The consumption of rainbow trout (Salmo gairdneri Richardson) eggs by macroinvertebrates in the field

Abstract

SUMMARY. 1. Perforated boxes containing live, dead or no eggs of the rainbow trout, Salmo gairdneri Richardson, were buried in a natural spawning redd in a stream in North Wales for the duration of the natural incubation period.2. A significant difference (P<0.001) was found between the mean number of invertebrates colonizing perforated boxes containing live eggs, dead eggs and no eggs.3. The number of eggs retrieved from boxes originally containing dead eggs decreased as the number of invertebrates colonizing the boxes increased.4. Using a serological method of prey identification it was demonstrated that Leuctra hippopus (Kempny), Gammarus pulex (L.) and Ptychopter‐idae sp. scavenged on trout eggs in the field.5. There was some evidence that Rhyacophila dorsalis (Curtis) and Diura bicaudata (L.) preyed on trout eggs, but in view of their scarcity, it is suggested that they were a minor mortality factor.