Species conservation requires a clear understanding of habitat availability and subsequent use of those habitats. In cases where species declines have occurred and gone undetected by conservation managers, habitat alteration, fragmentation, and loss are often the largest contributors. River fragmentation often results in altered flow regimes, subsequently impacting the availability of riverine habitats. Blue sucker (Cycleptus elongatus) is associated with riffle and run habitat, which is especially impacted when river flows are altered. The goal of this research was to identify the extent of blue sucker habitat and mobility of the species in the Colorado River, Texas. To understand habitat selection and use, blue suckers (N = 49) were surgically implanted with telemetry tags. During 2015-2017, thirty-eight attempts were completed to relocate individuals. Optimized hotspot analysis identified three river reaches critical for blue suckers that accounted for 20% of the study area. Blue suckers used these locations year-round including during spawning. Habitats used by blue sucker were composed of gravel, cobble, boulder, and bedrock typically in riffle and run habitat. Mobility, as measured by home range size, increased as riffle density decreased. Larger home ranges were presumably necessary to find habitat to complete aspects of their life history. Results of this study suggest suitable habitats are limited throughout the fragmented riverscape. Conservation action in the form of habitat construction or increased stream connectivity through barrier mitigation could have positive impacts on the future of blue suckers in the lower Colorado River, Texas.

Aim To review the conservation status of Headwater catfish Ictalurus lupus (Girard,1859) in the United States, including quantifying environmental correlates with range contraction and hybridization and introgression with Channel catfish Ictalurus punctatus (Rafinesque, 1818) to inform conservation prioritization. Location Texas and New Mexico, USA. Methods We used random forest models to construct species distribution models (SDMs) based on historical (1980–1999) and contemporary (2000–2019) data and 13 classes of remotely sensed stream network data. We measured hybridization and introgression with the widely introduced Channel catfish using external morphology, mitochondrial DNA (mtDNA), and a nuclear gene (RAG2). Results Species distribution models illustrated temporal reduction in suitability for Headwater catfish among the species’ namesake headwater streams, including streams with steeper slopes, faster velocities, and higher elevations. Modelling also revealed reduced suitability of larger streams greater distances from groundwater springs, the same streams frequently occupied by non‐native Channel catfish. A general pattern of increased use of streams draining watersheds with altered or developed land uses was apparent. Assessment of introgression and hybridization with non‐native channel catfish at nine locations showed evidence of ongoing or past hybridization at six locations. Persistence of potentially non‐introgressed populations were found at three locations with smaller sample sizes. Main conclusions Modelling temporal changes in Headwater catfish distribution provided critical insight into the types and locations of streams that should be targeted for habitat preservation or restoration. Conservation and management of Headwater catfish will require priority decisions based on existing levels of introgression and the practicality of preventing further contact with Channel catfish. Maintaining Headwater catfish populations in springs that are also heavily used by humans will be critical for conservation of the species in the United States.

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Seasonal movements cued by environmental variables are a critical component of riverine fish life history. Life‐history events for species such as blue sucker Cycleptus elongatus are likely cued by discharge and temperature and may be disrupted if those life‐history events and environmental regimes are mismatched. However, this effect may be dependent upon the habitat occupied when environmental cues are received by individuals. We tracked telemetered blue sucker in the Colorado River, Texas, USA, from 2015 to 2017 and modelled the relative effects of discharge, temperature and habitat structure on seasonal movement patterns. Tagged fish varied in their propensity to move, although most returned to their original tagging locations. Decreasing temperatures and increasing discharge resulted in increased seasonal movements. Temperature and discharge had the largest effect on movement behaviour, but the magnitude of movements was largely dependent on the year. Temperatures between 12 and 19°C and discharges between 10 and 240 m3s−1 resulted in greater probabilities of spawning movements. Spawning was most probable in 2015 and reduced or halted in 2016 and 2017. Future climate scenarios suggest North America will experience increased drought, warmer temperatures and more variable weather patterns. These future scenarios could negatively impact blue sucker by disrupting environmental cues and habitat availability for seasonal life‐history events. Our results suggest temperature and discharge are critical cues for the species, but that their combined effect is largely dependent on the occupied habitat.