The Promise of Aquaponics

This issue has a strong focus on aquaponics, and points to the future of food production systems at a practical level to feed a growing population. However, commercial aquaponics has a long way to go before devotees can earnestly claim it is a sustainable food production system.

At the top of the list of issues that need to be overcome, is the need to develop alternate fish foods that don’t use wild fish, and pH balancing that doesn’t require the inputs of inorganic buffers. There is also the issue of antibiotics to maintain fish health during the growing phase. Other issues up against commercial aquaponics include the production of enough nutrients from fish wastes to grow important food crops. While acquaponicists have mastered the production of herbs and leafy greens, more research is needed to feed fruiting crops, such as tomatoes and cucumber, which require larger volumes of nutrients than an aquaponics system can supply. These are the sorts of challenges that need to be overcome before aquaponicists can claim this production method is sustainable.

These comments are not meant to be a ringing endorsement for commercial hydroponics. It, too, has to overcome many challenges as a sustainable food production system, including universal conversion to ‘closed’ systems and Integrated Management Strategies for pest and disease control.

There can be little doubt our wild fish stocks are being seriously depleted by over-fishing. In Australia, fish and seafood consumption has doubled in the last 10 years and currently stands at around 13kg per person per year (pop. 23.7 million). This has been predicted to increase to 17kg by 2020 and 25kg per year by 2050, giving a total domestic requirement of 1.15kt annually. Given falling wild catches, aquaculture needs to double by 2020 and double again by 2050 to meet this demand. The pressure to expand the aquaculture industry will drive the development of aquaponic farming. Our story on Aquaponics in Hong Kong is an example of the demands of an expanding population on limited arable land.

A recent desktop study by Australian researchers to produce fishmeal based on insect larvae (rich in protein and fat), is an important development to find a replacement for wild fish feed. Our story, Production of Fish Feed from     Waste Vegetables reviews the report’s findings.

Observations that antagonistic fungi and bacteria that live in plant roots may benefit fish, is another clue to sustainable commercial aquaponics. These fungi and bacteria prevent high densities of pathogen species, which affect the fish in high density tanks and times of stress. In a once-only observation, the barramundi grown in an aquaponic system were less susceptible to disease infection to those that were not (pers. corresp. Paul Van der Werf). Although there is no scientific data to support this observation, more research into the micro flora populations that live in an aquaponic system would prove beneficial. These can be isolated and lab cultured to be used as treatment when required, instead of antibiotics or other medications in fish systems. This would be very much like integrated pest management, but at a microbial level, that will benefit aquaculture and integrated aquaculture through the reduced use of potentially harmful chemicals (to both the fish and humans). It would also help lift the stigma associated with aquaculture and the use of medications. However, what the industry lacks most is research funding to investigate these observations further.

Steven Carruthers

PH&G November 2014 / Issue 149