Optimum and favourable temperatures for growth of Cherax tenuimanus (Smith 1912) (Decapoda: Parastoacidae)

Abstract

The relationship between growth and water temperature for Cherax tenuimanus was described by fitting a multiple regression model employing a cubic polynomial equation in temperature and initial size to growth data obtained over the range 10-30� C. A physiologically based model for this relationship is unknown. The polynomial equation provides a mathematical method of defining features of the relationship that is preferable to curve-fitting by eye. Growth rate was dependent upon initial size and was suppressed by confinement of crayfish in individual compartments of a battery system. The lower temperature limits to growth were 11� C based on the minimum turning point of the growth-temperature curve, and 13� C based on the intercept of the lower limb of the curve on the temperature axis for the mean initial size of the test crayfish (0.82 g). The point of inflexion of the curve was at 18� C, and the optimum temperature for growth was 24� C based on the maximum turning point of the curve. The upper limit to the favourable range of temperature for growth and long-term survival was 30� C based on the intercept of the upper limb of the curve on the temperature axis for the mean initial size. The growth-temperature curves for three Australian Parastacidae- C. tenuimanus, C. destructor and C. quadricarinatus-all have a form similar to that for fish. This similarity further emphasizes the long-standing need for development of a physiologically based model for the relationship between growth and temperature for poikilotherms.