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Developing Fluvial Fish Species Distribution Models Across the Conterminous United States—A Scientific Framework to Support Management and Conservation

Scientific Investigations Report 2023-5088
Science Analytics and Synthesis Program
Prepared in cooperation with Department of Fisheries and Wildlife, Michigan State University
By: , , , , , and 
https://doi.org/10.3133/sir20235088

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Acknowledgments

We acknowledge the U.S. Geological Survey (USGS) Aquatic Gap Analysis Project for funding most of this effort (agreement numbers G17AC00185 and G21AC00013). We also acknowledge support from the Michigan Department of Natural Resources and from the U.S. Department of Agriculture National Institute of Food and Agriculture through Michigan State University AgBioResearch.

Fish data compiled specifically for this effort came from the Connecticut Department of Energy and Environmental Protection; Delaware Department of Natural Resources and Environmental Control; Florida Fish and Wildlife Conservation Commission; Idaho Department of Fish and Game; Illinois Department of Natural Resources; Indiana Department of Environmental Management; Iowa Department of Natural Resources; Kentucky Department of Fish and Wildlife Resources; Maine Department of Inland Fisheries and Wildlife; Maryland Department of Natural Resources; Massachusetts Department of Fisheries and Wildlife; Michigan Department of Natural Resources; Montana Department of Fish, Wildlife and Parks; Multistate Aquatic Resources Information System; New Hampshire Fish and Game; New Jersey Division of Fish and Wildlife; North Carolina Inland Fisheries Division; Oklahoma Conservation Commission; South Dakota Game, Fish and Parks; Tennessee Wildlife Resources Agency; Texas Parks and Wildlife; USGS BioData; USGS Lower Mississippi-Gulf Water Science Center; Virginia Department of Game and Inland Fisheries; and Washington State Department of Ecology. Additional data and approaches for managing data for this effort were supported by the U.S. Fish and Wildlife Service with funding for the 2015 National Assessment of Stream Fish Habitats. A list of fish data providers who supported that effort can be found in Crawford and others, 2016 (table 2 therein; “Stream fish data providers for 2015 national assessment of stream fish habitats”).

Others who have made important contributions to this project include Yin Phan Tsang (University of Hawaii), John Young (USGS Eastern Ecological Science Center), Elizabeth Sellers (data manager, USGS Science Analytics and Synthesis Program), and Wes Daniel and Matthew Neilson (USGS Nonindigenous Aquatic Species Program). Additionally, a team of individuals helped establish the need for national-scale efforts to model aquatic species distributions including Andrea Ostroff, Emmanuel Frimpong, William A. Gould, Robert Hughes, Andrew Loftus, and James E. McKenna. We also wish to thank Kyle Herreman for assistance in managing data used for this effort.

Abstract

This report explains the steps and specific methods used to predict fluvial fish occurrences in their native ranges for the conterminous United States. In this study, boosted regression tree models predict distributions of 271 ecologically important fluvial fish species using relations between fish presence/absence and 22 natural and anthropogenic landscape variables. Models developed for the freshwater portions of the ranges for species represented 28 families. Cyprinidae was the family with the most species (87 of 271) modeled for this study, followed by Percidae (34) and Ictaluridae (17). Model predictive performance was evaluated using four metrics: area under the receiver operating characteristic curve, sensitivity, specificity, and True Skill Statistic, which are all from tenfold cross-validation results. The relative importance of the predictor variables in the boosted regression tree models was calculated and ranked for each species. The three strongest natural predictors of fish distributions were network catchment area, the mean annual air temperature of the local catchment, and the maximum elevation of the local catchment, while the three strongest anthropogenic predictors were downstream main stem dam density, distance to downstream main stem dam, and the percentage of pasture/hay land use area within network catchment boundaries. Study results showed 61 fish species were sensitive to climate variables, and 40 fish species were sensitive to anthropogenic stressors. The models developed in this study can be used to derive critical information regarding habitat protection priorities, anthropogenic threats, and potential effects of climate change on habitat suitability, aiding in efforts to conserve fluvial fishes now and into the future.

Introduction

An overarching mission of the U.S. Geological Survey (USGS) Aquatic Gap Analysis Project (GAP) is to support national and regional assessments of the conservation status of vertebrate species and plant communities by providing information on the most common and abundant aquatic species found in the United States, while also advancing knowledge on distributions and habitat suitability of rarer, poorly characterized aquatic species. To meet these needs, Aquatic GAP uses spatial analyses and species distribution models (SDMs) to assess aquatic biodiversity and habitats to identify gaps in species protection or threats to habitats. Products of these analyses contribute to conservation planning and prioritization efforts throughout the United States. However, data characterizing habitat suitability and key landscape factors limiting species distributions are lacking for many fluvial fishes in the United States. Development of fluvial fish SDMs provides an opportunity to fill these knowledge gaps.

