The Annual Changes Of Chemical Composition And Predicted Model Of Energy Density In Pelteobagrus Vachelli

From December, 2000 to Octomber, 2001, 114 specimens of the adult fish in Pelteobagrus vachelli, with body weight of 47.60 - 165.30g, were collected in 5 periods, i.e. the winter, spring, spawing, spent and autumn, in the Jialing River. Of which there were 10 males and 10 females in each of the winter, spring spent.and autumn, 20 males and 14 females in the spawing. The fish chemical composition and energy density in the 10 samples were measured.For the female samples, in the winter, spring, spawing, spent and autumn, the mean values of dry mass content (%B.W) were 31.3, 27.7, 26.5, 27.0 and 32.5, the values of lipid content were 13.5, 10.0, 10.5, 8.73 and 14.3, the values of protein content were13.4, 13.2, 11.8, 13.8 and 13.7, the values of ash content were 3.29, 3.39, 2.98, 3.59 and 3.34, the values of energy density (KJ/g) were 8.49, 7.09, 6.93, 6.70 and 8.89, the values of gonadosomatic index (%B.W ) were 1.11, 1.74, 14.3, 1.67 and 1.33, the values of hepatosomatic index (%B.W) were 2.64, 2.59, 1.50, 1.68 and 2.40.For the male samples, in the winter, spring, spawing, spent and autumn, the mean values of dry mass content (%B.W) were 29.2, 26.9, 27.2, 27.3 and 32.1, the values of lipid content were 10.9, 9.40, 9.16, 8.72 and 13.5, the values of protein content were13.5, 13.0, 13.6, 14.0 and 14.3, the values of ash content 3.51, 3.56, 3.48, 3.62 and 3.22, the values of energy density (KJ/g) were 7.51, 6.78, 6.82, 6.74 and 8.69, the values of gonadosomatic index (%B.W ) were 0.44, 0.45, 0.87, 0.54 and 0.67, the values of hepatosomatic index (%B.W ) were 2.80, 2.15, 1.71. 1.25 and 2.03.There were significantly linear relationship in each sample between energy density and either dry mass or lipid content, respectively. So were in the male in autumn and in the female in the winter between energy density and protein content, and between, energy density and ash content in the male in the spring, spawing, spent and autumn, and in the female in the spent.By analysis of covariance (ANCOVA) on the regression equations, a common equation for the male was developed to predict energy density (EA:KJ/g) with dry mass content (D) as predictor as following: EA = -4.33 + 0.408D, that for the female in non-spawing periods, i.e. winter, spring, spent and autumn, as: EB = -3.09 +0.395D, and that for the spawing females as: EC - 3.16 + 0.381D.The energy density in either the male or female at the spawing was not different significantly from that at the spent, which suggested that the energy expended in the spawing might be mainly supplied by ingested food in this fish. The lipid content of the fish ranged from 8.72 to 14.3% based on the body weight and from 30.5 to 43.7% on the dry mass, which indicated that its lipid content was higher than those of the most reported species.