Energy budget of juvenile fat snook Centropomus parallelus fed live food

Abstract

The fat snook Centropomus parallelus is a tropical estuarine species with importance for recreational and commercial fisheries and further aquaculture potential. Considering ingested energy ( C) is channeled into growth ( P), metabolic expenditure ( R), excretion ( U) and feces ( F), a balanced energy budget was established for isolated and grouped juvenile C. parallelus (5.18 to 10.25 g wet mass) by experimental quantification of each of these parameters. Fish were fed live prawn ( Macrobrachium sp.) at 25 °C and 20‰ for 19 days and daily energy budgets could be calculated. Energy content of food (live prawn), fish whole body and feces were 17.7, 14.5 and 6.1 KJ g − 1 dry mass (DW), respectively. Mass-specific rates of oxygen consumption and ammonia-N excretion were 0.271 and 0.0082 mg of O 2 or NH 3–N g − 1 wet mass (WW) h − 1 , respectively, resulting in O : N = 23.4. Daily ingestion ( C) was dependent on the amount of food offered and ranged between 4.9% to 7.4% of initial wet weight. Growth ( P) was positively correlated with initial mass varying from 0.008 to 0.104 g day − 1 . Feces release also correlated to fish mass and averaged 9.53 mg dry mass day − 1 . The components of energy budget showed mean values of 2.39 ( C), 0.24 ( P), 1.96 ( R), 0.11 ( U) and 0.06 ( F) KJ ind − 1 day − 1 . As percentage of ingested energy, C. parallelus channeled 10% in growth ( P), 82% in metabolism ( R), 4.6% in excretion ( U) and 2.5% in feces ( F). Gross ( K 1) and net ( K 2) growth efficiencies were 9.2% and 9.9%, respectively. On the course of this period of juvenile development, K 1 and K 2 increased significantly. Partitioning of ingested energy in P, R, U and F was significantly different in individually and group maintained fish ( P < 0.05). Energy budget of C. parallelus fed a highly digestible diet (live prawn) revealed poor growth and growth efficiencies ( K 1 and K 2) possibly associated with an elevated metabolic demand and a high channeling of metabolized energy ( P + R) into metabolism ( R) in both isolated and grouped fish. Data can be applied to ecosystem modeling and may contribute to identify species potential to aquaculture.