Indirect effect of temperature on fish population abundances through phenological changes

Area of Science:

• Ecology
• Climate Change Biology
• Fisheries Science

Background:

• Climate change is causing shifts in phenological events across taxa.
• Differential phenological adjustments among interacting species can disrupt biotic interactions and lead to population declines.
• Few studies have investigated the direct impact of climate-driven phenological shifts on population abundances.

Purpose of the Study:

• To investigate how water discharge and temperature influence the migration timing and abundances of freshwater fish.
• To determine the direct and indirect effects of environmental variables on fish populations.
• To assess the long-term trends in fish migration timing and abundance.

Main Methods:

• Analysis of daily time series data for 21 fish species across four French sites over 9–21 years.
• Utilized piecewise structural equation models to analyze relationships between environmental variables, migration timing, and fish abundance.
• Examined inter-annual variations in temperature, water discharge, migration timing, and population abundances.

Main Results:

• No significant long-term trends were observed in migration timing or fish abundances over the study period.
• Inter-annual variations in fish abundances were significantly driven by inter-annual temperature variations, mediated through changes in migration timing.
• Temperature acts as a key environmental driver influencing fish population dynamics via phenological shifts.

Conclusions:

• Climate change can simultaneously affect multiple biological aspects of fish, including phenology and abundance.
• Differential responses of species to climate change are critical for understanding population dynamics.
• Integrating phenological and abundance data is essential for developing effective climate change conservation strategies for fish populations.