Aquaculture International

, Volume 10, Issue 1, pp 57-64

First online:

Effect of water hardness on egg hatchability and larval viability of Clarias gariepinus

  • C.N. MolokwuAffiliated withDepartment of Microbiology, University of Port Harcourt
  • , G.C. OkpokwasiliAffiliated withDepartment of Microbiology, University of Port Harcourt

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Studies were conducted to determine the effect of water hardness onClarias gariepinus egg hatchability and larval viability.The fertilized eggs were incubated at 28 °C and with waterhardnesses ranging from 10–700 mg/l CaCO3. Themean hatching rate fluctuated between 42.31% at hardness of 10mg/land 64.66% at 2000 mg/l. Abnormalities in the larvae were observedbeyond 200 mg/l and increased with increase in water hardness. Thehighest larval survival of 71.05% was recorded at 60 mg/l waterhardness. Based on statistics performed with analysis of variance (ANOVA) andfurther compared with Duncan's multiple range test (p = 0.05), the resultsimplythat very soft water (0–10 mg/l) and very hard water (300mg/l and above) are not suitable for Clariasegg incubation and larval rearing. A water hardness of 30–60mg/l CaCO3 is recommended for optimal normal hatching,high viability and maximum larval development of Clariasgariepinus.

Clarias eggs Incubation Rearing Water hardness Yolk sac larvae