Impact of duration of stunting on compensatory growth and biometrics of snubnose pompano, Trachinotus blochii(Lacepede,1801) in low saline conditions

Compensatory growth (CG) pattern in snubnose pompano, Trachinotus blochii, stunted in low saline condition (< 15 ppt) was evaluated for its field level application. The fish were stunted for 30, 60 and 90 days by stocking 100 fish m− 3providing a commercial feed (45% crude protein, 0.8 to 1.2 mm size) at sub-optimal level [3% of average body weight (ABW)]. Post-stunting rearing was carried out in triplicates for 30, 60 or 90 days at a stocking density of 20 fish m− 3providing the same feed approximately 15% of ABW. Normal fish were maintained in triplicate at 20 fish m− 3providing feed at optimum level (10% of ABW) throughout the experiment. Parameters such as weight gain pattern, final ABW and specific growth rate (%) per day (SGR/day) indicated near complete CG in 30 days stunted fish. A partial CG in 60 days stunted fish and no CG in 90 days stunted fish compared to corresponding normal fish was observed. The 60 days stunted fish was found ideal for field adoption with longer stunting period with better CG and survival. A field trial was conducted in circular cage by stunting the fish at 40 fish m− 3(ABW = 5.4 g) feeding at 3% of ABW for 60 days. During post stunting, the stunted fish (10 fish m− 3) were reared in two cages feeding approximately 15% of ABW for 190 days. Parallely, normal fish (10 fish m− 3) were reared by feeding at 10% of ABW for 250 days. During stunting phase, the experimental fish exhibited a retarded growth (ABW = 18.9 g; SGR/day = 2.1) compared to normal (ABW = 27.9 ± 0.5 g; SGR/day = 2.7). In contrast, in post stunting phase, stunted fish exhibited partial CG (ABW = 116.23 ± 2.1 g; SGR/day = 0.71) compared to normal (ABW = 139.5 ± 15. 7 g; SGR/day = 0.8) with similar production (28.9 ± 1.8 g for stunted and 30.36 ± 4.3 g for normal) and higher survival (88.7%) than normal (77.5%). Biometric characteristics such as length - weight relationship (b value near 3) and condition factor (above 1) indicate natural growth in both stunted and normal fish. But size variation was higher in normal fish than stunted fish. Over all the experiments suggests that 60 days stunting in low saline conditions is ideal for ensuring good quality seed for farming of snubnose pompano.