Environmental changes in a Mediterranean river: implications for the fish assemblage

Abstract

This study examined the impacts of climate change on hydrology and fish population dynamics in a river in central Spain. The objectives were to (i) contextualize long‐term trends in the hydrology (1943–2012) and climate (1985–2011) of the study area and (ii) identify the environmental factors driving fish population dynamics (1998–2012). Air and water temperatures progressively increased over the study period, whereas there were substantial reductions in mean spring river discharges but increases in peak‐flow discharges during the spawning and early larval period of endemic cyprinids in recent decades. In particular, the changes in spring river discharges could have fundamental implications for the future status of the endemic cyprinids because this study revealed a positive influence of stable and low‐flow conditions during the spawning and early larval period (in late spring) on recruitment success (young‐of‐the‐year densities). The density of young‐of‐the‐year Salmo trutta appeared most influenced by flow conditions during fry emergence and the early larval period (in early spring), with the highest densities associated with low peak‐flow hydrological pulses. Overall, fish abundances were significantly influenced by the frequency and duration of high and low hydrological pulses, but there were interspecific and ontogenetic differences in their influence. We conclude that although it is widely accepted that global warming should favour cyprinid over salmonid species, future shifts in hydrology due to climate change could negatively affect some cyprinids, including endemic species. Copyright © 2016 John Wiley & Sons, Ltd.

Extreme drought causes fish recruitment failure in a fragmented Great Plains riverscape

“…For some species, such as peppered chub that is now missing from >95% of its historical range and is relegated to a single population isolated between two reservoirs (Pennock et al, 2017), conservation actions must happen soon to avoid extinction. Outside of the Great Plains, there is emerging evidence that reduced water availability directly threatens fishes (Poff & Zimmerman, 2010;Xenopoulos et al, 2005), including arid and semiarid river systems in Australia (Baumgartner, Wooden, Conallin, Robinson, & Thiem, 2017;Humphries et al, 1999), Spain (Bernardo, Ilhéu, Matono, & Costa, 2003;Sánchez-Hernández & Nunn, 2016), South America (Fabré, Castello, Isaac, & Batista, 2017), and the United States (Ruhí, Olden, & Sabo, 2016). Given expectations of declining future water security for humans (Vörösmarty et al, 2010), there is a need to predict how such changes will affect fishes and inform fish conservation actions now and in the future (Closs, Krkosek, & Olden, 2015;Jaeger, Olden, & Pelland, 2014;Whitney, Whittier, & J. D., & Strecker, A. L., 2017).…”

“…Our findings help to fill previous knowledge gaps by demonstrating that recruitment during low flows is not a universal principle even among fishes that might be expected to recruit based on life history attributes alone. Outside of the Great Plains, there is emerging evidence that reduced water availability directly threatens fishes (Poff & Zimmerman, 2010;Xenopoulos et al, 2005), including arid and semiarid river systems in Australia (Baumgartner, Wooden, Conallin, Robinson, & Thiem, 2017;Humphries et al, 1999), Spain (Bernardo, Ilhéu, Matono, & Costa, 2003;Sánchez-Hernández & Nunn, 2016), South America (Fabré, Castello, Isaac, & Batista, 2017), and the United States (Ruhí, Olden, & Sabo, 2016). For some species, such as peppered chub that is now missing from >95% of its historical range and is relegated to a single population isolated between two reservoirs (Pennock et al, 2017), conservation actions must happen soon to avoid extinction.…”

Effects of Antecedent Streamflow and Sample Timing on Trend Assessments of Fish, Invertebrate, and Diatom Communities

“…Streamflow and stream temperature are primary drivers of populations and community structure in lotic environments (Jackson and F€ ureder 2006;Rolls et al 2012;Sanchez-Hernandez and Nunn 2016). We focused on streamflow in this study because stream temperature data were not available at most of our sites.…”

“…Because most of our sampling occurred in late summer/early fall, we selected 240 days prior to sampling (longer-term antecedent period) to characterize variability and average streamflow conditions during important seasonal transition periods over the previous winter, spring, and summer leading up to sampling. This was intended to capture among-year streamflow variability associated with life history events that may influence taxa richness and community composition during the sampling period (Lytle and Poff 2004;Harper and Peckarsky 2006;Sanchez-Hernandez and Nunn 2016). We selected 15 days prior to sampling (shorter-term antecedent period) to characterize variability and average streamflow conditions near the time of sampling.…”

“…Streamflow conditions prior to and during sampling can influence sampling efficiency of fish (Peterson and Shea 2014). Community composition also varies with the timing of sampling because of annual variability in water temperature and streamflow relative to the phenology of the organisms being sampled (Hynes 1970;Sanchez-Hernandez and Nunn 2016). Collectively, this body of work indicates that streamflow conditions prior to sampling influences variability in biological endpoints.…”