Physiological responses of the common clownfish, Amphiprion ocellaris (Cuvier), to factors related to packaging and long-distance transport by air

Abstract

The physiological response of the common clownfish, A. ocellaris, to factors pertinent to air transportation conditions was studied in three stages: (i) determination of temperature effect and exposure process on oxygen consumption rates; (ii) elucidation of excretion trends of selected metabolites in simulated packaging experiments, and (iii) preliminary tolerance studies of some packaging parameters. Temperature significantly affected the metabolic rates of the clownfish. Q 10 values were relatively constant in fish exposed to sudden changes in temperature (from 25°C to either 15, 20, 30 or 35°C). Those treated with gradual changes in temperature showed much greater increases in oxygen consumption at temperatures above 25°C. The temperature selected for subsequent experiments was 25°C. Dissolved oxygen levels of packaging water remained high throughout the 48-h period. Water [H +] and total dissolved and unionized CO 2 concentrations changed most significantly during the initial 24 h and then levelled off by 48 h. Similarities in changes of concentrations between these imply close interaction between the measured variables. The total dissolved NH 3 continued to increase with no signs of levelling off. The concentrations of unionized NH 3 increased four-fold to 1.4 μM. The excretion of CO 2 decreased linearly at a rate of 150 nmol/g per h while the excretion of NH 3 increased at a rate of 97 nmol/g per h. A temperature range between 24 and 32°C was found to be necessary for survival of the fish with an optimal temperature of 27°C. Clownfish started to die when the pH of the seawater fell to 6.34 or total dissolved NH 3 rose above 0.97 mM ([unionized NH 3] = 38.35 μM). At 15°C, the fish started to die at 20 mm Hg which was twice the oxygen level at 20°C or above.