Fish assemblage changes over half a century in the Yellow River, China

Area of Science:

• Ecology
• Ichthyology
• Environmental Science

Background:

• Riverine ecosystems face global threats from human activities, altering native fish populations through habitat changes and invasive species.
• The Yellow River, a major river system, has experienced significant anthropogenic pressures over decades.

Purpose of the Study:

• To assess temporal changes in fish assemblages in the Yellow River from 1965 to 2015.
• To identify key drivers of these changes and their spatial variations within the river.

Main Methods:

• Comparison of historical (1965) and contemporary (2015) fish species presence data.
• Analysis of species richness, native vs. non-native species composition, and community similarity (Bray-Curtis dissimilarity) across river reaches.

Main Results:

• A 35.4% decline in fish species richness over 50 years.
• An increase in non-native species and a decrease in native species.
• Homogenization of fish assemblages across different river reaches, with notable regional variations (e.g., species loss in lower reaches, increased richness in upper reaches).

Conclusions:

• Dam construction, exotic species invasions, and reduced river flow are critical factors shaping temporal fish assemblage dynamics.
• Anthropogenic stressors have varied impacts on river basins, leading to diverse effects on species assemblages over time.