Alteration of gonadal development of brook charr (Salvelinusfontinalis): Impact on salinity tolerance following transfer in estuarine conditions

Abstract

Sexual development of brook charr (Salvelinus fontinalis) was altered using ionizing radiation in order to study the implication of gonad development on salinity tolerance following transfer to estuarine conditions. Four groups of fish at the hatching stage were exposed to different doses of ionizing radiation: 0 (control), 6.2, 7.8, and 11.4 Gray. Prior to the estuarine introductions, the effects of ionizing radiations on mortality and growth of young brook charr reared in freshwater were examined over 19 months. Cumulative mortalities reached a maximum level after 90 days in all groups and did not exceed 20%. Final growth parameters were similar between all experimental groups. Significant sterility rates, were achieved on the female gender. The highest radiation dose resulted in the highest yield of sterile fish (59.5%). Transfer to estuarine conditions in June (period of enhanced osmoregulatory capacities) and in October (period of diminished osmoregulatory capacities) 1994, revealed that all sterile individuals survived the prolonged stay in hyperoosmotic environment during and beyond the spawning season, while the maturing fish suffered high mortality (up to 73.3%). It was found that low-level irradiation exposure had no direct negative effect on the survival capacity of brook charr in estuarine conditions. J. Exp. Zool. 279:273–283, 1997. © 1997 Wiley-Liss, Inc.