Exposures to low-level ionizing radiation: Effects on biochemical and whole-body indices of growth in juvenile brook charr (Salvelinus fontinalis)

Exposure to ionizing radiation (IR) was used to alter gonadal growth in bro ok charr (Salvelinus fontinalis). To evaluate the possible effects of low-l evel doses of IR on future seawater adaptability of brook charr, the physio logical state and growth performances of juvenile brook charr were examined for 15 months. Four groups of fish were exposed to different experimental doses of IR at the hatching stage: 0 (control), 6.2, 7.8, and 11.4 Gy. Grow th in length and weight and condition factors of the irradiated groups were initially impaired compared with the control. Differences in growth were o bserved and were proportional to the irradiation dose. Initial growth delay in the irradiated groups was followed by compensatory growth of sufficient magnitude and duration that similar weights and lengths among all groups w ere reached by the end of the growth trial. Changes in the concentration of nucleic acids, protein, and water content were evaluated at three trimestr ial intervals in the control and 11.4 Gy groups. DNA content was systematic ally found to be higher in the irradiated groups compared with the control (602.76 and 850.38 mu g/g wet tissue). No difference in protein content (mg /g) in relation to fish weight was found between both groups during the fre shwater growth period. Lipid analysis was performed on the final samples an d was found to be significantly higher in the irradiated groups displaying catch-up growth (8.2% and 11.4% wet weight). RNA/DNA, RNA/protein, and prot ein/DNA were also calculated. (C) 1999 Wiley-Liss, Inc.