SynopsisWe examined the influence of biotic and abiotic factors on the distribution, abundance, and condition of salmonid fishes along a stream gradient. We observed a longitudinal change in fish distribution with native cutthroat trout, Oncorhynchus clarki utah, and introduced brown trout, Salmo trutta, demonstrating a distinct pattern of allopatry. Cutthroat trout dominated high elevation reaches, while reaches at lower elevations were dominated by brown trout. A transition zone between these populations was associated with lower total trout abundance, consistent changes in temperature and discharge, and differences in dietary preference. Variation in cutthroat trout abundance was best explained by a model including the abundance of brown trout and diel temperature, whereas variation in brown trout abundance was best explained by a model including the abundance of cutthroat trout and discharge. These results suggest the potential for condition-mediated competition between the two species. The results from our study can aid biologists in prioritizing conservation activities and in developing robust management strategies for cutthroat trout.
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 m3/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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.