Hydrologic drought favors non-native fishes in a changing climate

Authors: Jane Rogosch, Julian Olden, Jonathan Tonkin, David Lytle, David Merritt, Lindsay Reynolds

Year: 2017 (xlix)

Abstract

Fishes of the American Southwest are poised to be impacted by non-stationary changes in flow regimes driven by increasing water consumption and climatic alterations in temperature and precipitation Population dynamic models play an important role to anticipate and respond to these looming conservation challenges Here, we apply matrix population models as a heuristic framework to explore how mixed native and non-native fish communities respond to hydrologic extremes that include increasing drought frequency The model is generically parameterized, but specifically applied to 7 fish species in the Upper Verde River, Arizona, USA Flow-ecology relationships were integrated into the population models by allowing key vital rates to vary according to flow year types (flood, drought, and non-event years), and species dynamics were coupled in a single model by using density-dependent reproduction based on the biomass carrying capacity at the river reach scale We validated model parameters by comparing population projections under the flow record to a long-term fish monitoring dataset (1994 - 2008), and then projected the model to recreate community response to increasing drought frequency observed over the past nine years (2009 - 2017) Model projections were moderately correlated with the long-term fish monitoring dataset, where 13 years had spearman correlation coefficients above 04 and seven of those years had strong correlations (r > 08) Droughts increased by 50% compared to the previous decade, with coincident increased abundances of non-native species such as Red Shiner (Cyprinella lutrensis) and Green Sunfish (Lepomis cyanellus) and decreased abundances of native species such as Desert Sucker (Catostomus clarkii) and Roundtail Chub (Gila robusta) Increased drought conditions resulted in a projected shift in community composition to one increasingly dominated by non-native species By integrating causal links between species biology and hydrologic variability, population dynamic models can increase our understanding of possible outcomes to environmental change