Osmoregulatory capacity, health status and growth as functions of moult stages from various weight classes in marron (Cherax cainii) and yabbies (Cherax destructor)

Abstract

The study investigated the relationship between five moult stages and the osmoregulatory capacities (OC), moisture content of hepatopancreas (HM%), hepatosomatic indices (HI_wet, HI_dry) and growth of 6 weight classes of 235 marron (Cherax cainii) and 235 yabbies (Cherax destructor) under laboratory conditions. In each moult stage, OC increased linearly with the increase in wet body weight. Intermoult stage C showed the highest OC significantly lower than premoult stages D₀, D₁, D₂ and postmoult stage AB in every weight class in both crayfish. HM% decreased from AB to D₂, while both HI_wet and HI_dry reduced from C to D₂. Percentage dry matter of whole body carcass was highest in stage C and lowest during the AB stage with a significant difference between the two species. Larger than 15-g marron and yabbies differ with each other in OC, HI_wet, and HI_dry, moult intervals and growth rates.

Keywords:

• Freshwater crayfish
• Cherax cainii, Cherax destructor, hepatosomatic indices
• moult stage
• osmoregulatory capacity

Acknowledgements

The authors would like to thank Jane Fewtrell, Simon Longbottom from Department of Environment and Aquatic Science, Curtin University for support and help in the ordering of materials and chemicals, to use in some of the new facilities and equipment in the laboratory, and to set up my experiments. Thanks to Louis Bourdon for proof reading service. This research was co-supported by Vietnamese government and Curtin University, Western Australia.