SUSTAINABILITY OF AQUACULTURE: A GLOBAL, INCREASING CHALLENGE
According to the United Nations, world population is projected to reach 9.8 billion in 2050 (United Nations, 2017). In parallel, fish consumption increased from 121 million tonnes in 2008 to 140 million tonnes in 2013 (FAO, 2017), with aquaculture contributing 90% of this growth. If we look into the future, growing, wealthier populations will continue to demand more fish, and aquaculture growth is expected to be the major force to satisfy this growth in demand (FAO, 2017). Considering these trends, demand for fish is estimated to increase by 30% by 2030 (Strategy and Markets, 2017). In order to meet such an increased demand for fish, aquaculture production will need to increase by 50% from the present level. Intensification of aquaculture has become the only meaningful solution to meet that demand.
However, intensification of aquaculture is challenged by the availability of fish feed sources, especially fish meal (FM) and fish oil (FO), primarily obtained from wild captured fish at the bottom of the food chain and essential for the formulation of fish feed. As production from wild fisheries is stagnating and competition for FM and FO from other sectors (mainly the food and health sectors) is increasing, marine-derived fish feed ingredients are only available in limited quantities, representing a long-term concern for the sustainability of aquaculture.
It is estimated that the amount of fish used in fish feed will need to contract by at least 50% from current levels for aquaculture to be sustainable in 2050 (European Commission, 2015). Partial substitution of FM and FO by plant-based alternatives has been employed by the industry as a solution to sustain growth in aquaculture. The industry is also constantly seeking new and innovative solutions to enhance fish health and welfare, while improving fish meat quality to meet the high standards demanded by final consumers. In this scenario, plant bioactive compounds, known as phytogenics, represent a great opportunity for use as natural feed additives in aquaculture practices (Rui Gonçalves and Gonçalo Santos, 2015).
THE OLIVE INDUSTRY AS A SOURCE OF BIOACTIVE COMPOUNDS
The olive (Olea europaea) probably originated in the Eastern Mediterranean region of the Middle East. Apart from its oil content, which is rich in oleic acid, a monounsaturated omega-9 fatty acid (C18:1) with healthy properties, olive fruits and leaves are rich in various bioactive phytochemicals: polyphenols (hydroxytyrosol, oleuropein, flavonoids, etc.), terpenoids, phytosterols, vitamins, and squalene, among others.
Present olive production is about 16 million tonnes of green and black table olives and 2.7 million tonnes of olive oil. Of total production, 95% is produced in the Mediterranean region, with Spain being the main producing country (FAOSTAT, 2001). The olive oil industry generates a high quantity of by-products, which in Spain alone accounts for more than 6 million tonnes, as leaves, pits, and wet pomace (Junta de Andalucía, 2015). Management of this biomass in Spain is currently yielding pomace olive oil, a second-quality oil obtained by hexane extraction, and energy production through the combustion of remaining biomass (defatted pomace, leaves, etc.). However, some valuable olive bioactive compounds are contained in olive oil by-products, meaning that tonnes of polyphenols, terpenoids, phytosterols, and other valuable compounds are currently literally being burnt to produce energy.
Current progress and advances in food waste treatment technology are supporting the establishment of alternative, innovative, sustainable management strategies aimed not only at reducing the amounts of olive oil by-products disposed of, but also at recycling and exploiting them.
One such practice with considerable potential for further development, and that has already seen practical applications, is the recovery of functional components with health-promoting properties (Gullón et al., 2018; Nunes, et al., 2018). The recovery of these compounds not only enables more sustainable olive biomass management, but also provides for additional income from the commercialisation of the extracts produced, thus contributing to increasing profitability in the olive oil agro-industry supply chain, while increasing global health.
Since its foundation, Natac has focused on the valorisation of agro-industrial biomasses through recovery of valuable compounds, in the framework of current bioeconomy and circular economy strategies. Olive biomass has appeared as a prime candidate for product development, given the great amount of olive bioactive compounds present in olive-derived by-products with promising functional applications, which, as mentioned, are currently underexploited.
OLIVE BIOACTIVE COMPOUNDS AS A SOLUTION
Over recent years, Natac has developed several olive-derived feed additives with application in different animal species. Natac has even patented the combination of certain bioactive compounds as having a synergistic effect against oxidative and inflammatory episodes when combined in specific proportions (Quintela et al., 2013). This research was conducted to define a series of new innovative products with proven activity in various markets (nutraceuticals and pharmaceuticals). One of these products has been aimed at salmon aquaculture, as a productivity-boosting input called AQUOLIVE. This product presents the capacity to reduce low-grade inflammation, thus protecting the fish from subclinical chronic inflammation episodes resulting from multiple challenges encountered during the growth cycle (e.g., potential diseases, high water temperature, elevated pathogen load, etc.). Additionally, AQUOLIVE also works as a functional antioxidant, thereby contributing to preventing or attenuating oxidative stress in salmon. By counteracting inflammation and oxidation in key organs (or tissues) at critical times, AQUOLIVE contributes to preserving gut integrity and improving lipid (energy) metabolism (lipid accumulation) in farmed salmon.
The benefits of this product have already been tested in a commercial fish farming setting. The results showed an improvement in both production parameters (increase in FCR) and meat quality parameters (less melanosis black spots in salmon flesh). Additional improvements associated with the fillet quality-higher fat content and better ω6:ω3 ratio, in line with EU salmon quality needs – were also observed. These benefits result from the double bioactive effect observed in olive phytochemicals (anti-inflammatory and antioxidant).
DEMONSTRATION SCALE VALIDATION
With the objective of fully validating the health benefits of olive bioactive compounds in salmon aquaculture, the Natac is conducting a series of salmon trials covering the entire fish production cycle, including the smoltification phase. It started a demonstration sea-cage trial in Norway last September that will study the effect of the AQUOLIVE product in salmon from 600 g to 5 kg. In parallel, a smoltification tank trial will be performed to evaluate the benefits of olive bioactives in this specific challenging phase of salmon aquaculture. During both trials, a complete set of variables will be analysed: zootechnical performance parameters, salmon meat quality, histology, biochemical, and transcriptomic analyses.
These trials are being conducted in collaboration with some of the most prestigious partners in the salmon aquaculture sector, such as LetSea – a reference Norwegian trial station located in Sandnessjøen – Nofima Feed Technology Centre, the Spanish Research Centre IRTA (Institute of Agrifood Research and Technology) and the University of Barcelona.
The valorisation of agro-industrial biomass offers great opportunities for development of new solutions to tackle current and future aquaculture challenges, providing the industry with new phytogenics capable of improving fish health and welfare. The AQUOLIVE project will link olive farmers from southern Europe with Norwegian salmon producers through the valorisation of olive biomass and the improvement of salmon quality and productivity, on a circular economy basis.
References available on request.
AQUOLIVE is funded by the European Union’s Horizon 2020 research and innovation program under Grant Agreement no. 830202.
José Carlos Quintela and José María Pinilla, Natac Group