Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout

Global Change Biology
By: , and 

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Abstract

Understanding how multiple extrinsic (density-independent) factors and intrinsic (density-dependent) mechanisms influence population dynamics has become increasingly urgent in the face of rapidly changing climates. It is particularly unclear how multiple extrinsic factors with contrasting effects among seasons are related to declines in population numbers and changes in mean body size and whether there is a strong role for density-dependence. The primary goal of this study was to identify the roles of seasonal variation in climate driven environmental direct effects (mean stream flow and temperature) versus density-dependence on population size and mean body size in eastern brook trout (Salvelinus fontinalis). We use data from a 10-year capture-mark-recapture study of eastern brook trout in four streams in Western Massachusetts, USA to parameterize a discrete-time population projection model. The model integrates matrix modeling techniques used to characterize discrete population structures (age, habitat type and season) with integral projection models (IPMs) that characterize demographic rates as continuous functions of organismal traits (in this case body size). Using both stochastic and deterministic analyses we show that decreases in population size are due to changes in stream flow and temperature and that these changes are larger than what can be compensated for through density-dependent responses. We also show that the declines are due mostly to increasing mean stream temperatures decreasing the survival of the youngest age class. In contrast, increases in mean body size over the same period are the result of indirect changes in density with a lesser direct role of climate-driven environmental change.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Changes in seasonal climate outpace compensatory density-dependence in eastern brook trout
Series title Global Change Biology
DOI 10.1111/gcb.13135
Volume 22
Issue 2
Year Published 2016
Language English
Publisher Wiley
Contributing office(s) Leetown Science Center
Description 17 p.
First page 577
Last page 593
Country United States
State Massachusetts
City Whately
Online Only (Y/N) N
Additional Online Files (Y/N) N