Huge numbers reached in survey of tiny fish larvae 

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The most comprehensive survey of fish larvae in Cockburn Sound has now uncovered more than 40,000 of the tiny creatures from at least 50 families.

Researchers started monthly surveys in September 2021 as part of the WAMSI Westport Marine Science Program.

Researcher Jake Nilsen, from Curtin University, said at least 128 unique taxa had been identified, including pink snapper, whiting, trevallies and flatheads. Sea garfish and yellowfin whiting were recorded for the first time.

Another first-time recording was larvae of the highly sought after King George whiting.

Mr Nilsen said the King George whiting (pictured) was a particularly interesting find given the species typically spawns further offshore.

DNA techniques are also being used for species that are more challenging to identify and where there is limited information on their larval stages, including species of whiting and baitfish.

Now fieldwork has been completed, researchers will focus on analysing the vast dataset to identify patterns of when and where fish use Cockburn Sound during their larval stages.

Researchers from the Department of Primary Industries and Regional Development are also working on the fish larvae project by providing research vessels and staff for the sampling.

Water quality improving but Cockburn Sound still impacted by pollution legacy

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Water quality in Cockburn Sound has been steadily improving for decades but seagrass and some fish stocks are still struggling to recover from the days of unrestricted pollution discharge, according to marine scientist Dr Fiona Webster.

Dr Webster, who works at the Department of Water and Environmental Regulation assessing marine proposals, was speaking to students about the impacts of marine pollutants as part of WAMSI’s Thinking Blue education outreach program.

The program features lectures by some of the state’s top marine scientists, including from WAMSI’s partner organisations.

Dr Webster told the students that in the 1970s there were concerns about the environmental impact of industry discharging pollutants such as nutrients and heavy metals straight into Cockburn Sound.

“Around 80 percent of seagrass was lost and there were concerns people couldn’t swim or couldn’t fish and many were worried,” Dr Webster said.

“Whilst the extent of environmental deterioration sounds extreme, you have to remember that the Environmental Protection Act didn’t exist until 1986,” she said.

To protect Cockburn Sound, the State Government introduced two key initiatives; firstly direct discharges were banned and secondly the State Environment Policy for Cockburn Sound was developed.

Dr Webster said that while parts of Cockburn Sound will remain industrialised, the State Environment Policy ensured environmental, social and cultural values were protected and the water was safe to swim in and fish were safe to eat.

“Monitoring has shown the water quality has been improving since then and most areas now have good water quality,” Dr Webster said. “But seagrass is not recovering so well.”

“Part of that could be the organic nutrient load in the sediment.”

“Some fish stocks are also still depressed including the garfish and blue swimmer crabs.”

Whilst water quality in Cockburn is looking good, there are always new and emerging contaminants to watch out for such as PFAS (a key constituent in fire fighting foam) and microplastics.

Dr Webster told the students there was good work going on to support the environment including the replenishment of fish stocks and the Seeds for Snapper program. This involved volunteers collecting seagrass seeds and dropping them in areas needing regeneration.

Early inspiration

One of the aims of Thinking Blue is to inspire students to study marine science.

Dr Webster told the students, until her dad gave her a pair of goggles when she was six years old, she’d been nervous of seaweed.

“When I had my goggles on, suddenly I could see fish and bubbles and kelp.”

She later studied science and did a PhD after completing researching at Ningaloo Reef.

She told the students her career had ‘meandered’ from measuring crayfish on commercial vessels at the Abrolhos Islands to spending 18 months on a yacht off Madagascar to working with an Australian aid organisation in Tonga.

It’s a career journey that certainly inspires.

You can watch Dr Fiona Webster’s lecture here.

Marine interdependence – From turtle hunting crabs to tongue eating louse

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A camera focused on a Ningaloo Reef beach captures life and death in a marine ecosystem in its rawest form: Ghost crabs scramble to catch freshly hatched loggerhead sea turtles before sea gulls swoop in to snap up others as they stagger towards the shoreline.

Once in the water, there are new predators for the few that make it that far, but also organisms for them to eat and fuel their growth.

The footage, shot by recent PhD graduate Casper Avenent, was played to students as part of a WAMSI Thinking Blue lecture on the ‘Interdependence of organisms in marine ecosystems’ by Professor Glenn Hyndes from Edith Cowan University.

“As for the golden ghost crabs, they are possibly eaten by rays and dingoes but we don’t know”.

