Recirculating aquaculture systems
Flavour saver
Managing the microbiome provided a solution to off-flavour compounds in Kuterra’s RAS system
O
ne of the challenges facing recircula�ng aquaculture systems (RAS) – especially when these are used for grow-out – is the presence of off-flavour compounds (OFCs) that can affect the smell and taste of the fish. Geosmin is a typical example. It is a by-product of bacteria in the system and, while harmless, it is a smell to which we are very sensi�ve. O�en described as “the smell of the soil” or the aroma of woodland a�er a rainy day, humans can detect as li�le as 100 parts in a trillion of geosmin – and it is not a flavour anyone wants in their fillet of salmon.
96
Recirculating aquaculture systems.indd 96
Geosmin (and another OFC, “MIB” or 2-Methylisoborneol) are created when non-beneficial microbes – o�en cyanobacteria or ac�nomyces – become established in RAS systems. These microbes produce Geosmin and MIB, which builds up in the recirculated water and is then taken up in the flesh of fish in the system. Off-flavour is commonly treated by “purging” the fish using large volumes of new, clean water, known as makeup water (MUW) for between five to 13 days before being harvested. Fish are not fed during this purge and therefore lose weight (reducing their value). The large volumes of water required also increase the environmental footprint of each fish produced. Raising land-based salmon on Vancouver Island in Bri�sh Columbia since 2013, Kuterra (now operated by Whole Oceans) produces high quality, sustainably reared fish. As one of the longest established grow-out facili�es, Kuterra has collated extensive OFC baseline data related to its systems. Typical for grow-out systems, Kuterra has historically managed OFC levels by
Above: Salmon Left: Full grown salmon Opposite from top: Cyanobacteria; Kuterra salmon; young smolt; Kuterra’s RAS facility
www.fishfarmermagazine.com
11/04/2022 14:16:12
