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Published on: July 30, 2019
Upstream-downstream gradient in infection levels by fish parasites: a common river pattern?
Isabel Blasco-Costa1, Anson V Koehler, Alice Martin
1Department of Zoology, University of Otago, Dunedin, New Zealand. Isa.Blasco.Costa@gmail.com
Parasitology
|October 13, 2012
Summary
River flow and invertebrate drift create a downstream-to-upstream gradient in trematode parasite abundance in fish. This pattern, observed in three of four species, highlights how lotic systems influence parasite distribution.
Area of Science:
- Ecology
- Parasitology
- Freshwater Biology
Background:
- Physical habitat structure influences organism distribution and abundance in aquatic ecosystems.
- Stream drift, driven by unidirectional water flow, disperses invertebrates downstream in rivers.
- This invertebrate drift may create longitudinal gradients in parasite infection levels within river systems.
Purpose of the Study:
- To test the hypothesis that riverine parasite abundance exhibits a longitudinal gradient, decreasing upstream.
- To investigate the influence of river flow and invertebrate drift on trematode infection dynamics in fish.
- To analyze the relationship between trematode abundance, distance from the river junction, and host fish size.
Main Methods:
- Studied four trematode species infecting the fish Gobiomorphus breviceps in the Manuherikia River, New Zealand.
- Employed generalized linear models to analyze trematode infrapopulation abundance.
- Assessed abundance as a function of distance from the river junction and fish size.
Main Results:
- A significant longitudinal gradient in trematode abundance was observed, with decreasing abundance from downstream to upstream.
- This pattern was supported for three out of the four trematode species studied.
- Results suggest a commonality of this gradient in riverine parasite populations.
Conclusions:
- Unidirectional river flow and invertebrate drift significantly impact trematode distribution and abundance in lotic systems.
- The observed gradient indicates that physical river processes can shape parasite-host dynamics.
- Host and parasite traits, alongside environmental factors, may modulate the strength of these longitudinal gradients.
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