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Linking Environmental Heterogeneity to the Distribution and Prevalence of Myxobolus cerebralis : A Comparison across Sites in a Northern Utah Watershed
Author(s) -
Hoz Franco Ernesto,
Budy Phaedra
Publication year - 2004
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t03-167.1
Subject(s) - trout , salmo , biology , oncorhynchus , parasite hosting , streams , ecology , fish <actinopterygii> , fishery , computer network , world wide web , computer science
Given the variable effects of Myxobolus cerebralis (the parasite that causes whirling disease) on trout populations in different streams across the intermountain West, it is important to understand the role of environmental variation in determining the distribution and prevalence (percent infected) of M. cerebralis in newly infected watersheds. We investigated the relationship between a selected group of environmental factors and the distribution and prevalence of M. cerebralis in wild salmonid populations in the Logan River, Utah. We also compared the results of polymerase chain reaction analyses of wild (free‐ranging) fish and fish reared in sentinel cages. These results indicated that despite its recent widespread distribution, the prevalence of the parasite varied greatly across sites. The lowest prevalence among cutthroat Oncorhynchus clarki was found at the headwaters, where the average summer temperature was below 9.5°C, whereas high prevalence was associated with temperatures above 12°C. Furthermore, prevalence in brown trout Salmo trutta and cutthroat trout increased with discharge, reaching its highest levels at sites where the average base flow ranged between 0.7 and 1.1 m 3 /s. Despite hypothesized mechanistic links to one or more stages or hosts in the M. cerebralis life cycle, we observed no relationship between M. cerebralis prevalence and substrate composition, nutrients (total nitrogen and total phosphorus), periphyton, and oligochaetes. However, multiple linear regression models that included average temperature and discharge explained more than 70% of the variability in prevalence across sites for both species. The diagnosis of the parasite also revealed inconsistencies among wild and sentinel fish, suggesting that fish movement and life history may be key components leading to the spread and effects of the parasite along the drainage. These results indicate that changes in stream temperature or discharge, either natural or anthropogenic, could reduce or increase the prevalence and ultimate effect of M. cerebralis on wild trout populations.