Macrhybopsis Aestivalis Research Articles

Under the radar: genetic assessment of Rio Grande Shiner (Notropis jemezanus) and Speckled Chub (Macrhybopsis aestivalis), two Rio Grande basin endemic cyprinids that have experienced recent range contractions

The Rio Grande drainage of the southwestern United States and Mexico has undergone intense anthropogenic alteration by water diversions, extraction and associated habitat changes. These alterations have disproportionately impacted the pelagic broadcast spawning guild of minnows (pelagophils). Several Rio Grande endemic pelagophils, including the co-occurring Rio Grande Shiner (Notropis jemezanus) and Speckled Chub (Macrhybopsis aestivalis), have experienced dramatic recent range-wide declines yet have slipped under the radar of conservation efforts. The status of N. jemezanus and M. aestivalis in the Rio Grande and Pecos River was evaluated and standing genetic variation was characterized. Genetic evidence indicates that populations of both species found in the Rio Grande and Pecos River are genetically distinct. Additionally, 159 outlier loci were identified in M. aestivalis suggesting possible local adaptation in the Rio Grande and Pecos River populations. Though range-wide genetic data are limited, N. jemezanus populations in both rivers harbor considerable genetic diversity. Mitochondrial data from both taxa are consistent with a history of secondary contact between formerly isolated populations with deeply divergent haplotypes found within the Rio Grande and Pecos River populations of N. jemezanus and within the Rio Grande population of M. aestivalis. Extensive survey efforts in the lower Rio Grande and its tributaries in Texas document significant range contraction and near extirpation of N. jemezanus from this part of the basin; highlighting the need for immediate action to protect the species.

Mass Upstream Dispersal of Pelagic-Broadcast Spawning Cyprinids in the Rio Grande and Pecos River, New Mexico

Pelagic-broadcast spawning minnows are a reproductive guild of fishes, of which several species occur in the American Great Plains and Southwest. The eggs and larvae of these species drift laterally and downstream, with drift distances varying depending on channel conditions and flow. Persistence or recolonization of these species in upstream reaches must depend on retention of eggs and larvae or upstream dispersal of later life stages, otherwise net downstream displacement of eggs and larvae would result in upstream extirpations. However, only a few individuals of several species have been observed dispersing. Here, we describe 2 direct visual observations of the young-of-year of 4 species of pelagic-broadcast spawning minnows dispersing upstream en masse. In August 2009, we observed Plains Minnow (Hybognathus placitus), Speckled Chub (Macrhybopsis aestivalis), and Rio Grande Shiner (Notropis jemezanus) dispersing upstream. The continuous shoal of fish was >200 m in length and was dispersing upstream at a rate of >1000 fish/min. In July 2017, we observed a continuous shoal of Rio Grande Silvery Minnow (Hybognathus amarus) approximately 1.9 km in length dispersing upstream at a rate between 350 and 1500 fish/min. While such dispersal events are rarely observed, they may be important for maintenance of populations in upstream areas.

Morphological and genetic evolution in eastern populations of the Macrhybopsis aestivalis complex (Cypriniformes: Cyprinidae), with the descriptions of four new species.

