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Dr. Katerina Kousoulaki: The future of fish nutrition in aquaculture

October 14, 2019

Strategic management of aquaculture byproducts can lead to increased production with less fish.

With global population growth and an increasing demand for fish products, the aquaculture sector is facing more pressure for seafood production. Dr. Katerina Kousoulaki, senior researcher at Nofima AS in Bergen, Norway, discusses the future challenges and opportunities for fish nutrition, including microalagae, in aquaculture.

The following is an edited transcript of Tom Martin’s interview with Dr. Katerina Kousoulaki. Click below to hear the full audio.

Tom:              Considering the increased demand for raw materials in a growing aquaculture sector, do we need to revisit nutrient requirements for farmed fish? Dr. Katerina Kousoulaki is a senior researcher at Nofima AS in Bergen, Norway. She leads research projects in fish nutrition and physiology, raw material processing and feed technology related to aquaculture, fisheries and the development of new ingredients for the aquaculture and food industries. Her current work focuses mainly on the effects of new dietary ingredients on fish health, welfare, production characteristics and final product quality for consumers. Dr. Kousoulaki joins us to talk about the future challenges and opportunities within evolving raw materials basket. Thanks for joining us.


Katerina:        Thank you for having me.


Tom:              So, we're experiencing something of a perfect storm here: global population growth, increasing per-capita seafood consumption, including increasing human demand for omega-3s found in fish products, and the maxing out of wild fisheries. This would seem to place increasing pressures for future seafood production on aquaculture. Is that an accurate assessment, would you say? Why is the availability of raw materials important?


Katerina:        This is very true, Tom, and along with the population increase, our nutrition standards also increased, and we consume more protein and are becoming increasingly aware of the health benefits of more marine omega-3s. So, aquaculture products that combine both can still grow in a sustainable way.


Tom:              What sorts of raw materials are we talking about here?


Katerina:        To manufacture feeds, of course, we need raw materials that should come from sustainable sources in industries, and these are mainly byproducts from maize and soya production. They're from wheat and sunflower oil, peas, animal byproducts. There are, in some markets, byproducts from fisheries, capture fisheries, so there are all sorts of ingredients that could potentially also end up as food, but they are also used in the aquaculture market, which is increasing.


Tom:              Why is the availability of these raw materials a challenge for the aquaculture feed industry?


Katerina:        Exactly because capture fisheries have been stagnant during the last years, and as fish eat fish, fishmeal has always been the golden standard for aquafeeds. Replacing fishmeal is possible to a degree but requires substantial processing to refine materials from plant origins and make them available to fish.


Tom:              As I mentioned in the introduction, your work focuses on the effects of new dietary ingredients on fish health, welfare, production characteristics in the final product quality that consumers see. Let's unpack that, and let me first ask: do we need to revisit nutrient requirements for farmed fish, and why?


Katerina:        Yeah. Going back to the time that fish like salmon, trout, bass and bream were fed fishmeal-based feeds, those covered their needs and requirements as we know them, but moving to vegetable-based diets and also considering the changes in the environment, like climate change and temperatures, the changes of the technologies and more efficient production, like closer circulation systems that challenge the fish, we need to reconsider and make sure that we provide all that the fish need to grow both fast and robust.


Tom:              Researchers at the University of Stirling have developed a model that shows an increasing availability of raw material from byproduct that is derived from aquaculture as that sector continues to grow. Are you familiar with this research? And if you are, what can you tell us about the raw material derived from aquaculture byproducts?


Katerina:        Yes, that’s true. Strategic management of byproducts can lead to increased production from, actually, less fish. This study emphasizes the need to fully utilize the byproducts from aquaculture. In the case study, they have demonstrated that the potential of Scottish salmon farms, for example, could increase food production by 60% and the revenues by 800% and a total of 5% increase in the baseline of the company. These byproducts are, for example, the blood, the frames, the heads, the skin, the belly flaps, trimmings, viscera, and all that amounts to up to 50%, almost, of the whole bodyweight. So, if we find clever ways to use these byproducts in fish products, then that could actually increase a lot of production of food from aquaculture.


Tom:              Can marine phytoplankton and seaweed be used instead of fishmeal and marine fish feed?


Katerina:        Yeah. This is actually an exciting new way of feed for relation development. Phytoplankton is like microalgae. It's the base of the food chain and the primary producers of vitamins and omega-3 fatty acids, essential amino acids, so microalgae production is growing, and we are already testing this biomass against fish pill and fish oil with very exciting results.


Tom:              So, what are the effects of these new dietary ingredients on fish health and fish welfare?


Katerina:        Such materials, they contain bioactive compounds that can increase the gut health of the fish. The performance of the fish in aquaculture relies very much on the fish and digestion and also the immune system to fight pathogens and stress, so then we can reduce, also, the use of antibiotics.


Tom:              How do they impact production characteristics?


Katerina:        What we have experienced, actually, is that the use of microalgae can make fish grow faster, and that's possibly due to the improvement of the gut function — also, in particular, in suboptimal conditions. Microalgae, when you use the whole organism, they contain oil, the nutrients that the fish actually needs. Also, that enhances, naturally, the quality of the filler like color attributes. We have seen better pigmentation, which is important in salmon, among others. Also, the fish seemed to like the taste, so they can eat more and grow faster.


Tom:              So, what are the challenges in producing a high-quality product?


Katerina:        There are actually many different quality standards, and that's a tricky one. The farmers, they have to address them all, depending on their markets, and some are related to the nutritional value of the product and proteins in fish. They nearly always meet the requirement of high-quality, but the levels of the omega-3 in the filler may vary, the looks of the filler may vary, their shelf life, and also the environmental friendliness of the production, so these consumers are increasingly aware of welfare issues, so how the animals were treated during production. It's very important, also, that there are no undesirable compounds, toxic contaminants, pesticides, PCBs — so this is very important. Some markets actually demand no use of GM products, and the sourcing of the raw materials for feed production is important, that it comes from sustainable industries.


Tom:              How will these adjustments affect the full life cycle of the fish?


Katerina:        If we decrease fishmeal in the diet without making the necessary compensation for important nutrients, the fish may not actually have a robust immune system and may suffer more from disease and grow slower, so it is very important that we become completely aware of what we're removing when we take away the marine ingredient and what we are bringing back when we are using different alternative sources. Some are very rich, as I said, so it goes very well, actually.


Tom:              I think you just touched on this a moment ago, but just to kind of expand on it, can the consumer anticipate noticing any influence on the final product quality?


Katerina:        I would say not really. Those eating fish will still enjoy them in a way, but, for example, microalgae may even improve the taste. Lowering fishmeal in the diets may also reduce the fishiness of the product, which consumer segments appreciate, so they want to use the sources on top of a fish that doesn’t really smell or taste fishy.


Tom:              Dr. Katerina Kousoulaki is a senior researcher at Nofima AS in Bergen, Norway. Thank you so much for joining us.


Katerina:        Thank you for having me.


Dr. Katerina Kousoulaki spoke at ONE: The Alltech Ideas Conference (ONE). Click here to learn about ONE and how you can access innovation on demand.