bryozoans become the dominant components of the seabed communities.

“Thanks to the combined efforts of the Solander and the Linnaeus this month,” said Andrew, “we’re beginning to understand a lot more about what the seafloor of the Lalang-garram-Camden Sound Marine Reserve looks like, and the benthic biodiversity that lives there.”

Dr Iain Parnum from Curtin University is busily compiling all the gathered multibeam sonar data now. “In terms of outputs, first of all, we’ll deliver some much-needed improved bathymetry information for Camden Sound,” he explained. “Secondly, sonar backscatter data – both from the seafloor and the water column – will give us good insights into the kinds of underwater terrain and ecosystems at each sampled location.”

In addition, Dr John Keesing from CSIRO took advantage of the presence of the RV Solander in the Kimberley to advance another WAMSI project investigating historic changes in water quality. He collected sediment cores (each ~1.5 m long) at ~20 m depth from two locations in Roebuck Bay. “These cores will be used to reconstruct a time series of water quality in the Bay, which is expected to go back about 100 years,” he said.

As with all WAMSI projects, the data and outputs will be freely available to everyone with an interest in the marine environments of the Kimberley.

Map showing sites in Camden Sound where towed video surveys were conducted in November 2014 


A still image from one of the towed video surveys showing mixed filter-feeding community (including bryozoans, sponges and soft corals) growing on a rock outcrop (Photo courtesy of AIMS)


Kimberley Marine Research Program

Kimberley crocodile numbers triple in biggest survey in three decades

Early results from WAMSI’s crocodile survey in Western Australia’s north suggest their numbers have tripled over the last 30 years.


(Video: Croc Watch: ABC Landline)


Kimberley Marine Research Program

School’s out on tropical fish nurseries in the Kimberley

It’s an amazing journey for most tropical fish starting out life as larvae floating in the open ocean to making it back to the coast to settle down and live out the rest of their days.

During this process many species undergo rapid and often radical changes in their appearance changing from transparent larvae to the beautiful diversity of shapes and colours we are most familiar with.

Understanding when, where and how many tropical fish settle into different Kimberley habitats will provide an important management tool to help protect essential nursery areas and ensure there are plenty of reproductive adults to resupply following generations.

Alongside the Bardi-Jawi Marine Rangers and Traditional Owners, a WAMSI team from the Australian Institute of Marine Science (AIMS), CSIRO, Western Australian Museum and Departments of Fisheries and Parks and Wildlife, began surveys of fish recruitment in April.

Diversity of larval fish (and other) forms captured from the open ocean. Image from Robert Cowen Laboratory, University of Miami, USA.

“The first stage was to develop the right technique to do this accurately in the challenging Kimberley environment,” AIMS researcher Martial Depczynski explained.

“We assessed nine different methods among seagrass, coral reef, inter-tidal and mangrove habitats typical of the Kimberley region.

“We found in most cases that different nursery habitats were best quantified using different methods but that one single method was sufficiently efficient, easy, cost-effective and safe to use in all four habitats,” Dr Depczynski said.

Lifecycle of a juvenile reef fish. Fish begin their lives in the open ocean as semi-transparent larvae before recruiting and settling into their juvenile and adult coastal habitat often for the rest of their lives. During recruitment, they undergo metamorphosis losing their larval features to take on their characteristic shape and colouration. Image from Reefkeeping South Africa.

The investigators found that remote underwater video, although new to the task of recording small juvenile fishes, was able to provide robust relative estimates of abundance and diversity in fish nursery habitats and was the best option among the nine methods.

“Now that the correct methodology has been developed, our next trip in October, which will run in conjunction with a team investigating the same recruitment process in corals, will concentrate on getting a solid data set together to answer questions such as; what nursery habitats are important to what fish species, are there hotspots of fish recruitment activity and what is the strength of fish recruitment in dry versus wet seasons,” Dr Depczynski said.

“We will continue to work in with the Bardi-Jawi Marine Rangers and the Traditional Owners on the Cape Leveque – Sunday Island – Cygnet Bay area to better understand the processes that govern fish recruitment processes in this area.

