Effects of dietary restriction on growth, feed conversion and cost of feeding juveniles of mullet Mugil platanus Günther, 1880
Feeding is the most expensive item in intensive fish farming. Therefore, knowing the feeding rate that promotes the best growth without waste of feed, is fundamental for the financial viability of aquaculture activity. The objective of this work was to monitor the survival, growth and feeding of juveniles of the mullet Mugil platanus fed with different amounts of feed. For this, four hundred and fifty wild mullet juveniles (0.21 ± 0.03g) were randomly stored in 15 tanks with 200L, in a system with biofilter and individual aeration. The average temperature and salinity were 29ºC and 25 ‰ respectively. Five levels of feeding were evaluated in triplicate, a control where the fish were fed until satiety (100%) and another four levels, equivalent to 80, 60,40 and 20% of satiety. The fish were fed four times a day, during the 30 experimental days. Biometrics were performed every 15 days to determine weight. The results were submitted to ANOVA analysis of variance and later to Duncan's test (P <0.05). Food levels were related to the results of feed conversion (AC) and protein efficiency rate (PTE) using quadratic regressions to determine the optimal level of food. Survival showed no significant difference between treatments, remaining above 90%. At the end of the experiment, average weight and specific growth rate of the treatment were 100% higher than in the other treatments. Fish fed with 20% satiety showed lower AC and TEP (P <0.05).In this same treatment, the lowest value of the hepatosomatic index was observed and also the lowest expenditure on food (P <0.05), which increased as the fish received a greater amount of food. The regressions calculated from WC and PTE indicate that 72% of satiety promoted better use of the food consumed.