Brandon K. Peoples

Bluehead chub nesting activity: a potential mechanism of population persistence in degraded stream habitats

Aquatic biodiversity continues to decline as humans modify the landscape, mainly because of stream habitat alterations and loss caused by urban development. Bluehead chubs may mitigate some effects of instream habitat degradation by providing clean gravel substrate via their spawning nests. We used path analysis, an extension of multiple linear regression, to explore the relationships among instream habitat degradation, adult chub abundance, chub nesting activity, and chub reproductive performance. Age-0 chub abundance was best explained by small adult abundance and nest abundance. Habitat disturbance indirectly and negatively influenced age-0 chub abundance through adult chubs and nest abundance. Percentages of pool and run habitat also had indirect negative effects on age-0 chub abundance. Several metrics of chub nesting activity (nest density [proportion of substrate occupied by nests], average nest size, and number of nests) were explained by both adult chub abundance and nesting site conditions. Variability among stream systems described significant variation in adult chub abundance and nesting characteristics and, if unaccounted for, would have resulted in large unexplained variability. Chub nesting activity served as a link between habitat degradation, adult chub abundance, and their reproductive performance. Our study provides preliminary evidence that bluehead chubs’ nesting activity may be a mechanism of their persistence in degraded stream reaches. We recommend confirmatory studies through in-stream manipulative experiments.

Among-Pass, Interregional, and Single- versus Multiple-Season Comparisons of Detection Probabilities of Stream Fishes

Abstract Unequal detection of stream fishes must be accounted for when estimating assemblage composition. Detection probabilities (p) may differ among electrofishing passes, regions, and methods of estimation. We used data sets collected from (1) the middle New River basin, Virginia, using three-pass electrofishing; (2) the upper Wabash River system of northern Indiana, using the U.S. Geological Survey (USGS) National Water Quality Assessment (NAWQA) protocol; and (3) the NAWQA database, collected throughout the United States. We tested for among-pass differences in p using the New River data set. To test for interregional differences, we compared average detection probability (p avg) between the New and Wabash river data sets. We compared single- and multiple-season estimates using the New River and NAWQA data sets. We found no differences among pass-specific p for 97% of the species in the New River data set. No significant differences in p avg were found between the New and Wabash river systems for 73%...

Recognizing gape limitation and interannual variability in bluehead chub nesting microhabitat use in a small Virginia stream

Understanding the reproductive microhabitat requirements of keystone species such as the gravel mound nesting bluehead chub Nocomis leptocephalus can be useful for whole-community management. Nocomis have been shown to be microhabitat specialists, but no study has accounted for interannual variability in microhabitat use or for the possibility that substrate choices are constrained by mouth size. Our goals were to quantify the spawning microhabitat requirements of bluehead chub in the North Fork Roanoke River, Virginia, USA. Specifically, we sought to (1) account for gape limitation of nesting chubs when quantifying substrate size preference and (2) to examine interannual variability in their nesting microhabitat preferences. In June 2012 and 2013, we measured pebbles on chub nests and determined the gape limit as the largest measured pebble. With the gape limit as a ceiling for measurable particles, we compared substrate used by chubs to randomly selected particles adjacent to each nest. Depth and velocity were also measured at nests during both years and compared to random points near nests. Patterns in microhabitat selection differed between years. Chubs exhibited substrate size preference in 2012, but not 2013. The mean size difference in 2012 was approximately 3 mm but we do not consider this biologically meaningful. This stands in contrast with other studies showing large mean differences in preferred and available substrate. We suggest that the gape limitation of adult male Nocomis imposes a restriction on usable nesting substrate, causing observed significant differences between preferred and available substrate sizes. Current velocities used by chubs were significantly slower than paired measurements in 2013, but did not differ in 2012; depth preference did not differ between years. Differences in velocity preference likely represent adjustment to the above-average instream flow conditions of 2013. This study demonstrates the importance of examining interannual variability in fish spawning habitat requirements.

Nesting microhabitat comparison of Central stoneroller and Bluehead chub: potential inference for host-switching by nest associates

Several nest-building North American minnows (Cyprinidae) function as reproductive hosts to nest associates–species that require nests of other species for spawning. Understanding the microhabitat preferences of hosts can yield insight into the reproductive ecology of many species, especially of nest associates that can utilize nests of two or more hosts. We observed nests of Central stoneroller Campostoma anomalum in which several associate species were actively spawning. Bluehead chubs Nocomis leptocephalus began constructing nests two days later in the same stream, at which time associates abandoned stoneroller nests and continued on to spawn on chub nests. This presented a unique opportunity for accomplishing two objectives: (1) quantifying stoneroller nesting microhabitat preference and (2) comparing stoneroller and chub habitat preference to gain insight into the mechanisms that may drive host switching by nest associates. We measured substrate size, current velocity, water depth, and egg depth on seven paired stoneroller and chub nests, and compared these measurements to paired microhabitat measurements at a randomly selected point near each nest. Repeated measures analysis of variance with post hoc Tukey tests revealed that stonerollers exhibited distinct nesting microhabitat preferences from chubs. Gravel on stoneroller nests was considerably smaller than on chub nests and stonerollers nested in shallower depths than chubs. However, both species nested at similar current velocities. If nest associates switch partners based on the physical characteristics of nests, then substrate size is likely the most important factor. The larger gravel sizes on chub nests likely provide better egg aeration than stoneroller nests. Chub nests may also be safer for associate broods because male Bluehead chubs cover eggs with gravel after spawning; stonerollers do not. Future work should take an experimental approach to elucidate these mechanisms.

