Circular Systems

The pace of innovation within the Aquaculture industry is phenomenal.  Many of the current advancements focus on monitoring systems linked to artificial intelligence in order to optimise feed usage efficiency and to perfect fish health.  Another area of improvement that is enjoying attention is the circular nature of biological resources, whereby the waste from one component becomes a supply to another in a manner that means the whole is greater than the sum of its parts.  The waste is usually used to produce a marketable product or as feed for the fish being cultivated.  There are several benefits to this, some or all of which may be possible for you to include, depending on which technology you follow, these benefits include:
 
·       Reduced capital costs relative to income
·       Reduced operational expenditure
·       Reduced environmental impact
·       Reduced water usage
·       Reduced reliance on external service providers
 
The best known of these technologies is probably Aquaponics because the commercial case has been demonstrated for more than a decade, resulting in this technology enjoying widespread adoption within the industry.  In simple terms, Aquaponics is fitted onto a recirculating fish farm, either at the design stage or retrospectively, in such a way that the water flows continuously or periodically between the fish and plants.  Bacteria convert the nutrient rich fish wastes into a form that can easily be accessed by the plant crops, which take up these nutrients as they grow.  The crops from these plants can be sold as a second income stream.  Nutrient removal by the plants purifies the water which then returns to the fish in a continuous cycle.  If the ratio of plants to fish is correctly balanced, the fish provide adequate nutrients for the plants to grow optimally and the plants strip the nutrients from the water for the fish.  In this case the addition of plants to the fish system does add to the capital required and to the operational cost of running the business, but the significant increase in profit, through the plant sales, more than justifies this economically.  Another major plus associated with Aquaponics is that it decreases the volume of raw water which is required to operate the fish farm because the Aquaponics system returns the bulk of the water used in a continuous loop.
 
Duckweed can also be produced in an Aquaponics system and then used as a fish feed, but the use of the valuable water and nutrients to supplement the fish feed does not make economic sense.  However, if you are farming in a water scarce region where vegetable prices are low, then this could be an option.
 
Another example of a circular system that is enjoying some success currently is the production of black soldier fly (BSF) larvae on the mortalities, culls, processing wastes and, if you do Aquaponics, the plant wastes coming out of the production systems.  The larvae are fed directly to the fish, or if adequate quantities are available, they can be added to the fish feed, with a consequent saving on the feed bill and potentially other nutritional benefits associated with feeding a live feed.  Additionally, the use of BSF is an appropriate way of dealing with the challenge of wastes that could otherwise present an environmental problem.  Earthworms can be farmed in a similar fashion and also make excellent fish feed.
 
A final demonstration of a circular system within Aquaculture is to farm catfish along with other fish.  This would typically be done where a significant amount of biological waste (either processing wastes or culls) is produced which can be used as a feed source for the catfish, thereby producing a second fish crop at minimal extra cost while simultaneously dealing with the waste challenge.
 
A final word of caution on circular systems relates to balance.  For one biological ecosystem to support another the two must be in balance, or one will need to be supplemented in some way.  However, the benefits of using the waste from one system to feed another, thereby generating additional income and possibly enjoying other benefits is an attractive option, hence the attention it receives within Aquaculture.
 
Circular Aquaculture principles that use discarded (waste) products as the raw materials for a new product offer the Aquaculture farmer exciting options in terms of crops, income and reduced environmental impact.  Time to start thinking in circles!