PRELIMINARY EVALUATION OF THE EFFECTS OF LONG-TERM PERIODIC SUBLETHAL EXPOSURE TO HYDROGEN-SULFIDE ON THE HEALTH OF ATLANTIC SALMON (SALMO-SALAR L)

Atlantic salmon smelts (Salmo salar L) were exposed to periodic (6 hourly) sub-lethal levels of hydrogen sulphide over 20 weeks. Histological examination of gill tissues showed that after an initial period (6 weeks), during which the condition of the gills deteriorated, there was a gradual recovery. By the end of the experiment (20 weeks) gill tissues appeared normal. Fish growth was not significantly affected except during the period of maximum gill damage (6-8 weeks) when there was a small but significant decrease In growth rate with respect to the control group.