Context-dependent outcomes in a reproductive mutualism between two freshwater fish species.

Abstract The development of encompassing general models of ecology is precluded by underrepresentation of certain taxa and systems. Models predicting context‐dependent outcomes of biotic interactions have been tested using plants and bacteria, but their applicability to higher taxa is largely unknown. We examined context dependency in a reproductive mutualism between two stream fish species: mound nest‐building bluehead chub Nocomis leptocephalus and mountain redbelly dace Chrosomus oreas, which often uses N. leptocephalus nests for spawning. We hypothesized that increased predator density and decreased substrate availability would increase the propensity of C. oreas to associate with N. leptocephalus and decrease reproductive success of both species. In a large‐scale in situ experiment, we manipulated egg predator density and presence of both symbionts (biotic context), and replicated the experiment in habitats containing high‐ and low‐quality spawning substrate (abiotic context). Contradictory to our first hypothesis, we observed that C. oreas did not spawn without its host. The interaction outcome switched from commensalistic to mutualistic with changing abiotic and biotic contexts, although the net outcome was mutualistic. The results of this study yielded novel insight into how context dependency operates in vertebrate mutualisms. Although the dilution effect provided by C. oreas positively influenced reproductive success of N. leptocephalus, it was not enough to overcome both egg predation and poor spawning habitat quality. Outcomes of the interaction may be ultimately determined by associate density. Studies of context dependency in vertebrate systems require detailed knowledge of species life‐history traits.

A snapshot analysis of age distributions of fishes in urban and forested Virginia streams

An understanding of the spatial variation in the population structure of lotic fishes is vital to their conservation. Population level approaches may be more suitable than community level approaches for identifying stream fish response to urbanization. Lithophilic (clean mineral substrate) spawners are disproportionally affected by common habitat disturbances, and are thus expected to exhibit great demographic variation along gradients of disturbance. We related age distributions of six stream fishes, exhibiting four different types of lithophily (speleophily, saucer-pit nesting, gravel mound nesting, and simple broadcasting/nest association), to land cover and instream habitat variables. Fishes were collected from 18 urban or forested reaches of three 2nd-4th Strahler-order tributaries of the New River, Virginia. Individuals were assigned to age classes based on length-frequency histograms verified by sagittal otolith analysis. Chi-square tests and multiple polytomous logistic regression were used to relate population structure to land cover types and associated instream habitat variables. Age distributions of broadcast lithophils were unbalanced (containing relatively higher proportions of adults than juveniles) in urban reaches, whereas those of nest-constructing spawners were always balanced. Mixed responses were observed between the two speleophils. Differences in the directional effect of urbanization on population structure may be attributable to species’ tendency to: a) modify available substrate, b) to provide parental care to their brood, and c) life-history traits other than spawning mode (e.g. age at maturation). Although nest association may confer greater reproductive success to participants, this activity was not beneficial enough to give associates balanced age distributions in urban reaches. These results suggest that source-sink dynamics may operate to prevent populations of various fishes in urban reaches from being extirpated. Future research should focus on differences in population dynamics of stream fishes among land cover types.

Reproductive life history of Heterandria bimaculata (Heckel, 1848) (Poeciliinae: Poeciliidae) in the Honduran interior highlands: trait variation along an elevational gradient

This study examined reproductive traits and growth rates of Heterandria bimaculata (Poeciliidae) in Cusuco National Park (CNP), a cloud forest reserve in northern Honduras, Central America. In CNP, H. bimaculata occurs in the absence of other fish species and major invertebrate predators along an approximately 1000 m elevation gradient. This allowed for the examination of trait variation along the gradient without the confounding effects of interspecific interactions or habitat patchiness. Heterandria bimaculata exhibited traits characteristic of a low-predation environment: balanced sex ratio, slow growth, late maturity and large female size. Females produced more, smaller eggs from upstream to downstream, but overall reproductive allocation remained constant along the gradient. Maximum male length and annual growth rates increased from upstream to downstream, but female growth showed no trend. The patterns of growth and reproductive allocation tradeoff are consistent with predicted response to a longitudinally-increasing productivity gradient in which food resources become more abundant downstream. Macrobrachium and Bellastoma could have caused some predation, but were sparse and patchily distributed. Fish density remained fairly constant among elevations; if food resources were limiting in upstream habitats, per-capita resource availability would be lower and density-dependent competition would drive selection for larger but fewer, more competitive offspring. Future work should quantify longitudinal changes in productivity and conduct experiments to decouple the effects of stream order and fish density dependence.

DNA Barcoding Elucidates Cyprinid Reproductive Interactions in a Southwest Virginia Stream

AbstractChubs Nocomis spp. (Cyprinidae) in freshwater streams build conspicuous gravel mounds upon which they and other nest-associative cyprinids spawn. Our understanding of such interactions is incomplete and hindered by the inability to observe all interactions directly and to identify the larvae that emerge from the mounds based on morphological traits. We used visual surveys and DNA barcoding to identify cyprinids that were associated with the nests of spawning chub in Catawba Creek, a small tributary of the James River in southwestern Virginia. All individual fish on nests were identified to species and categorized as spawning or feeding. Eggs were subsequently removed from the nests and hatched in captivity, and DNA was extracted from the larvae. The DNA sequences for region 3 of the mitochondrial cytochrome-c oxidase I gene in individual larvae were amplified, and the resulting sequences were compared to entries in GenBank by using the Basic Local Alignment Search Tool for nucleotide data. Of the ...