The scene on a small part of one Australian beach represents a much bigger ecological story.

“On this one beach at Ningaloo, there are different species of ghost crabs with very different diets,” Professor Hyndes said.

“We have found from gut analysis, the horned eyed ghost crabs feed a lot on insects and the golden ghost crabs will feed on carrion including dead rats, birds, fish, as well as turtle eggs and hatchlings.”

Professor Hyndes’ talk incorporated the many ways various species of plants and animals are interdependent and along with the video from the Exmouth area, he used an example of life along the south coast of Western Australia.

“There is algae, consumed by abalone and sea urchins, which are eaten by animals such as western blue groper. Bronze whaler sharks are consuming fish.”

One theme of Professor Hyndes’ talk was ‘Habitat Matters’.

Certain jellyfish provided shelter for juvenile fish and seagrass also played a vital role in a number of ways including giving a habitat for fish.

“The different seagrass species will be important for different fish species. For instance, the sea trumpeter fish prefer the canopy formation of the Amphibolis griffithii seagrass and blow fish are more likely to swim among the more sparce Posidonia coriacea.

Another example of interdependence was the anemone fish which can have sea louse feeding on its tongue and the inside of its mouth.

“This has a negative impact on the fish but there are cleaner wrasse fish that feed on the louse” Professor Glenn Hyndes said.

Professor Hyndes’ talk, including his slides and video footage from Ningaloo, can be found here on the WAMSI YouTube page.

Snapper research helping to evaluate hatchery release programs

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Researchers are working on non-lethal ways of evaluating the success of programs that release hatchery-reared snapper fingerlings into Cockburn Sound.

The WAMSI Westport Marine Science Program project, led by the Department of Primary Industries and Regional Development, involves analysing photographs of hatchery snapper to ultimately determine any physical differences with wild snapper.

DPIRD’s Dr David Fairclough, who is working on the WAMSI Westport Marine Science Program project, said the release of hatchery – reared juvenile snapper was perceived as a positive way of improving wild stocks but it was not always clear whether the fish thrived or how long they survived.

“Such information is crucial to assess how hatchery-reared fish may contribute to stocks,” Dr Fairclough said.

The project also involves research scientists from Murdoch University and Flinders University.

“For the research, photographs of the hatchery-reared snapper are imported into a computer program that allows 16 physical features on the fish to be assigned and the distances between them measured,” Murdoch University’s Dr James Tweedley said.

The same process will be conducted on juvenile snapper collected from Cockburn Sound but these fish will also be dissected and have their otoliths – a bone in their ear – removed to determine whether they were grown in the hatchery.  A non-toxic substance is used to stain the otoliths of live hatchery snapper before their release, allowing them to be identified later in biological samples.

“If significant differences end up being detected then, in future, citizen scientists or recreational fishers could become involved in monitoring released snapper by providing photos of their catches for analysis,” Dr Tweedley said.

The project is also investigating whether snapper from inside Cockburn Sound are genetically different than snapper in the open ocean outside the Sound. In addition, it will test if hatchery-reared juveniles contain the same levels of genetic diversity and are as well adapted as those found in the wild population in Cockburn Sound.

“The role of Cockburn Sound as a spawning and nursery area for snapper is well recognised. However, the level of contribution made by those fish to the population and associated fishery along the lower west coast is not fully understood,” Dr Fairclough said.

“Information from this project will help with future identification of where hatchery-reared fish move to, either in Cockburn Sound or along the west coast,” Dr Fairclough said.

Fish frames donated by fishers to DPIRD as part of their ‘Send Us Your Skeletons’ citizen science project, would give researchers an understanding of where hatchery-reared fish move by removing their otoliths to see if they are stained.

 

Huge state delivers vast array of marine ecosystems

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From mud skippers in Kimberley mangroves to orcas in south coast canyons and bizarre looking sea pigs in the deep ocean, Western Australia with its 12,500 kilometre coastline, boasts a vast array of ecosystems, according to marine scientist Dr Tom Holmes.

“In fact, if you include the islands, WA’s coastline is closer to 20,000km which is equivalent to almost half the circumference of the earth,” Dr Holmes said.

In a recorded talk to students, as part of the Western Australian Marine Science Institution’s Thinking Blue series, he discussed WA’s coral reefs, estuaries, mangroves and deep-sea ecosystems.

