The combined effects of temperature and salinity on growth and survival of juvenile mud crabs (Scylla serrata Forskal)

An experiment was conducted to determine the effects of temperature and salinity on the growth and survival of the mud crab Scylla serrata, and the combined optima for these parameters during the nursery phase. Instar 2 crablets, mean weight 18.43 +/- 0.42 mg were individually reared at combinations of temperature (20, 25, 30, and 35 degreesC) and salinity (0parts per thousand, 5parts per thousand, 10parts per thousand, 20parts per thousand, 30parts per thousand, and 40parts per thousand) for 18 days. Crablets were fed an artificial penaeid diet to satiety each day and at harvest were weighed, and the carapace width was measured. All crablets held at 0parts per thousand, regardless of temperature, were dead the morning after stocking and were therefore excluded from any data analysis. Survival was significantly different among treatments due to temperature but not due to salinities between 5parts per thousand and 40parts per thousand. The mean survival for the various temperatures were 36.0%, 98.0%, 96.0%, and 94.0% for temperatures of 20, 25, 30, and 35 degreesC, respectively. Growth, As measured by individual wet weight at harvest, carapace width, instar 3 intermoult duration, and weight-specific growth rate (WSGR percentage per day), was influenced more by temperature than by salinity, although both had significant effects on all parameters examined. Analyses indicate that maximum WSGR of around 16% day(-1) was achieved at 30 degreesC and 10-20parts per thousand salinity. Based on the findings of this experiment, S. serrata juveniles from the Northern Territory of Australia should be reared at approximately 30 degreesC with salinities in the range of 10-25parts per thousand in order to achieve maximal production. (C) 2004 Elsevier B.V. All rights reserved.