Joshuah S. Perkin

Collapsing Range of an Endemic Great Plains Minnow, Peppered Chub Macrhybopsis tetranema

Abstract The Peppered Chub Macrhybopsis tetranema was once found throughout the Arkansas River basin in portions of Texas, New Mexico, Oklahoma, Kansas, and Colorado. Range-wide declines in both abundance and distribution have occurred over the past three decades coinciding with habitat loss and fragmentation. Over the last decade or more, only two geographically isolated Peppered Chub populations persisted in the Arkansas and Ninnescah rivers in Kansas and a portion of the Canadian River in New Mexico and Texas. Intensive sampling between 2011 and 2013 documented the decline of this species from Kansas during consecutive years of region-wide drought in 2011 and 2012. Equally intensive sampling in 2015 in reaches of the Ninnescah and Arkansas rivers yielded no individuals, suggesting the potential extirpation of this population. Conversely, Peppered Chub were consistently collected in the Canadian River in New Mexico from 2012 to 2015 with increasing numbers in recent years with higher flows. Therefore, Peppered Chub is either extirpated or has declined below detection in Kansas and a stable population only remains in a 220 km reach of the Canadian River. A recovery plan for the Peppered Chub might consider restoration and maintenance of adequate seasonal fluctuating river flows, removal of barriers, and repatriation to river reaches that have experienced extirpation.

Groundwater declines are linked to changes in Great Plains stream fish assemblages

Significance Nature and society depend on groundwater to sustain aquatic ecosystems and human livelihoods, but local and regional groundwater supplies are dwindling where human water extraction exceeds aquifer recharge. Although groundwater depletion is a global problem, ecological consequences for aquatic species such as fishes are rarely examined. We demonstrate that more than half a century of groundwater pumping from the United States High Plains Aquifer has been associated with collapses of large-stream fishes and expansion of small-stream fishes where hydrologic conditions were altered most. Projections indicate that these habitats will continue to shrink over the next half-century if groundwater pumping practices are not modified. Our findings highlight a mechanism for biotic homogenization with global implications given the worldwide extraction of groundwater. Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950–2010) and prospective (2011–2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish assemblages associated with groundwater pumping from the United States High Plains Aquifer. We modeled the relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes. Scaling down to subwatersheds revealed consistent transformations in fish assemblage structure among western subwatersheds with increasing depths to groundwater. Although transformations occurred in the absence of barriers, barriers along mainstem rivers isolate depauperate western fish assemblages from relatively intact eastern fish assemblages. Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater. Our work illustrates the shrinking of streams and homogenization of Great Plains stream fish assemblages related to groundwater pumping, and we predict similar transformations worldwide where local and regional aquifer depletions occur.

Testing Cross-System Transferability of Fish Habitat Associations Using Cottus carolinae (Banded Sculpin)

Abstract Assessing stream fish habitat associations across contrasting ecosystems can inform generality of habitat predictions. We tracked Cottus carolinae (Banded Sculpin) in Little Creek, TN, to test transferability of habitat predictions developed from independent studies. Predictions included shifting habitat use across size classes (prediction 1), over the diel period (prediction 2), and during variable flows (prediction 3), as well as maintaining associations with depth, velocity, and substrate gradients across scales (prediction 4). Size 1 (80–99 mm TL) and size 2 (100–140 mm TL) Banded Sculpin used similar habitats (prediction 1 not supported), shifted to pools with little cover at night (prediction 2 supported), and adjusted habitat uses according to flow (prediction 3 supported), and depth, velocity, and substrate associations were similar for small and large streams when size classes were combined (prediction 4 supported). Our synthesis highlights consistencies in fish habitat associations that manifest due to behavioral, morphological, and physiological constraints that operate across ecosystems.

Assessing riverscape-scale variation in fish life history using banded sculpin (Cottus carolinae)

Advancing the field of fish ecology requires a shift in focus from describing patterns in species occurrences to understanding the mechanisms that regulate distributions and abundances across broad scales. For stream fish ecology, this includes understanding environmental mechanisms that regulate stream fish demographic properties at the scale of stream networks or riverscapes. Despite the fact that Banded Sculpin Cottus carolinae occupy a diversity of habitats and stream sizes across the southeastern United States, relatively little is known about the demography of this species. We assessed annual demographic properties (reproduction, growth, and survival) of C. carolinae collected monthly from four sites distributed longitudinally along the Roaring River riverscape in Tennessee to simultaneously describe life history attributes of the species and address riverscape-scale variation in population dynamics. Cottus carolinae lived for a maximum of four years, local populations were dominated by age-0 and age-1 individuals, reproduction began after one year, spawning occurred during December and January, and mean ova number was 398. A life history tradeoff between growth (robustness) and survival was evident at one site where water temperature and flow were least variable, otherwise life history attributes were consistent across the riverscape despite longitudinal changes in abiotic variables. Our work illustrates the potential for muted population responses to a strong hydrologic gradient in stream size and highlights the stability inherent with fish life history adaptations to natural environmental regimes across broad spatial scales.

