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Ichthyocotylurus erraticus (Digenea: Strigeidae): factors affecting infection intensity and the effects of infection on pollan (Coregonus autumnalis), a glacial relict fish

Published online by Cambridge University Press:  10 June 2005

C. HARROD
Affiliation:
School of Environmental Sciences, University of Ulster, Coleraine BT52 1SA, UK Current address: Department of Physiological Ecology, Max Planck Institute for Limnology, Postfach 165, 24302 Plön, Germany.
D. GRIFFITHS
Affiliation:
School of Environmental Sciences, University of Ulster, Coleraine BT52 1SA, UK
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Abstract

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Lough Neagh pollan are heavily infected with the strigeid Ichthyocotylurus erraticus, with 100% prevalence and median infection intensities of 600+ metacercariae in the pericardial cavity of mature fish. Female fish were more heavily infected than males. Infection intensity, which rose in summer, varied with pollan size, year, sampling bay within the lough and water depth within bays. Heavily infected pollan were caught further offshore than lightly infected fish. Spatial variation in pollan infection intensity corresponded to variation in the abundance of the first intermediate host, Valvata snails. The data suggest that heavily infected fish had lower food intakes. Parasitism reduced condition and liver size in male fish but condition in heavily parasitized females increased. Infection intensity was greater in larger fish of a given age. These patterns are discussed in the context of risks and rewards. The data suggest that inshore waters in summer are the preferred habitat of pollan and that the greater infection intensity of offshore fish results from their reduced competitive ability as a consequence of parasitism and the increased risk of infection there.

Information

Type
Research Article
Copyright
© 2005 Cambridge University Press