SDMs are widely used as a management tool to analyze freshwater species distributions and quantify habitat suitability (Bouska and others, 2015). Regression-based approaches are commonly used in SDM development (Guisan and Zimmermann, 2000). Through a logit link function, species presence/absence data are used as the response variable, whereas landscape data can be used as predictor variables for habitat characteristics. This is based on the established understanding that landscape factors of stream catchments can affect fishes through effects on habitats (Allan, 2004). However, regression-based models have several limitations, such as sensitivity to multicollinearity, influence of outliers, and difficulties representing interactions among predictor variables (Elith and others, 2008). Nonparametric machine learning models can overcome limitations inherent in regression-based models (Elith and others, 2008). Machine learning models can improve model performance automatically by experience; this occurs through building a model based on part of the sample data (training set) and using the remaining data points (testing set) to tune the model. This process is done iteratively to improve model predictions and maximize the proportion of model deviation that is explained (Hastie and others, 2009). Among machine learning approaches, boosted regression trees (BRT) have been recognized as a powerful and robust method for SDM development (Elith and others, 2008).

An important aspect of SDM development is the evaluation of candidate model performance and final selection of the model with the best predictive ability. Reporting this predictive ability assures users of the validity of SDMs and their corresponding use in conservation planning and biodiversity assessments. Many evaluation metrics can be derived from a confusion matrix (Liu and others, 2011), which is a simple table that records numbers of correctly and incorrectly predicted presences and absences. Sensitivity and specificity, two metrics commonly derived from a confusion matrix, indicate the proportions of correctly predicted presences and correctly predicted absences.

Most evaluation metrics are calculated by identifying a threshold value associated with probabilities of SDM predictions. For example, 0.5 is often used as a threshold value for sampling data with similar numbers of presences and absences (Liu and others, 2011). However, the number of presences is often much smaller than the number of absences in an aquatic species survey, and 0.5 may not be suitable in these situations. Besides threshold-dependent evaluation metrics, threshold-independent metrics (for example, area under the receiver operating characteristic curve [AUC]) are frequently used in model evaluation (Liu and others, 2011). Due to inherent differences among evaluation metrics and associated strengths and weaknesses in measuring accuracy, no single metric provides a comprehensive measure of model predictive ability. Therefore, combining multiple evaluation metrics is crucial to appropriately assess model performance.

In addition to predicted habitat suitability, another important outcome of SDM development is the ability to characterize potential species responses to environmental factors that may be important drivers of species distributions. In the context of SDMs, this information can be derived from predictor variable contributions and evaluation of partial dependence plots. In SDMs, the contribution of each predictor variable to response variable prediction (species presence or absence) provides information on the major natural and anthropogenic factors influencing species distributions. Predictor variable contributions often vary among species; thus, SDMs can reveal critical patterns of predictor variable relative importance across multiple species. For instance, including both climate and anthropogenic predictor contributions in each model can help identify climate-sensitive species and species sensitive to anthropogenic stressors. Partial dependence plots investigate the influence of each individual predictor independently by holding all other predictors to their mean values, and they can be used to visualize complex, nonlinear species responses to predictors. Collectively, this information can assist managers in prioritizing conservation policies and management of habitats such as forest cover, dam density, and water withdrawals, based on the relative importance and fish responses to these landscape variables.

This report describes the development of SDMs for 271 fluvial fish species across the conterminous United States. Descriptions of SDM development include the following: (1) an overview for developing SDMs for the Aquatic GAP, (2) results from five diagnostic metrics evaluating overall model performance, (3) important model predictor variables that provide insights into the natural and anthropogenic factors limiting fluvial fish species distributions, (4) species presence/absence predictions for all stream reaches within their native ranges, and (5) habitat suitability assessment that offers valuable information for natural resources management.

Materials and Methods

This section includes detailed descriptions of response variables, predictor variables, statistical models, and model evaluation metrics. The following section titled “Spatial Framework and Landscape Predictors” describes the variables that were used to predict distributions of species.

Spatial Framework and Landscape Predictors

The 1:100,000 scale National Hydrography Dataset Plus Version 2.1, or NHDPlusV2.1, was used as the spatial framework for this project (McKay and others, 2012). This dataset includes ~2.3 million stream reaches in the conterminous United States. In this framework local catchments are defined as the land area draining directly to a given stream reach, while network catchments are defined as the entire upstream drainage area above a stream reach including a stream reach’s own local catchment. Similarly, local buffers include riparian land area within the local catchment that is 90 meters (m) on either side of stream reach, while network buffers include the 180-m riparian land area in the entire upstream network, including a stream reach’s own local buffer. Nine natural and 13 anthropogenic landscape factors were attributed to the spatial framework and used as predictor variables in species distribution modeling (table 1). These predictor variables have also been used in earlier Aquatic GAP fluvial fish distribution model development (Cooper and others, 2019; Yu and others, 2020) and were summarized within five spatial units, including the stream reach, catchments, or buffers (fig. 1).

Table 1.    

