Emmanuel A. Frimpong

Hydrologic filtering of fish life history strategies across the United States: implications for stream flow alteration

Lotic fish have developed life history strategies adapted to the natural variation in stream flow regimes. The natural timing, duration, and magnitude of flow events has contributed to the diversity, production, and composition of fish assemblages over time. Studies evaluating the role of hydrology in structuring fish assemblages have been more common at the local or regional scale with very few studies conducted at the continental scale. Furthermore, quantitative linkages between natural hydrologic patterns and fish assemblages are rarely used to make predictions of ecological consequences of hydrologic alterations. We ask two questions: (1) what is the relative role of hydrology in structuring fish assemblages at large scales? and (2) can relationships between fish assemblages and natural hydrology be utilized to predict fish assemblage responses to hydrologic disturbance? We developed models to relate fish life histories and reproductive strategies to landscape and hydrologic variables separately and then combined. Models were then used to predict the ecological consequences of altered hydrology due to dam regulation. Although hydrology plays a considerable role in structuring fish assemblages; the performance of models using only hydrologic variables was lower than that of models constructed using landscape variables. Isolating the relative importance of hydrology in structuring fish assemblages at the continental scale is difficult since hydrology is interrelated to many landscape factors. By applying models to dam-regulated hydrologic data, we observed some consistent predicted responses in fish life history strategies and modes of reproduction. In agreement with existing literature, equilibrium strategists are predicted to increase following dam regulation, whereas opportunistic and periodic species are predicted to decrease. In addition, dam regulation favors the selection of reproductive strategies with extended spawning seasons and preference for stable conditions.

Quantitative determination of rarity of freshwater fishes and implications for imperiled-species designations.

Conserving rare species and protecting biodiversity and ecosystem functioning depends on sound information on the nature of rarity. Rarity is multidimensional and has a variety of definitions, which presents the need for a quantitative classification scheme with which to categorize species as rare or common. We constructed such a classification for North American freshwater fishes to better describe rarity in fishes and provide researchers and managers with a tool to streamline conservation efforts. We used data on range extents, habitat specificities, and local population sizes of North American freshwater fishes and a variety of quantitative methods and statistical decision criteria, including quantile regression and a cost-function algorithm to determine thresholds for categorizing a species as rare or common. Species fell into eight groups that conform to an established framework for rarity. Fishes listed by the American Fisheries Society (AFS) as endangered, threatened, or vulnerable were most often rare because their local population sizes were low, ranges were small, and they had specific habitat needs, in that order, whereas unlisted species were most often considered common on the basis of these three factors. Species with large ranges generally had few specific habitat needs, whereas those with small ranges tended to have narrow habitat specificities. We identified 30 species not designated as imperiled by AFS that were rare along all dimensions of rarity and may warrant further study or protection, and we found three designated species that were common along all dimensions and may require a review of their imperilment status. Our approach could be applied to other taxa to aid conservation decisions and serve as a useful tool for future revisions of listings of fish species.

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.

Comparative Utility of Selected Frameworks for Regionalizing Fish-Based Bioassessments across the United States

Abstract Regional frameworks for bioassessment are necessary to stratify natural geographic variation in biotic assemblages and to calibrate bioassessment metrics and indices. In the United States, alternative frameworks have not been evaluated over large geographic extents (nationwide or continent-wide) or compared with neutral models to document the relative utility of existing frameworks. We used the U.S. Geological Surveys National Water Quality Assessment fish assemblage data from 1,140 fluvial sites to evaluate the utility of physiographic regions, U.S. Environmental Protection Agency ecoregions, aquatic zoogeographic regions, and hydrologic landscape regions (HLRs). A zoogeographic—physiographic (Z-P) region combination was tested along with nesting of HLR within all other frameworks. All frameworks were compared with a hierarchical grid that represented a neutral spatial framework and enabled us to examine effects of spatial autocorrelation. Classification strengths were inferred from the intracl...