“The main aim and best possible outcome from this WAMSI project is to have definitive quantitative data on fish and coral nursery areas which identify nursery hotspots and can feed into both State and Indigenous management plans such as the next Bardi-Jawi Indigenous Area Management Plan.

Remote underwater video unit deployed to record newly recruited fishes in an intertidal rock pool during low spring tides on Sunday Island.

The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government’s Kimberley Science and Conservation Strategy co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 



Kimberley Marine Research Program

The big comeback: it’s time to declare victory for Australian humpback whale conservation

Written by: Michelle Bejder, , and for The Conversation

When it comes to conservation, good news is pretty thin on the ground – and the ocean, for that matter. We have grown much more used to hearing about marine species that face extinction, decline or negative impacts than about those that are thriving. But if we are to avoid getting demoralised, conservation biology needs victories to celebrate.

So here’s one: the remarkable recovery of humpback whales that breed in Australian waters. Our review of the available data, published today in Marine Policy, suggests that humpback whale populations in Australian waters have recovered to the extent that we should consider downlisting them from the official list of threatened species.

The humpback whale should be a cause for optimism and hope. It’s an important counterbalance to the seemingly relentless communication of marine conservation problems with little in the way of good news. We hope this kind of optimism will convince politicians and the public that conservation problems can indeed be solved, and to stay dedicated to making that happen.

Turning the tide

Australia has one of the highest rates of species extinction in the world. But despite this, the past decade has seen rare examples of animals that are rebounding and thriving.

Humpback whales are one such example. They are listed as “vulnerable” on Australia’s official list of threatened species, under the Environment Protection and Biodiversity Conservation (EPBC) Act.

But our review, led by Michelle Bejder of BMT Oceanica and based on the best available scientific data, suggests that humpback whales no longer need to be on the EPBC Act’s Threatened Species list. Both the east and west Australia populations of humpback whales have recovered substantially from the damage done in the commercial whaling era (roughly from 1912 to 1972).

As of 2012, Australia’s east coast humpback population was at 63% of the pre-whaling-era level. The west coast population had bounced back to 90%. Australian humpback whale populations are increasing at remarkable rates: 9% a year for the west coast population and 10% a year for the east coast – the fastest documented increases worldwide.

A recent global assessment of humpback whales suggested that nine populations from around the world (including the east and west Australian populations) are no longer at risk of extinction. This is to be expected when exploitation through commercial whaling is replaced with conservation legislation (both in Australia and worldwide). Though we don’t quite fully understand the biological forces driving this extraordinary population increase, it’s fair to say that the removal of the dominant negative human pressure has been a huge factor.

On the rise: humpback whale populations are rebounding at a startling rate. Ari S. Friedlaender (under NMFS permit), Author provided
Click to enlarge

We believe that conservation biologists have a responsibility to protect species that are in peril by providing a sound, scientific basis for effective management. It therefore follows that we also have a responsibility to present information on recovering populations. The listing of threatened species under the EPBC Act is a dynamic process that is periodically assessed to determine the most appropriate management actions – so if species no longer needs to be on the list we should say so.

The future challenge will be to protect a marine environment that contains growing humpback whale populations and to develop alternative approaches to ecological sustainability. The history of environmental protection is based on saving depleted species, with very little guidance on how to manage recovering and recovered ones.

If humpback whales are downlisted from the threatened species list, the EPBC Act would still protect them from significant impacts because migratory species are deemed under the Act to be nationally significant. Beyond Australia, the International Whaling Commission manages the global moratorium on commercial whaling, which is essential for the humpback whales’ recovery to continue.

Management efforts must now balance the need to ensure humpback whale growth and recovery within a marine environment that is also expanding with industrial and exploration activities. There will be increases in interactions with ocean users, including acoustic disturbance from noise, collisions with vessels, entanglements in fishing gear, habitat destruction from coastal development, and interactions with the whale-watching industry. It will be vital to gain public support to help maintain the growth and recovery of Australian humpback whales and prevent future population declines.

