Blue swimmer crabs studied at all stages of life in Cockburn Sound surveys

A research team has, for the first time, been able to build a comprehensive picture of the distribution and abundance of blue swimmer crabs in Cockburn Sound over the species’ entire life cycle.

Dr Danielle Johnston, a senior research scientist from the Department of Primary Industries and Regional Development, is leading the collaborative project as part of the WAMSI Westport Marine Science Program.

She said blue swimmer crabs (Portunus armatus) were once the Sound’s biggest commercial fishery but stocks declined in the early 2000s with fishery closures in 2006 and 2014.

While DPIRD researchers have been surveying juvenile and adult blue swimmer crabs in the area for more than 20 years as part of fishery monitoring programs, they hadn’t had the opportunity to survey larvae.

“The juvenile and breeding stock data we have collected over the two years of the WAMSI Westport Marine Science Program builds on the historical data we already have but the collection of crab larvae is something we haven’t been able to achieve before,” Dr Johnston said.

“Collection, identification and counting crab larvae requires highly specialised skills and we were very fortunate to collaborate with scientists at WA Museum to achieve this.”

“This has meant we have a couple of years of data on crab larvae, juveniles and adult breeding stock which gives us a much better understanding of the whole life cycle of the blue swimmer crabs.”

Researchers are investigating the spatio-temporal distribution, or where and at what times of the year, the short-lived crustaceans are most abundant and whether observed trends can be explained by relationships with environmental conditions and habitat.

These findings can then be used to inform the Westport program.

The research team has caught about 8,500 adult blue swimmer crabs and around 1,500 juveniles over the areas of Cockburn Sound and Owen Anchorage which were measured before being returned to the water.

Collecting data on each life history stage has meant using multiple sampling methods.

“We’re looking at all life stages so we used bongo nets and light traps to collect crab larvae, trawl nets to collect juvenile recruits and hourglass traps for adult crabs and breeding stock.”

“Juvenile and adult crabs bury themselves in the sediment during the day and emerge for feeding at night, so much of our sampling occurred at night when the blue swimmer crabs are most active”.

Sampling for this project has now finished and the next stage will be to complete a comprehensive analysis, interpretation and write-up of the data.

But Dr Johnston said preliminary results show abundance was higher in the first year of the sampling in 2021-22.

“Crab abundances will differ from year to year based around environmental conditions, with warmer temperatures generally resulting in higher abundance as blue swimmer crabs are a tropical species,” Dr Johnston said.

Refer to the DPIRD website for the latest information on fishing regulations for blue swimmer crabs:

How Ningaloo whale shark snaps help international research

Commercial tour boat photographers take tens of thousands of photos every year of excited snorkellers enjoying close encounters with Ningaloo Reef’s magnificent whale sharks. But their photos, showing the distinctive spots and markings on the big fish, are also being shared in scientific catalogues to be used by researchers around the world.

It’s a scientific spin-off to a tourism industry that has taken off in Exmouth since swimming with whale sharks was allowed under regulated conditions.

Dr Kelly Waples, from the Department of Biodiversity, Conservation and Attractions, spoke to year 12 marine science students this year, as part of WAMSI’s Thinking Blue lecture series, about whale shark tours and other ecotourism ventures.

“We know humpback whales and whale sharks have long range migratory movement so this area around Ningaloo Reef near Exmouth is only a small part of where they spend their time,” Dr Waples said.

“Photographs of the whale sharks can be used in an international scientific catalogue.”

“We can identify individuals and get a better understanding of their movements including how often they might return to the marine park as well as some of the other places they might visit, how many times they are interacted with by tourists and how these interactions fit into the lifespan of the animals.”

“We use a range of other information that the tour operators provide through an electronic management system to help us evaluate the industry,” she said.

Other ecotourism operations that are allowed under regulation in Western Australia include swimming with humpback whales in Ningaloo and snorkelling interactions with Australian sea lions.