For many years the North American cyprinid fish Macrhybopsis aestivalis (common name: Speckled Chub) was regarded as a single widespread and morphologically variable species, occurring in rivers throughout much of the Mississippi Valley and geographically adjacent eastern Gulf slope drainages, west to the Rio Grande basin in Texas, New Mexico, and Mexico. Eisenhour (1997) completed a morphological study of western populations of the Speckled Chub, the results of which appeared thereafter in published form (Eisenhour 1999, 2004). He demonstrated the existence of five valid species west of the Mississippi River (aestivalis, marconis, australis, tetranema, hyostoma), of which the name aestivalis was shown to be restricted to the population occurring in the Rio Grande and the geographically adjacent Rio San Fernando system, in northeastern Mexico. Eisenhour (2004) considered populations throughout the middle Mississippi Valley and its major tributaries to be a single morphologically variable species (hyostoma), and he also indicated that populations of Macrhybopsis from eastern Gulf slope drainages may represent a complex of species. Genetic confirmation of Eisenhour's conclusions regarding western species appeared in the publication by Underwood et al. (2003), who also showed that western populations of M. hyostoma, as presently recognized, are genetically much more complex than previously considered. Meanwhile, the present authors were involved in a companion study of eastern populations of Macrhybopsis, for which a genetic summary of the eastern Gulf coast species was published by Mayden & Powers (2004). Based on their findings, four species were recognized from southeastern drainages (identified as species A-D), although no formal taxonomic descriptions were included. Their genetic data, in combination with meristic, morphometric and other morphological data presented herein, form the basis for a revised classification of eastern Macrhybopsis populations, including formal descriptions of the four new species from eastern Gulf coast drainages.

Intrafragment riverscape conservation for an imperiled, small-bodied, pelagic-broadcast spawning minnow: speckled chub (Macrhybopsis aestivalis)

Intrafragment ecology is little studied for imperiled riverine fishes although river fragmentation and habitat loss increasingly threaten sensitive species. A long-term population-monitoring program in the Pecos River, New Mexico, provided detailed data for 15 annual cohorts of speckled chub (Macrhybopsis aestivalis), which were used to assess intrafragment patterns in recruitment and year-class strength in relation to distributional patterns, flow-regime characteristics, and air temperature. Cohorts avoided a degraded upstream reach. Age-1 and older individuals had distributions consistently centered within a central, relict-ecosystem reach that contained high-quality habitat. Age-0 individuals were widespread within the relict-ecosystem reach and a channelized reach downstream. Distributional patterns suggested that some individuals that recruited in the channelized reach dispersed upstream into relict-ecosystem habitat thereafter. One cohort always numerically dominated the population because cohorts never lived beyond 2 years. Recruitment was density-independent and predicted year-class strength. No aspect of the flow regime explained variation in recruitment. Year-class strength was consistent among cohorts because of density-dependent mortality. High-quality habitat in a centralized location, potential for dispersal between channelized and relict-ecosystem reaches, and diffuse distribution of pelagic-broadcast propagules throughout both reaches combined to facilitate successful annual recruitment and population persistence.

Heterogeneous detection probabilities for imperiled Missouri River fishes: implications for large-river monitoring programs

Occupancy modeling was used to determine (1) if detection probabilities (p) for 7 regionally imperiled Missouri River fishes (Scaphirhynchus albus, Scaphirhynchus platorynchus, Cycleptus elongatus, Sander canadensis, Macrhybopsis aestivalis, Macrhybopsis gelida, and Macrhybopsis meeki) differed among gear types (i.e. stationary gill nets, drifted trammel nets, and otter trawls), and (2) how detection probabilities were affected by habitat (i.e. pool, bar, and open water), longitudinal position (five 189 to 367 rkm long segments), sampling year (2003 to 2006), and season (July 1 to October 30 and October 31 to June 30). Adult, large-bodied fishes were best detected with gill nets (p: 0.02-0.74), but most juvenile large-bodied and all small-bodied species were best detected with otter trawls (p: 0.02-0.58). Trammel nets may be a redundant sampling gear for imperiled fishes in the lower Missouri River because most species had greater detection probabilities with gill nets or otter trawls. Detection probabilities varied with river segment for S. platorynchus, C. elongatus, and all small-bodied fishes, suggesting that changes in habitat influ- enced gear efficiency or abundance changes among river segments. Detection probabilities var- ied by habitat for adult S. albus and S. canadensis, year for juvenile S. albus, C. elongatus, and S. canadensis, and season for adult S. albus. Concentrating sampling effort on gears with the great- est detection probabilities may increase species detections to better monitor a population's response to environmental change and the effects of management actions on large-river fishes.

