From small fry to a big catch

The AquaWales cluster was a collaborative initiative between Cardiff University, Swansea University, Aberystwyth University, and Natural Resources Wales amongst other partners. It was funded by the Low Carbon Energy and Environment Research Network Wales to advance the field of sustainable aquaculture. Read on to hear more about the linear progression from funding, through people-power to career success.

Amy Ellison was an early career researcher

when she joined the AquaWales cluster

of scientists from across Welsh universities.

Based in Cardiff she was part of the team investigating the stresses on farmed fish as a response to the increased demand for aquaculture, the world’s fastest growing food sector.

“Around 1 billion people on the planet are relying on fish farming as their primary source of protein”

As a part of the project, we studied the genes of rainbow trout and tilapia to better understand what role they play in affecting their health in stressful environments”.

AquaWales PI Professor Jo Cable

With the importance of farmed fish to food security around the world, there are well documented problems with the process that AquaWales were seeking to address. Funding from the research network allowed the interested parties to invest in a dedicated team to directly pursue real-world issues that would have a tangible effect on the fish-farming industry and natural environment going forward.

The team were able to conclude that the stocking density of fish in farms affects the expression of their genes; one example being that they are less able to fight off disease when not stocked at an optimal density reflective of their natural communities.             

The unanticipated result was that it appeared that the artificial light periods used to rear fish in farms was actually affecting their genes too, translating into tangible effects on the fishes’ health.

To further the understanding of how artificial light affects the health of fish, Amy was successfully awarded a Biotechnology and Biological Sciences Research Council fellowship under the UK Research and Innovation scheme.

The concept underpinning Amy’s research is that of the circadian rhythm – the ‘body clock’ that we refer to in aspects of our life when we’re talking about jet lag or choosing not to eat late in the evening.

This rhythm is present in all living things and in animals enables sleep at the right time, effective immune responses and hormone release. Research into genomes in the past decades has shown that these daily rhythms are directly controlled by our genes. The genes responsible, therefore, have been named ‘clock genes’.

"What we’ve seen in our trials, is that artificial light regimes in fish farms is actually disrupting how the clock genes function."

With circadian rhythm being so important for health and immune responses, the artificial light is having a direct effect on the wellbeing of the animals being farmed.”

Amy Ellison

With little known about how clock genes affect non-mammalian species, Amy’s research is pivotal. With global aquaculture set to supply over 60% of the fish destined for human consumption by 2030 and Welsh fisheries alone contributing £30 million a year to local economies, the need to perfect fish-farming is urgent.

But why use artificial light in fish farms at all? Like any business, the farms are seeking to make profit and using artificial light encourages fish feeding and growth around the clock, increasing yields.


Amy and her fellow researchers have been working with the fish farming industry to better understand how aquaculture may be affecting the health and success of their product with a knock-on benefit to the health of the ecosystems these farms inhabit.

Artificial light is not the only stressor shown to effect clock gene expression in captive fish. Having lice, a common side-effect for fish in the farm environment, was yet another determinant. How do light, feeding regimes, circadian rhythms, parasites and gut microbes all interact to affect fish health?

Taking her research to Bangor University in the north of Wales, Amy has continued to explore how stresses impact farmed fish and their immune systems on a molecular level.

Her research published in 2021 shows that, rainbow trout reared under constant light were not significantly different in size to those provided with standard day and night light levels.           

In addition, the fish reared under constant light suffered a higher lice burden; suggesting that they were mounting a less efficient immune response than those reared in normal light conditions.

“Overall, our findings show that rearing fish in an environment with an absence of light cues is detrimental to their health”

Aside from the effects on farmed fish, Amy is keen to point out that this has a bearing on the health of wild fish too. With light pollution affecting 22% of the world’s coastal areas, what effect will this be having on the circadian rhythms of the animals there, and consequently, how is this affecting their health and immune responses? This is a question currently being explored by a collaboration between Bangor University, Aberystwyth University and the Plymouth Marine Lab.

Amy is now a lecturer in the Bangor University School of Natural Sciences and lead of the university “One Health” research theme. Her research group continues to further our understanding of host-parasite interactions, with current projects examining the use of chronobiology in aquaculture, the impact of light pollution on wild animal health, and the interactions of amphibian immune systems and their beneficial skin microbes.

“Without a doubt, the stimulation of investment that our initial Low Carbon Energy and Environment Research Network Wales grant enabled was vital to a great many research outcomes for us. The careers of researchers like Amy are a clear example of how, with the right support, our research excellence shines through”

Jo Cable, Cardiff University & Principal Investigator of the AquaWales cluster of researchers.

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