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.

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.

 

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.

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.”

Seagrass put to test to find best species for withstanding climate change impact

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Researchers looking at the possible impact of climate change on seagrass have tested the tolerance of the plants to rising temperatures after collecting samples at locations spanning 600 kilometres.

Nicole Said, a research associate from Edith Cowan University who is part of the WAMSI Westport Marine Science Program project, said six seagrass species were collected within Cockburn Sound and one, Posidonia sinuosa was collected along Western Australia’s coast from Geraldton to Geographe Bay.

The samples, which represent species that are all found in Cockburn Sound, were then put in chambers and subjected to incremental increases in water temperature from 15 to 43 degrees over 12-hours.

Oxygen changes in the water were measured to calculate the plant’s photosynthetic rate or the rate at which light energy was converted into chemical energy during photosynthesis. The experiments allowed researchers to understand at what temperature the plants thrived or were stressed.

“It appears from the species that we looked at in Cockburn Sound, the one most at risk from rising temperatures was Zostera nigricaulis which is commonly known as eel grass,” Ms Said stated.

Halophila ovalis, a species found in temperate to tropical areas and commonly known as paddle weed, spoon grass or dugong grass, was most able to withstand the higher temperatures.

Other species tested were Amphibolis griffithii, Posidonia sinuosa (the most widespread species in Cockburn Sound), Posidonia australis and Amphibolis antarctica, which are larger plants than the other two species assessed.

The research team found a heatwave in Perth that produced temperatures between three and four degrees higher than average summer temperatures would be likely to have a negative impact on the larger species which are generally able to withstand pressures for a greater duration than smaller species, but once damaged take longer to recover.

Heatwaves are predicted to become more frequent and more intense under climate change. An extreme marine heatwave in 2010 and 2011 saw a large area of seagrass in Shark Bay destroyed.

“With increasing ocean temperatures and an increase in marine heatwave events, seagrass species living close to their thermal limits are at risk from rising temperatures. There is limited temperature threshold information for seagrass species, which is critical information and can forewarn both present and future vulnerability to ocean warming.”

“There are other researchers around the world looking at climate resilience, but we have been missing this key baseline data to look at the physiology of seagrasses and how they may respond to these climate scenarios.”

ECU School of Science Associate Professor Kathryn McMahon, who co-leads the research on seagrass resilience said the findings were significant.

“These findings are really exciting as they indicate there are differences among seagrass species and population along our WA coast to ocean warming,” Associate Professor McMahon said.

“We can harness these differences and take actions to try and build resilience into our spectacular seagrass meadows.”

Thousands of creatures uncovered in sediment samples

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Sediment sampling by scientists in Cockburn Sound and Owen Anchorage has uncovered thousands of tiny marine animals and more than 200 unique species.

Researchers from Edith Cowan University, Murdoch University and Western Australian Museum found the animals, known as benthic invertebrates, living in and on top of sediment in 30 sites.

Professor Glenn Hyndes, from ECU, said the sediments were collected across two seasons using a Van Veen Grab Sampler which was operated on a boat to scoop up sediment.

“Sorting and species identification is continuing but at the moment more than 17,000 individuals from eight major invertebrate groups have been found.”

“Sediments from the sites were sieved to remove fine mud which left behind coarse sediment along with the animals,” Professor Hyndes said.

“During hundreds of hours work we found animals such as adult worms, snails, crustaceans, urchins and bivalves which ranged from one to five millimetres in size,” he said.

“We used tablespoons to locate and separate often fragile animals from the sediment.

“Taxonomists at WA Museum have been working constantly to identify the species, characterising the hidden diversity of this urban seafloor habitat.”

He said invertebrates were important because they played a significant role in healthy ecosystems as food for commercially important species, burrowers of sediment and by using multiple life strategies such as parasitism on bigger animals.

“This is the first benthic survey targeting invertebrates to be carried out at this scale in the Cockburn Sound area and the sheer quantity and diversity of invertebrates has been an interesting and exciting discovery.

“The data produced from this work will tie into similar projects focused on the abundance, diversity, distribution and diets of larger animals in Cockburn Sound and the ecosystem of which they are an important part.”

Professor Hyndes is working on the project, conducted under the WAMSI Westport Marine Science Program, with Dr James Tweedley and Dr Sorcha Cronin-O’Reilly from MU, Henry Carrick and Leah Beltran from ECU, along with, Dr Peter Middelfart from WAM, Dr Lisa Kirkendale, Dr Andrew Hosie, Associate Professor Zoe Richards, Oliver Gomez and Ana Hara.

