Cultivo de pós-larvas de tilápia do Nilo utilizando diferentes proporções de substrato concha/brita no biofiltro

Abstract

ResumoA avaliação da proporção ideal de concha calcária/brita em biofiltro no cultivo de pós-larvas de tilápia do Nilo foi o objetivo deste trabalho. O experimento foi realizado no Laboratório de Aquicultura e Ecologia Aquática da Universidade Federal dos Vales do Jequitinhonha e Mucuri -UFVJM, entre os dias 21 de julho a 3 de agosto de 2011. Pós-larvas de tilápia do Nilo na densidade de 13,3 pós-larvas/L foram cultivadas em aquários contendo biofiltros com 100% concha calcária; 70% concha calcária/30% brita; 50% concha calcária/50% brita; 30% concha calcária/70% brita; 10% concha calcária/90% brita; 100% brita e como controle, aquário sem biofiltro, em DIC, totalizando sete tratamentos com três repetições. A presença de concha calcária no biofiltro proporcionou melhores condições da água, quando comparado com os aquários sem biofiltro e com brita apenas, mantendo os parâmetros adequados para o cultivo de tilápia do Nilo. Apesar dos níveis de amônia estarem próximos ao limite superior desejado para o cultivo da espécie, eles não comprometeram o crescimento (comprimentos total e padrão, altura e peso). A proporção 30% de concha calcária e 70% de brita é recomendada como substrato de biofiltro, por apresentar a melhor taxa de nitrificação ao longo do experimento. Palavras-chave: biofiltração, larvicultura, nitrificação, resíduos nitrogenados, Oreochromis niloticus. AbstractThe evaluation of the optimal ratio of calcareous shell/gravel substrate in biofilters was evaluated in post-larval culture of Nile tilapia the was objective of this work. The experiment was conducted at the Laboratory of Aquaculture, UFVJM University, Brazil, from July 21 to August 3, 2011. Post-larvae of Nile tilapia at density 13.3 post-larvae/L were grown in tanks containing biofilters with 100% calcareous shell; 70% calcareous shell/30% gravel; 50% calcareous shell/50% gravel; 30% calcareous shell/70% gravel; 10% calcareous shell/90% gravel; 100% gravel; tank without biofilters and control, in completely randomized design with seven treatments and three repetitions. Calcareous shell provided better water conditions than tanks without biofilter or containing only gravel, keeping the parameters suitable for Nile tilapia farming. Although ammonia levels were close to the desired upper limit, they had no influence on morphological parameters (total length, standard length, height and weight). The rate 30% shell/70% gravel is recommended as biofilter substrate, as it provided the best nitrification rate during the experiment.

Substrates for biofilter in recirculating system in Nile tilapia larviculture production

“…Anim., Salvador, v.17, n.3, p.553-560 jul./set., 2016 http://www.rbspa.ufba.br ISSN 1519 9940 http://dx.doi.org/10.1590/S1519-99402016000300020 The shell plus granitic crushed stone substrate provided a high conductivity of the water due to its limestone composition. The high conductivity due to compounds in biofilter with shell has been reported by (PEDREIRA & RIBEIRO, 2008;DUARTE et al, 2013), and similar results of water conductivity were reported by Pedreira et al (2009) in comparing the efficiency of biofilter using the same substrates of this experiment. The water turbidity of the control (no substrate) differed from all other treatment (P<0.05) because the substrates trap water particles and significantly reduce level of water turbidity.…”

“…This result is corroborated by other studies (PEDREIRA et al, 2009). The nitrate concentrations observed in the present experiment can be indicated the studied species, since similar results were also observed by Duarte et al (2013) in the cultivation of tilapia. The low nitrate concentrations should be maintained because high levels typically result in algal blooms and over time can result in a lowering of pH (WATSON & HILL, 2006 ).…”

“…The nitrite of biofilter with quartz gravel and granitic crushed stone substrates were higher than other treatments (P<0.05). No differences in nitrate were observed for biofilter with porcelain, seashell plus granitic crushed stone and control (no substrate) (P≥0.05) and the nitrite was within the range observed for Nile tilapia (DUARTE et al, 2013). The lowest concentrations of nitrite for the biofilter with porcelain and seashell plus granitic crushed stone evidence the efficient functioning and proper acclimation of the biofilter that depends on the initial conditions of the trial (SHEINTUCH et al, 1995), and also demonstrating the role of bacteria in maintaining the water for intensive aquaculture (HOROWITZ & HOROWITZ, 2000).…”

“…The seashell increases the conductivity, pH (DUARTE et al, 2013) and alkalinity of the water (FRITZSONS et al, 2009), forming a buffer effect, and stabilizing the farming system. Similar result was found by Pedreira et al (2009) using seashell plus crushed stone into external and internal biofilter, in comparison to gravel and no substrate filter No differences among subtracts were found for water oxygen concentration (P≥0.05), and the level of oxygen were appropriate for the species studied according Duarte et al (2013). In general Seashell plus granitic crushed stone and porcelain provided better nitrification because these substrates have higher nitrate concentrations and lower concentrations of ammonia and nitrite.…”

“…The nitrification efficiency can vary according to type of substrate (HOROWITZ & HOROWITZ 2000;CHEN et al, 2006;PEDREIRA et al, 2009), concentration of dissolved oxygen, temperature, pH, alkalinity, turbulence, salinity (CHEN et al, 2006), specific surface area of substrate, and uniformity of water flow into of the biofilter (LEKANG & KLEPPE, 2000). Though there is a few experiments comparing substrates in biofilters in the cultivation of Nile tilapia (DUARTE et al, 2013). The use of different substrates in biofilters have task of verifying the best material to filter and purify the water used for fish production.…”