COMPENSATORY GROWTH OF BLACK SNOOK Centropomus nigrescens JUVENILES UNDER TWO DIFFERENT SALINITIES

Black snook Centropomus nigrescens is one of the least studied species of the genus Centropomus. Its distribution ranges from Southern Gulf of California to northern Peru and represents an important contribution to traditional fishery incomes that are annually diminishing due to overfishing. Thus, the high market price and demand translates to having good aquaculture potential. Research also indicates that aquaculture production efficiency may benefit from feeding strategies that stimulate compensatory growth, that is an accelerated growth that occurs in some species after a growth depression period, which may lead to less feed costs. The objective of this study was to investigate the compensatory growth response of black snook juveniles reared in high (35ppt) and low salinity (1.5ppt), after a nutritional restriction period.

Black snook juveniles (68 dph) were separated by sizes (small 0.45±0.23 g, medium 0.91±0.19 g and large 1.28 ± 0.22 g) to avoid cannibalism and distributed into two systems, low (1.5 ppt) and high (35 ppt) salinity, each consisting of 6-110 L tanks. For each salinity treatment, two feeding treatments were applied, a non-digestible experimental diet (CG) and a commercial diet (Control) (Otohime, Marubeni Nisshin Feed Co.).

Fishes were fed 5 times a day to apparent satiation; after a 2 week period, the CG organisms were fed with control diet. Feed was weighed to know how much food was consumed after Weight, TL, FL, and ST measurements were taken at the beginning and every two weeks thereafter. After 8 weeks, the data was processed by two-way ANOVA. Comparisons were made between salinities and GC and C treatments, at each two-week period within a minimum significance level of P<0.05.

At week 2, the GC groups did not experience notable weight gain, and even lost weight in 1.5 ppt (growth depression period). By week 4, after a reestablished diet GC showed significant growth in both salinity treatments, which continued steadily until the end of the exp. Finally, at week 8 all treatments in both salinities attained the same final weight (Fig.1). These results show clear full compensatory growth in black snook at low and high salinities thus increasing our knowledge of their plasticity and the species potential for aquaculture.