Detection and Population Estimation for Small-Bodied Fishes in a Sand-Bed River

Multiple-pass removal by use of small-mesh seines within enclosed areas was performed to estimate numbers of nine small-bodied fish species at 17 sites in the Pecos River, New Mexico, during October 2007. Site-level population estimates were most precise for age-0 red shiners Cyprinella lutrensis (coefficient of variation [CV, calculated as SE/mean] = 0.02–0.06) and least precise for age-1 and older plains minnow Hybognathus placitus (CV = 0.03–0.42). Site estimates were expanded to derive species- and age-specific population estimates for 284 km of river, including the full range of the threatened Pecos bluntnose shiner Notropis simus pecosensis (101,131 fish; 95% confidence interval = 76,437–125,825; CV = 0.12). Population estimates and species detection from multiple-pass removal were compared with a closed, comprehensive, single-pass catch rate index obtained on the first pass of the removal estimate (comprehensive catch per effort [C-CPE]) and with an open, single-pass catch rate index (single-pass catch per effort [S-CPE]), where a set of representative mesohabitats was seined in proportion to their availability (mean = 12.6 hauls/site). Compared with removal estimates, C-CPE provided a reliable index of population size for the nine small-bodied species combined (r2 = 0.90, P = 0.010) but did not perform as reliably for adult Pecos bluntnose shiners (r2 = 0.51) or age-0 speckled chub Macrhybopsis aestivalis (r2 = 0.70). On average, C-CPE detected 89% of species at a site, missing predatory species most frequently. By contrast, S-CPE was a poor index of population size for all species (r2 = 0.16, P = 0.010) and detected an average of 52% of species at a site. The S-CPE failed to detect the Rio Grande shiner N. jemezanus at 28.5% of sites, the sand shiner N. stramineus at 41.2% of sites, the Pecos bluntnose shiner at 29.4% of sites, and the speckled chub at 23.5% of sites; all of these are small-boded native species. For applications that require reliable species detection and precise abundance estimates of small-bodied fishes, the multiple-pass removal method is recommended.

Habitat used by Macrhybopsis chubs associated with channel modifying structures in a large regulated river: implications for river modification

AbstractWe examined use of channel modifying structures (CMS; e.g., engineered rock dikes, channel sandbars) and their associated smaller spatial‐scale habitats (SSH) on lower Missouri River, USA, by speckled chub (Macrhybopsis aestivalis), sicklefin chub (M. meeki) and sturgeon chub (M. gelida) from June through October, 2006 to identify important habitat characteristics that could aid conservation. We sampled chubs primarily in six CMS types: L‐dikes, wing‐dikes, kicker dikes, rootless dikes, channel sandbars and bank‐lines. Ninety‐three per cent of chubs were collected from L‐dikes, wing‐dikes and channel sandbars. Unidentifiable Macrhybopsis chubs (UHY) were less than 35‐mm TL, were collected early in the sampling season and were most associated with L‐dikes where mean bottom current velocity was slow (0.07 m/s). Chubs large enough to be identified to species were associated with large channel sandbars where mean bottom current velocity was faster (0.34 m/s). Chubs from wing‐dikes were more abundant in shallow water (<1.2 m deep) adjacent to bars than in deeper (>1.2 m deep), open‐water areas (p = 0.007). Month accounted for 54% and CMS with SSH 18% of explained variation in chub species distribution and abundance. Our results demonstrate that CMS in the contemporary lower Missouri River channel provide multiple habitats for multiple life‐stages of Macrhybopsis chubs (e.g., nursery and post‐nursery habitats). L‐ and wing‐dikes may provide surrogate nursery habitats for chubs where in‐channel slow‐velocity areas were lost after river channelization. Managing CMS to address life history stages and an ecologically appropriate proportion and distribution of dike to channel sandbar habitats may be critical for conservation of native Macrhybopsis chubs in lower Missouri River. Published in 2008 by John Wiley & Sons, Ltd.