Ocean optimism

The recovered humpback whale population could bring a positive shift in scientific research throughout Australia. If Australian humpback whales are removed from the list of threatened species, one of the most beneficial consequences could be the reprioritisation of research and funding to support other species that are at a greater risk.

Hopefully, other animal species such as the threatened blue whale, the understudied Australian snubfin and Australian humpback dolphins might get the same chance of scientific scrutiny that has been afforded to humpback whales.

For the first time in more than a generation, Australia’s iconic humpback whales have become a symbol of both hope and optimism for marine conservation, providing a unique opportunity to celebrate successful scientific and management actions that protect marine species. Optimism in conservation biology (which even has its own social media hashtag, #OceanOptimism) is essential to encourage politicians and the public to solve conservation problems.

Around the world, many marine mammal populations remain in peril, and conservation biologists should not detract from these cases. But we should still highlight the successes, as they provide hope that ongoing conservation actions can prevail. Ultimately, inspirational examples such as humpback whales can motivate people to use ocean resources wisely and to take sustainable and effective actions to safeguard marine wildlife for the future.

Related links:

Embracing conservation success of recovering humpback whale populations: Evaluating the case for downlisting their conservation status in Australia, Marine Policy review

Attention whale watchers: scientists want your snaps


Exploring innovation to monitor the humpback whale

As the annual humpback whale migration begins from the Antarctic to the Kimberley coast, one WAMSI project, working to model their spatial distribution, is looking to combine satellite imagery and bathymetric LiDAR (Laser or Light Detection and Ranging) for the first time as an efficient and safe means to monitor these giants of the sea.

The number of humpback whales travelling the coast of Australia from their feeding grounds in the Antarctic to their breeding grounds in the Kimberley has increased from around 300 in 1963 to some 30,000 today since hunting was outlawed.

The challenge now for lead researcher on the WAMSI project Michele Thums, from the Australian Institute of Marine Science, is to map habitats that are important to them when they are on their breeding grounds in the Kimberley which, in turn, could help to manage marine park boundaries and the potential to overlap with human activities such as boating and industry.

“We already understand quite a lot – timing of the migration, spatial extent of the calving area, and general distribution of migrating whales but there has been very little attempt to bring this data together and synthesise it to get a quantitative understanding of their habitat requirements and the specific habitats that breeding humpbacks rely on,” Dr Thums said.

The project is analysing data from some of the extensive aerial and vessel line transect surveys gathered over the last 25 years mostly on behalf of industry. This study is predominantly relying on data released by WAMSI research collaborator Curt Jenner, Inpex and Woodside.

“It’s very expensive to do these surveys,” Dr Thums said. “Collecting data from aerial and boat surveys is especially prohibitive in the Kimberley because it is so remote. So we’re fortunate to get access to this rich source of data collected by industry as part of their legislative requirements to operate.”

In September the project team is going to take an opportunity to head out into the field and test the reliability of monitoring whales using a scanning laser fixed to an aircraft that is capable of generating precise 3-dimensional information about the characteristics on the earth’s surface (bathymetric LiDAR system), in this case whales.

“We’re still developing this project but, if successful, it doesn’t require observers on the flight, so it’s safer and it could still allow us to analyse the data later to count the whales,” Dr Thums said. “We’re also hoping to get satellites tasked to capture high resolution images so we can compare the satellite data with LiDAR and, if it’s a good match, we might be able to rely on monitoring the Kimberley humpback whales with satellite in the future.”

The findings for the WAMSI Humpback project are expected to be released by early next year.

Related articles:

Whales from Space: Counting Southern Right Whales by Satellite PLOSONE





The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 


Kimberley Marine Research Program

The good-news El Niño story for Western Australia’s oceans

By Jaci Brown, Madeleine Cahill, Ming Feng and Xuebin Zhang, CSIRO The Conversation.

While eastern Australia trembles at the impending El Niño this year, potentially increasing heat waves and bushfires, the coastal waters of Western Australia (WA) would find El Niño a welcome relief from the heat.

