Abstract: The ecological energetic parameters of Pneumatophorus japonicus ( Houttyn ) , such as food consumption, growth and ecological conversion eff iciency, were determined by gut content method in net cages which were situated in f ish reproductive waters in offshore area of Shandong peninsula. The results indicated that, ( 1) under constant experimental conditions, the f ish.. s maximum daily food consumption and daily growth change as irregular sine wave. The wave distance is constant, but the wave height .. s change is bigger; ( 2) the Relationship between instantaneous food content in stomach and corresponding time could be described as St = 9. 0876e - 0. 1868 t , and instantaneous gastric evacuation rate calculated by the formula was Rt = 0. 1868g .. ( 100g ) - 1..h - 1 ; ( 3) the daily food consumption calculated according to Eggers.. formula was Cd = 15. 60 .. 2. 55g..( 100g) - 1..d - 1 = 69. 84 .. 11. 42kJ..( 100g ) - 1..d - 1 ; ( 4) the change of f ish.. s body weight with time was linear, which could be described as Wt = 2. 23t + 16. 71. The daily growth could be obtained by the linear formulae and average body weight at experiment period and was Gd = 3. 72g .. ( 100g ) - 1 ..d- 1 = 30. 00kJ.. ( 100g) - 1 ..d - 1 . So ecological conversion ef ficiency could be obtained as Eg = 23. 85% = 42. 96% kJ from known Cd and Gd values.