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

Abstract

Dryland stream fishes are adapted to highly connected habitats with unpredictable hydrologic conditions, including frequent low flows and sometimes extreme drought.The low flow recruitment hypothesis predicts that some fishes spawn in main channel habitats during low flows when water temperatures and prey densities are high.However, extreme low flows during drought periods might be disruptive even among fishes whose life histories otherwise benefit from lower flows. We studied recruitment dynamics of six fishes (family Cyprinidae) at 15 sites in a fragmented Great Plains riverscape in Kansas, USA, during 2 years of extreme drought. We tracked the chronology of gonadal development and age 0 recruitment to test the hypothesis that recruitment by fishes that broadcast spawn planktonic ova would be less successful compared with fishes that spawn demersal or adhesive ova. We found all six taxa were reproductively active but recruitment was evident for only four.The two species for which recruitment was not evident, peppered chub (Macrhybopsis tetranema) and silver chub (Macrhybopsis storeriana), are confirmed or suspected pelagic-broadcast spawning fishes that have declined in other fragmented and dewatered Great Plains riverscapes. Our data highlight the potential for extreme low flows within isolated stream fragments to cause complete or near-complete recruitment failure for pelagic-broadcast spawning fishes, especially those with small population sizes. Failed recruitment during extreme drought may be related to spawning mode, ova characteristics, or both. Our work informs management of fish diversity in drought-prone riverscapes by establishing mechanistic linkages among extreme drought, fish recruitment, and assemblage structure.

No quarter: Lack of refuge during flow intermittency results in catastrophic mortality of an imperiled minnow

“…In some areas, channel drying can be a major source of mortality during summer months (Archdeacon, 2016; Scheurer, Fausch, & Bestgen, 2003; Whitney et al., 2016), and coupled with fragmentation, may be leading to the demise of these unique fish assemblages (Dudley & Platania, 2007; Perkin et al., 2015; Worthington et al., 2018). However, some species are able to persist despite river intermittency, while others experience recruitment failure (Durham & Wilde, 2009; Perkin et al., 2019; Whitney et al., 2016). Discovering how species persist through drought and streamflow intermittency can provide insight to resource managers by directing limited resources to actions that will affect the species positively and avoiding actions that may exacerbate the effects of intermittency on the population.…”

Characteristics of the natural flow regime paradigm explain occurrence of imperiled Great Plains fishes

“…Although theory and our empirical work suggest restoring all characteristics of the natural flow regime will benefit the maximum number of species (Poff et al 1997), our work provides guidance for which characteristics of the natural flow regime might be prioritized for instances in which not all flow characteristics can be restored at once (e.g., Propst and Gido 2004) or where nonstationarity among hydrologic regimes prevents the restoration of some flow characteristics (Poff 2018). For example, prioritizing flow management during periods of drought may serve as a useful target for environmental water transaction strategies that seek to restore or preserve flow regimes during a time when Great Plains fishes are vulnerable to water stress (Perkin et al 2019).…”

Temporal distribution modelling reveals upstream habitat drying and downstream non‐native introgression are squeezing out an imperiled headwater fish

“…Streams in drylands rely on vertical connectivity with groundwater to maintain base flow, which usually has limited spatial extent and can vary seasonally (Murray et al., 2003). Human water demand and the frequency and intensity of extreme hydrologic events, such as drought, also affect the availability of water for dryland fishes (Heino et al., 2009; Perkin, Starks, et al, 2019). Thus, the preservation of perennial water sources in dryland regions is a major challenge for conserving aquatic biodiversity (Davis et al., 2017).…”