Geology topics

Sarah J.H. Beech

Publications and source records attributed to Sarah J.H. Beech.

3 recordsLinked to original sources

USGS2026

Drivers of population dynamics vary across biophysical gradients and after ecosystem regime shifts for a freshwater fish

Long-term, cross-system comparisons can help disentangle global- to local-scale biophysical drivers of fish population dynamics and clarify context-dependent, nonstationary responses to broad-scale ecosystem change. Lake Whitefish ( Coregonus clupeaformis ) is a coldwater, demersal fish species that is socioecologically valuable across its range, including in the Laurentian Great Lakes of North America. Unfortunately, many Great Lakes populations have experienced poor recruitment over recent decades, threatening the sustainability of Lake Whitefish fisheries in the world's largest freshwater ecosystem. In this study, we characterized the suite of important drivers of Lake Whitefish recruitment among six large lakes spanning a broad geographic area and multiple gradients of ecosystem structure and disturbance. We parameterized a suite of regression models by leveraging spatially and temporally extensive data describing Lake Whitefish year-class strength (YCS) and biophysical processes hypothesized to regulate their recruitment. The relative importance of biophysical drivers and their relationships to YCS differed among lakes (i.e., context-dependence) and through time in response to ecosystem shifts (i.e., nonstationarity). Results emphasized the role of a major ecosystem regime shift following establishment of invasive dreissenid mussels—and the varying consequences of this regime shift across biophysical gradients—in explaining recent cross-lake trends in Lake Whitefish YCS. Specifically, benthic food web perturbations and oligotrophication were major broad-scale drivers that appear to have constrained Lake Whitefish recruitment. Climatic changes such as warming temperatures and decreasing ice cover were also important broad-scale drivers with differing consequences across lake morphology and latitude. Our cross-lake analysis provided novel insights into the relative importance of Lake Whitefish recruitment drivers and the underlying mechanisms by which they act to regulate recruitment across biophysical gradients. This research informs stewardship of important populations and fisheries and illustrates how population dynamics spanning biophysical gradients respond non-uniformly to ecosystem change.

Ecosphere↗

USGS2024

Reconstructing half a century of coregonine recruitment reveals species-specific dynamics and synchrony across the Laurentian Great Lakes

Understanding how multiple species and populations vary in their recruitment dynamics can elucidate the processes driving recruitment across space and time. Lake Whitefish ( Coregonus clupeaformis ) and Cisco ( C. artedi ) are socioecologically important fishes across their range; however, many Laurentian Great Lakes populations have experienced declining, poor, or sporadic recruitment in recent decades. We integrated catch and age data from 38 long-term surveys across each of the Great Lakes and Lake Simcoe, resulting in a combined time series spanning 1960–2019. We estimated Lake Whitefish and Cisco year-class strength (YCS) in each lake using longitudinal mixed-effects regressions of relative cohort abundance. We subsequently quantified interspecific, spatial, and temporal synchrony in YCS using correlation and dynamic factor analyses. Lake Whitefish YCS was positively spatially synchronous on average, and YCS in all six lakes was elevated during the 1980s–1990s. In contrast, Cisco YCS was sporadic, not spatially synchronous, and highly variable around long-term, lake-specific means. YCS was not synchronous between species in any lake. Collectively, our analyses demonstrate that these species exhibit differential recruitment dynamics that may be regulated by species-specific factors. Results from this study can be leveraged in future research on the causes and consequences of cross-species, cross-basin recruitment variability.

Laurentian Great Lakes↗

USGS2024

Synthesizing professional opinion of Lake Whitefish and Cisco recruitment drivers across the Great Lakes

Disentangling the suite of ecological drivers that explain recruitment variability for Lake Whitefish Coregonus clupeaformis and Cisco C. artedi is of critical importance for their conservation, management, and stewardship in the Laurentian Great Lakes. However, recruitment is inherently variable and can be regulated by many interacting processes, the relative importance of which can vary spatially, temporally, and ontogenetically. Given this complexity, comparisons across lakes and species that identify overarching hypotheses could efficiently guide future research. Using facilitated deliberations among fishery professionals (n = 57) with expertise in Great Lakes Coregonus spp., we synthesized current knowledge regarding (1) which biophysical processes are most important for driving contemporary recruitment between species, among lakes, and across life stages and (2) mechanisms by which those drivers regulate recruitment at key life stages. Participants affirmed the hypothesis that many drivers interact in complex ways to regulate Lake Whitefish and Cisco recruitment. Large-scale climatic processes affecting early life-stage growth and survival were consistently considered important. Other drivers were only deemed influential in certain lakes, highlighting perceived context-dependent recruitment dynamics. Notably, recruitment in Lakes Superior, Michigan, and Huron was considered limited during larval and early juvenile life stages by low productivity, whereas spawning-habitat degradation and reduced metapopulation diversity were hypothesized to limit recruitment during embryonic and larval stages in Lakes Erie and Ontario. Several drivers were hypothesized to similarly impact Lake Whitefish and Cisco during early life stages, while drivers acting on post-larval life stages were typically distinct between species. The hypotheses synthesized herein can guide future research on Lake Whitefish and Cisco recruitment dynamics in the Great Lakes.

Great Lakes↗