Growth performance and energy budget of the yellowfin seabream, Acanthopagrus arabicus (Iwatsuki, 2013) affected by the combined effects of water temperature and salinity

A 56-day research was carried out to determine the interactive effects of water temperature (WT) and salinity (WS) on physiological responses of yellowfin seabream, Acanthopagrus arabicus (Iwatsuki, 2013) (10.0 +/- 0.2 g). Three salinities (S; 12, 35 and 50 parts per thousand) and four temperatures (T; 16, 23, 30 and 35 degrees C) were selected to design 12 experimental treatments. The husbandry system consisted of thirty-six 300-L cylindrical polyethylene tanks that were filled with 250 L of water. Each treatment had three replicates (tanks) containing 20 fish in each tank. Fish were handfed on a commercial feed (440 g kg(-1) crude protein and 180 g kg(-1) crude fat) twice daily at visual satiation. Five fish from each tank were transferred into an experimental chamber to evaluate their oxygen consumption and ammonia excretion. There was a positive correlation between fish oxygen consumption and WT (r=0.594; p=0.001). In addition, there was a negative relationship between WS and ammonia excretion (AE) (r = -0.865; p=0.029), meanwhile the relationship between WT and AE was positive (r=0.422; P=0.01). Growth parameters were significantly affected by WT, WS and their interactions so that the highest final body was recorded in the highest temperature and salinity treatment. On the other hand, the lowest body weight was observed in the lowest WT (i.e., 16 degrees C) irresponsive to WS. The moisture level in the whole body was affected by WT (p=0.012). The crude lipid in the whole body was influenced by only WS (p=0.04). The ash content in the whole body was profoundly affected by WT (p=0.0001), WS (p=0.0001) and their interaction effect (p=0.04). The energy content of the whole body was only affected by WT (p=0.025). The energy budget of fish was influenced by WT (p=0.0001) and its interaction with WS (p=0.015). In summary, the present findings indicated that the preferred WT for A. arabicus is between 30 to 35 degrees C in brackish water.