Dr Waples said ‘in-water’ encounters with humpback whales were first trialled in 2016. A humpback whale interaction program has since been developed with management strategies including a permanent licenced industry for up to 15 licensed operators in Exmouth and Coral Bay. Exmouth and Coral Bay are the only locations in the state that provide in-water interactions with humpback whale tours.

“Managing ecotourism activities in WA is an ongoing process and we assess and evaluate the businesses regularly.

“One of the key principles of ecotourism is to promote conservation, so we need to make sure messages about the environment are getting out there,” she said.

“Licensing is often used as a way of managing ecotourism and this can include creating time and zone restrictions, so the animals can have a break from interactions and not be disturbed during critical activities.”

Dr Waples said the licensed operators must adhere to numerous conditions around attempted in-water interactions with humpback whales. They are not allowed closer than 75 metres to the side of a humpback whale and swimmers must not approach the humpback whale closer than 30 metres.

There are also interaction limits to minimise potential disturbance to humpback whales and requirements for operators intending to interact with mothers and calves. This included aerial support to determine the presence and size of the accompanying calf.  Licence conditions are administered to minimise risk to animal welfare and swimmers.

You can see Dr Waples’ lecture here.


Underwater gardens provide hope for seagrass restoration

Researchers and commercial divers have created underwater garden beds in Cockburn Sound, using dredged sediment from a nearby area, as part of a project aimed at improving the survival rates of transplanted seagrass.

About 80 percent of the Sound’s seagrass meadows were wiped out by the 1970s because of excessive nutrient discharge and they have struggled to recover.

Capping existing seabed sediment, which contains residual nutrient contamination, is seen as a potential solution.

The project, involving researchers from Murdoch University and The University of Western Australia, is part of the Western Australian Marine Science Institution Westport Marine Science Program.

Seagrass researcher Dr Giulia Ferretto, from UWA’s School of Biological Sciences, said the project had been a big undertaking and involved many months of planning to organise a barge, large bags of sediment from Cockburn Cement’s dredging operation and divers who could set up the gardens.

“We used a small barge to take 15 garden bed rings out to the site in Cockburn Sound, then commercial divers fixed them on the seafloor” Dr Ferretto said.

“The barge also carried out tonnes of dredge spoil in 700-kilogram bags and a hoist helped lower the contents into the water.”

A garden ring for the sediment and seagrass sprigs is assembled on the barge.

A garden ring for the sediment and seagrass sprigs is assembled on the barge.

Dr Ferretto said capping the existing nutrient rich sediment with new dredged material may be a solution to a problem that’s hampered restoration attempts.

“We are going to compare the health and survival of seagrass sprigs planted in existing sediment to those planted in the dredged material,” she said.

“We have mixed a controlled amount of organic seagrass wrack into some of the dredged sediment to see if that natural ‘compost’ also makes a difference.

“We want to see whether sediment manipulation and addition is going to help the seagrass grow and whether there are better ways to develop new underwater meadows.”

Dr Ferretto said it was like gardening but more complicated underwater.

“Once the beds were put in place, divers raked the sediment and then dug small trenches to plant the seagrass sprigs,” she said.

Henry Evans, a research assistant at Murdoch University, said seagrasses were a vital part of the Cockburn Sound ecosystem and helped to stabilise sediment and provide food and habitat for marine fauna.

“If the addition of dredge spoil is shown to improve sediment conditions for seagrass, then we would be able to increase the survivability of future restoration efforts as well as expand the area that is suitable for seagrass restoration in Cockburn Sound,” Mr Evans said.

The seagrass shoots were planted in September and scientific divers will check them at regular intervals.





High tech equipment collecting data beneath the waves

Wave, current, sonar and camera equipment has been deployed underwater to allow researchers to track sediment flow in and around Cockburn Sound as part of a project which is expected to improve sand nourishment.

Research Fellow Dr Michael Cuttler, from The University of Western Australia’s Oceans Institute, said the research team had set up the high-tech instrument suites during dive trips to three sites.

