Abstract

The Australian freshwater crayfish marron (Cherax tenuimanus) was investigated as a possible candidate for aquaculture in acidified waterbodies. The study examined seasonal variations in the health and condition of marron collected from two acidified mining voids (Ewington No. 2 and Stockton Lake) and one non-acidified water reservoir (Wellington Dam), located in the Collie Coal Basin, Western Australia, over three years. Total circulating hemocyte levels (THC) and reproductive activity were used as indicators of crayfish health; organosomatic ratios (HI_wet and HI_dry), and hepatopancreas and tail muscle moisture levels (HM% and TM% respectively) were used as indicators of crayfish condition. Seasonal comparisons showed that during the warmer months (summer, autumn) THC and HI_dry levels at all sites were significantly higher (P<0.05) than those recorded in the cooler months (winter, spring); however, HM% and TM% displayed higher levels in winter and spring compared to summer and autumn. Consistently higher levels of THC and lower organosomatic ratios were observed in marron from acidified sites in all four seasons. Hepatopancreas and tail muscle moisture levels were consistently higher in marron from Stockton Lake compared with those of marron from the other two sites, possibly reflecting changes in osmoregulation due to lower water conductivity and fluctuating pH. Results suggest that marron from acidified sites possess lower energy reserves than marron from non-acidified sites. However, continuous exposure to high environmental acidity did not preclude reproduction, with juvenile offspring being located at all sites. Results suggest that marron resident in acidified waterbodies are unlikely to exhibit compromised immunity, but display mild stress due to acid exposure.

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