JOURNAL OF THE WORLD AQUACULTURE SOCIETY zyxwvut Vol. zy 28, No. 1 March, 1997 Freshwater Crayfish Growth Under Culture Conditions: Proposition for a Standard Reporting Approach LOUIS H. EVANS' zyxw Aquatic Science Research Unit, Curtin University of Technology, Unit 7, R&D Centre, Technology Park, I Sarich Way, Bentley 6102 Western Australia JAPO JUSSILA~ Department of Applied Zoology, University of Kuopio, P.O. Box zyx 1627, 7021 I Kuopio, Suomi-Finland Abstract A review of approaches currently used to measure growth in freshwater crayfish under experimental and pond grow-out conditions is presented. The review examined zyx 206 papers on growth and production of freshwater crayfish of which zyxw 34 were selected for detailed in- vestigation. Selection was based on the amount of information provided in the published re- port and on the species studied. The review was restricted to six crayfish species: zyx Cherax tenuimanus (marron), C. destructor (yabbie), C. quadricarinatus (red claw), Procambarus char- kii (red swamp crayfish), Astacus astacus (noble crayfish), and Pacifastucus leniusculus (sig- nal crayfish). Growth indices reported included instantaneous growth rate (IGR), absolute growth rate (AGR), slope of log weight against time (GRE) and specific growth rate (SGR, IGR*100). Studies were performed for varying time intervals under a wide range of stocking densities. Most reports did not express growth rate as an index but simply reported growth in terms of initial and final weights. The range of approaches used to express growth perfor- mance in freshwater crayfish growth studies hinders comparisons of growth rate and pro- duction findings. It is suggested that the reports of studies of growth performance in cul- tured crayfish include a growth rate parameter as well as initial and final weights. SGR is recommended as the parameter of choice since it is based on an exponential growth trend which is typically observed in measurements of weight increase with time in cultured juve- nile and early adult crayfish. The growth of commercially viable crayfish aquaculture industries in Louisi- ana, USA, Australia and elsewhere has provided a stimulus for research investiga- tions on growth rate and biomass produc- tion for several species under a variety of experimental conditions (Momssy et al. 1990; Huner 1994). Crayfish growth is generally reported as a function of time, initial weight and final weight of experi- mental animals. In addition, estimates of annual production (P) are frequently made by extrapolating the results obtained over a zyxwv ' Corresponding author. * Current address: Aquatic Science Research Unit, Curtin University of Technology, Unit 7, R&D Centre, Technology Park, 1 Sarich Way, Bentley 6102, West- em Australia. short experimental period to a predicted annual value. The methods used to express growth rate or estimate annual production are generally based on the assumption that growth, as de- termined by weight increase over time, is a linear function. However, various studies of weight increase of juvenile and early adult cultured freshwater crayfishes, and farmed crustaceans in general, has shown that the growth pattern is exponential (Morrissy 1979; Aiken 1980; Brewis and Bowler 1982; Lowery 1988; Aiken and Waddy 1992; Huner 1994). The use of a linear model to es- timate growth rate leads to errors in com- parisons of growth performance under dif- ferent experimental conditions and inaccura- cies in estimates of annual production val- ues. 0 Copyright by the World Aquaculture Society 1997 11