Evaluating insect meal proteins in aquafeeds, PhD candidates Kat Doughty and Isobel Sewell are drawn to the potential of aquaculture to address food security and climate issues

Words and photos by Corrina Ridgway

“I’ll get one shot at this,” comments Katarina ‘Kat’ Doughty, concentrating on the water in the research tank as she glides a scoop net towards an evasive trout. Isobel Sewell stands by, ready, if needed, to herd the fish toward Doughty’s practised hands.

It’s a scene that encapsulates the physical skills that aquaculture requires of its researchers beyond laboratory-based analysis.

The two are PhD candidates at the University of Western Australia (UWA), working together on an FRDC-funded project evaluating protein alternatives to fishmeal in aquafeeds – specifically insect meal.

They admit that before beginning their current research they had little knowledge of the aquaculture sector. But they’ve since become converts, advocating for its potential in addressing some of the world’s biggest challenges: food security and climate change.

Sewell’s path

Sewell grew up in WA and spent time on the coast, with family holidays at Rottnest Island and Dunsborough. As with many others who study marine science, she has a long-standing appreciation for the ocean and the environment.

After a degree in Marine Science, Conservation and Wildlife Biology at Murdoch University in Perth, she went on to her master’s at the University of Western Australia where the chance to work on the FRDC aquafeeds project came along. Her master’s project soon evolved to become the pilot for her current PhD research.

“Learning about the high dietary protein that’s required [for aquafeeds], which is often in the form of fishmeal, really shocked me,” she says. One thing that drew her to the current project is its circular economy approach, using insects raised on food waste to help solve a feed issue for the aquaculture sector, which in turn has the potential to address human food security. “It’s nice to do a project where you know there’s a real-world impact,” she says.

Doughty’s journey

Doughty is originally from Canada, where she studied premedical science before an interest in genetics led her to honours study, looking at the genetic adaptation of the Guppy (Poecilia reticulata) to increasing water temperatures. A master’s soon followed, with similar research involving farmed Chinook Salmon (Oncorhynchus tshawytscha).

“That got me into aquaculture,” she says.

“I worked on feeds and hybridisation through genetic breeding programs. It opened my eyes to a lot of global issues and how efficient aquaculture is and how, as a young industry, we have a real opportunity to drive positive change.”

She went on to manage the nutrition laboratory for the Canadian Government’s aquaculture sector before being offered her PhD opportunity
in Australia.

The project Doughty is working on with Sewell is in conjunction with sector partner Future Green Solutions, a Perth-based business that produces insect meal using the Black Soldier Fly (Hermetia illucens).

Their trials use Black Soldier Fly larvae produced solely on food waste. Carrots, broccoli, bread, spent grains from brewers and leftover wheat dust are collected and processed into a pulp at Future Green Solutions. The larvae live in and eat the waste substrate. Given this, when compared to other aquaculture diets, the insect meal diet has a much lower environmental impact.

Black Soldier Flies are generalised eaters.

With their pupae-dominant life cycle and narrow temperature and humidity thresholds, they are easy to manage, posing a low biosecurity threat.

Rainbow trout

Doughty is investigating dietary substitution and maintenance of Rainbow Trout (Oncorhynchus mykiss). This carnivorous salmonid species is farmed on every continent except Antarctica.

“If they can handle massive changes in diet ingredients, it’s a good baseline to move to other species,” explains Doughty.

Doughty started her investigations in April 2019, running nutritional composition analyses of the flies before establishing feed trials. The pellets have up to 30 per cent insect inclusion; that being the standard commercial inclusion of fish or poultry meal in Rainbow Trout aquafeeds.

Most aquafeed trials are run with juveniles over a short period of time; however, Doughty’s trial is also addressing the longevity and maintenance of adult trout.

Assessing the long-term effects of a specific diet is vital. The aquaculture sector has been cautious about relying too heavily on a single protein substitution since the prolonged use of soybean meal in Atlantic Salmon (Salmo salar) feeds was found to cause nutritional deficiencies.

“My juveniles were fed diets including insect meal for 21 weeks and I continued to feed the fish for another 18 months,” she says. This included breeding adults. The results have not yet been finalised, but fish health was maintained for the full trial.

Once processed, the data will give Doughty applied results that can be used by producers with confidence about the long-term dietary effects on maintenance and reproduction.

Barramundi and marron

Meanwhile, Sewell is evaluating diets based on Black Soldier Flies for Barramundi (Lates calcarifer) and marron (Cherax cainii). She is backing up growth trials with analysis of biological indices such as gut histology and microbiome analysis, blood samples and the basic nutritional composition of fillets.

She has trialled numerous diets that compared several variables. Commercial and reference diets have been compared to insect meal alternatives, which in turn have been further teased out by comparing pellets using full-fatted or defatted larvae.

Two years in, her preliminary data based on growth trials and blood analysis is looking promising. “For Barramundi, it looks like performance is the same across all diets, which is what we’re after – we want to perform the same or better,” she says.

Although they’re still analysing marron data, early results indicate insect meal diets may outperform the reference and commercial diets and they suggest that Black Soldier Fly meal will be viable for both Barramundi and marron.

Future directions

The FRDC project provides scope to push other research areas once key milestones are met. Doughty hopes to do some extra research, possibly value-adding the insects, rather than increasing the number required in the feeds.

“It’s not necessary work for the initial incorporation of insect meal in aquaculture diets, it’s really for my curiosity,” Doughty admits.

Tying research into the broader global environmental and consumption picture is vital for the pair. They’re passionate about aquaculture for food security and environmental benefits.

“Globally, it’s the most efficient and least environmentally destructive way to produce massive amounts of protein. Feed conversions are generally two to one,” Doughty explains.

Paired with her research background, Doughty is keen to push forward into the global policy and advisory arena. She points out, “I’d like to understand how we can globally implement these practices, making sure it’s easy and accessible to do, but also ensuring proper implementation. I’d love to be able to get to a point where I’m doing that.”

Doughty believes it will become increasingly important to rely more on aquaculture and less on other terrestrial production to address global climate change.

“I’m not saying aquaculture’s a perfect solution, but if you compare it to other foods per kilo of edible protein, it’s remarkably better,” she says.

Sewell, for now, is focused on her current work: “[Aquaculture] is really multifaceted and I don’t think people realise that,” she says.

The pair are the only women they know of involved in aquaculture research in WA and they say working together in the FRDC project has been a timely benefit.

“Other areas in UWA have 10 or so people who work together. It’s just us, so being able to share the workload is great,” says Sewell.

But she believes that both the lack of people and the lack of women in aquaculture research will soon change. She reports that many of her peers had no idea about the impacts or depth the sector has to offer, but have since been impressed.

“A lot of my friends are happy to come and help on the weekends, they love the hands-on experience,” she says. “Now that Kat and I are doing research here, there’s been a lot more conversation about aquaculture. People are interested, given that it’s such a tangible solution.” f