Stephen R. Davenport

Spatiotemporal Population Trends of Notropis simus pecosensis in Relation to Habitat Conditions and the Annual Flow Regime of the Pecos River, 1992–2005

Abstract The threatened Pecos Bluntnose Shiner, Notropis simus pecosensis, is restricted to a 333-km segment of the Pecos River, New Mexico. This is a relatively long, undammed segment, but the flow regime is highly modified and the river channel is degraded. Within the occupied segment, upstream river sections are less-degraded with a wider river channel and shifting-sand substrata, whereas downstream river sections have increasingly narrow river channels and compacted, silt-sand substrata. We studied the longitudinal distribution, length-structure, and population status of N. s. pecosensis from 1992 through 2005. On average, individuals were larger upstream and smaller downstream. Highest densities were in upper-middle portions of the study area. Infrequent high-density collections from lower river sections included only small juveniles that were displaced from upstream. In contrast, high-density collections from upper-middle river sections included all life stages. Thus, we concluded that the core population was restricted to upstream river sections. These river sections have relatively diverse habitat when streamflow is perennial, but are largely desiccated during streamflow intermittence. The core population of N. s. pecosensis was evenly distributed between 1992 and 2000, when streamflow was perennial, but became patchily distributed among refugial habitats between 2001 and 2003, in response to low discharge and periodic streamflow intermittence. High density collections resulted from the concentration of fish in refugia. However, N. s. pecosensis percent species composition declined during this period, indicating that refugia were unsuitable. Low density collections observed after perennial streamflow was restored in 2005 indicated a population collapse between 2001 and 2005. Streamflow intermittence is a threat to the core population of N. s. pecosensis, but habitat degradation appears to limit its distribution. Thus, channel restoration and perennial base-flow will both be important for conservation and recovery.

Genetic effective size, Ne, tracks density in a small freshwater cyprinid, Pecos bluntnose shiner (Notropis simus pecosensis)

Genetic monitoring tracks changes in measures of diversity including allelic richness, heterozygosity and genetic effective size over time, and has emerged as an important tool for understanding evolutionary consequences of population management. One proposed application of genetic monitoring has been to estimate abundance and its trajectory through time. Here, genetic monitoring was conducted across five consecutive year for the Pecos bluntnose shiner, a federally threatened minnow. Temporal changes in allele frequencies at seven microsatellite DNA loci were used to estimate variance effective size (NeV) across adjacent years in the time series. Likewise, effective size was computed using the linkage disequilibrium method (NeD) for each sample. Estimates of Ne were then compared to estimates of adult fish density obtained from traditional demographic monitoring. For Pecos bluntnose shiner, density (catch‐per‐unit‐effort), NeV and NeD were positively associated across this time series. Results for Pecos bluntnose shiner were compared to a related and ecologically similar species, the Rio Grande silvery minnow. In this species, density and NeV were negatively associated, which suggested decoupling of abundance and effective size trajectories. Conversely, density and NeD were positively associated. For Rio Grande silvery minnow, discrepancies among estimates of Ne and their relationships with adult fish density could be related to effects of high variance in reproductive success in the wild and/or effects of supplementation of the wild population with captive‐bred and reared fish. The efficacy of Ne as a predictor of density and abundance may depend on intrinsic population dynamics of the species and how these dynamics are influenced by the landscape features, management protocols and other factors.

Consumption of a Dangerous Ant (Camponotus vicinus) by a Threatened Minnow (Notropis simus pecosensis)

Abstract We report a live Pecos bluntnose shiner (Notropis simus pecosensis) with a dead, major-worker, carpenter ant (Camponotus vicinus) locked onto its lower jaw. The shiner apparently ingested the ant. Resumen Reportamos el hallazgo de una carpita chata del río Pecos (Notropis simus pecosensis) vivo con un trabajador mayor muerto de una hormiga carpintera (Camponotus vicinus) encajada en su mandíbula inferior. Al parecer, el pez ingirió la hormiga.

Predation by Age-0 Smallmouth Bass (Micropterus dolomieu) on Bigscale Logperch (Percina macrolepida) in the Pecos River, New Mexico

Abstract Piscivory in age-0 smallmouth bass (Micropterus dolomieu) on native species is documented widely; however, few studies report size of prey. On 16 July 2008, we collected a smallmouth bass (65 mm in total length) with a bigscale logperch (Percina macrolepida; 44 mm in total length) in its gastrointestinal tract, from the Pecos River near Puerto de Luna, Guadalupe County, New Mexico. Smallmouth bass are nonnative in New Mexico. Bigscale logperch are listed as threatened in New Mexico, and the ability of age-0 smallmouth bass to take bigscale logperch at least 68% of their total length as prey should raise concerns about stocking smallmouth bass in areas where bigscale logperch and other native species occur.

Range Extensions for Pimephales vigilax and Percina macrolepida in the Rio Grande, New Mexico

Abstract We collected 409 Pimephales vigilax (bullhead minnow) and 32 Percina macrolepida (bigscale logperch) from Elephant Butte Reservoir, Sierra Co., New Mexico, during a small-bodied fish survey in August and December 2005, and January and August 2006. The bullhead minnow is considered nonnative in the Rio Grande in New Mexico, but has been collected downstream of Elephant Butte Reservoir. Collections of this species document its establishment within Elephant Butte Reservoir. The bigscale logperch had not been collected previously from the Rio Grande in New Mexico and these collections represent a range extension for this species. Both species are now established in Elephant Butte Reservoir and these unnatural range extensions are related to human activities, but the exact cause remains unknown.