The aim of this study was to evaluate the effect of different salinized water (0, 3 and 6 g L-1) and stocking densities (10, 15 and 20 larvae L-1) in Heros severus larviculture. The experimental design was completely randomized, in a 3x3 factorial design, with three replicates. For this, a total of 405 larvae of H. severus were randomly distributed in 27 aquariums (1L) according to the treatments and after 15 days all the larvae were measured, weighed and counted. Higher values for final length, length gain and specific growth rate were observed in H. severus larvae raised at any stocking density tested at 3 g L-1 of salinized water (p < 0.05). The final weight and weight gain followed the same trend of the length, being higher in fish submitted to 3 g L-1 of salinized water (p < 0.05). On the other hand, the salinized water of 6 g L-1 was detrimental to larvae weight uniformity and survival rate (p < 0.05). The fish stocked at densities of 15 or 20 larvae L-1 presented the best results of final weight and weight gain (p < 0.05). The stocking density of 20 larvae L-1 in salinized water at 3 g L-1 is recommended for H. severus larviculture.

Over the years, aquaponics has become a powerful technological tool that allows the sustainable production of food, integrating conventional fish farming with vegetable production. The present study evaluated the production of late seedlings of açai Euterpe oleraceae in an aquaponic system with tambaqui Colossoma macropomum. A total of 36 tambaquis with an initial average weight and length of 1086.75 ± 16.38 g and 38.49 ± 0.90 cm were distributed in 12 independent aquaponic units, totaling 3.62 kg m−3. The fish were fed three times daily with commercial feed at a rate of 3%. Three flooding levels of 5, 10 and 15 cm, with constant water flow through the hydroponic bed (0.5 m2), were evaluated, and a control-hydroponic bed with flooding levels of 10 cm was established, all in triplicate. In the 5 and 10 cm treatments, 3450 açai seedlings with an initial height of 12.3 ± 1.9 cm were used (575 per aquaponic units), while the 15 cm treatment contained non-germinated açai seeds. The control group did not receive açai seeds and remained empty. Analyses to monitor total dissolved solids (TDS), electrical conductivity, dissolved oxygen, temperature, pH, alkalinity, hardness, nitrogenous compounds, and phosphate levels were performed. At the end of the 30-day trial, the growth performance of tambaqui and plants was evaluated. Water quality was significantly (p < 0.05) affected by different flooding levels. Electrical conductivity and TDS decreased with an increasing in flooding levels. The flooding levels significantly influenced (p < 0.05) the concentration of total ammonia and nitrate between the treatments. The 5 cm flooding level showed the best plant development indexes for total height, aerial portion height, root height and aerial portion fresh mass. No significant differences (p < 0.05) were observed in tambaqui growth performance. The aquaponic system proved to be effective in reusing fish waste (excreta and feed leftovers) generated in the system. The biotransformation of waste into nutrients allowed the growth of plants and nitrifying bacteria, which, through their metabolic pathways, ensured the purification and reuse of water, avoiding the discharge of this waste into the environment.

The present study aimed to evaluate the growth performance, batch uniformity, and survival rate of the Amazonian ornamental fish Heros severus and Pterophyllum scalare during the post-larvae growing stage, fed with diets containing levels of Euterpe oleraceae essential oil (EOO) during 30 days. In the first experiment, 160 H. severus post-larvae were distributed in 16 aquariums (1 L), and in the second, 200 P. scalare post-larvae were randomly distributed in 20 aquariums (1 L). The experiments were carried out in a completely randomized design, with four treatments for H. severus (0.0%, 0.50%, 1.00%, and 2.00% of dietary EOO) and five treatments for P. scalare (0.0%, 0.5%, 1.0%, 2.0%, and 4.0% of dietary EOO), both with four replications and dietary EOO being included in replacing soybean oil. A quadratic effect (p < 0.01) was observed for the final length, length gain, specific growth rate for length, final weight, weight gain, specific growth rate for weight, and batch uniformity for weight for both fish species. As for ornamental fish larviculture, survival rate and batch uniformity are the most important parameters to be considered. For P. scalare and H. severus post-larvae, the inclusion of dietary EOO was beneficial in up to 2.48% and 0.88%, respectively.

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