Evaluation of the zootechnical performance of Tilapia (Oreochromis mossambicus) fed at low protein concentrations

In Mozambique, there is still no production of typical commercial fish feed. It was in this context that an experimental feed based on Mudskipper flour, was produced under low protein conditions since there is no quality feed in order to verify the weight gain with protein less than 25% focused on family aquaculture and it was evaluated, the zootechnical performance of Tilapia Oreochromis mossambicus fed by these diets. The research was carried out in the net tanks of the School of Marine and Coastal Sciences of the Eduardo Mondlane University (ESCMC), from July 2017 to February 2018, contributing with a practical formula and with low component acquisition costs. The work consisted of two phases, namely: (i) feed production and (ii) Tilapia cultivation. A design model was established, with three treatments, TI-19%, TII-20%, and TIII-24%, with one repetition for each treatment. 90 sexually reverted Tilapia O. mossambicus fingerlings were populated with about 15 fingerlings per net tank, from the Aquapesca company breeders, with an initial average weight and length of 6.2g for TI, 6.6g for TII and 6.2g for TIII. During cultivation the fish were fed four times a day (6:00, 10:00, 14:00 and 18:00). Weekly biometrics were carried out covering 10% of the population, water quality indicator parameters were controlled, such as: dissolved oxygen, temperature and pH (twice a day, 6:30 am and 4:30 pm) and salinity (once a day) . The following zootechnical parameters were determined: growth rate (TCS), weekly growth percentage (PCS), specific growth rate (TEC), and total biomass produced (BTP). The results obtained showed statistically significant differences (p<0, 05) between the three treatments. The three treatments show results with a positive and increasing trend of increment for the growth in weight and in length, however the net tank experiments of TI-19%, TII-20% obtained the high values at the end of the experiment (18.8 g and 10.8 cm) and (21.5 g and 12.08 cm), comparing with another experiment that recorded lower growth TIII-24% (14.6 g and 9.6 cm). The results obtained in the study show that the Mudskipper meal (Periophthalmus sobrinus) meal can replace fish meal made from anchovies and sardines without compromising the result of the Tilapia's zootechnical performance.