Relationship of Fish Mesohabitat to Flow in a Sand‐Bed Southwestern River

AbstractWe quantified the availability and utilization of habitat types by eight small‐bodied cyprinid fish species, including the federally threatened Pecos bluntnose shiner Notropis simus pecosensis, in the Pecos River, New Mexico. The Pecos River is a medium‐sized, sand‐bed river with a highly variable hydrograph and some reaches characterized by historic and recent periods of flow intermittency. Fish habitat was described in four reaches at flows of 0.05–2.29 m3/s by means of a simultaneous, coordinated program of channel topographic surveys, mesohabitat mapping, fish sampling, and measurement of microhabitat and chemical parameters. We determined that fish habitat in this sand‐bed river was effectively described at the mesohabitat scale. Furthermore, mesohabitats were visually distinguishable and separable by means of hydraulic and geomorphic parameters and the relationship between flow and depth, velocity, and velocity : depth ratios. The eight cyprinid species in the Pecos River primarily used four mesohabitat types that were consistently available at the full range of flows examined, including perpendicular and parallel plunges, backwaters, and slackwaters. In winter, five species (red shiner Cyprinella lutrensis, plains killifish Fundulus zebrinus, plains minnow Hybognathus placitus, Arkansas River shiner N. girardi, and sand shiner N. stramineus) shifted to backwaters, where water temperatures were relatively warmer than those of the main channel. Runs, flats, and riffles were generally the most available mesohabitat types, but their availability changed with flow; only four species (red shiner, plains killifish, speckled chub Macrhybopsis aestivalis, and sand shiner) selected these types, and they did so infrequently in summer. The Pecos bluntnose shiner was a habitat specialist that selected primarily rare plunge pools at sandbar faces, whereas species such as the red shiner were habitat generalists that used a variety of mesohabitat types. We found that a range of base flows sustained the preferred habitats of the eight cyprinid species and that no single flow maximized this preferred habitat because of a scaling effect of flow on sand bedforms.

Decline of the Frecklebelly Madtom in the Pearl River Based on Contemporary and Historical Surveys

AbstractThe Pearl River has experienced numerous human‐caused disturbances since the 1950s, including completion of a navigation channel, reservoir construction, and channel modifications on the main stem of the river. These types of disturbances are known to negatively impact the biotic and abiotic components of riverine ecosystems. Since the 1960s, several fish species in the drainage have declined in abundance or have been extirpated from the drainage. We undertook this study to assess the current conservation status of the frecklebelly madtom Noturus munitus in the Pearl River drainage. A 1999 survey of 53 sites within the historic range of the frecklebelly madtom yielded only 13 specimens from eight localities. We also examined historical population trends for the frecklebelly madtom and other benthic fishes using archived museum material (1950– 1988). After standardizing for variation in collection effort, analysis of long‐term collection data indicated that frecklebelly madtom populations have declined significantly since the 1960s. Despite greater sampling effort in the postmodification period (1965–1988), frecklebelly madtoms were most abundant in samples during the modification period (1950–1964). Similar declines were observed for the brighteye darter Etheostoma lynceum, a gravel–riffle‐dependent species. Other percid taxa (including the crystal darter Crystallaria asprella (formerly Ammocrypta asprella), the saddleback darter Percina vigil, the Gulf logperch P. suttkusi, and the dusky darter P. sciera) showed no significant changes between modification and postmodification periods. However, benthic taxa (including the naked sand darter Ammocrypta beani, longnose shiner Notropis longirostris, channel catfish Ictalurus punctatus, hogchoker Trinectes maculatus, gulf darter E. swaini, speckled chub Macrhybopsis aestivalis, and silver chub M. storeriana) increased in abundance between modification and postmodification study periods. We suggest that channel changes and the loss of gravel substrates are related and are contributing to the decline of the frecklebelly madtom in the Pearl River drainage.

