Aquaculture International

, Volume 10, Issue 1, pp 57–64

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

  • C.N. Molokwu
  • G.C. Okpokwasili

DOI: 10.1023/A:1021395122919

Cite this article as:
Molokwu, C. & Okpokwasili, G. Aquaculture International (2002) 10: 57. doi:10.1023/A:1021395122919


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 eggsIncubationRearingWater hardnessYolk sac larvae

Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • C.N. Molokwu
    • 1
  • G.C. Okpokwasili
    • 1
  1. 1.Department of MicrobiologyUniversity of Port HarcourtPort HarcourtNigeria