In the summer of 2010-11 WA’s oceans were struck by devastating marine heatwaves, with temperatures rising up to 5C above average, causing mass deaths of marine life and coral bleaching.

Temperatures have remained warm since, due to the lingering effects of the large 2010-11 La Niña. But El Niño could be the relief these waters need for marine life to recover.

Why is the water so warm?

The water temperature off the WA coast is determined largely by the Leeuwin Current, which flows south along the WA coast from Indonesia. The Leeuwin Current is unique in the world as it is the only subtropical poleward-flowing boundary current on the eastern side of an ocean basin.

Most coastal currents, such as the East Australian Current and the Gulf Stream, are found on the western side of ocean basins.

The Leeuwin Current occurs because of the “gap” between Australia and Indonesia that connects the Pacific and Indian Oceans. The easterly winds over the Pacific Ocean pile warm water up on the western side of the ocean basin. This increases the sea level through the Indonesian archipelago. The high sea level signal is then transferred down the coast of WA, creating pressure gradients that draw in warm water and push it southward, forming the Leeuwin Current.

Satellite map of south west Australian coast with red colouring off the western coast, green and yellow colours elsewhere
A composite satellite image of sea surface temperature anomalies in July.
The Leeuwin Current can be identified as a narrow band of warmer water adjacent to the coast. Image: CSIRO

The easterly winds over the Pacific Ocean vary over time, being stronger in La Niña years and weaker in El Niño. The changing wind strength alters the amount of water piled up in the west of the Pacific and hence the sea level near Indonesia: higher in La Niña years and lower in El Niño. The changing sea level then influences the strength of the Leeuwin Current.

La Niña drives marine heatwaves

In a La Niña year, a stronger-than-normal Leeuwin Current forms off the northwest coast and flows southward, finally wrapping into the Great Australian Bight, extending to the west coast of Tasmania. The current also means warmer-than-normal water is transported further south along the WA coast, so temperatures are higher. In an El Niño year, the current weakens, and ocean temperatures fall.

La Niña drove the 2010-2011 marine heatwave (as well as the exceptional flooding in eastern Australia). Warm water has been flowing in the Leeuwin Current since 2010 without the usual reprieve brought from El Niño events.


Sea level anomaly 2010-2015

The warm water has led to extensive coral bleaching along with flooding and damage to sea grasses. Species along the coast of southwestern Australia are used to living in cooler temperate waters, and the heat wave resulted in mass deaths for a wide range of species.

Coral reef with white coral sections and fish above
Coral Bleaching at Rottnest Island (40m) in 2011. Photo taken by Damian Thomson, CSIRO.

How will El Niño alter the Leeuwin Current this year?

An El Niño has been forecast for this year and the easterly winds over the Pacific ocean have weakened. As a result satellites are already detecting a lower than normal sea level signal in the western equatorial Pacific.

Sea level map for March 2015 from satellite data. Blue areas near Indonesia show sea levels are lower then normal. AVISO
Sea level map for March 2015 from satellite data. Blue areas near Indonesia show sea levels are lower then normal. AVISO


A typical measure of El Niño is the Nino3.4 index which measures sea surface temperatures in the Pacific Ocean. The Nino3.4 index is very strongly correlated with sea level in the western equatorial Pacific.

Sea level at Fremantle is a good indicator of the strength of the Leeuwin Current. It tends to follow the Nino3.4 index and western equatorial sea level observations but with a delay of a few months. This few month delay is the time taken for the sea level change in the western Pacific to influence the strength of the Leeuwin Current near Fremantle.

Given that an El Niño has been forecast for 2015 and the sea level is dropping in the western Pacific, it seems very likely that we will see a weakening in the Leeuwin Current and cooler water temperatures along the coast of WA.

Graph with lines tracking up and down representing sea level
Timeseries of Nino3.4 (a measure of the El Niño and La Niña variability) compared to sea level in
the western tropical Pacific and sea level at Freemantle (a measure of the strength of the Leeuwin current)
So while eastern Australia watches for heat and drought, El Niño could be the cool relief WA’s oceans have been waiting for.