Genetic Variation in Western Members of the Macrhybopsis aestivalis Complex (Teleostei: Cyprinidae), with Emphasis on Those of the Red and Arkansas River Basins

We used protein electrophoresis of the allozyme products of 21 gene loci to examine relationships among five western species of the Macrhybopsis aestivalis complex (sensu Eisenhour, 1997), with emphasis on three species recognized from morphology in the Red and Arkansas river basins. Monophyly was supported for both species endemic to those basins, M. australis in the Red and M. tetranema, in the Arkansas. However, support was weak because of high genetic similarity between these species and the more wide-ranging species, M. hyostoma. Within the Arkansas and Red river basins, only 2% and 5%, respectively, of total genic diversity was attributable to differences between the endemic species and M. hyostoma. Across all samples from the two basins, only 14% of total diversity was attributable to among-species differences. Phenetic and allele-frequency parsimony analyses grouped M. hyostoma from the Red and Arkansas river basins with the associated endemic in the respective basin rather than with populations of M. hyostoma from elsewhere. The results are consistent with the indication from morphology that M. tetranema and M. australis are sister species, if it is assumed that the present patterns of allozyme variation are a result of subsequent contact and introgressive hybridization with M. hyostoma. Collections of M. aestivalis from the Rio Grande Basin and M. marconis from the San Marcos River Basin were markedly divergent from each other and from other members of the complex.

Long-Term Changes in the Fish Assemblages of the Big Blue River Basin 40 Years after the Construction of Tuttle Creek Reservoir

Long-term changes in the fish assemblage of the Big Blue River basin, Kansas, were examined by comparison of a stream survey conducted prior to the construction of Tuttle Creek Reservoir (1957 to 1958) with two surveys conducted approximately 40 years later. The most recent survey, in 2001, included 14 of the original sites sampled in the late 1950s. The most notable changes to the fish assemblages were the introduction and presumed establishment of four species (Notropis atherinoides, Pimephales vigilax, Gambusia affinis, and Notemigonus crysoleucas) and the apparent extirpation of Macrhybopsis aestivalis. Other than the loss of M. aestivalis, incidence and relative abundance of other species remained similar to that which occurred before the construction of the reservoir. Percent similarity of the fish assemblage between the 1950s and the recent samples ranged between 34.7% and 84.4%, dependent on stream type (mud, gravel, or sand substrate). In addition, species incidence patterns were significantly concordant between the 1950s and the two recent surveys, with the exception of mud-bottomed streams sampled during 2001. Finally, Jaccard's index was used to compare assemblage similarity between 14 sites sampled in both the late 1950s and 2001. Although assemblage similarity between time periods was on average low (x̄ = 0.411), a Mantel test suggested a significant concordance between sampling periods, indicating the spatial structure of the assemblage was stable. We conclude that Tuttle Creek Reservoir has served as a source for the establishment and subsequent dispersal of introduced species in the Big Blue River system and that it is important to monitor routinely these assemblages because species may continue to invade the Big Blue River system with unpredictable consequences for the native fish fauna.

Declining Status of Two Species of the Macrhybopsis aestivalis Complex (Teleostei: Cyprinidae) in the Arkansas River Basin and Related Effects of Reservoirs as Barriers to Dispersal

From 1991 to 1997, we made 323 seine collections at 187 sites to determine the distributional status of two species of the Macrhybopsis aestivalis complex, M. tetranema (Gilbert) and M. hyostoma (Gilbert), in the Arkansas River Basin. A total of 545 M. hyostoma and 112 M. tetranema were taken in 39 collecting visits to 30 sites. Our survey indicated that the endemic M. tetranema has been extirpated from about 90% of its historic range, whereas the more widespread M. hyostoma has been extirpated from about 55% of its former range in the basin. Approximate year of extirpation for six populations of M. hyostoma in major stream segments was significantly correlated with year-of-completion for reservoirs that would have prevented recolonization from existing populations. This is consistent with the hypothesis that extirpations resulted from disruption of previously existing source/sink relationships among populations. No such correlation was detected for extirpations of seven populations of M. tetranema. This result would be expected from the metapopulation model in which the now-extirpated populations of M. tetranema were self-sustaining except during unusually harsh conditions (e.g., droughts). This factor apparently explains recolonization of the Cimarron River by M. hyostoma subsequent to extirpation of both species of Macrhybopsis from this river. The recolonization was delayed by about 25 years, apparently because of reservoir habitat between the Cimarron River and the other major stream draining into the reservoir, the upper Arkansas River, where there was a persistent population of the species.

