Evidence for density‐dependent establishment and survival of Pomphorhynchus laevis (Müller, 1776) (Acanthocephala) in laboratory‐infected Salmo gairdneri Richardson and its bearing on wild populations in Leuciscus cephalus (L.)

Experimental primary and superimposed infections of Salmo gairdneri with various dosages of Pomphorhynchus laevis indicated that density‐dependent parasite establishment and survival occurred such that the number of parasites which survived to reproduce within an individual fish reached a ceiling level. The possibility that this mechanism is responsible for the generation of the observed positive relationship between the length and worm burden of Leuciscus cephalus taken from a natural population in the River Severn, England is discussed in the light of these experiments.