As part of the project, researchers are also investigating the settlement of species on different hard substrates and under different conditions and locations. This project forms part of the WAMSI Westport Marine Science Program and understanding how to improve the effectiveness of substrate in a concentrated area will help develop successful, large-scale initiatives.

 

Fishing line and plastic endangering young dolphins

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A leading Perth dolphin researcher is urging fishers to be extra vigilant with the proper disposal of fishing lines and hooks after seeing several of the marine mammals in Cockburn Sound caught up in discarded line.

Dr Delphine Chabanne, from Murdoch University’s Harry Butler Institute, said she had seen two young bottlenose dolphins within about eight months that had line wrapped tightly around their bodies. Others had been seen caught in line in previous years.

“We want people to understand the harm fishing line and other pollutants cause to marine animals, including dolphins,” Dr Chabanne said.

“Many of the animals recorded with fishing gear entanglement are calves or juveniles and as they grow the lines dig into their skin.“

Dr Chabanne, who is also researching dolphin behaviour as part of the Western Australian Marine Science Institution Westport Marine Science Program, said she feared what researchers saw from boats was the tip of the iceberg.

“More individuals may have injuries from fishing line gear that’s not always visible to us.  As an example, we don’t always get to see the pectorals and tail fin, or fluke, of individuals which makes it difficult to evaluate the full extent of fishing gear impact on dolphins.”

Dr Chabanne said the risk of fishing lines to the animal varied but it could result in death.

“There are some dolphins that manage to get rid of the line by themselves with minimal harm to their bodies but for others, the injuries are too serious and they die, which can be a slow process.”

Some dolphins had been euthanised when their injuries were considered too serious.

Dr Chabanne said line wasn’t the only danger to the animals.

“I have seen a dolphin with a plastic bag around its dorsal fin. If this was to become stuck around its blowhole it would suffocate,” Dr Chabanne said. “Plastic too is a problem when it breaks up into microplastics which are ingested by fish, the main diet of dolphins.”

Studying the elusive syngnathids of the Sound

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Dozens of Perth divers and keen underwater photographers are helping research into the seahorses and pipefishes of Cockburn Sound and Owen Anchorage as part of a project which will also see water-borne DNA tested for evidence of the beautiful but elusive animals.

The project forms part of the WAMSI Westport Marine Science Program and Dr Glenn Moore, the Curator of Fishes at Western Australian Museum, is leading a research team looking into the diversity and distribution of syngnathids, a family of highly specialized and often cryptic fishes that also includes seadragons.

The fish have national protection under the Environmental Protection and Biodiversity Conservation Act of 1999.

“They are one of the most challenging groups of fish to survey,” Dr Moore said.

“We can’t run fine nets over the reef because they get caught up and the fish are difficult to spot diving, so we are using multiple methods including looking at historical records.”

“We are using as many data sources as we can to try and compile as much information as possible about the syngnathids in the Sound.”

Dr Moore said citizen scientists had so far uploaded more than 1,000 images to an online portal along with the location where the fish were spotted.

He said one limitation of citizen scientists was they tended to head towards common dive areas where seahorses were well known but the information was still valuable.

Environmental DNA testing will also start soon on water collected from Cockburn Sound to add to information about their distribution.

“We have done some water sampling and we will do eDNA work in the next few months.

“We have frozen water samples and these will be analysed at a specialist laboratory at Curtin University.

“We are hoping we can start to build a picture of their distribution and habitat preferences,” Dr Moore said.

He said part of the eDNA work involved building a DNA library.

“You need to have something to match the eDNA to when we are doing the analyses.

“We need to get DNA from specimens we are looking for and that is a challenge because we don’t get to collect all the species we know are there.”

Dr Moore said most syngnathids lived in shallow coastal waters and were especially reliant on habitats well represented in Cockburn Sound, including seagrass, filter-feeder communities, shallow detritus, reefs and artificial structures.

He said the distribution, habitat preferences and abundance, particularly of seahorses and pipefish, wasn’t well known but the research aimed to find out more with the aim of improving their protection.

Photos: Western Australian Museum

Big pods and ‘fearless mums’ among the dolphins of Kwinana Shelf

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A dolphin with a distinctive white flash and a female bearing the scars of a shark bite, likely suffered while protecting her calf, were among about 120 individual dolphins recorded by researchers in the Kwinana Shelf area last year.

Dr Delphine Chabanne, from Murdoch University’s Harry Butler Institute, is leading the project which forms part of the WAMSI Westport Marine Science Program and involves monitoring dolphin distribution from Woodman Point to James Point within Cockburn Sound.

