by Arkadios Dimitroglou, Assistant Professor in Fish Nutrition, Agricultural University of Athens, Greece
Climate change has been documented for decades and is being mentioned more often day by day. The problem gets greater when this change has been accelerating continuously over recent years. More specifically, rising temperature is the most common characteristic that most people are familiar with but we are also witnessing rapid and more severe changes in weather conditions which include quick temperature fluctuations, sudden rainstorms followed by hail during the summer period and high-speed winds and small hurricanes in random places without history of such weather phenomena. All these incidents are related mainly with El-Niňo, the warm phase of the natural climate cycle with a usual period of 2-7 years. Of course, there is La-Niňa the opposite phase of the El-Niňo with both lasting 9 -12 months. Unfortunately, El-Niňo occurs more frequently compared to La-Niňa, helping to maintain higher temperatures for longer periods and shifting the overall rising temperature on the planet.
Climate change can affect fish feed production at every level up to and including aquaculture operations. More specifically, it can affect the availability and quality of conventional raw materials. In most feed formulation cases, more than 60 percent of the formulation relies on plant-derived ingredients. The production volume of such ingredients such as soy, corn, wheat, rapeseed, sunflower, etc can be significantly affected by climate change, causing great price volatility. This price volatility is always translated into an increase in feed production cost and subsequently the cost of the final product in the market. Despite the cost, variations in the nutritional value can also occur, adding more concerns to feed production. Furthermore, the plants often require higher quantities of irrigation water, adding even more difficulty in production and increasing the environmental footprint too.
Besides plant-derived ingredients, marine ingredients are also affected by climate change. Fishmeal and fish oil produced by wild catch are susceptive to the effects of climate change. Rising water temperatures can alter the planktonic communities which can lead to changes in fish distribution and reduced productivity in some fisheries. Fishmeal and fish oil production are closely linked to the management of forage fisheries and can negatively impact fishing efforts, quotas and landings. Furthermore, production from forage fisheries is (rightly) limited through fisheries management regulations that restrict catches to sustainable levels. Thus, fishmeal and fish oil are likely to become the restricting factors for the aquafeed production and aquaculture due to limited availability, accelerating further transition towards alternative and circular feed ingredients.
Fish nutritional requirements will change too. Fish metabolism and feed consumption is closely related to water temperature. As water temperature increases for prolonged periods, the feed consumption will increase, leading to increased feed demands. The dissolved oxygen level drops as water temperature rises, creating unfavorable rearing conditions with the risk of mortality. In some cases, due to higher water temperature and lower dissolved oxygen levels, fish will be stressed and their appetite will be reduced, impacting their growth and affecting production. Conversely, feed conversion ratio may be reduced due to reduced growth performance. Rising water temperatures therefore requires changes in the feed formulation, usually including higher digestible energy, changes in protein to energy ratio and the incorporation of higher levels of antioxidants. At the same time, stressed fish will be more vulnerable to disease outbreaks including parasite infections, requiring more medicated feeds and more prophylactic measurements such as functional feed additives to be included in the feeds.
The necessity for alternative ingredients with greater resilience to the impacts of climate change should be prioritised for the aquafeed sustainability. Regional circularity offers a promising pathway by transforming the available regional waste streams into valuable, novel, functional ingredients which can reduce the dependence on traditional feed ingredients and at the same time are able to reduce the environmental footprints and strengthen the stability of feed supple chains. Examples of such ingredients include the production of insect meal (high quality protein from incest biomass reared on organic side streams), microalgae (nutrient biomass rich in protein, essential fatty acids, vitamins and antioxidants), microbial/ single-cell proteins (high-quality protein produced low-resource substrates), fermented by-products (agro-industrial residues with enhanced nutritional value and digestibility) and seaweeds (source of protein, lipids, minerals and bio-active compounds). Currently, such alternatives may be more costly compared to the conventional ingredients but utilising the local availability, the circularity, the integration of efficient processing technologies and production scale-up should improve price competitiveness in the future.
Concluding, due to climate change, fish nutrition is changing and more specifically it is shifting from feeding to cover the nutritional needs and achieve maximum growth performance to feeding with precision for resilience and low environmental footprint, using sustainable aquafeeds, reducing the environmental impact, promoting circular bioeconomy and climate adaptation.
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