Culture of juvenile Murray cod, trout cod and Macquarie perch (Percichthyidae) in fertilised earthen ponds

juvenile Murray cod (Maccullochella peelii peelii). trout cod (Maccullochella macquariensis). and Macquarie perch (Macquaria australasica) (family Percichthyidae) are reared in fertilised earthen ponds to produce fingerlings for aquaculture and stock enhancement purposes to support recreational fisheries and conservation efforts in South eastern Australia. A total of 102 pond stocking trials were conducted over 13 production seasons to quantify growth, survival, condition and yield of juvenile percichthyids and to explore interactions between these variables and a range of biotic and abiotic factors. Water chemistry and zooplankton within ponds fluctuated widely from I week to the next and varied considerably between ponds. Zooplankton was composed of rotifers, cladocerans (mainly Moina and Daphnia), calanoids and cyclopoids. Fish Length-weight. length-age and weight-age relationships are described. Specific growth rates (SGRs) were negatively correlated with both size-at-stocking and stocking biomass for all species. SGRs and fish condition were highest in the weeks immediately following stocking, but declined in latter weeks. Survival rates were variable (0.2 99%). but generally increased and became less variable over the 13 seasons. Increasing stocking density reduced the growth and condition of fish. but did not affect survival. Significant correlations were detected between various fish production indicators (growth, survival and yield) and several water chemistry and biota parameters (prey abundance), but none were consistent for all three species of fish. Some water chemistry parameters reached levels that may have stressed fish and reduced growth and Survival. Declines in growth and condition at higher densities, and in latter weeks following stocking, were attributed to a reduction in the availability of preferred prey due to overgrazing by fish. The influence of percichthyid fish on plankton communities in nursery ponds depends largely on fish biomass and size-selective predation. This Study has contributed significantly to the knowledge of nursery pond ecosystems. and led to improved pond management and increased reliability of the production of fingerling percichthyids in Australia. Crown Copyright (c) 2008 Published by Elsevier B.V. All rights reserved.