Effects of exposure to the water‐soluble fraction of crude oil on the swimming performance and the metabolic and ionic recovery postexercise in Pacific herring (Clupea pallasi)

The swimming performance and recovery from exercise were determined in juvenile Pacific herring (Clupea pallasi) following exposure to the water‐soluble fraction (WSF) of North Slope crude oil for more than eight weeks. Total polycyclic aromatic hydrocarbon concentrations (mean ± standard error) at the beginning of exposures were as follows: control, 0.2 ± 0.1 μg/L; low, 9.6 ± 2.5 μg/L; medium, 40.7 ± 6.9 μg/L; and high, 120.2 ± 11.4 μg/L. Biological availability of hydrocarbons was confirmed by a significant induction of hepatic cytochrome P450 content and ethoxyresorufin‐O‐deethylase activity. Critical swimming speed (Ucrit) was significantly reduced in fish exposed to the highest concentration of WSF for 96 h (11% ± 3.7% reduction) and at the two highest concentrations at four weeks (16% ± 3.6% and 29% ± 5.4% reductions) and eight weeks (11% ± 3.8% and 40% ± 5.7% reductions). Mortality occurred in all groups 24 h following Ucrit swim trials, with significantly higher mortalities observed in fish exposed to WSF in a concentration‐ and time‐dependent manner (maximum mortality of 72.2% ± 5.5% in the eight‐week, high‐exposure group). Burst swimming alone resulted in increased plasma cortisol, lactate, Na+, and Cl− concentrations and decreased muscle glycogen levels that returned to baseline values by 24 h. An interpretation of the effect of WSF exposure on postexercise metabolic recovery was complicated by pre‐exercise alterations in several parameters. The time courses and magnitudes of several key postexercise parameters, including plasma cortisol, lactate, and muscle glycogen, were significantly altered by exposure to WSF. The present study clearly shows that hydrocarbon exposure can reduce the swimming ability of fish and their ability to recover from exhaustive exercise.