Notes on the biology of Gammarus pulex in the River Endrick

Between 1959 and 1962 the River Endrick in Scotland was studied and Gammarus pulex sampled. It was found that Gammarus pulex is common in most parts of the River Endrick except the extreme upper and lower reaches. It appears to be most abundant under stones and weed where the current is moderate and where there are more than 4 mg of calcium per litre of river water. Breeding occurs from March to September, but ceases in the winter months. The main predators of Gammarus pulex in the River Endrick appear to be fish, especially Salmo salar, Salmo trutta, Phoxinus phoxinus and Nemacheilus barbatula.