**1.2 Climate change and multiscale fish conservation in arid and semiarid landscapes**

Flow-regime alteration and stream fragmentation are expected to increase due to climate change and growing human water demands. The combination of extended periods of drought and increased human water demands magnify threats to the longterm persistence of many stream fishes [35–37]. Native fish species in arid and semiarid ecoregions are particularly vulnerable because they have both the highest level of damming [33, 38] and naturally harsh environmental conditions [39–41]. Fishes native to arid and semiarid streams have evolved to tolerate intermittent drying,

*A Hierarchical Approach to Fish Conservation in Semiarid Landscapes: A Need to Understand… DOI: http://dx.doi.org/10.5772/intechopen.105602*

flashy changes is flow, and extreme physicochemical conditions [38, 41, 42]. However, interactions of dams, loss of base flows due to water withdrawals, and increased drought have intensified already harsh environments [37, 38, 43]. Identifying multiscale stream-fish relationships with fragmentation and flow regimes is essential to developing successful conservation strategies in arid and semiarid ecoregions. Understanding coarse-scale constraints on species distributions is particularly important to guiding finer-scale conservation and recovery efforts. For example, the stream reach is a natural scale for fish conservation and management activities, but effective strategies are dependent on basin-scale relationships [5, 44].

### **1.3 Great Plains small-bodied minnows**

Streams of the semiarid North American Great Plains ecoregion (hereafter Great Plains) are unique, dynamic ecosystems and home to endemic fish species. The Great Plains is one of the most impounded areas of the world [33, 38, 45]. Damming largely ceased in the 1980s, but resulting fragmentation is extensive and flow regimes remain severely altered [33]. Substrate in Great Plains streams is predominately sand and silt, with constantly changing streambed formations [44]. Channel characteristics differ from gravel-bed streams with stable riffle-run-pool formations except during high flows. Environmental conditions are extreme with periods of long drought followed by large flooding and highly variable and wide-ranging water temperatures and salinities [42, 46]. Natural stream drying has been exacerbated by harsher drought periods due to climate change and excessive groundwater pumping [37, 42, 43]. Small-bodied fishes are common in the Great Plains, with brackish (i.e., salt-tolerant) species dominating areas of higher salinity [46, 47]. True minnows (Leuciscidae), particularly smaller-bodied species, also occur in varying abundances throughout the ecoregion. True minnows are a large, diverse family of fishes (700 species) within the order Cypriniformes [48, 49]. In particular, true minnows display a wide range of lifehistory traits. This includes a group of species, some endemic to the Great Plains, that have a unique reproductive strategy in stream ecosystems.

Pelagic-broadcast spawning [50] is a common reproductive strategy globally in marine and coastal species, but rare in inland freshwater systems. In inland streams of North America, pelagic-broadcast spawning is restricted to mooneyes (Hiodontidae) and three genera of true minnows (*Hybognathus*, *Notropis*, and *Macrhybopsis*, hereafter pelagophils) that occur in the Great Plains [51]. Pelagophils typically spawn in higherorder streams and release transparent, non-adhesive ova that are semi-buoyant [47]. The downstream displacement of eggs and larvae relies on drift [52]. Thus, both minimal fragmentation and higher flow magnitude are essential to successful recruitment [53–55]. There are similarities between pelagophils and marine pelagicbroadcast spawners in juvenile dispersal strategies to microhabitats with high nutrient concentrations and reduced predation pressure [51, 56]. High-flow events increase nutrient loads and create disconnected temporary slackwater habitats that serve as nurseries for juvenile pelagophils. The pelagophil life cycle is completed through extensive upstream movement by juveniles and adults [53, 57, 58]. Great Plains pelagophils have been strongly negatively affected by damming, water withdrawals, and climate change due to disrupted stream networks, altered flow patterns with reduced magnitude, and loss of floodplain habitats [42, 52, 59]. Numerous studies have reported declines in pelagophil relative abundance and range reductions in the Great Plains (e.g., [43, 54, 60–62]).
