Growth and metabolic parameters of red tilapia reared in floating net cages in a small reservoir

Abstract

The objective of this study was to provide information on growth and metabolic parameters of red tilapia reared in cages in a small reservoir. Twelve floating net cages (5 m³) placed in an 1-ha reservoir were stocked with 25, 50, 75 and 100 sex-reversed red tilapias/m³, fed with two commercial floating feeds (32 and 28% crude protein), during 213 days. No effect (P > 0.05) of stocking density was observed at the end of the experimental period on body weight, body length, condition factor, feed conversion rate, survival rate, mean daily weight gain and specific growth rate. No differences (P > 0.05) on liver glycogen, liver somatic index (LSI), and total liver lipid were verified among the tested densities. However, blood glucose decreased slightly (P > 0.05) from the onset of the experiment to the 64^th day, and then returned to initial values from the day 118 on. Liver glycogen showed the highest value (P < 0.05) at the 64^th day, and total liver lipid, at the end of the experimental period (P < 0.001) Otherwise, K showed higher values (P < 0.05) at the 28^th, 64^th, and 213^th days. Dissolved oxygen and water transparency decreased along the experimental period. The poor growth, FCR, and the changes on metabolic parameters observed in this experiment might have been caused by environmental stimuli, such as poor water quality, despite the different densities tested in the study