Nile tilapia fingerling cultivated in a low-salinity biofloc system at different stocking densities

Abstract

A 42-day trial was conducted to evaluate the effects of a low-salinity biofloc system with different stocking densities on water quality and zootechnical performance of Nile tilapia fingerlings (10 g/L). Four treatments were tested at different densities: 500 fish/m³, 750 fish/m³, 1,000 fish/m³ and 1,250 fish/m³, all in triplicate. Fingerlings of Oreochromis niloticus (initial mean weight of 1.17 ± 0.05 g) were stocked in twelve experimental black-plastic tanks (40 L) with no water exchange during the experimental period. Molasses was added daily to the system at 30% of the amount of feed, and fish were given four daily rations of a formulated feed composed of 36% crude protein and 9% lipids. Water quality variables (dissolved oxygen, pH, salinity, TAN, NO2, NO3 and PO43) did not demonstrate significant differences between the treatments. However, significant influences (α ≤ 0.05) of the stocking densities were observed for total suspended solids, settleable solids, final weight, yield, and protein efficiency ratio. The results showed survival over 96%, final weight values between 12 and 18 g, yield between 9.49 and 15.27 kg/m3, water consumption of 52 to 101 L/kg fish, and total time of settling chambers between 238 and 305 h/kg fish. These results indicate a negative effect of stocking density on final weight, survival, alkalinity, NO2, PO43 and water consumption, and a positive effect on yield in Nile tilapia fingerling culture (1-20 g) in a low-salinity biofloc system with densities up to 1000 fish/m³.

TILAPIA CULTIVATED IN A LOW-SALINITY BIOFLOC SYSTEM SUPPLEMENTED WITH <i>Chlorella vulgaris</i> AND DIFFERENTS MOLASSES APPLICATION RATES

“…Moreover, the low nutritional content of the commercial feed used probably influenced the reduced growth and higher FCR (2.03 to 5.86), due to the low lipid content found in the commercial feed (2.61%), different from the information described in the label. Lima et al (2018) found similar values to those of the present study at a lower time (42 days), from 12.40 to 18.99g, 96.82 to 100% of the survival, and lower values of FCR (1.24-1.40) when cultivating tilapia at different densities in biofloc with 36% protein and 4% lipid feed. However, the difference in the feed conversion factor between treatments with 30% and 50% addition of molasses is due to the fact that the animals of the treatments with the highest application of molasses showed signs of stress.…”

“…A similar result was found by Jung et al (2017) where WC decreased about 82% when supplementation with two microalgae species were used. The WC was similar (52.48 L kg -1 with 500 fish m -3 ) that reported by Lima et al (2018) and lower compared with 750 to 1250 fish m -3 (76.32 to 101.54 L kg -1 ).…”

“…Some authors reported successfully culturing Nile tilapia in BFT (Long et al, 2015;Miranda-Baeza et al, 2017;Zapata-Lovera et al, 2017), including a study in brackish water (8 g L -1 ) (Brol et al, 2017;Lima et al, 2018). However, due to the high stocking densities and minimal water exchange, nutrients accumulate, mainly nitrogen and phosphorus, in the biofloc culture (Krummenauer et al, 2011).…”

Growth of Chlorella vulgaris using wastewater from Nile tilapia (Oreochromis niloticus) farming in a low-salinity biofloc system

“…After the end of this experiment, the three effluents were homogenized and used in the biomass production of the microalga Chlorella vulgaris. The water quality, centesimal composition and the data productivity of Nile tilapia fingerlings in BFT are available in Lima et al (2019).…”

“…However, there is a discussion about the accumulated nitrogen (N) and phosphorus (P) compoundsduring farming in these systems, which are mainly from feed residues and excreta from cultivated organisms. On average, 75% of the feed-N and 50-70% of feed-P ends up in the water (Crab, Defoirdt, Bossier, & Verstraete, 2012;Lima et al, 2019). This accumulation is due to one of the main characteristics of this system, the stagnant water system (Mishra et al, 2008;Krummenauer, Cavalli, Poersck, & Wasielesky, 2011).…”