Respiratory response of juvenile Chinook salmon and striped bass exposed to crude oil

Interest surrounding the potential effects of crude oil on aquatie organisms has increased in recent years due to the i n c i d e n c e o f accidental oil spills. There are f e w experimental results reported, however, dealing with the ef fect on aquatic species o f water-soluble aromatic hydro-carbons contained in crude oil. Such compounds are highly toxic to mammals. Experiments were conducted using juvenile chinook salmon, Oncorhynchus tshawytscha, and striped bass, Morone saxatilis. The fish were exposed to sub-lethal con-centrations o f the aromatic hydrocarbon benzene, for periods ranging from 1-96 hours. Prior to exposure, and after exposure to the benzene, respiration rates o f individ-ual fish were measured. Results show increases in respira-tory rate up to I15 percent above that o f control fish after exposure periods o f 24 hours for striped bass and 48 hours for chinook salmon. Fish exposed to benzene concentra-tions o f 10 p p m for periods longer than those listed ex-hibited a narcosis that caused a decrease in respiratory rate. The narcotic state induced by exposure to benzene was shown to be reversible when the fish were placed in fresh water and kept for periods longer than 6 days. Possible biochemical mechanisms leading to this response are hypothesized