Can data from disparate long-term fish monitoring programs be used to increase our understanding of regional and continental trends in large river assemblages?

Abstract

Understanding trends in the diverse resources provided by large rivers will help balance tradeoffs among stakeholders and inform strategies to mitigate the effects of landscape scale stressors such as climate change and invasive species. Absent a cohesive coordinated effort to assess trends in important large river resources, a logical starting point is to assess our ability to draw inferences from existing efforts. In this paper, we use a common analytical framework to analyze data from five disparate fish monitoring programs to better understand the nature of spatial and temporal trends in large river fish assemblages. We evaluated data from programs that monitor fishes in the Colorado, Columbia, Illinois, Mississippi, and Tallapoosa rivers using non-metric dimensional scaling ordinations and associated tests to evaluate trends in fish assemblage structure and native fish biodiversity. Our results indicate that fish assemblages exhibited significant spatial and temporal trends in all five of the rivers. We also document native species diversity trends that were variable within and between rivers and generally more evident in rivers with higher species richness and programs of longer duration. We discuss shared and basin-specific landscape level stressors. Having a basic understanding of the nature and extent of trends in fish assemblages is a necessary first step towards understanding factors affecting biodiversity and fisheries in large rivers.

Poleward shift in large‐river fish communities detected with a novel meta‐analysis framework

“…However, other environmental changes are likely to have occurred locally over the same period and may also have contributed to the observed biological changes (Malmqvist & Rundle, 2002;Zajicek et al, 2018). Several studies demonstrated that improved water quality has ecological consequences for various organisms all along the trophic network, such as phytoplankton (Larroudé et al, 2013) and macroinvertebrates (Floury et al, 2013) in the Loire River or fish in various large rivers in the U.S.A. (Counihan et al, 2018) and probably also in France (Poulet et al, 2011). Several studies demonstrated that improved water quality has ecological consequences for various organisms all along the trophic network, such as phytoplankton (Larroudé et al, 2013) and macroinvertebrates (Floury et al, 2013) in the Loire River or fish in various large rivers in the U.S.A. (Counihan et al, 2018) and probably also in France (Poulet et al, 2011).…”

“…One widely held idea is that rising temperatures are expected to favour non-native over native species, particularly in aquatic environments, as the former generally show broader thermal tolerance and reproduction capacity than the latter (Britton et al, 2010;Rahel & Olden, 2008). Some recent studies hypothesised, and even demonstrated, that replacement of native by non-native species has strongly contributed to biotic homogenisation from regional to global scales (Cardinale et al, 2018;Counihan et al, 2018;Kuczynski, Legendre, & Grenouillet, 2018). The present study found that several nonnative species experienced strong increases in density, which may have contributed to the observed biological changes through biotic interactions such as transmission of parasites (e.g.…”

“…Undeniably, rivers are among the most threatened ecosystems, undergoing decline in biodiversity far greater than terrestrial and marine ecosystems (Dudgeon et al, 2006;Malmqvist & Rundle, 2002). Among freshwater environments, large rivers are the focus of outstanding economic and societal issues as well as complex and vast challenges regarding conservation of their biodiversity (Counihan et al, 2018;Tockner, Uehlinger, & Robinson, 2009;Vörösmarty et al, 2010), and further research is required to better identify and characterise the impact of global changes on these ecosystems.…”

“…ca. Long-term data provide valuable opportunities to better understand the effects of cumulative stressors(Counihan et al, 2018) or large-scale restoration measures(Daufresne et al, 2015; on aquatic biodiversity at spatial and temporal scales relevant to the effective management of these complex river ecosystems. While the overall trend in the relative abundance of non-native species was not significant (TMES ± SE = −7.SE = −63.8 ± 25.5; p = 0.012) and increased significantly (TMES ± SE = 99.9 ± 50.1; p = 0.046), respectively (Figures 5 and 6d,e,f).Adding the position of the station relative to the NPP (i.e.…”

Effective monitoring of freshwater fish

“…The need for effective monitoring in ecological research is wellrecognized and there are many monitoring programmes that have provided important scientific advances and crucial information for environmental policy (Lovett et al, 2007). For example, freshwater fish monitoring has highlighted changes in species diversity and species status in rivers and lakes (e.g., Counihan et al, 2018;Holmgren, Degerman, Petersson, & Bergquist, 2016;Wagner, Deweber, Detar, Kristine, & Sweka, 2014), played a central role in fish-based assessment systems (e.g., for the European Water Framework Directive, Pont, Hugueny, & Rogers, 2007), and resulted in guidelines on standardized fish sampling methods (e.g., Bonar, Hubert, & Willis, 2009).…”