“There are more than 3,000 species of fish in Western Australia and there are a large number of animal and plants that are not found anywhere else in the world,” Dr Holmes said.

Thinking Blue is WAMSI’s school outreach program which allows students to hear from the state’s top marine scientists on a range of topics.  It’s run with passionate educator and marine scientist John Ryan, who is a teacher at Sacred Heart College in Sorrento.

Dr Holmes, the Marine Science Program Leader at the Department of Biodiversity, Conservation and Attractions, was the first speaker in the latest series of talks and told the students the state they lived in boasted eight of Australia’s 15 biodiversity hotspots.

He explained that mangroves, which are predominantly in the north of the state, supported a lot of life including molluscs, birds and mud skippers. Roots from the plants emerged from the sediment trapping organic matter and allowing the plant to breathe.

“Around Roebuck Bay near Broome scientists have found mangroves are an important area for juvenile green turtles and the area is like a nursery or creche for the animals.”

“There are 13 species of mangroves in the Kimberley and six or seven in the Pilbara.”

Speaking about estuaries, Dr Holmes said they contained a ‘mix of fresh and saltwater species’. One of these was the sawfish, which was a threatened species.

Dr Holmes shared photographs of life in the depths of the Indian Ocean including the sea pig, which is a pink coloured sea cucumber with modified legs and face tentacles.

“It’s a complete alien world at those depths where animals have adapted to live where the environment is cold, with high pressure, low oxygen and low light,” Dr Holmes said.

His talk also covered Western Australia’s spectacular coral reefs, of which Ningaloo is the most famous. He also explained that the biggest individual plant in the world was in WA, a seagrass in the sheltered embayments of Shark Bay.

“This plant has cloned itself over an enormous scale and is now 180km long.”

Dr Holmes finished his lecture, which will be shared with other schools and on the WAMSI website, by taking questions including one from a student about how they could find work in marine science.

He explained he grew up three hours from Queensland’s spectacular coast and learned to dive by retrieving golf balls. Once he had the chance to dive in the ocean, he was hooked on marine life and went on to study marine science.

He said it was a competitive area and it helped to get higher education qualifications.

“But there are many other jobs in this area that don’t require a doctorate including in policy and out in the field as a ranger.

“Get experience where you can, perhaps work towards a skipper’s ticket. It all helps.”

Check out Dr Tom Holmes’ Thinking Blue talk here:

Study examines 30 years of seagrass restoration to find best methods

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A major review of seagrass programs in Cockburn Sound has helped identify the best methods for restoring large scale seabed meadows and found community involvement was a key to success.

Seagrass meadows were decimated from the 1950s and restoration attempts in the past three decades have included everything from sprig and seed-based methods to mechanical plantings, seagrass in sandbags being placed on the seabed and wire coils being used to fix small plants into the sediment.

The project, which is part of the WAMSI Westport Marine Science Program, looked at more than 110 restoration efforts since the 1990s and re-visited 31 sites to assess their success.

The study was led by Professor Gary Kendrick from The University of Western Australia and Professor Jennifer Verduin from Murdoch University.

Professor Verduin said sprig-based programs, where mature seagrass shoots were collected by divers from natural meadows, were found to have achieved high transplant success rates.

“Survival was as high as 90 percent on larger scale sprig-based restoration trials of up to three hectares,” Professor Verduin said.

“We found over a period of 15 to 20 years, the growth of sprigs resulted in the formation of new meadows.”

The study found both sprig-based restoration and seeding programs, such as Seeds for Snapper, had developed viable methods for revegetating large areas of bare seafloor. But large-scale sprig-based restoration programs, while labour intensive, were particularly efficient in quickly stabilising the sediment and creating almost instant meadows. This accelerated the formation of natural meadows.

“Cockburn Sound and Owen Anchorage suffered a major loss of seagrass from the 1950s to the 1990s and while there have been dozens of programs since to rehabilitate the area, there has been limited follow-up to gauge their success,” Professor Verduin said.

“Restoration programs are important and contribute to the rapid natural recovery of seagrass habitats by ameliorating loss and supporting the recovery of grasses.”

“Some of the projects in the past have been on areas of no more than three hectares and we wanted to see if we could recommend a restoration package that could be scaled up to ten times that area to enhance restoration success.”

One of the main findings of the review was confirmation that engaging with local communities was key to the success of large-scale seagrass restoration programs.

Community-based citizen science and restoration projects working with volunteers were recommended as cost-effective approaches to increase the scale of restoration.