The Conversation


Jaci Brown is Senior Research Scientist at CSIRO.
Madeleine Cahill is Oceanographer at CSIRO.
Ming Feng is Principal research scientist, Oceans and Atmosphere Flagship at CSIRO and WAMSI.
Xuebin Zhang is Senior Research scientist, Sea level rise at CSIRO.

This article was originally published on The Conversation.

Video: Understanding ENSO

This Bureau of Meteorology video explains what El Niño–Southern Oscillation (ENSO) is, how the cycle works including the science behind the phases, and the potential impacts on Australia’s climate and weather.

Kimberley reef life considered on microscopic level

Written by Natasha Prokop (SNWA)

Using cutting-edge genomic analyses researchers are investigating how the Kimberley marine environment’s unique conditions affect organism movement in the region.

CSIRO researcher Dr Oliver Berry says the Kimberley’s massive 10m-plus tidal ranges and complex geography are likely to produce unique dispersal patterns.

These movement patterns influence the inter-dependence (connectivity) between reef populations.

“The movements of water in the Kimberley are amazingly complex and powerful,” Dr Berry says.

“But does this mean that populations are well-mixed? Or does it mean that they are very insular because the tides and currents disrupt movements?”

“By the end of the year we hope to have an answer.”

Dr Berry says defining the degree of connectivity in the region will help identify the appropriate scale for management.

One of seven focal species, the seagrass Halophila ovalis, selected for its significance as a key habitat. Credit: Kathryn McMahon


But he says despite the Kimberley’s high biodiversity and distinctiveness this is the first dedicated genetic study on marine connectivity.

The ongoing study has involved collecting more than 5,000 minute tissue biopsies of important organisms from the upper Dampier Peninsula and Buccaneer Archipelago for genetic analysis.

“We sampled species that have a spectrum of types of life histories that will expose them in different ways to the currents,” Dr Berry says.

The researchers targeted seven ‘focal species’ including the coral reef damselfish (Pomacentrus milleri), harvested molluscs (Trochus niloticus), coral (Acropora aspera), harvested fish (Lutjanus carponotatus) and seagrass (Thalassia hemprichii and Halophila ovalis) for their importance as habitat-formers or harvested species.

The movements of marine organisms, which affects connectivity amongst reefs and regions, happens mostly at larval life stages during which time larvae are transported by tides and currents.

But researchers can’t put tags or transmitters on microscopic larvae to track their movements, so they must infer this from the genetic relationships between populations.

Reefs in the Kimberley are exposed for only a few hours a day before massive tides submerge them again. Credit: Zoe Richards


Dr Berry says this genetic analysis poses its own challenges.

“In the marine environment, historically it has been difficult for genetics to resolve relationships between populations,” he says.

Therefore they used cutting-edge genomic techniques that have only recently been adopted by ecologists.

The scientists plans to use thousands of single sequence polymorphisms or SNPs (“snips”), which are regions of DNA where a single nucleotide differs in a sequence.

For example, ‘AGTTA’ might be a version of a gene carried by one individual, while another might carry ‘ACTTA.’ These variations act like ‘tags’ for the movements of organisms.

The benefit of using SNPs is the large number of markers that can be used, which should give researchers the ability to detect subtle patterns of connectivity.


This project relates to themes 2 and 3 of the Kimberley Science and Conservation Strategy.

Study co-investigators include James Gilmour, Kathryn McMahon, Glenn Moore, Zoe Richards, Mike Travers and Jim Underwood.

The project was undertaken with the assistance and support of the Bardi Jawi rangers and traditional owners and Mayala traditional owners whose local knowledge was invaluable to the fieldwork component.


The $30 million Kimberley Marine Research Program is funded through major investment supported by $12 million from the Western Australian government co-invested by the WAMSI partners and supported by the Traditional Owners of the Kimberley. 



Kimberley Marine Research Program