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Map indicating the distribution of study sites in the Colorado River Basin. Inset C-E indicate major tributary sites and B shows sites located on the lower Colorado River below Longhorn Dam in Austin, Texas.

Map indicating the distribution of study sites in the Colorado River Basin. Inset C-E indicate major tributary sites and B shows sites located on the lower Colorado River below Longhorn Dam in Austin, Texas.

Contexts in source publication

Context 1
... mainstem Colorado River, flowing through the Edwards Plateau in central Texas (Figure 1), is one of the major rivers within the Guadalupe Bass range. Human populations are expected to increase drastically in the basin by 2050, with some areas expected to more than double in size, increasing demands on water resources ( Hoque et al. 2014;Colby and Ortman 2015). ...
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... (Figure 1). ...
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... were conducted at thirty 100-m long sites (Figure 1) throughout the Colorado River Basin from March 2014 to May 2016 using backpack electroshocking and seining. Boat electroshocking was used when applicable on the mainstem Colorado River in the study reach starting at the 130-highway crossing just east of Austin downstream to the agricultural dam in Garwood, Texas. ...
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... were no significant correlations between PC1 or PC 2 and standardized growth for all aged individuals in the San Saba River. Similar trends in standardized growth showing differences in rivers and strong overall influences of PC2 were shown in all aged Guadalupe Bass otoliths (F1,208 = 5.22, P=0.02; Table 6, Figure 13, Figure 14). The first three relative warps cumulatively explained 63.33% of the variation in shape across rivers. ...
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... were no significant correlations between PC1 or PC 2 and standardized growth for all aged individuals in the San Saba River. Similar trends in standardized growth showing differences in rivers and strong overall influences of PC2 were shown in all aged Guadalupe Bass otoliths (F1,208 = 5.22, P=0.02; Table 6, Figure 13, Figure 14). The first three relative warps cumulatively explained 63.33% of the variation in shape across rivers. ...
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... first environmental canonical dimension separated the sites by decreasing rise rate and overall fall monthly flows from sites with increased baseflow, 7-day maximum flows and summer monthly flows (Table 10). The second morphological canonical axes represented morphological variation amongst and within sites throughout the Colorado River Basin (Figure 15). The first morphological canonical axis was largely associated with differences in the placement of the pectoral fin, indicating body depth, discriminated Guadalupe Bass with slender and shallower bodies (Table 11). ...
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... second morphological canonical axis differentiated Guadalupe Bass individuals with shorter maxillary and mouth regions ( Figure 15). Head shape changes were largely correlated with hydrologic variables related to the second canonical environmental axis. ...
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... Bass tagged at Altair and Bastrop showed the largest movement in March and June of 2015 ( Figure 16, Figure 17). These movements coincided with a large flood pulse that occurred in the spring of 2015. ...
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... Bass tagged at Altair and Bastrop showed the largest movement in March and June of 2015 ( Figure 16, Figure 17). These movements coincided with a large flood pulse that occurred in the spring of 2015. ...
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... individuals previously tracked were never relocated again following the 2015 October flood pulse. Seasonal movement patterns observed were relatively small movements in the fall and upstream movements in the spring followed by trends in downstream movement in the summer (Figure 18, Figure 19). Total length of tagged individuals did not affect overall displacement; where displacement is quantified as the minimum movement from the previous location. ...
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... upstream movement is indicated by positive displacement values, while negative values indicate downstream movement. Mean absolute movement, defined as total movement from tagging location with no associated upstream or downstream value, was highest in individuals greater than 300 mm ( Figure 18, Figure 20). ...
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... mean overall 50% core area was 0.44 ha (0.05-0.90 ha) and increased to an average 95% core area of 93.42 ha (39.10 -178.66 ha). Both 95% home range and 50% mean core area were smallest at the upstream sites of Bastrop and Utley and increased moving downstream from Bastrop ( Figure 21). Individuals in Altair had the largest core areas. ...