“These transplanting projects have already been successful at Southern Flats, Cockburn Sound, and Oyster Harbour, Albany,” Professor Verduin said.

Seagrasses, sometimes referred to as the ‘oceans’ lungs’ are a vital part of the ecosystem. They reduce coastal erosion by stabilising sediment, provide critical habitat for marine animals and efficiently store carbon.

Dozens of recreational uses identified, valued and mapped in project surveys

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Researchers have used data from hundreds of community surveys to create ‘heat maps’ showing the popular spots for 31 recreational activities in Cockburn Sound.

Bird watching, kayaking, jet-skiing and snorkeling were among the many uses identified by almost 600 people who responded to questions as part of the WAMSI Westport Marine Science Program project, which looked at community values in the Sound.

Beach activities, walking, running and swimming were commonly reported forms of recreation and the survey revealed recreation in Cockburn Sound was most highly valued for its contribution to people’s ability to have fun, improve their physical health, socialise with others, and to relax.

Dr Abbie Rogers, a Premier’s Mid-Career Fellow from The University of Western Australia School of Agriculture and Environment, who is leading a theme of socio-economic research for the program, said Cockburn Sound was one of the most intensively used bays in WA.

“The Sound is highly valued by the community for its ecological and recreational values and it hosts a vital part of the State’s economy,” Dr Rogers said.

Woodman Point Reserve, at the northern end of the study area, was found to be the most frequently visited location and beach.

The results were used to create ‘heat’ or kernel density maps that showed activity density or occurrence using circular patterns. Economic valuations were also calculated for recreational use of various sites.

Murdoch University’s Dr Michael Hughes, the project’s lead investigator, said the area was important for recreation.

“The variety of non-fishing recreational activities and associated values that coexist in the Sound highlights the importance of this area for the public,” Dr Hughes said.

The area studied included the shore and waters between Woodman Point and Cape Peron along with Garden Island and Carnac Island. The entire study area was associated with one or more recreational activity values.  “Understanding how people use marine coastal areas for recreational activities and the values associated with such uses, are important considerations for the development and management of these areas,” Dr Rogers said.

Dr Hughes said the ability of the Sound to host such a diverse range of recreational activities suggested the social and physical carrying capacity was considerable.

“Furthermore, management decisions and planning will require engagement with a wide range of recreational activity representatives,” he said.

Of the recreational activities identified and mapped, 16 were land based and 15 water based. They did not include recreational fishing, which is the focus of another project in the program. Other socio-economic projects are measuring the Perth community’s values for Cockburn Sound’s natural environment and ecology.

Students take a dive into marine science with ‘Thinking Blue’

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Students in their final two years of high school are being given access to some of Western Australia’s top marine scientists in a series of lectures on topics ranging from artificial reefs and ecotourism to coral bleaching and aquaculture.

‘Thinking Blue’, which is the Western Australian Marine Science Institution’s school outreach program, lets students hear from inspiring experts across a range of specialist areas.  WAMSI runs the program with John Ryan, a Marine Science graduate who is now a science teacher at Sacred Heart College in Sorrento.

WAMSI CEO Dr Luke Twomey said Thinking Blue was about inspiring year 11 and 12 students as well as taking the latest scientific research into schools.

“The Thinking Blue lectures allow students to hear from people at our partner universities and organisations who are among the leaders in their field,” Dr Twomey said.

“Some students may be inspired to study marine science but all of them develop a greater understanding of the world’s oceans, the threats they face and the role of science in finding solutions.”

The topics for the next school terms include marine pollutants, ecotourism around marine mammals and whale sharks, marine ecosystems, aquaculture as a solution to declining fish stocks and seagrass meadows and mangroves.

The lectures are presented by video link to students at Sacred Heart College and the recordings are shared with other schools and online to the community through the WAMSI website.

John Ryan said the outreach program helped open students’ minds to the wonders of marine science.

“The impact of Thinking Blue extends far beyond the classroom,” Mr Ryan said.

“By connecting students with scientists, it ignites a spark of inspiration, paving the way for a new generation of marine enthusiasts.”

“It is heartening to see that several Sacred Heart College students, driven by their experiences in this program, have chosen to pursue marine-based tertiary education courses, furthering their understanding and commitment to the conservation of our oceans.”

Links to previous recorded lectures can be found here.