“At each site, we have the same instrument packages which are designed to measure sediment transport,” Dr Cuttler said.

“They include acoustic instruments to measure waves and currents, and a three-dimensional scanning sonar and custom camera system to map and track seabed morphology.

“The instruments take measurements throughout the day and have already captured significant storm events this winter.”

The equipment is mounted on frames that are attached to steel poles which are fixed to the sea floor.

Dr Cuttler said the systems work to track how and where the sediment moves.

“A lot of our coastal processes work is focused on understanding the beach dynamics – are they accreting or eroding and under what conditions,” Dr Cuttler said.

Dr Cuttler said one of the key knowledge gaps researchers had been trying to fill was sediment transport from the offshore source to the beach.

“Some of the applications for this work is understanding the potential beneficial reuse of dredge material,” Dr Cuttler said.

“So, if they have excess material and want to use it for beach nourishment, where would be the best place to put it and then how long could we expect for that material to move onshore to act as sediment nourishment for the beach.

“One thought is that if you can understand the sediment transport pathways, you can optimise that nourishment, so it continually feeds the beach using natural processes.”

The Coastal Processes project, led by UWA’s Dr Jeff Hansen, is part of the WAMSI Westport Marine Science Program.

The equipment has been deployed three times since the start of the year during different seasons and a final deployment is planned for early 2024.





Cards, cocktails in yurts and community chats help inspire climate action

As a climate change ecologist and passionate science communicator, Professor Gretta Pecl knows the challenges of talking about dire threats to the oceans and species extinction, without people feel overwhelmed and ‘switching off’.

Professor Pecl, the Director of the Centre for Marine Socioecology at The University of Tasmania, and a researcher at the Institute for Marine and Antarctic Studies, gave the plenary presentation recently at the International Conference and Workshop on Lobster (and Crab) Biology and Management in Fremantle. The presentation was on ‘Fisheries in a warming world and changing ocean: What’s in store and what’s needed to ensure a thriving future?’.

The Western Australian Marine Science Institution was a conference sponsor.

“People need to understand the oceans; how they are changing and will change and one of the best things we can do is share stories of successful adaption programs,” Professor Pecl said.

She told delegates there seemed to be an increased acknowledgement of what was happening globally.

“In 2010 we surveyed fishers and 80 percent didn’t think climate change was happening,” Professor Pecl said.

“If we surveyed the same people now, I think it would be a very different response.”

Professor Pecl is a regular presenter at conferences but told delegates creating a two-way dialogue in smaller, informal venues was just as important. She talks with people about climate change and broader science issues in podcasts, over ecology themed playing cards and even while sharing cocktails at science events in yurts (round tent-like dwellings).

“I have toured pubs doing community question and answers and people are curious and want to know more.

Professor Gretta Pecl speaks in a pub at the ECCW05 in Bergen Norway

Professor Gretta Pecl speaks in a pub at the 5th International Symposium on the Effects of Climate Change on the World’s Ocean in Bergen Norway. Photo: Dr Jenny Shaw

“We also collaborate with media experts and psychologists because as humans we can be hard wired to not believe in climate change or to find it overwhelming to the point where it limits our capacity to take action.”

The evidence of climate change impacts is worrying. Professor Pecl said the sea surface temperatures hit 38 degrees in Florida Keys this July and heat-stressed corals began bleaching.

There were marine heatwaves on the Great Barrier Reef in Australia in 2016, 2017, 2020 and 2022.

“Reefs are resilient and can recover but the recovery period needs to be 10 to 20 years.

“They can’t be bleached year in, year out.

“Reducing other human caused pressures on reefs can help improve their natural adaptive capacity and for kelp forests, transplantation of heat tolerant phenotypes is useful.

“But without carbon emissions reduction these systems are still at risk.

“Five percent of species are at risk of extinction from 2 degrees of warming alone and that jumps to 16 percent at 4.3 degrees warming.

“The loss of biodiversity is not only an environmental issue but a developmental, economic, security, social and moral issue as well,” Professor Pecl said.

