While these comprehensive datasets have revealed that body mass and temperature are the major predictors of fish respiration rates, habitat depth has emerged as an additional predictor for the respiration rates of mesopelagic and bathypelagic fishes (Torres et al., 1979; Smith and Laver, 1981 ; Donnelly and Torres, 1988; Torres and Somero. 1938: Cowles and Childress. 1995).