The dolphins that were recorded included 24 calves under two years of age.

The research team did the surveys from a boat travelling along parallel lines, 500 metres apart.

Dr Chabanne said 55 percent of the non-calf dolphins were re-identified from the last survey work between 2011 and 2015, indicating there are long term dolphin residents in Cockburn Sound.

“The long-term connection with other resident communities is also supported with four of the Swan Canning estuary resident male dolphins observed interacting with dolphins in Cockburn Sound,” Dr Chabanne said.

The team photographed the animals, noted their GPS coordinates and recorded water temperature and depth at the locations.

“One of the challenges was to make sure we have photographs for all dolphins when the groups are large,” Dr Chabanne said.

“We were seeing 15 to 35 dolphins in a pod, sometimes breaking into smaller groups then re-joining before breaking again into smaller groups all in less than 30 minutes. This fission-fusion behaviour is typical in bottlenose dolphins.”

Dolphin with shark bite mark on fin. Photo: Delphine Chabanne

Dr Chabanne said ‘Tippy’, one of the adult females, had a damaged dorsal fin from a shark bite.

“The females are more vulnerable to being attacked because the sharks will often target the calves and the mothers will work very hard to protect them.”

The first time ‘Tippy’ was recorded with fresh shark bites, her calf was only two months old. Two weeks later, ‘Tippy’ had suffered from further shark bites. The next time she was seen, unfortunately, her calf had disappeared.

Predation by other animals is not the only risk. Dr Chabanne said researchers spotted at least two calves with fishing lines around their bodies or pectorals.

Dr Chabanne said ’Tippy’, was first recorded in the early 1990s and is believed to be close to 40 years old. In fact, several individual dolphins observed in Cockburn Sound during the last year are between 30 and 40 years old.

Another female called ‘Jinx’, with a distinctive white mark on her back, is believed to be close to 30 years old and gave birth to a new calf this year.

Dr Chabanne said the average life expectancy for a female in the wild was 40 years, with males often not surviving beyond 35 because of fighting and riskier behaviour such as venturing into less protected areas.

The researchers are looking at where the dolphins in the Kwinana Shelf area spend most of their time during the year and working out why they are in certain areas.

Dr Chabanne said data was collected over four seasons to see how dolphins responded to changes in the environment.

Dolphin dreams a reality for WAMSI scientist

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On International Women’s Day, March 8, WAMSI Science Coordinator Dr Kelly Waples reflects on her career

As a young girl in beachside California, Kelly Waples dreamt of being a dolphin trainer from the first time she visited a marine aquarium. Her interest soon shifted from spectacle to science but a passion for the marine mammals remained.

Dr Waples, now a Principal Scientist for Department of Biodiversity, Conservation and Attractions and a Science Coordinator for Western Australian Marine Science Institution (WAMSI), ultimately did her doctoral research on rehabilitating and releasing captive dolphins.

“I was always interested in dolphin behaviour, but as I spent more time in the field, I became interested in applying what we learn about these animals to conservation questions,” Dr Waples said.

“The opportunity to work on a dolphin release came up and I jumped at the chance to return to Australia and participate in what was, at the time, a groundbreaking project.”

She described finishing her PhD and moving to Australia as a time when her career hit a crossroads.

“It became clear to me that to pursue a career in marine mammal field biology was not going to be easy or provide much in the way of job security.”

A move to wildlife conservation as a coordinator of wildlife management in New South Wales was ultimately a rewarding opportunity.

“I was responsible for coordinating and advising on a range of issues from nuisance flying foxes and possums to whale strandings and oil spills,” Dr Waples said.

“I was lucky to again have a career change when I returned to Perth and joined the Marine Science Program at DBCA.

“I have more of a science coordination role at WAMSI and have the opportunity to interact with a wide range of scientists from various disciplines to participate in research supporting conservation decisions and to advise on a number of marine mammal issues.”

In her role at WAMSI, Dr Waples is back working on a project involving her first research ‘love’- marine mammals.

“I’ve really enjoyed this last year with the opportunity, through the WAMSI Westport Marine Science Program, to be out in the field in our own backyard here in Perth learning more about the endangered Australian sea lions.”

“I’m learning new skills and working with a wide range of fantastic scientists, veterinarians and marine staff.”

Reflecting on International Women’s Day, Dr Waples said while most of her early mentors and colleagues were male scientists it had been heartening to see that change over time with many amazing and dedicated female scientists joining the ranks.

“I hope that I have done my part (improving the gender balance) by championing young female scientists where I can and giving them the advice and support to choose their paths well.”