The influence of calcium on aluminium‐induced changes in the growth rate and mortality of brown trout, Salmo trutta L.

Abstract

Yearling brown trout, Salmo trutta L., were maintained in a synthetic medium at pH 5.2 with various concentrations of calcium (4–400 μumol l−1) and aluminium (0–3 μumol l−1). In general, higher mortality and lower growth rates were found at higher aluminium concentrations, with these effects being reduced at high ambient calcium. Aluminium toxicity was greater in an experiment conducted in February–March than in an experiment conducted in October–December; this could be due to a seasonal variation in tolerance of the fish. Aluminium exposure resulted in an initial period of weight loss and high mortality followed by some recovery over the 6‐week period of the experiments. In the first experiment, as in previously reported work, adaptation was incomplete in that aluminium‐induced growth rate reduction was still evident to the end of the test. In the second experiment, however, no significant effect of aluminium treatment on growth was found during weeks 4 to 6 of the exposure period.