The effect of cadmium exposure on repeat swimming performance and recovery in rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta) and lake whitefish (Coregonus clupeaformis).

摘要

Swim performance provides a measure of the integrated metabolic costs of sublethal exposure to stressors, including Cd. While the impacts to sustained swimming performance in Cd exposed fish have already been characterised, effects to repeat swimming ability have not. This thesis identifies the effects of sub-lethal waterborne Cd exposure on ionoregulatory function, repeat swimming ability, anaerobic metabolism and stress response in rainbow trout ( Oncorhynchus mykiss), brown trout (Salmo trutta) and lake whitefish (Coregonus clupeaformis).;Repeat swimming ability was assessed in brown trout and lake whitefish over a 30 day period. Cd exposure resulted in 31% and 38% decreases in secondary swimming ability of each species, with the greatest decreases observed after one week of exposure. This reduction in swimming ability was associated with ionoregulatory disruption and reduced resting ATP stores in the white muscle. As a result, a second study was performed in order to identify the role of the recovery period. Recovery ability was evaluated in rainbow trout following 6 d exposure to 0 or 18 nM Cd. Three recovery periods were employed; 0.5, 1.5 and 6 h so as to identify the effect of Cd exposure on the recovery of metabolic parameters. As anticipated, Cd exposed fish had decreased swimming ability when given a short, 0.5h recovery period. However, a 1.5 hour recovery period resulted in significantly increased swimming performance in Cd exposed fish compared with controls. Improved swimming ability in Cd exposed fish corresponded to increased rates of recovery of muscle and liver glycogen and ATP and reductions in lactate, compared with control fish.;Repeat swim trials included an initial swim to 85% of the Ucrit of control fish and a recovery period of varying duration, followed by a second, exhaustive, swim trial. Fish were terminally sampled prior to and directly following each of the two swim challenges so as to evaluate fluctuations in metabolic (glycogen, lactate, ATP) and stress (cortisol) parameters as a result of exercise and Cd exposure. All exposures were performed in duplicate with an exposure concentration of 18 nM Cd in moderately hard water (120 mg CaCO3 L-1) and a control group.