Growth reduction in trout induced by naphthenic and isoprenoid hydrocarbons (Dodecylcyclohexane and pristane).

Rainbow trout were fed a diet containing 1% dodecylcyclohexane or pristane for 9 weeks. Feed intake was recorded daily and weight gain every 3 weeks. These animals were compared with fish receiving a hydrocarbon-free diet (groups fed ad libitum and pair-fed groups for which the ration provided was the amount of food consumed by the hydrocarbon-contaminated fish, the day before). The total food ingested by the pristane and dodecylcyclohexane groups amounted to 66 and 70%, respectively, of that eaten by the controls. The final mean weight of the controls was twofold their initial weight. The average weight gain of the dodecylcyclohexane and pristane groups was 37 and 25%. During the same period the fish of the pair-fed groups gained approximately 70% of their initial weight. Significant effects of hydrocarbon consumption on food conversion factors, viscerosomatic index, hepatosomatic index, and liver lipid concentration were observed. The results are discussed in relation to the possible causes of such changes.