Geology topics

Corey G. Dunn

Publications and source records attributed to Corey G. Dunn.

5 recordsLinked to original sources

USGS2021

Accounting for dispersal and local habitat when evaluating tributary use by riverine fishes

Conservation practitioners increasingly recognize the conservation value of tributaries for supporting mainstem, large-river specialist fishes. A tributarys discharge at its mouth is a coarse indicator of large-river specialist fishes found within the tributary, but the relative influences of regional dispersal and local habitat underpinning this species-discharge relationship is often unknown. We sampled large-river specialist fishes at sites within two nonwadeable tributaries of the Missouri and Mississippi rivers with contrasting prairie (Grand River) versus upland (Meramec River) habitats to address four research questions: (1) do mean site-level species richness (alpha diversity) and beta diversity (among-site species compositional differences) vary between tributaries? (2) does mean annual discharge correlate with local habitat and downriver distance to mainstem rivers (i.e., mainstem connectivity)? (3) are slopes of species-discharge relationships consistent between tributaries? and (4) do local habitat and downriver distance explain residual richness at sites beyond variation already explained by species-discharge relationships? We detected 30 of 42 potential large-river specialist fishes, demonstrating most mainstem species use tributaries. Mean site-level richness was higher in the Grand River (12.5 species versus 9.8 species in Meramec River), but partitioning of lower reaches (sites < 116 km from river mouth) and dispersal limitation in upper reaches (sites 116 km from river mouth) caused Meramec River beta diversity to be three times higher. Mean annual discharge correlated with habitat availability at sites and downriver distance. Although site-level alpha richness increased with discharge in both tributaries, slopes of species-discharge relationships varied between tributaries. Analyzing species-discharge residuals revealed downriver distance explained additional variation in site-level richness not accounted for by local discharge. For example, discharge alone underrepresented richness in lower-discharge, accessible sites (maximum underestimate = 8.7 species) and overrepresented richness in isolated sites (maximum overestimate = 5.8 species). Thus, predictive performance of species-discharge relationships can be improved by accounting for varying habitats among tributaries and downriver distance of sites when valuing tributaries for fishes with dispersal-dependent life cycles.

Missouri↗

USGS2020

A flexible survey design for monitoring spatiotemporal fish richness in nonwadeable rivers: optimizing efficiency by integrating gears

We designed a flexible protocol for monitoring fish species richness in nonwadeable rivers. Nine sites were sampled seasonally with six gears in two physiographic regions in Missouri (USA). Using resampling procedures and mixed-effects modeling, we quantified richness and compositional overlap among gears, identified efficient gear combinations, and evaluated protocol performance across regions and seasons. We detected 25–75 species per sample and 89 185 fish. On average, no single gear detected >62% of observed species, but an optimized, integrated-gear protocol with four complementary gears on average detected 90% of species while only requiring 51.9% of initial sampling effort. Neither season nor physiographic region explained low spatiotemporal variation in percent richness detected by the integrated-gear protocol. In contrast, equivalent effort with an electrofishing-only protocol was 53.5% less efficient, seasonally biased and imprecise (36.1%–82.3% of richness), and on average detected 15.9% less of observed richness. Altogether, riverine fish richness is likely underestimated with single-gear survey designs. When paired with existing wadeable-stream inventories, our customizable approach could benefit regional monitoring by comprehensively documenting riverine contributions to riverscape biodiversity.

Missouri↗

USGS2018

Remaining populations of an upland stream fish persist in refugia defined by habitat features at multiple scales

