Sublethal effects of treated liquid effluent from a petroleum refinery. III. Avoidance and other locomotor responses of rainbow trout

Locomotor behaviour of individual rainbow trout ( Salmo gairdneri) was observed in a chamber with side-by-side flows of clean water and 0, 1, 10, or 30% oil refinery effluent, with a steep gradient between the two flows. None of the concentrations caused statistically significant avoidance or preference as measured by changes in time spent by fish in the four areas of the chamber (upstream or downstream and north or south side). Similarly, the side of entry of the effluent was not related to any differences in relative activity in the four areas, as measured by the numbers of movements fish made within the areas. When 30% effluent was present, the general level of activity in all parts of the chamber appeared to be lower than activities for the other concentrations, but the difference was at the borderline of statistical significance ( P=0.06). Behavioural response to the effluent was less important than direct physiological effects on trout, previously documented with the same effluent. The tested batches of effluent had an overall 3-day LC 50 of about 100% effluent. The effluent exceeded Canadian regulations in average level of ammonia, was somewhat elevated in oil-plus-grease and residue, but was well below regulatory limits for phenols and sulphides.