Fish Welfare in Aquaponic Systems: Its Relation to Water Quality with an Emphasis on Feed and Faeces—A Review

Abstract

Abstract:Aquaponics is the combination of aquaculture (fish) and hydroponic cultivation of plants. This review examines fish welfare in relation to rearing water quality, fish feed and fish waste and faeces to develop a sustainable aquaponic system where the co-cultured organisms, fish, bacteria in biofilters and plants, should be considered holistically in all aquaponics operations. Water quality parameters are the primary environmental consideration for optimizing aquaponic production and for directly impacting fish welfare/health issues and plant needs. In aquaponic systems, the uptake of nutrients should be maximised for the healthy production of the plant biomass but without neglecting the best welfare conditions for the fish in terms of water quality. Measures to reduce the risks of the introduction or spread of diseases or infection and to increase biosecurity in aquaponics are also important. In addition, the possible impacts of allelochemicals, i.e., chemicals released by the plants, should be taken into account. Moreover, the effect of diet digestibility, faeces particle size and settling ratio on water quality should be carefully considered. As available information is very limited, research should be undertaken to better elucidate the relationship between appropriate levels of minerals needed by plants, and fish metabolism, health and welfare. It remains to be investigated whether and to what extent the concentrations of suspended solids that can be found in aquaponic systems can compromise the health of fish. Water quality, which directly affects fish health and well-being, is the key factor to be considered in all aquaponic systems.

Stress and Welfare of African Catfish (Clarias gariepinus Burchell, 1822) in a Coupled Aquaponic System

“…The absence of roots leads most likely to the murky water conditions in the control system as shown by measurements of the water turbidity (Table 2). Other effects, such as the release of substances from the roots into the process water, were not a matter of this study, but cannot be excluded [10]. As discussed in Section 4.1, the plants inside the hydroponic units helped to maintain system stability, reducing water replacement due to their nutrient uptake.…”

“…They grow quickly have an effective feed conversion ratio (FCR). However, it remains uncertain to what extent the aquaponic environment influences the wellbeing of this fish species [10].…”

Opportunities and Challenges of Multi-Loop Aquaponic Systems

“…In addition to the fact that discharging aquacultural waste might cause eutrophication, valuable nutrients are simply wasted. P is mainly lost through faeces in fish production (Neto and Ostrensky, 2013;Yavuzcan Yildiz et al, 2017). Håkanson et al (1998) even reported that 70% of the P fed to fish is lost through faeces.…”

“…However, this type of model can demonstrate to what degree the implementation of a third loop, in addition to the RAS and hydroponic loops, can impact the required scale of hydroponic cultivation area. For these calculations, it was assumed that 55% of the nutrient input (via fish feed) ends up in sludge (Neto and Ostrensky, 2013;Yavuzcan Yildiz et al, 2017), and that the remineralization potential of an upflow anaerobic sludge blanket (UASB) reactor is approximately 90% (Mirzoyan and Gross, 2013).…”

Aquaponics – A Process Control Approach

“…The wastewater treatment also allows solids to be removed or reintroduced back into the system as dissolved solids (Hijran Yavuzcan Yildiz, 2017) that supply plants additional nutrients. The fish species to be grown have limitations on the amount of (Zealand, 2000)Total Dissolved Solids and other water quality requirements that must be met if the produce is to be resold.…”