Ecosystem change as a driver of fish recruitment dynamics: A case study of two Lake Erie yellow perch populations

Abstract

Abstract Although previous research has identified ways in which environmental conditions influence population processes in many ecosystems, these relationships often weaken or break down with the inclusion of additional years of data, for reasons that remain unclear. To better understand if and how the relationships between historically important environmental drivers of yellow perch (Perca flavescens) recruitment varied during 1969–2018 in two Lake Erie basins characterised by contrasting productivity, we used dynamic linear modelling, which allows for nonstationary relationships between predictor and response variables to be quantified. Our analyses revealed that abiotic conditions during egg and larval development (i.e. winter temperature, springtime river inflows, and thermal conditions) were important in the productive west basin, whereas a combination of abiotic (i.e. winter temperature and river inflows) and biotic (i.e. small‐bodied and large‐bodied predators) conditions were important in the less‐productive central basin. While the importance of most environmental factors to yellow perch recruitment remained static through time, the importance of river inflows changed through time in the west and central basins. Large‐bodied predators (i.e. walleye, Sander vitreus) also varied in their importance through time in the central basin. These changes in recruitment drivers were independent of temporal changes to the environmental conditions themselves, coinciding instead with the timing of major shifts in Lake Erie's nutrient status. Our results demonstrate that ecosystem change can cause the relationships between environmental conditions and population processes (e.g. recruitment) of aquatic organisms to vary through time and space. They also highlight the value of periodically revisiting their applicability, especially if these relationships are used to help manage or sustain populations in ecosystems experiencing human‐driven environmental change.