“Although oceans are changing fast, everyone is looking to the ocean for solutions.

“The ocean contains 50 times as much carbon as the atmosphere and acts as a biotic and abiotic thermostat by absorbing and releasing carbon dioxide and heat.”

Professor Pecl told conference delegates seafood had a relatively low carbon footprint compared to land base sources of food protein such as beef, lamb and cheese. Wild catch seafood rated better than aquaculture.

She said there had been a high level of coordination and collaboration in the research and industry sectors across Australia for more than 15 years and there was a well-networked research community.

“We can’t continue into a ‘business as usual’ future but it is possible to show a positive vision and create a mobilising narrative that supports action on climate change,” Professor Pecl said.

Project to predict and manage marine heatwave threats

Scientific experts from around Australia will work together on a major new UN-endorsed research project that aims to better forecast and respond to extreme marine heatwaves, as warnings mount that the devastating events will become more frequent and severe.

Lead scientist Professor Nicole Jones, from The University of Western Australia, said the project would uncover new data as well as gather historical information.

“These marine heatwaves have had a serious ecological and economic impact on the state in recent decades including the loss of coral, kelp and seagrass,” Professor Jones said.

“We have seen an impact on fisheries and there are also long-term changes to the function of the various ecosystems.”

The Western Australian Marine Science Institution will manage the project, ‘Advancing predictions of Western Australian marine heatwaves and impacts on marine ecosystems’ with funding from the Department of Jobs, Tourism, Science and Innovation. The project was recently endorsed as part of the UN Decade of Ocean Science for Sustainable Development 2021-2030.

The multi-disciplinary project team of 26 includes researchers in oceanography, marine ecology, atmospheric science and data science.

“Our key aim is to develop tools to efficiently create seasonal forecasts of ocean temperature and the associated habitat response to marine heatwave events for the coastal ocean. This information can be used to manage responses to future marine heatwave events,” Professor Jones said.

The project also aims to identify areas most at risk from marine heatwaves and those that are more likely to be resilient.

WAMSI Chief Executive Officer Dr Luke Twomey said the four-year project was an important one for WA.

“This will help the WA Government agencies make management decisions for the marine environment threatened by marine heatwaves,” Dr Twomey said.

Project scientists come from organisations including Bureau of Meteorology, Curtin University, Department of Biodiversity, Conservation and Attractions, Department of Primary Industries and Regional Development, Edith Cowan University, Murdoch University, and UWA.

The project is also funded by the Indian Ocean Marine Research Centre Strategic Infrastructure Investment Fund, the Jock Clough Marine Foundation and Fisheries Research and Development Corporation.


Coral reefs vital for ocean life

A quarter of all marine species depends on coral reefs but these vital parts of the oceans’ ecosystem are at risk from acidification, pollution, over-fishing and rising water temperatures.

The University of Western Australia’s PhD candidate Josh Bonesso spoke to high school students recently about the significance of coral reefs, as part of the Western Australian Marine Science Institution’s Thinking Blue outreach program. Josh was a finalist in the Student Scientist of the Year category in this year’s Premier’s Science Awards for his innovative research on coral reef islands. He’s also a keen science communicator.

“Coral reefs are nursery grounds for fish, they’re important too for megafauna and the building of coral reef islands that provide nesting areas for many species of seabirds and turtles,” Josh said.

“So, while coral reefs aren’t a large component of the ocean, about 25 percent of marine species rely on them directly and indirectly.”

Josh explained to the Year 12 students how coral reefs formed over thousands of years but that higher-than-normal temperatures and storm events caused by climate change threatened the survival of many coral varieties, particularly fragile branching corals. Mound corals were generally more resilient, but Josh said it was important for reefs not to become homogenous.

“At 34 degrees a species of branching coral, Acropora aspera, exerts a stress response and experiences bleaching.

“We know less about how these corals cope with stress at temperatures below bleaching, at around 32 degrees, and how this impacts their recovery from injury following storm events.”