Land-use Impacts on Watershed Health and Integrity in Indiana Warmwater Streams

Abstract Many warmwater streams in the midwestern United States have been negatively influenced by human land-use practices. From Jun. through Aug. 2002 and 2003, tributaries (n  =  50) of the upper Wabash River basin, Indiana, were sampled to investigate ecosystem health and integrity. Stream fish and macroinvertebrates were sampled along with in-stream habitat according to National Water-Quality Assessment Program protocols to examine relationships among fish community structure, benthic macroinvertebrate assemblages, physical-habitat complexity and water chemistry under varying land-use practices. Stream fish abundance was best explained by in-stream habitat quality (QHEI), watershed area and the amount of forested land use upstream of each sampling site. Overall index of biotic integrity (IBI) scores were low (mean  =  35.58; range, 20 to 52), and varied predictably by riparian land-use type. The abundance of benthic macroinvertebrate taxa was best explained by the substrate QHEI metric (λ  =  0.24; P  =  0.005). Macroinvertebrate community index (ICI) scores showed more variability than IBI scores (mean  =  20.40; range, 0 to 36). In-stream habitat quality (QHEI) was directly related to riparian land-use practices. Forested sites had higher QHEI scores than fallow field and agricultural sites due to increased habitat heterogeneity, large-woody debris loading and larger substrate sizes. The best model for predicting IBI scores incorporated both watershed and reach-scale variables combining slope and erosion power with maximum depth, percent canopy closure, percent fine substrates, degree of channelization and LWDI (r2  =  0.24; adjr2  =  0.19). Reach-scale variables (i.e., QHEI score, stream width, the proportion of unstable banks and percent fine substrates) best predicted ICI scores (r2  =  0.69; adjr2  =  0.66). Based on these results, we recommend that resource managers incorporate both biotic and abiotic factors at various temporal and spatial scales to predict the effects of land-use practices on community health in agriculturally dominated, warmwater streams.

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%...

Using Historical Atlas Data to Develop High-Resolution Distribution Models of Freshwater Fishes

Understanding the spatial pattern of species distributions is fundamental in biogeography, and conservation and resource management applications. Most species distribution models (SDMs) require or prefer species presence and absence data for adequate estimation of model parameters. However, observations with unreliable or unreported species absences dominate and limit the implementation of SDMs. Presence-only models generally yield less accurate predictions of species distribution, and make it difficult to incorporate spatial autocorrelation. The availability of large amounts of historical presence records for freshwater fishes of the United States provides an opportunity for deriving reliable absences from data reported as presence-only, when sampling was predominantly community-based. In this study, we used boosted regression trees (BRT), logistic regression, and MaxEnt models to assess the performance of a historical metacommunity database with inferred absences, for modeling fish distributions, investigating the effect of model choice and data properties thereby. With models of the distribution of 76 native, non-game fish species of varied traits and rarity attributes in four river basins across the United States, we show that model accuracy depends on data quality (e.g., sample size, location precision), species’ rarity, statistical modeling technique, and consideration of spatial autocorrelation. The cross-validation area under the receiver-operating-characteristic curve (AUC) tended to be high in the spatial presence-absence models at the highest level of resolution for species with large geographic ranges and small local populations. Prevalence affected training but not validation AUC. The key habitat predictors identified and the fish-habitat relationships evaluated through partial dependence plots corroborated most previous studies. The community-based SDM framework broadens our capability to model species distributions by innovatively removing the constraint of lack of species absence data, thus providing a robust prediction of distribution for stream fishes in other regions where historical data exist, and for other taxa (e.g., benthic macroinvertebrates, birds) usually observed by community-based sampling designs.

Characterisation of potential aquaculture pond effluents, and physico-chemical and microbial assessment of effluent-receiving waters in central Ghana

An understanding of specific aquaculture systems and the impacts of their management practices leads to sound and cost-effective policies to protect the aquatic environment. Water samples were collected in 2009 from fish ponds, streams that receive effluents directly from ponds and reference streams in Ghana to assess potential environmental impacts of pond aquaculture. Although relatively dilute, fish ponds had higher levels of all physico-chemical variables measured compared to those of locations upstream and downstream of farms, and to reference locations. Total nitrogen and BOD5 were most clearly statistically significant. Of 292 earthen fish ponds surveyed in central Ghana, approximately 92% were used for either Oreochromis monoculture or Oreochromis–Clarias polyculture. These had similar pond water (i.e. potential effluent) quality but different management practices. The study ponds had the potential to pollute effluent-receiving streams, but their actual impacts will depend on how pond effluents are managed. Conventional treatment of effluents from these small-scale, low-volume operations, which discharge relatively dilute effluents infrequently, might not be cost-effective.

IchthyMaps: A Database of Historical Distributions of Freshwater Fishes of the United States

Fish occurrence data to support high-resolution distribution models and test various community and macroecological hypotheses have not been available at the national scale. We present IchthyMaps, a high-resolution database of historical freshwater fish occurrences throughout the conterminous United States. Designed on the principles of metacommunity ecology, IchthyMaps is a large compilation of fish presence records collected through approximately 1990, digitized from regional atlases, appended to 1:100,000 National Hydrography Dataset plus version 2 (NHDPlusV2) interconfluence stream segments, and readily aggregated within hierarchically coarser units (e.g., 8-digit and 12-digit U. S. Geological Survey [USGS] hydrologic units). IchthyMaps contains 606,550 presence records for 1,038 species and subspecies, spatially joined to 224,305 NHDPlusV2 interconfluence stream segments, representing more than 10% average sampling intensity considering all the NHDPlusV2 segments as the sampling frame. IchthyMaps is f...

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.