Compreendendo a associação de fatores bióticos e abióticos na larvicultura de tilápia (Oreochromis niloticus) em diferentes fotoperíodos

Abstract

The increase in fish consumption makes it essential to design more efficient production systems, in this context, environmental modifications as is the case of photoperiod can contribute to this improvement. The tilapia responses to photoperiod were not well studied in the environmental conditions of the Brazilian semiarid and become important for the conception of more sustainable managements, management of natural resources (water) and maximization of the production system. Thus, it was considered the hypothesis that tilapia fingerlings respond positively to photoperiod. This study investigated the influence of photoperiod on the development and Association of biotic and abiotic factors in the larviculture of tilapia (Oreochromis niloticus) in different photoperiods. The experiment was conducted between December 02, 2017 to January 02, 2018, in the experimentation with aquatic organisms, belonging to the Academic Unit of Serra Talhada (UAST) of the Federal Rural University of Pernambuco (UFRPE), Serra Talhada, Pernambuco. The tilapia Alevines initially presented weight, width and length equal to 0.018 ± 0.0047 g, 2.36 ± 0.16 mm and 10,57 ± 0.70 mm, respectively. The animals were fed six times a day (08:00, 10:00; 12:00; 14:00; 16:00 and 18:00) with commercial ration (55% of crude protein) equivalent to 2.5% of the biomass of the individuals. We used a completely randomized design with four treatments represented by the luminosity conditions: 0L: 24D, 12L: 12D (Control), 18L: 6D, 24L: 0D and four replications,where L (light) and D (dark). Abiotic factors were considered: temperature, conductivity, hydrogenionic potential, potential oxide reduction, total dissolved solids, dissolved and saturated oxygen. In turn, biotic factors were related to zootechnical parameters. Information related to water quality (temperature, dissolved oxygen, oxide reduction potential, conductivity and pH) were obtained daily in the morning and afternoon periods. Additionally, biometric analyses were performed throughout the experimentto determine the length, width and mass of the animal. This information was used to quantify the mass gain, specific growth rate and apparent feed conversion. The final number of individuals was also counted for the determination of the survival rate. The data were subjected to descriptive statistical analysis and analyses of variance, use of the main component technique and multiple regression model to estimate the weight gain of the alevines. Mass gain values of 0.1028 were observed; 0.1219; 0.1512 and 0.1746 for the treatments of 0l: 24D, 12L: 12D, 18L: 6D and 24L: 0D respectively. The photoperiod influenced the mass gain, and the light exposure of 18L: 6D and 24L: 0D promoted improvements in the survival rate and apparent feed conversion of the Alevinos. The mass gain of tilapia alevines was especially affected by dissolved and saturated oxygen, length and photoperiod.