Libor Zàvorka: warming shrinks juvenile Atlantic salmon by decreasing their fatty acids

In this blog, postdoc Libor Zàvorka from Inter-University Centre for Aquatic Ecosystem Research (Lunz) discuss his research on climate change effects on salmon diet, shows the relevance of physiological changes in ecosystems and presents his long record as fish catcher. 

About the paper

The big question: how does variability in content of essential fatty acids in natural prey drive development and evolution of brain and cognition in wild animals?

Libor Zàvorka with a male adult Atlantic salmon during milt and eggs collection.
Libor Zàvorka with a male adult Atlantic salmon during milt and eggs collection.

In this paper we’ve had a look at how decrease of essential fatty acids in diet of juvenile Atlantic salmon affects their physiology, brain development, and behaviour at different temperatures. Climate change is predicted to lead to reduction of essential fatty acids at the base of aquatic food-webs, so we were interested in exploring how would this ecosystem change affect juvenile salmon that is often on the top of the trophic chain in their nursey streams.

I have an ongoing project looking at how diet quality influences brain development and behaviour of salmonids and talking to colleagues at University of Glasgow during the “Friday beer in the Museum” we have figured that it would be interesting to do an experiment on juvenile Atlantic salmon and besides the behaviour also look more into the effects on fish physiology.

We found that juvenile salmon fed a diet deprived of essential fatty acids, contained less of these micronutrients in their muscle and brain, and that mitochondria in their muscles were less efficient in production of energy. Intriguingly, both the functioning of mitochondria in the brain and learning ability of the fish were unaffected, despite the substantial decrease of the essential fatty acids content in the brain. Our findings indicate that juvenile salmon have a capacity to mitigate at least some negative effects of temporarily reduced diet quality on brain functioning even at elevated temperatures. However, we also found that this adaptation comes at an energetic cost, which translates into reduced body growth.

We showed that the effect of climate change is not just about the physical parameters of the environment (e.g. increase of the temperature), but also about some more subtle biotic changes such as the reduction of essential fatty acids production at be base of the aquatic food-web. These factors receive little attention but can have far reaching ramifications for the fitness of all consumers.

The knowledge about the key role of essential fatty acids for fitness of fishes and also humans have been out there for a long time, especially among people interested in aquaculture production or studying brain development in humans. However, we ecologists did not have much interest in exploring the importance of these micronutrients in wild animals. Our study is one of the first showing the importance of essential fatty acids for wild fishes and calls for more research into this topic in the context of wild animals feeding on their natural prey. Our paper is relevant for everyone who is interested in how changes at the ecosystem level can trickle-down all the way to an individual consumer. I think that this work can be of interest for academic ecologists looking for a new and unexplored research topic as well as for policy makers and stakeholder interested in ecosystem management.

About the research

Looking at the research more broadly, the reduction of essential fatty acids in aquatic ecosystems will eventually also affect availability of these micronutrients for terrestrial consumers such as birds and mammals feeding on fish and aquatic insect, including humans. We need these essential fatty acids to build our brains and have our mitochondria working properly, so the lack of them can have negative impact on cognition, but also on other traits such as metabolism or body growth rate. So, the reduced availability of fatty acids in aquatic food-web can spill out from the aquatic ecosystems to the terrestrial consumers.

Juvenile Atlantic salmon in respirometric chambers.
Juvenile Atlantic salmon in respirometric chambers.

The most challenging, but also exciting part of the study was the trip to Northern Scotland to the catchment of Connon River to strip eggs and milt from the adult Atlantic salmon returning for spawning to the nursery streams.

About The Author

As many other people, when I was small I used to play a lot in small streams, build dams and try to catch fish from under the rocks, but unlike my friends from that time I’ve stuck to this activity until today.

My current position is Postdoc/Father (or the other way around, it depends which day you’d ask me) I’m still trying to find balance between the work and parenting of my small son.

I am very excited about my current project and the article published in Functional Ecology is the first research output that came out of it, so I am definitely happy and proud of this paper.

The best part about being an ecologist is the diversity of the work that ranges from outdoors activities during the fieldwork to intellectual challenges when designing an experiment, analysing data, and writing papers. I also like to discuss with stake holders and policy makers about the natural processes that I study, because it sometimes lead to positive changes in how they, on behalf of us all, treat the nature. 

The flipside of this is not unique to ecology, but I feel really down when I get stuck on a problem that I cannot solve and when I get research proposals and papers rejected. But patience usually helps to overcome this. 

I generally don’t have much of free time just for myself these days, but when I do, I like to sleep, go running, read a good book (e.g. Kafka, Steinbeck, Hůlová) or go hiking or ski-touring to the mountains. 

One piece of advice for someone in your field… Find a joy in every step of the work you do and don’t focus too much on the results. It makes the work more enjoyable and rejections less painful. I loved when I presented some side project to my Swedish PhD advisor and his answer was “That sounds like fun, let’s do it!”

Read the article in full here.

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