First major study of fish larvae in Cockburn Sound

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While fishers head out into Cockburn Sound in search of prized catches such as pink snapper, a team of scientists has been targeting fish larvae to better understand which species are in the area during their earliest life stage and where they are most abundant.

Since late 2021, they have recorded more than 12,000 larvae during monthly sampling.

The researchers say while Cockburn Sound is known to be an important spawning ground for key fishes such as pink snapper, local studies on the larval stage of their development have been limited until now.

Jake Nilsen, a Research Assistant at Curtin University, is part of the team working on the WAMSI Westport Marine Science Program project which also involves scientists from WA Museum Boola Bardip, CSIRO and the Department of Primary Industries and Regional Development.

“We haven’t known a lot about the larval fish in this system,” Mr Nilsen said. “There have only been a few studies and nothing as comprehensive or long-term as the current project. This is the first of its kind to be looking at Cockburn Sound in such detail.”

He said of the thousands of larvae recorded by the team, the most abundant were baitfish, dragonets and filefish, which have to be individually identified to species (if possible) using a microscope.

This was a difficult and time-consuming task given there are so few larval fish taxonomists in WA.

“Important fishery species have also been common, including whiting, trevallies and flatheads which is exciting as it gives new information about their early life stages we didn’t previously understand,” Mr Nilsen said.

“Pink snapper larvae abundance has been relatively low compared to previous studies but observations indicate their abundance is likely to increase following the spawning in October of this year.”

“We are seeing spikes in the number of pink snapper larvae in the most recent samples over the summer period.”

“We know pink snapper use these areas for nurseries and that’s been backed up by the data we’re collecting for the fish larvae.”

“Cockburn Sound is proving to be really important for fish larvae and they are quite vulnerable to environmental stressors.”

Mr Nilsen said two methods were being used to sample larvae.

“The main one is bongo tows which is a net with a small mesh size towed behind a small boat. It basically goes from the surface almost to the seabed and comes back up.”

“In collaboration with DPIRD, we are also using light traps over the summer period to capture larvae that are attracted to light, and just after the snapper spawning period.”

“A promising finding from the light trapping method is the exceptionally high number of invertebrate larvae captured including the larvae of the blue swimmer crab.”

“Work is underway to determine the abundance of the early stages of this species, which remains largely unstudied.”

“Findings from this work may prove useful in restoring that fishery, which remains closed in Cockburn Sound because of concerns about declining numbers.”

He said there was a lot happening in the Sound that couldn’t be seen without a microscope.

“There is a lot going on in the water column.”

How does the ocean’s only flowering plant cope with being buried?

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In water tanks at Edith Cowan University, pots containing Posidonia sinuosa, the most widespread species of seagrass in Cockburn Sound, have been tested to see how much burial under sediment they can withstand. The research, part of the WAMSI Westport Marine Science Program, is looking at the resilience of the ocean’s only flowering plant, to dredging.

ECU researcher, Chanelle Webster, said seagrass was an important part of the ecosystem – providing not only food and habitat for marine animals but also stabilising the seabed and storing carbon which could help combat climate change.

Seagrasses tend to occur in the shallow waters along coastlines as they require a lot of sunlight, but they are easily affected by disturbances in the light reaching the plants.

“One of the main impacts of dredging is changing the amount of light plants receive when sediment is stirred up during operation,” Ms Webster said.

“Another effect of dredging on seagrass is when sediment gets moved and dumped in an area, the particles can settle on seagrass and bury it. This is where my experiment comes in.”

“There are about 10 different species of seagrass in the Sound but Posidonia sinuosa is the main species, you can find it in all areas of the Sound from Kwinana to Garden Island, and this is why we decided to do the experiment with this species.”

“We have been trying to understand how much burial Posidonia sinuosa can tolerate before you start seeing negative impacts to their growth or survival.”

Some of the potted seagrasses had no sediment added, others had up to 16 centimetres of sediment put on them in controlled conditions over four months.

The research team measured the amount the plants grew and noted cellular changes.

“From preliminary analysis, plants tolerate up to four centimetres of burial by sediment but with eight centimetres and more of burial they are impacted.

“When plants were buried by 8cm or more of sediment the growth was significantly less.”

The research indicated Posidonia sinuosa could tolerate burial of four centimetres of sediment for 16 weeks which was the duration of the experiment.

Ms Webster said while further analysis was still to be done, the preliminary results were promising in terms of being able to minimise impacts to seagrasses in the Sound.