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Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout
Ronald D Bassar1,2, Benjamin H Letcher1,2, Keith H Nislow2,3
1S.O. Conte Anadromous Fish Research Center, US Geological Survey, Leetown Science Center, Turners Falls, MA, 01376, USA.
Global Change Biology
|October 23, 2015
Summary
Climate change impacts brook trout populations. Rising stream temperatures and altered flow decrease population size, while density changes influence body size, with direct climate effects being more significant than density-dependence.
Area of Science:
- Ecology
- Population Dynamics
- Climate Change Biology
Background:
- Understanding population dynamics requires integrating extrinsic (density-independent) and intrinsic (density-dependent) factors.
- Seasonal climate variations and their effects on population size and body size are poorly understood, especially concerning density-dependence.
Purpose of the Study:
- To determine the roles of seasonal climate variations (stream flow, temperature) versus density-dependence on population size and mean body size in eastern brook trout (Salvelinus fontinalis).
Main Methods:
- Utilized a 10-year capture-mark-recapture dataset for eastern brook trout in Western Massachusetts.
- Developed a discrete-time population projection model integrating matrix population models and integral projection models (IPMs).
- Employed both stochastic and deterministic analyses to assess demographic rates as functions of body size.
Main Results:
- Population size decreases are primarily driven by changes in stream flow and temperature, exceeding density-dependent compensation.
- Increasing mean stream temperatures significantly reduce the survival of the youngest eastern brook trout age class.
- Increases in mean body size are mainly attributed to indirect density changes, with a minor direct role from climate change.
Conclusions:
- Climate-driven environmental changes, particularly rising stream temperatures, are the dominant factor causing declines in eastern brook trout populations.
- Density-dependent mechanisms play a lesser role in population size regulation compared to direct climate impacts.
- Changes in population density, influenced by climate, are the primary driver of increased mean body size in eastern brook trout.
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