Lead and cadmium in stone loach (Noemacheilus barbatulus L.) from three rivers in Derbyshire.

Fish Noemacheilus barbatulus L. (stone loach) were caught at about 4-week intervals from single sites in three Derbyshire rivers, with different concentrations of cadmium and lead in sediments and water, during a 1-year sampling program. Fish were classified by age, site, and sampling occasion. Growth was allometric and affected by temperature. A steady state of cadmium burden was reached by fish of 2 years old or more but not by younger fish. For lead, fish rarely showed an increase in body burden. Differences in body size accounted for most of the variation in cadmium levels between loach of different age groups but were less important for lead levels. The exponent for body weight was not affected by age of fish and was about 0.79 +/- 0.06 for cadmium and 0.13 +/- 0.21 for lead. There was some correlation between cadmium levels in fish of different age groups taken at the same time from any site; levels of significance were higher when differences due to body size were discounted. Then, sampling time did not explain a significant part of the residual variation. Fluctuations in the cadmium and lead burdens for fish in the same age group from each of the sites were correlated for some comparisons. Loach from sites with higher metal concentrations had higher levels of both cadmium and lead. It is suggested that cadmium uptake from food contributed considerably to the body burden of loach.