Cardiovascular, ventilatory and haematological responses of brown trout ( Salmo trutta L.), to the combined effects of acidity and aluminium in humic water at winter temperatures

Abstract

Two year old brown trout ( Salmo trutta L.) were exposed for 7 days to pH 4.7 alone and with aluminium at concentrations of 0.28 and 0.45 mg l −1, respectively, in the water of River Rutajoki, Central Finland. The labile aluminium accounted for less than 30% of the total added amount in the humic water. During the exposures the fish were monitored by a non-contact bioelectronic monitoring system which records heart and ventilation rates of the fish. Terminal blood samples were obtained to evaluate the degree of stress. No mortality occurred during any of the exposures. Acid stress alone and with aluminium caused an immediate acute response in heart and ventilation rates, which remained higher in combination with aluminium. Based on both the haematological and biomonitoring data, the fish were experiencing only slight ionoregulatory stress, but more severe hyperglycaemia in combination with respiratory stress. Aluminium had no or only minor additional effects on ionoregulation at the end of the exposures.