Macrophytes shape trophic niche variation among generalist fishes

Area of Science:

• Ecology
• Freshwater Ecology
• Ichthyology

Background:

• Generalist species play key roles in ecosystems by connecting habitats and influencing trophic levels.
• Individual niche variation in generalist populations can be influenced by habitat complexity.
• Macrophytes are hypothesized to increase niche variation by providing resources and shelter.

Purpose of the Study:

• To compare individual niche variation in three generalist fish species between a macrophyte-rich and a macrophyte-poor lake.
• To test if macrophyte presence facilitates greater individual niche variation in fish.
• To investigate how macrophyte cover affects fish reliance on littoral food resources.

Main Methods:

• Stable isotope analysis (δ15N and δ13C) to assess trophic positions and food resource reliance.
• Comparison of individual niche variation (variance) in trophic position and littoral resource use among fish species.
• Utilizing isotopic mixing models to quantify dietary contributions.

Main Results:

• Perch and rudd exhibited greater individual variation in trophic position in the macrophyte-rich lake (Milada) compared to the macrophyte-poor lake (Most).
• Roach showed no significant difference in trophic position variation between lakes.
• Contrary to the hypothesis, all three species displayed lower individual variation in reliance on littoral resources in the macrophyte-rich lake.

Conclusions:

• Macrophyte vegetation significantly influences individual niche variation and food-web structure in lake ecosystems.
• Fish species-specific responses to macrophyte cover, driven by diet and ontogeny, alter resource use patterns.
• Habitat complexity, particularly macrophyte density, plays a crucial role in shaping niche dynamics of generalist fish populations.