Positioning of Aquaculture in Blue Growth and Sustainable Development Goals Through New Knowledge, Ecological Perspectives and Analytical Solutions

The effects of two aquatic plants, duckweed (Lemna sp.) and azolla (Azolla sp.), on the growth performance of fantail goldfish (Carassius auratus) and dissolved nutrient concentrations were studied. The experiments were carried out in triplicate sets over a period of seven weeks. Eight specimens of fantail goldfish (length = 5.16 ± 0.06 cm; body weight = 2.30 ± 0.06 g) were released into each of the aquariums containing 40 L of water. Submerged sponge filters were used as the substrate (bed) for the nitrifying bacteria to facilitate nitrification. The fish were provided feed at the rate of 2% of their body weight twice daily. In situ and ex situ water parameters (temperature, dissolved oxygen, pH, total suspended solids, ammonia, nitrite, nitrate, and phosphate), body weight and length of the Fantail goldfish, and wet weight of aquatic plants were measured weekly. The results showed no significant differences (p > 0.05) in any of the three aquariums in water temperature, pH, and dissolved oxygen. Survival of the fish was 100%. The highest food conversion ratio and specific growth rate were observed in the aquarium stocked with duckweed, followed by the aquarium with azolla and the control set (p < 0.05). The concentrations of nutrients (ammonia and nitrate) were recorded lowest (p < 0.05) in the aquarium with azolla, followed by duckweed and the control. The results suggested that aquatic plants were effective in absorbing nutrients and can serve as biofilters to create better conditions for the growth of the fantail goldfish.

Aim of study: To evaluate the biomass production of green bean (Phaseolus vulgaris) in a media-filled aquaponics system together with Genetically Improved Farmed Tilapia, GIFT (Oreochromis niloticus).Area of study: Kota Kinabalu, Sabah (Malaysia).Material and methods: The experiment involved modulating and optimizing the density of extractive species (plants) in the hydroponic tank (55 cm × 35 cm). Five treatments were carried out: T0 (control-without plant), T2 (2 plants), T4 (4 plants), T8 (8 plants), T12 (12 plants) where the stocking density of GIFT was 30 tails (identical in all the treatments). Water volume in each treatment was 800 L and the experimental set up was closed recirculating type. The trials were carried out over a period of 90 days.Main results: Growth of the GIFT was not affected by the presence of green bean or by manipulation of the stocking density. Treatment T4 yielded significantly higher biomass production of green beans (1556.4 ± 88.9 g), compared to T2 (1083.6 ± 86.9 g), T8 (404.6 ± 47.9 g), and T12 (401.8 ± 98.1 g). There were noticeable fluctuations in the concentrations of NH3-N (ammonia), NO2-N (nitrite), NO3-N (nitrate) and PO4-P (phosphate) over the experimental period that indicated the process of nitrification and absorption of nutrients.Research highlights: The nitrogenous waste produced by the fish supported the biomass of the green beans in the aquaponics system and the waste uptake of this extractive species is effective enough for reuse of the water for rearing of GIFT.