“But experiments have been done in tanks at that lower temperature where the tops of coral branches are snipped off, to replicate storm damage, and they haven’t grown back,” Josh said.

Thinking Blue is WAMSI’s education outreach program which is designed to educate students about marine science and inspire them to do further studies in the field.

Josh is a PhD candidate at UWA’s Oceans Institute. He did his undergraduate science degree at La Trobe University and initially studied alpine and conservation ecology. But he told the students after a field trip to the Heron Island Research Station on the Great Barrier Reef, he ‘fell in love with coral reefs’.

You can watch Josh’s lecture here.

Fly larvae offers hope for future food security

Insects could be part of the solution to future global food security pressures, according to an aquaculture researcher looking at black soldier flies as a potential fish feed source.

PhD candidate Isobel Sewell, from The University of Western Australia, told students in a Thinking Blue lecture there was growing pressure on wild stocks from overfishing.

This, combined with the world’s population forecast to exceed nine billion by 2050, meant there was an increased focus on aquaculture as a sustainable alternative.

Thinking Blue is WAMSI’s school outreach program which gives students in Years 11 and 12 a chance to hear from marine scientists doing innovative research. It also aims to inspire school leavers to study marine science.

“The main question is, where will we find enough food for another one billion people and we think black soldier flies and their larvae could help,” Isobel said.

“Aquaculture is the most rapidly growing food production sector globally and there’s a lot of research looking at the feed given to fish that are reared in tanks and sea pens.”

“I am running trials at UWA with barramundi and marron to see how experimental diets containing black soldier fly larvae compare to a more traditional aquaculture diet, which typically contains wild-caught fish as a protein source.”

“For black soldier fly larvae to be considered a suitable alternative protein source, we need to ensure fish growth is promoted whilst still maintaining fish well-being.”

“So far, we have found barramundi fed the insect-based food are growing successfully and tests on their biological parameters, such as blood health, are within healthy parameters,” Isobel said.

She said the principal behind the experiment was to try to find ways of ensuring aquaculture fitted into the black soldier fly circular economy model.

“The three principles of the circular economy are to design out waste and pollution, to keep products and materials in use and to regenerate natural systems.”

Isobel said the ingredients for traditional barramundi aquaculture fish food was about 40 per cent plant dry matter, 30 per cent land animals, 15 per cent marine animals, 7 per cent land animal oil, and 1 per cent marine animal oil.

“There has been research on using more protein-rich plants such as soybean, but results showed they had the potential to cause inflammation of the fishes’ digestive tract.”

She said fish was an important food source for humans and had significant health benefits and there were concerns about the world’s growing population being able to nutritionally sustain itself without putting more pressure on ocean or land resources.

“Food insecurity affects 820 million people around the world, which is the equivalent of the combined populations of Canada, the United States of America and the European Union,” Isobel said.

Isobel told the students she had improved her experience during her studies by volunteering on projects including looking at plastic abundance on Albany beaches, tagging turtles on Barrow Island as part of a project investigating light pollution and working on a coral nursery in the Seychelles.

Find a link to Isobel’s talk here.

Wildlife watch: Keeping a protective eye on Carnac Island’s sea lions

A camera mounted above a beach at Carnac Island is giving researchers real time footage of Australian sea lions and allowing them to monitor the endangered animals.

The equipment, which was installed in 2022, provides a window into the world of the male sea lions that use the A-class reserve to ‘haul out’ or recuperate between foraging and making return trips to their breeding islands.

The project involves researchers from the Department of Biodiversity, Conservation and Attractions, Edith Cowan University, and The Australian National University.

Associate Professor Chandra Salgado Kent from ECU, who is studying the mammals as part of the WAMSI Westport Marine Science Program, said the camera was providing valuable information.

“We are hoping to get an estimate of how many sea lions actually use the Perth metropolitan area and how many sea lions might use a particular haulout site like Carnac Island, which is south west of Fremantle,” Assoc Prof Salgado Kent said.

