Effects of stocking ratio on growth and blood parameters of Oreochromis niloticus and Clarias gariepinus juveniles in polyculture system

Abstract

One hundred and fifty Oreochromis niloticus (Nile Tilapia) (30.01±0.29 g) and 90 Clarias gariepinus (African catfish) (40.08±0.44 g) juveniles were randomly assigned four treatments: tilapia: catfish ratios 4:0 (TT₁), 3:1 (TTC₂), 1:1 (TTC₃), and 1:3 (TTC₄) at 20 fish/m² triplicate in hapas. Fish were fed 40% crude protein diet at 5% body weight daily. Mean weight gain (MWG), mean length gain (MLG), survival rate (SR), water and blood parameters were investigated. ANOVA and Duncan Multiple Range Test were used for analyses at p<0.05. Highest MWG of tilapia was in TTC₂ (24.62±3.96 g) while least was in TTC₄ (15.03±1.25 g). In catfish, highest MWG was in TTC4 (116.52±4.10 g), followed by TTC₃ (116.35±0.14 g) while TTC₂ had 98.53±19.28 g. MLG in tilapia was highest in TTC₂ (4.07±0.25 cm) and least in TTC₄ (1.15±0.64 cm). In catfish, highest MLG value was in TTC₃ (17.38±0.93 cm) and lowest in TTC₂ (14.47±1.19 cm). SR for both species and all treatments ranged between 93.33±4.40% and 97.76±2.23%. Highest number of tilapia fry was found in gut content of catfish in TTC₄. Water and blood parameters were within acceptable limits. With increasing catfish to tilapia ratio, MWG decreased in tilapia but increased in catfish due to stiffer competition. Gut content analyses reaffirmed that C. gariepinus predates better under high stocking density.

Key Words: Utilization, predator, stocking arrangement, growth performance