Blue sucker habitat use in a regulated Texas river: implications for conservation and restoration

Abstract

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.

Mismatch between temperature and discharge disrupts spawning cues in a fluvial specialist, blue sucker Cycleptus elongatus

“…Although this movement pattern was observed across many individuals over the course of the study, the movements did not appear to be synchronous as has been documented in other blue sucker populations (Neely et al, 2009). Frequently during this study, fish appeared to be passing each other in opposite directions during the spawning season, moving between what has been reported as limited spawning habitat (Acre et al, 2021). The Colorado River, like many rivers, has been fragmented by large and small barriers – a known contributing factor of habitat homogenisation (Bunn & Arthington, 2002; Ligon et al, 1995; Poff et al, 1997; Ward & Stanford, 1983).…”

“…The Colorado River, like many rivers, has been fragmented by large and small barriers – a known contributing factor of habitat homogenisation (Bunn & Arthington, 2002; Ligon et al, 1995; Poff et al, 1997; Ward & Stanford, 1983). It is possible that as little as 50 rkm, or approximately 20% of the lower Colorado River, is suitable for spawning habitat (Acre et al, 2021), which may be a product of discharge alterations (Bunn & Arthington, 2002; Poff et al, 1997). Fish associated with that 50 rkm near Bastrop had the smallest movements and were the least likely to leave that area during the spawning season.…”

“…Received signal strength has been shown to be a strong predictor of distance to radio tag transmitters (Heim et al, 2018); therefore, the lowest gain and the strongest received signal strength were considered a “detection” and marked as the position of the tagged fish. A series of range tests were performed with stationary tags to determine the accuracy of triangulated fish locations, and we determined that fish locations were accurate within ±3 m with a GPS error of ±2 m (Acre, 2019). Fish locations were then imported into ArcGIS 10.3.1 (Esri, Redlands, California) and translated from GPS locations to rkm.…”

“…Using this temperature criterion (±SD), 18 months were identified as possible spawning windows (Table S1). This method was previously described by Acre et al (2021).…”

“…Today, the blue sucker is listed as a species of greatest conservation need, threatened, presumed extirpated or endangered in 19 of the 23 states where they are known to occur (Steffensen et al, 2015). Limited research has been focused on the spawning cues of the species, but it is assumed that the species' diminished range and population sizes are a result of habitat fragmentation, reduced spawning habitat, discharge regime and temperature alterations (Acre et al, 2021; Pflieger, 1997; Warren & Burr, 2014). Neely et al (2009) found that upstream migrations of the species begin when the water temperature reaches 13°C in the Missouri River.…”