Growth efficiency of juvenile barramundi, Lates calcarifer, at high temperatures

Abstract

Temperature is recognized to be the most important environmental factor affecting growth in fish. Barramundi are cultured over a wide range of temperatures and extreme high temperatures which they can experience under culture approach the upper thermal tolerance limit for this species. A growth trial was conducted on juvenile barramundi to examine the effects of high temperatures ranging from the minimum optimal temperature (27 degrees C) for growth efficiency to the extreme upper thermal limits (39 degrees C) for feed intake, growth and growth efficiency. Juveniles (4.87 plus or minus 0.32 g) were held at four different temperatures 27, 33, 36 and 39 degrees C and fed twice daily to satiation (503.5 g kg-1 crude protein, 182.5 g kg-1 lipid, 150.1 g kg-1 ash, 20.52 GE MJ kg-1). Feed intake (g per day) and SGR (% per day) increased with increasing temperature up to 36 degrees C. At 39 degrees C feed intake, growth, feed efficiency ratio, protein efficiency ratio and productive energy value were significantly lower than at the other temperatures. This demonstrates that growth was optimized at temperatures from 27 to 36 degrees C and that barramundi have a much wider range for maximum growth efficiency than preciously thought.