Which species, how many, and from where: Integrating habitat suitability, population genomics, and abundance estimates into species reintroduction planning

Extirpated organisms are reintroduced into their former ranges worldwide to combat species declines and biodiversity losses. The growing field of reintroduction biology provides guiding principles for reestablishing populations, though criticisms remain regarding limited integration of initial planning, modeling frameworks, interdisciplinary collaborations, and multispecies approaches. We used an interdisciplinary, multispecies, quantitative framework to plan reintroductions of three fish species into Abrams Creek, Great Smoky Mountains National Park, USA. We first assessed the appropriateness of habitat at reintroduction sites for banded sculpin (Cottus carolinae), greenside darter (Etheostoma blennioides), and mottled sculpin (Cottus bairdii) using species distribution modeling. Next, we evaluated the relative suitability of nine potential source stock sites using population genomics, abundance estimates, and multiple-criteria decision analysis (MCDA) based on known correlates of reintroduction success. Species distribution modeling identified mottled sculpin as a poor candidate, but banded sculpin and greenside darter as suitable candidates for reintroduction based on species-habitat relationships and habitats available in Abrams Creek. Genotyping by sequencing revealed acceptable levels of genetic diversity at all candidate source stock sites, identified population clusters, and allowed for estimating the number of fish that should be included in translocations. Finally, MCDA highlighted priorities among candidate source stock sites that were most likely to yield successful reintroductions based on differential weightings of habitat assessment, population genomics, and the number of fish available for translocation. Our integrative approach represents a unification of multiple recent advancements in the field of reintroduction biology and highlights the benefit of shifting away from simply choosing nearby populations for translocation to an information-based science with strong a priori planning coupled with several suggested posteriori monitoring objectives. Our framework can be applied to optimize reintroduction successes for a multitude of organisms and advances in the science of reintroduction biology by simultaneously addressing a variety of past criticisms of the field.

The river continuum concept predicts prey assemblage structure for an insectivorous fish along a temperate riverscape

The river continuum concept (RCC) provides a framework for processes structuring lotic ecosystems by synthesizing sources and transport of C in streams. Considerable attention, refinement, and testing of the RCC has occurred since its inception >35 y ago, but few investigators have tested its predictions by explicitly linking consumer groups. We assessed insect assemblage structure in the diet of a broadly distributed insectivorous fish (Cottus carolinae) in the Roaring River continuum of Tennessee to test 3 predictions from the RCC: 1) longitudinal change in relative biomass of insect functional feeding groups (FFGs) including decrease for shredders, increase for collectors, intermediate maximum for grazers, and consistency for predators; 2) maximum taxonomic diversity at stream orders 3 to 5; and 3) temporal turnover in taxonomic composition across 1 y. We found that relative biomass of insect FFGs consumed by C. carolinae broadly matched predictions from the RCC. Maximum taxonomic diversity assessed at the family rank occurred at stream order 4 where diel and annual water temperature fluctuations were greatest, and monthly prey assemblages followed a sequence of turnover and a return to starting conditions across 1 y. Our novel approach illustrates proof of concept that RCC tenets are integrated into the diet of at least 1 higher-level consumer and, therefore, transcend assemblage boundaries in regulating the longitudinal (up- to downstream) and vertical (multiple consumer groups) flow of C in streams.

Occurrence of Lepomis miniatus (Redspotted Sunfish) in the Cumberland River Basin of Tennessee

Abstract n The reported, natural distribution of Lepomis miniatus (Redspotted Sunfish) encompasses the Mississippi Valley and Gulf Slope drainages, but not the Cumberland River basin of Tennessee. We provide an account of 3 cataloged specimens collected from Mill Creek in the Cumberland River basin at Standing Stone State Park, TN. Review of previously unpublished records around Lake Barkley and Standing Stone Lake combined with collection of multiple specimens upstream and downstream of Standing Stone Lake suggest a naturalized population now exists 421 river km outside of the previously documented range. Range expansion in the Cumberland River basin is likely related to human introduction ultimately arising from stock contamination.