Citations

... While the area was historically farm and ranch land, single-family home developments are now commonplace (Hill Country Alliance 2008). The associated increase in impervious surfaces from this change has altered the natural flow regime in portions of the Colorado River watershed (Pease et al. 2017(Pease et al. , 2018. With few exceptions, local land- development regulations and ordinances for protecting water quantity and quality are generally lacking, and further land development in sensitive areas (e.g., riparian areas or aquifer recharge zones) will likely have deleterious effects on groundwater and surface water systems. ...
... Many small springs and streams throughout Texas have experienced general declines in annual flows or ceased to flow permanently as a result of increased demands on groundwater (Bowles and Arsuffi 1993). Changes to Guadalupe Bass population structure resulting from altered hydrology have been hypothesized (Grabowski 2014a) but are largely unstudied, with a few exceptions (e.g., Edwards 1978;Groeschel 2013;Pease et al. 2017). Filling this knowledge gap would be critical to effectively managing populations. ...
... Filling this knowledge gap would be critical to effectively managing populations. Long-term reduction in base flow could decrease growth of Guadalupe Bass (Groeschel 2013) and ulti-mately change population structure (Pease et al. 2017). Reduction of spring flows would also likely negatively impact the 13 endemic species of fish in the Edwards Plateau ecoregion considered spring-associated obligates (Craig et al. 2016). ...
Chapter
Full-text available
The Colorado River of Texas originates in the northwest portion of the state and runs southeasterly across the environmentally sensitive Edwards Plateau ecoregion, eventually emptying into Matagorda Bay on the Gulf of Mexico. The Texas Parks and Wildlife Department (TPWD) and other conservation partners have worked for decades to conserve native fishes in the river and its associated estuary. The river and its tributaries are also the major water source for millions of people, and portions of the watershed are undergoing unprecedented human population growth and a concomitant increased demand for water. Drought, which is a frequent occurrence in Texas, exacerbates these effects. Providing adequate streamflow and water quality to conserve aquatic species while still fulfilling obligations for municipal, industrial , agricultural, hydropower, and recreational water use is increasingly challenging. Since the 1980s, the TPWD has promoted water management policies in the watershed to benefit aquatic life, conducted research to maintain a sound ecological environment for fish and other aquatic taxa, provided technical guidance and financial incentives to private landowners to improve land practices that benefit water quality and quantity, and improved public access to foster increased stewardship of the river. The TPWD has also collaborated with researchers to study the potential impacts of altered hydrology on two endemic, flow-dependent fish species, Guadalupe Bass Micropterus treculii and Blue Sucker Cycleptus elongatus. Two portions of the Colorado River watershed have been identified as native fish conservation areas in part for persistence of populations of these native fishes. Outcomes from these activities are now being leveraged using federally funded research and conservation delivery programs to further advance the conservation of native fish populations and other aquatic life in native fish conservation areas of the Colorado River watershed.
... . Habitat degradation, resulting from urbanization in central Texas, is a chronic threat to the conservation of Guadalupe Bass populationsCurtis et al. 2015;Pease et al. 2017). Blue Sucker is listed as State Threatened in Texas and of Special Concern in North America(Jelks et al. 2008), with early life history stages hypothesized as vulnerable to flow alteration(Adams et al. 2006).Threats to these focal fishes and other flow-dependent aquatic species in the Central Edwards Plateau Rivers and Lower Colorado River NFCAs are largely associated with increasing human populations and associated demands for surface and groundwater. ...
... Groeschel 2013, Pease 2017. The clear and fast-flowing headwater streams of the Central Edwards Plateau Rivers NFCA meet the habitat requirements of Guadalupe Bass, while river base flows are largely dependent on spring discharge from groundwater that is under increased threat of pumping due to human development pressures. ...
... Numerous springs and streams throughout Texas have experienced general declines in annual flows, or ceased to flow permanently as a result of groundwater pumping(Bowles and Arsuffi 1993). Long-term reductions in base flow could decrease growth of Guadalupe Bass(Groeschel 2013), and change their population structure(Pease et al. 2017).Reduction of spring flow would also likely negatively impact the thirteen endemic species of fish in the Edwards Plateau ecoregion that are considered spring-associated obligates(Craig et al. 2016).River flows in the Lower Colorado River NFCA downstream of the City of Austin are largely dependent on controlled releases from the upstream Highland Lakes. Unlike the fast flowing, narrow and clear headwater streams located in the Central Edwards Plateau Rivers NFCA, this portion of the river is relatively wide and slow moving with intermittent pools, riffles, occasional rapids, and intermittent boulder fields(Magnelia 2018). ...
Technical Report
Full-text available
Native Fish Conservation Areas of the southwestern USA consist of springs, ciénegas, creeks, rivers, and associated watersheds uniquely valued in preservation of freshwater fish diversity. These freshwater systems were identified through a spatial prioritization approach that identifies areas critically important to the long-term persistence of focal fish species. Through a shared mission of collaborative stewardship, conservation partnerships have formed among non-governmental organizations, universities, and state and federal agencies to plan and deliver actions to restore and preserve native freshwater fishes and aquatic habitats within the Native Fish Conservation Areas. Furthermore, the Native Fish Conservation Areas have increased awareness of the ecological, recreational, and economic values of freshwater systems in the region, and helped increase interest and capacity of local landowners, communities, and recreational users (e.g., paddlers, anglers) to act as advocates and local stewards of these systems. By facilitating partnership development, coordinating multi-species, watershed-based conservation planning, and leveraging technical and financial resources toward strategic conservation investments, Native Fish Conservation Areas have served as a catalyst for collaborative, science-based stewardship of native freshwater fishes and aquatic habitats in the southwestern USA. Efforts described herein to prioritize and deliver a network of Native Fish Conservation Areas in the southwestern USA offer a successful case study in multi-species and watershed approaches to freshwater fish conservation transferrable to other states and regions of the USA. This report offers a synthesis of recent (2011-2018) multi-species aquatic assessments, Native Fish Conservation Area prioritizations, conservation planning, and conservation delivery within the southwestern USA explicitly focused on implementation of the Native Fish Conservation Areas approach.
Article
Full-text available
Predicting how stream fishes may respond to habitat restoration efforts is difficult due, in part, to an incomplete understanding of how basic biological parameters such as growth and ontogenetic habitat shifts interact with flow regime and riverscape ecology. We assessed age-specific Guadalupe Bass Micropterus treculii habitat associations at three different spatial scales in the South Llano River, a spring-fed stream on the Edwards Plateau of central Texas, USA, and the influence of habitat and flow regime on growth. Substrates were classified using a low-cost side-scan sonar system. Scale microstructure was used to determine age and to back-calculate size at age. Over 65% of captured Guadalupe Bass were age-2 or age-3, but individuals ranged from 0-7 years of age. Habitat associations overlapped considerably among age classes 1-3+, but age-0 Guadalupe Bass tended to associate with greater proportions of pool and run mesohabitats with submerged aquatic vegetation. While habitat metrics across multiple scales did not have a large effect on growth, river discharge was negatively correlated with growth rates. Understanding age-specific Guadalupe Bass habitat associations at multiple scales will increase the effectiveness of restoration efforts directed at the species by assisting in determining appropriate ecological requirements of each life-history stage and spatial scales for conservation actions.