“The animals are not here year-round. They do migrate up to Jurien Bay for the breeding season which typically takes place every 17 to 18 months.  Sea lions also spend a fair amount of time at sea foraging.”

Australian sea lion numbers have struggled to recover since hunting was banned. And while historically there may have been breeding in the Perth region, currently the area is only used by males.

“The camera there gives us a chance to keep an eye on the sea lions, see how many are there every day, if the numbers change throughout the day and what they may be doing.”

Assoc Prof Salgado Kent said staff from the Department of Primary Industries and Regional Development had set up the camera and were managing and maintaining it, which had been an enormous help for the project.

Project co-investigator Dr Sylvia Parsons, from DBCA, said researchers could change the direction the camera pointed and zoom in on particular animals.

The researchers have marked nearly 50 sea lions with numbers using hair dye and have also fitted some with satellite trackers.

“We are hoping to be able to use the camera to identify some of the individuals that we have marked or tagged. We can then use this information to determine how long sea lions may spend on land between foraging trips and hopefully the data will help estimate the size of the population using this space,” Dr Parsons said.

While the project is ongoing, she said the camera had helped them observe sea lions without disturbing them in any way.

“The camera provides a real-time window to be able to observe the behaviour and dynamics of the sea lions on the beach.

“The juveniles in particular seem to be the most active, coming out of the water and settling right next to other sea lions, which may result in the whole group reorganising themselves, before they relax and go back to their resting state again,” Dr Parsons said.

The technology is also helping support other research including on fairy terns, which are another threatened species.

“It is one of the reasons that Carnac Island is closed every year during the breeding season,” Assoc Prof Salgado Kent said.

“If nesting fairy terns are disturbed, they won’t sit with their eggs which means the chicks won’t hatch.”

Researchers say the camera has also been valuable for DBCA management staff to detect if people are illegally going ashore and disturbing birds and sea lions.

“We want the community to be aware of the regulations and appropriate behaviour to ensure the conservation of these species,” Dr Parsons said.



WAMSI coral researcher a Student Scientist of the Year finalist

Marine scientist Josh Bonesso said he was honoured to be a ‘Student Scientist of the Year’ finalist in the Premier’s Science Awards and hoped it shone a light on the impact of climate change on coral reefs.

Josh is a PhD student at The University of Western Australia’s Oceans Institute and works part time at the Western Australian Marine Science Institution. The Premier’s Science Awards winners were announced at a ceremony in Perth on 11 September.

Josh was named as a finalist for his work developing ways to rapidly assess the sensitivity of coral islands to climate change.

“I hope being a finalist helps draw attention to the impacts of climate change and the vulnerability of the world’s coral reefs and their islands,” Josh said.

“Coral reef-islands are the landform most threatened by the effects of climate change such as rising sea levels and ocean warming,” Josh said. “But much of our knowledge of changes to these islands has come from two-dimensional satellite images. My research, using three-dimensional mapping technology, captured the largest regional-scale group of islands globally, here in WA’s Pilbara.”

“This led me to develop a unique tool to rapidly assess changes to key features which could act as a crucial warning of imminent threats to the islands.”

He said he was thrilled for the winner, medical researcher Denby Evans, from Telethon Kids Institute and Curtin University.

The awards recognise remarkable achievement and innovation of scientists and science students in the state.

WAMSI CEO Dr Luke Twomey said Josh was an innovative scientist with a passion for educating and inspiring people about marine science and he congratulated him on being an award finalist.

“Josh’s research, which has now been published in a leading scientific journal, has broad ranging benefits worldwide,” Dr Twomey said.

“Josh’s ability to think laterally has established opportunities to lead and collaborate across government and scientific institutions to better safeguard WA’s marine assets.”

“Josh has been a regular speaker with WAMSI’s Thinking Blue outreach program and is always happy to share his knowledge about coral reefs and islands. He does terrific work communicating marine science within the community.”