CARAPACE MINERALIZATION AND HEPATOPANCREATIC INDEXES IN NATURAL AND CULTURED POPULATIONS OF MARRON (CHERAX-TENUIMANUS) IN WESTERN-AUSTRALIA

Marron (Cherax tenuimanus) were sampled from three wild populations in south-western Western Australia (Warren River, Donnelly River and Gar dner River) and from five farmed populations in south-western, lower-w estern and central-western Western Australia. Mean calcium concentrati ons in the carapace were higher in wild populations (from 182320 to 21 3140 mg kg(-1) dry matter) than in farmed populations (from 141960 to 182090 mg kg(-1)). The average calcium concentrations in the carapace were two-thirds those of other freshwater crayfish species. Mean carap ace magnesium concentrations varied from 970 to 1880 mg kg(-1) with no evident difference between wild and farmed populations. The proportio n of calcium and magnesium in carapace inorganic matter varied from 54 % to 78% and from 0.32% to 0.75%, respectively, being higher in the wi ld than in the farmed populations. With minor exceptions, carapace min eralization parameters correlated positively with calcium magnesium an d hardness of the water, and negatively with water pH. The wet hepatos omatic index, 4.5-6.0%, and the dry hepatosomatic index, 1.3-2.5%, wer e both higher in the farmed than in the wild populations, indicating b etter condition in the farmed marron. Hepatopancreas moisture concentr ation varied inversely with hepatosomatic index, ranging from 56.2% to 71.9%.