Interaction between afternoon aeration and tilapia stocking density

The present study aimed at determining the effects of the interaction between afternoon aeration and stocking density of Nile tilapia on variables of water and soil quality, growth performance and effluent quality. The experiment was a 3 x 2 factorial randomized block design, with three stocking densities (8, 12 and 16 fish per tank or 43.5, 65.3, and 87.0 g m^-3) under two mechanical aeration regimes, absence (control; three replicates) and afternoon aeration (four replicates). The afternoon aeration was carried out from 12.00 a.m. up to 18.00 p.m. from the 3^rd week until the end of the experiment. Except for the 16-fish tanks, the lowest concentrations of total ammonia nitrogen were found in the tanks with higher density of fish provided with afternoon aeration. Nitrite concentrations were lower in the 8-fish aerated tanks. In intensive system, the afternoon aeration of the fish culture water is an efficient management of water quality to remove gaseous ammonia and nitrite from water, but it is not appropriate to remove hydrogen sulfide from water.

Keywords:
fish farming; total ammonia nitrogen; unionized ammonia; nitrite

Authorship

Francisco Roberto dos Santos Lima

Centro de Ciências Agrárias, Departamento de Engenharia de Pesca, Laboratório de Ciência e Tecnologia Aquícola, Universidade Federal do Ceará, Av. Mister Hull, s/n, 60356-000, Fortaleza, Ceará, Brazil. Universidade Federal do CearáBrazilFortaleza, Ceará, BrazilCentro de Ciências Agrárias, Departamento de Engenharia de Pesca, Laboratório de Ciência e Tecnologia Aquícola, Universidade Federal do Ceará, Av. Mister Hull, s/n, 60356-000, Fortaleza, Ceará, Brazil.

Davi de Holanda Cavalcante

Vanessa Tomaz Rebouças

Marcelo Vinícius do Carmo e Sá ^** Author for correspondence. E-mail: marcelo.sa@ufc.br

* Author for correspondence. E-mail: marcelo.sa@ufc.br

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (2)
Tables (4)

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Figure 1
Diel monitoring of selected water quality variables of juvenile Nile tilapia tanks. The tanks were stocked with different fish densities and were subjected or not to afternoon aeration. NA: no aeration; AfA: afternoon aeration; 8, 12 and 16 refer to the number of fish per tank.

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Figure 2
Quality of Nile tilapia tank effluents 48 hours after the final harvest. The rearing tanks were subjected or not to afternoon aeration for eight weeks. The afternoon aeration has not significantly affected any of these variables (p > 0.05). Numbers 8, 12 and 16 refer to the number of fish per tank.

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Table 1
pH, electrical conductivity, dissolved oxygen, total alkalinity, total hardness and carbon dioxide of juvenile Nile tilapia tanks (initial body weight = 1.36 ± 0.03 g). The rearing tanks were stocked with different fish densities and were subjected or not to afternoon aeration (mean ± SD).

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Table 2
Concentrations of total ammonia nitrogen (TAN), unionized ammonia (NH₃), nitrite (NO₂ and nitrate (NO₃ in juvenile Nile tilapia tanks (body weight = 1.36 ± 0.03 g). The tanks were stocked with different fish densities and were subjected or not to afternoon aeration for eight weeks (mean ± SD).

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Table 3
Concentrations of reactive phosphorus, dissolved iron, total dissolved sulfide, hydrogen sulfide, and organic matter of water; soil pH and organic carbon of juvenile Nile tilapia rearing tanks (body weight = 1.36 ± 0.03 g). The tanks were stocked with different fish densities and were subjected or not to afternoon aeration for eight weeks (mean ± SD).

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Table 4
Growth performance of juvenile Nile tilapia (body weight = 1.36 ± 0.03 g) stocked for eight weeks in outdoor tanks at different stocking densities and subjected or not to afternoon aeration (mean ± SD).

Figure 1 Diel monitoring of selected water quality variables of juvenile Nile tilapia tanks. The tanks were stocked with different fish densities and were subjected or not to afternoon aeration. NA: no aeration; AfA: afternoon aeration; 8, 12 and 16 refer to the number of fish per tank.

Figure 2 Quality of Nile tilapia tank effluents 48 hours after the final harvest. The rearing tanks were subjected or not to afternoon aeration for eight weeks. The afternoon aeration has not significantly affected any of these variables (p > 0.05). Numbers 8, 12 and 16 refer to the number of fish per tank.

Table 1 pH, electrical conductivity, dissolved oxygen, total alkalinity, total hardness and carbon dioxide of juvenile Nile tilapia tanks (initial body weight = 1.36 ± 0.03 g). The rearing tanks were stocked with different fish densities and were subjected or not to afternoon aeration (mean ± SD).

¹Mean of 8 and 15h readings; ²Non-significant (ANOVA p > 0.05). ³ For the same variable, means in the same column with different capital letters are significantly different by tukey's test (ANOVA p < 0.05); absence of letters indicates no significant differences between the mean values (p > 0.05)

Table 2 Concentrations of total ammonia nitrogen (TAN), unionized ammonia (NH₃), nitrite (NO₂ and nitrate (NO₃ in juvenile Nile tilapia tanks (body weight = 1.36 ± 0.03 g). The tanks were stocked with different fish densities and were subjected or not to afternoon aeration for eight weeks (mean ± SD).

¹For the same variable, means followed by different small and capital letters in the same row and column, respectively, are significantly different by tukey's test (ANOVA p < 0.05); absence of letters indicates no significant differences between the mean values (p > 0.05); ² Non-significant (ANOVA p > 0.05)

Table 3 Concentrations of reactive phosphorus, dissolved iron, total dissolved sulfide, hydrogen sulfide, and organic matter of water; soil pH and organic carbon of juvenile Nile tilapia rearing tanks (body weight = 1.36 ± 0.03 g). The tanks were stocked with different fish densities and were subjected or not to afternoon aeration for eight weeks (mean ± SD).

¹For the same variable, means followed by different small and capital letters in the same row and column, respectively, are significantly different by tukey's test (ANOVA p < 0.05); absence of letters indicates no significant differences between the mean values (p > 0.05); ² Non-significant (ANOVA p > 0.05).

Table 4 Growth performance of juvenile Nile tilapia (body weight = 1.36 ± 0.03 g) stocked for eight weeks in outdoor tanks at different stocking densities and subjected or not to afternoon aeration (mean ± SD).

¹Specific growth rate (SGR) = [(Ln final weight - Ln initial weight) number of days^-1] x 100; ² feed conversion ratio (FCR) = feed allowance (g) fish weight gain^-1 (g); ³ Protein efficiency ratio (PER) = weight gain (g) protein consumed^-1 (g); ⁴ Non-significant (ANOVA p > 0.05). ⁵ For the same variable, means followed by different capital letters in the same column are significantly different by tukey's test (ANOVA p < 0.05); absence of letters indicates no significant differences between the mean values (p > 0.05)

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Interaction between afternoon aeration and tilapia stocking density

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[1] * Author for correspondence. E-mail: marcelo.sa@ufc.br