Live plankton supplementation improves growth and health status of marron (Cherax cainii Austin 2002)

Abstract

Plankton communities were cultured and provided separately or mixed, with formulated food, to juvenile marron (Cherax cainii Austin, 2002) under laboratory conditions for 90 days. Four dietary treatments included formulated food (control; T1), formulated food with phytoplankton (T2), formulated food with zooplankton (T3) and formulated food with a mixture of phytoplankton, zooplankton (T4). The effects of these dietary treatments were evaluated on the growth, survival, moulting, immune and health indices, and on histology of the hepatopancreas, midgut and tail muscle tissue of marron. In addition, the dietary contributions using signatures of δ13C and δ15N of all food sources towards the diet of juvenile marron were analysed with a multi-source mixing model. Results showed that, zooplankton and mixed plankton supplementation improved the specific growth rate, weight gain percentage and survival rate of juvenile marron. Increased total haemocyte count, granular cell percentage and decrease in time required to clot the haemolymph were observed in marron provided with live plankton in comparison to control. Improved lysozyme activity, tail muscle dry weight indices, midgut epithelium height and tail muscle tissue myofibres were observed in marron provided with zooplankton. Stable isotope analysis showed that zooplankton contributed most towards the diet, followed by detritus. Formulated feed represented the most significant input towards the diet of marron in control tanks, but resulted in lower growth and survival rate. From the findings, it can be concluded that the live plankton are an important food source for the better growth, survival and health of juvenile marron.