ALGAE FOR AQUAFEEDS - EUROPEAN ACTVITIES AND BEYOND

Aquaculture is a very relevant European production activity that includes a wide range of fish and mollusk species. It has grown rapidly from a craft and family-run business in the 1960s into an industrial sector that contributes substantially for the current food supply. At present it is facing increasing challenges due to a more demanding and selective market combined with competition from outside the EU both in fresh or processed final products and aquafeeds.  

Historically, microalgae have been used in European aquaculture as live feeds for all growth stages of bivalve mollusks (e.g. oysters, scallops, clams and mussels), for the larval/early juvenile stages of abalone, crustaceans, some fish species, and for zooplankton used in aquaculture food chains. Over the last four decades, several hundred microalgae species have been tested as feed, but less than twenty have gained widespread use in aquaculture. A number of processed dried forms of microalgae have also been assessed as alternatives to live microalgae. One of the first, in the mid-80s, was Algal 161 from CellSys from Cambridge, UK. This was heterotrophically produced from Tetraselmis suecica and had a cost at the time of US $ 180 /kg. However, this product had a moderate value as a diet component for mollusks and did not achieve a highmarket penetration, it is now unavailable.  

The products from microalgae have currently only three distinct forms, each with a large range of possible applications. Algae paste is produced in a range of dry weight concentrations, usually from 5 to 15%, dependent on the microalgae species and application. The advantage of such products is that they can be used "off-the-shelf", thus providing potential cost-efficiencies to hatcheries and currently, algae pastes are the main application for microalgae in Aquaculture. Microalgae are, however, more commonly spray-dried or freeze-dried, and even sun-dried. Extracts can be obtained using solvents, organic or supercritical gases, or with mechanical processes.  

Looking ahead, microalgae are expected to play a game changing role in Europe, as the limiting production costs are gradually reduced. Microalgae can be included in aquaculture food chains as premix feeds and contribute to the cost reduction of fishmeal and fishoils. A new trend is also emerging - Aquaponics, a relatively new field, capturing a great interest in Europe with several research projects trying to integrate aquaculture, plant hydroponics and algae production technologies in synergy using the same water. Water is recycled and reused, resulting in many advantages: Aquaponics consumes only 10-20% of water used in agricultural crops and fertilizer inputs are reduced as nutrient enriched water serves as liquid fertilizer to grow plants. This integrated approach has captured a great interest in north European countries.  

Although there are examples of macroalgae species containing relatively high levels of protein or lipid, it seems likely that microalgae will provide the most suitable bulk feedstuffs for use in finfish diets, whereas macroalgae may be more suitable for use with terrestrial livestock and with lower trophic level aquaculture species.