Abstract
The objective of the present study was to develop models for predicting live weight from the length-weight relationship and body composition of Nile tilapia. A total of 3,000 juvenile fish (initial weight = 28.6±4.16 g and standard length = 13.8±0.16 cm) were distributed into three circular cages (12 m3 each). The fish were hand-fed extruded diets containing 332 g kg-1 of crude protein and 3,230 kcal kg-1 of digestible energy, until apparent satiety, twice daily, for 100 days. Twelve fish were collected from each cage every 20 days for measurements of body weight and length, and proximate composition analysis; statistical analysis was conducted using linear regression. The value of the slope b and the intercept for the length-weight relationship were 3.0604 and 0.0203, respectively. The prediction equations obtained for body moisture (MO), crude protein (CP), crude lipid (CL), and ash against body weight (BW) in g/100 g of fish were as follows: MO = 70.0090 - 0.0071BW; CP = 13.7550 + 0.0037BW; CL = 9.2636 + 0.0057BW; and ash = 4.2392 - 0.0024BW. It is possible to develop equations to predict body weight and composition, which can be used to control the production of Nile tilapia and improve its commercial value.
Highlights
Mathematical models of fish growth offer an objective and practical method for describing patterns of growth data and estimating fish weight at times between sampling intervals
The daily weight gain of fish in the present study was higher than that reported by Moraes et al (2009) for Nile tilapia reared in indoor cages at the same density
Feed intake is a major factor for tilapia growth (Tran-Duy et al, 2012), and in our study, fish preferred to be fed to apparent satiation because of the constant and high dissolved oxygen concentration during trial studies
Summary
Mathematical models of fish growth offer an objective and practical method for describing patterns of growth data and estimating fish weight at times between sampling intervals. Knowledge of the relationships between body weight and composition supports selection during efforts for the improvement of aquaculture genetics.An accurate length-weight relationship equation allows for the conversion of growth-in-length to growth-in-weight in stock assessment models, as well as the estimation of biomass from the length frequency distribution, condition (Petrakis and Stergiou, 1995), and morphological characteristics of fish populations (Stergiou and Moutopolous, 2001); the relationship equation, is an important aquacultural management tool. Despite the usefulness of the length-weight relationship and body composition, as well as the great economic importance of Nile tilapia (Oreochromis niloticus) to global aquaculture, little information on these factors is available in cagefarmed growing-finishing populations of the species. The present study was conducted to determine the lengthweight relationship and develop prediction equations of body composition for growing-finishing cage-farmed Nile tilapia by using regression analysis
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