Systematics of Macrhybopsis tetranema (Cypriniformes: Cyprinidae)

Morphometry, meristic features, pigmentation, and tuberculation were examined from 632 specimens of the Macrhybopsis aestivalis complex from the Arkansas River basin. Patterns of morphological variation support the recognition of two species in the basin: M. hyostoma in the middle and lower portions of the basin in Arkansas, Kansas, and Oklahoma; and M. tetranema in the middle and upper portions of the basin in Colorado, Kansas, New Mexico, Oklahoma, and Texas. Macrhybopsis tetranema is redescribed and compared to M. hyostoma, from which it can be distinguished by longer barbels, smaller eyes, smaller scales, reduced belly squamation, thicker lips, more conical head, and biserial pectoral fin tuberculation. These species are sympatric and maintain their identities in the Cimarron, Salt Fork of Arkansas, and Arkansas Rivers. Morphological intermediacy of M. tetranema in some areas of sympatry may reflect convergent adaptation to local conditions or hybridization with M. hyostoma. THE rivers of the western half of the Arkansas River Basin support cyprinids adapted

Reproductive Strategies and Egg Types of Seven Rio Grande Basin Cyprinids

Reproductive strategy and egg type of Hybognathus amarus, H. placitus, Macrhybopsis aestivalis, Notropis girardi, N. jemezanus, N. simus pecosensis, and N. stramineus were determined from laboratory experiments conducted between 1991 and 1995. The first six taxa were pelagic-broadcast spawners that produced nonadhesive, semibuoyant eggs, whereas N. stramineus was a broadcast spawner that laid demersaladhesive eggs. High-speed cinematography revealed that a spawning event consisted of a single male wrapping around the female's midsection and fertilizing the eggs upon expulsion. The perivitelline space of recently expelled nonadhesive eggs filled rapidly with water, thereby increasing both egg diameter and buoyancy. Semibuoyant eggs remained in suspension as long as water current was maintained. Discovery of the spawning behavior and egg types of these species allowed for the development of hypotheses to explain extirpations and extinctions of several endemic Rio Grande Basin fishes. We believe the synergistic effects of downstream transport of eggs and larval fishes and dam-related modifications of flow and habitat was probably responsible for the decline and demise of these taxa in the Rio Grande Basin.

A Molecular Perspective on the Phylogenetic Relationships of the Barbeled Minnows, Historically Assigned to the Genus Hybopsis (Cyprinidae: Cypriniformes)

Allozyme products of 32 gene loci were compared for the North American cyprinid fishes Campostoma oligolepis, Cyprinella galactura, Cyprinella monacha, Erimystax cahni, E. dissimilis, E. insignis, E. x-punctatus, Hybopsis amblops, H. labrosa, H. rubriforns, H. zanema, Macrhybopsis aestivalis, M. gelida, M. meeki, Nocomis biguttatus, Phenacobius uranops, Platygobio gracilis, and P. storeriana. Triose-phosphate isomerase was found to be duplicated in all species examined. Parsimony analysis revealed that Hybopsis sensu lato did not form a monophyletic group. Cyprinella monacha was found to be the sister species to members of the genus Cyprinella and was excluded from the genus Erimystax. A clade of four species of Erimystax was identified although relationships among the four species could not be resolved. Phenacobius was identified as the sister group to Erimystax. The genus Macrhybopsis was expanded to include M. aestivalis. Macrhybopsis gelida was identified as the sister to M. meeki and M. aestivalis as the sister to the former two species. The genus Platygobio was expanded to include P.storeriana. Hybopsis labrosa and H. zanema were found to be more closely related to members of the genus Hybopsis sensu stricto than to members of Cyprinella.