Experimental Tainting of Marine Fish by Three Chemically Dispersed Petroleum Products, with Comparisons to the Braer Oil Spill

Fish tainting thresholds, and rates of development and loss of taint, have been measured using two salmonid and two shellfish species exposed to three petroleum products in a study concurrent with the examination of fish affected by the spillage of oil from the wreck of MV Braer. The range of (24 h) fish tainting thresholds varied from 0.098 to 0.331 mg/l for trout exposed to the three oils, and was no greater than the difference between the values obtained for the diesel oil used in this study and another sample examined previously by the same group. Thresholds were little different for salmon and trout exposed to the same (Forties) crude oil but, although the lowest tainting threshold was observed with mussels (0.032 mg/l), crabs appeared to show some resistance to tainting. The rate of induction of oil into fin-fish and mussels produced a readily detectable taint within 6 h of exposure to oil-contaminated water, but rates of uptake, and losses after transfer to clean water, contrasted with the measured fish tainting thresholds for the three different products. Diesel-derived taint persisted for over 10 weeks, much longer than both the medium fuel oil and the Forties crude oil-derived taints, and depuration time increased with oil loading and duration of exposure. Data from analyses of hydrocarbons in depurating salmon are presented, and criteria used to declare fish to be tainted or untainted are discussed.