Consequences of Sublethal Polychlorinated Biphenyl Exposure on the Swimming Performance of Rainbow Trout Oncorhynchus mykiss

Abstract

Freshwater teleost fish often experience natural and anthropogenic conditions that result in fluctuating energy availability, therefore the ability to acquire, transform and use energy is essential for the survival of these fish. Polychlorinated biphenyls (PCB's) are recognized as physiological sources of stress to fish as they incite defense mechanisms that are generally costly in terms of metabolic resources. Over time, such responses may decrease individual performance and possibly fitness by changes in foraging, migration and escape behaviors, and the population in terms of reproductive capacity due to the alterations in energy allocation following an exposure. The main goal of this study was to determine if a sublethal exposure to PCB-126 affects the energy budget of the fish and can therefore be responsible for functional deficiencies associated with their locomotion. Fish were injected low (100 mug/kg) and high (400 mug/kg) concentrations of PCB-126 and swimming performance parameters including critical swimming speed, metabolic rate and recovery ratios were evaluated. EROD activity was also measured in the liver as an indication of PCB-126 intoxication while blood and white muscle tissue metabolites were analyzed to quantify the physiological disturbance levels associated with this exposure. A significant decrease was observed in the swimming performance of rainbow trout for the low and high PCB-126 treatments as well as an impaired recovery with increasing level of PCB exposure following exhaustive exercise. This study also showed the occurrence of physiological disturbance by a reduction in the hepatosomatic and spleen somatic indices and elevation of plasma cortisol and glucose levels, as well as white muscle reductions in glucose and glycogen indicating higher metabolic costs during recovery and muscle restoration for PCB-exposed fish. Overall, this research provides insights into the sublethal effects of toxic organic compounds on fish.