Aim Conserving stream biota could require strategies that preserve habitats conveying resistance to ecological impacts of changing land use and climate. Retrospective analyses of species’ responses to anthropogenic disturbances can inform such strategies. We developed a hierarchical framework to contrast environmental conditions underlying persistence versus extirpation of an imperilled stream fish, Candy Darter ( Etheostoma osburni ), over decades of changing land use. The decline of E. osburni may broadly represent the challenge of conserving sensitive freshwater species in intensively used upland environments. Location New River drainage, Appalachian Mountains, USA. Methods We surveyed fish and habitat in historically occupied sites to identify population refugia, and used multivariate and spatial analyses to address three questions: (a) what are the environmental correlates of refugia? (b) are the pathways by which land use impacts instream habitat constrained by catchment- and/or segment-scale features? and (c) are E. osburni distributional dynamics spatially structured and explained by fine sediment and warm stream temperatures? Results We confirmed a recently localized distribution similar to other upland species, marked by at least seven extirpations from streams throughout E. osburni 's southern range. Catchment-scale features primarily constrained land use and finer-scale habitat, leading to either extirpations or population-supporting refugia defined by features at multiple scales. Refugium habitats contained cooler temperatures and less fine sediment. Rare mismatches between persistence and habitat suitability were explained by network location , suggesting unmeasured environmental gradients and/or dispersal contributed to distributional dynamics. Main conclusions We provided insight at multiple spatial scales into how aquatic species’ distributions become fragmented and localized. Our results demonstrate that natural landscape heterogeneity imparts spatially variable resistance of sensitive species to intensive land uses. By recognizing the scale-specific features that buffer populations from extirpation, conservation strategies could be tailored to protect naturally occurring refugium habitats and focus restoration in systems where such habitats are broadly lacking.

Virginia, West Virginia↗

USGS2018

Intensive sampling reveals underreported use of great-river tributaries by large-river fishes in Missouri

Large tributaries may help sustain large-river fish populations by mitigating fish-habitat losses within the highly modified great rivers of the Mississippi River basin. These tributaries are likely most beneficial for fish species specializing on non-degraded large-river habitat for some portion of their life histories. Few great-river tributaries, however, have been surveyed using methods that comprehensively target all fish species, resulting in uncertainty or bias in the reported composition of many tributary fish assemblages. We report important distributional records, including 23 new accounts, for 12 large-river specialist fishes in Missouri —Alosa alabamae (Alabama Shad), Cycleptus elongatus (Blue Sucker), Pimephales vigilax (Bullhead Minnow), Notropis wickliffi (Channel Shiner), Polyodon spathula (Paddlefish), Hybognathus placitus (Plains Minnow), N. blennius (River Shiner), Macrhybopsis hyostoma (Shoal Chub), Scaphirhynchus platorynchus (Shovelnose Sturgeon), M. storeriana (Silver Chub), Ichthyomyzon unicuspis (Silver Lamprey), and Alosa chrysochloris (Skipjack Herring)—following 38 comprehensive fish surveys in tributaries of the Missouri and Mississippi rivers. New accounts collectively demonstrate tributaries support more large-river specialists than historically documented and thus may be currently undervalued sources of habitat for large-river fishes.

Missouri↗

USGS2016

Development of habitat suitability indices for the Candy Darter, with cross-scale validation across representative populations

Understanding relationships between habitat associations for individuals and habitat factors that limit populations is a primary challenge for managers of stream fishes. Although habitat use by individuals can provide insight into the adaptive significance of selected microhabitats, not all habitat parameters will be significant at the population level, particularly when distributional patterns partially result from habitat degradation. We used underwater observation to quantify microhabitat selection by an imperiled stream fish, the Candy Darter Etheostoma osburni , in two streams with robust populations. We developed multiple-variable and multiple-life-stage habitat suitability indices (HSIs) from microhabitat selection patterns and used them to assess the suitability of available habitat in streams where Candy Darter populations were extirpated, localized, or robust. Next, we used a comparative framework to examine relationships among (1) habitat availability across streams, (2) projected habitat suitability of each stream, and (3) a rank for the likely long-term viability (robustness) of the population inhabiting each stream. Habitat selection was characterized by ontogenetic shifts from the low-velocity, slightly embedded areas used by age-0 Candy Darters to the swift, shallow areas with little fine sediment and complex substrate, which were used by adults. Overall, HSIs were strongly correlated with population rank. However, we observed weak or inverse relationships between predicted individual habitat suitability and population robustness for multiple life stages and variables. The results demonstrated that microhabitat selection by individuals does not always reflect population robustness, particularly when based on a single life stage or season, which highlights the risk of generalizing habitat selection that is observed during nonstressful periods or for noncritical resources. These findings suggest that stream fish managers may need to be cautious when implementing conservation measures based solely on observations of habitat selection by individuals and that detailed study at the individual and population levels may be necessary to identify habitat that limits populations.

Transactions of the American Fisheries Society↗