Predictor variables used in species distribution model development.

[km2, square kilometer; EPA, U.S. Environmental Protection Agency; USGS, U.S. Geological Survey; %, percent; km, kilometer; mm, millimeter; OCS, Oregon Climate Service; °C, degrees Celsius; m/m, meter per meter; cm, centimeter; MRLC, Multi-Resolution Land Cover Characteristics Consortium; m, meter; NA, not applicable; no./km, number per square kilometer; PCS, permit compliance system; ICIS, Integrated Compliance Information System; SEMS, Superfund Enterprise Management System; NPDES, National Pollutant Discharge Elimination System; TRIS, toxic release inventory system; kg/km2; kilogram per square kilometer; SPARROW, SPAtially Referenced Regression On Watershed attributes; HUC8, 8-digit hydrologic unit code; HUC12, 12-digit hydrologic unit code; TIGER, Topologically Integrated Geographic Encoding and Referencing]
Variable and description (units) Source Dataset Scale or resolution
N_areasqkm: network catchment area (km2) Ross and others, 2022 National Hydrography Dataset Plus version 2 1:100,000
N_bfi: network catchment base-flow index (% of base flow contribution to total flow) Ross and others, 2022 Base-Flow Index Grid for the Conterminous United States (2003) 1 km
N_precip: network catchment mean annual precipitation (mm) Ross and others, 2022 OCS PRISM 1990–2010 4 km
L_temp: local catchment mean annual air temperature (°C) Ross and others, 2022 OCS PRISM 1990–2010 4 km
L_fl_slope: stream reach gradient (m/m) Ross and others, 2022 National Hydrography Dataset Plus version 2 1:100,000
L_maxelev: local catchment maximum elevation (cm) Ross and others, 2022 National Hydrography Dataset Plus version 2 30 m
NB_nlcd11_41_43: network buffer forest land cover (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_nlcd11_11c: network catchment water land cover (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_nlcd11_90_95: network catchment woody and emergent herbaceous wetland land cover (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_nlcd11_21_24: network catchment urban land use; developed open, low, medium, and high intensity (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_nlcd81: network catchment cultivated crops (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_nlcd82: network catchment pasture/hay (%) Ross and others, 2022 2011 National Land Cover Database 30 m
N_pop11den: network catchment human population density (no./km2) Ross and others, 2022 U.S. Census 2010 1:100,000
N_allepa_den: network catchment density of EPA point-source pollution sites (PCS, ICIS, SEMS, NPDES, and TRIS sites) (no./km2) Ross and others, 2022 EPA Facility Registry Service NA
N_allmine_den: network catchment mineral, coal, and uranium mine density (no./km2) Ross and others 2022 Locations of mines and mining activity in the United States NA
N_total_p_yield: network catchment total phosphorus yield (kg/km2) Ross and others, 2022 SPARROW HUC8
N_totww_mgalc: network catchment total water withdrawal (million gallons/year) Ross and others, 2022 EnviroAtlas HUC12
UDOR: degree of regulation: estimated annual discharge stored in upstream reservoirs (%) Cooper and Infante (2022) Dam fragmentation 1:100,000
UNDR: upstream network dam density (no./100 km) Cooper and Infante (2022) Dam fragmentation 1:100,000
DMD: downstream main stem dam density (no./100 km) Cooper and Infante (2022) Dam fragmentation 1:100,000
DM2D_fishtail: distance to downstream main stem dam if present; otherwise distance to network outlet if no downstream dam is present (km) Cooper and Infante (2022) Dam fragmentation 1:100,000
N_rx_stlen_dens: stream network road crossing density (no./km) Ross and others, 2022 2006 TIGER Roads SE 1:100,000
Table 1.    Predictor variables used in species distribution model development.
Color-coded diagram showing differences between a stream reach, local buffer, local catchment, network buffer and network catchment
Figure 1.

Simplified diagram representing the five spatial units used to summarize landscape variables.

Nine natural landscape variables were used as predictors in modeling. These included five at the network catchment scale, including catchment area, mean annual precipitation, percentage of overall wetland (combining forested and emergent wetlands) and open-water land-cover types, and base-flow index (percentage contribution of base flow to overall streamflow). The remaining four natural landscape predictor variables included mean annual air temperature and maximum elevation in local catchments, amount of forest land cover within network buffers, and stream reach slope (gradient). The 13 anthropogenic variables used as model predictors included the following: total urban land use (combining open, low, medium, and high urban), row crop land use, pasture land use, human population density, total water withdrawal, total phosphorous yield, mine density, and point source pollution site density in network catchments. Dam influences were represented by downstream main stem dam density, downstream main stem availability, upstream network dam density, and upstream degree of regulation (percentage of predicted annual streamflow volume stored in all upstream reservoirs) (Cooper and others, 2017), while road influences were represented by upstream road-crossing density in network catchments for stream reaches.

Fish Community Data

The fish data used for presence/absence species distribution modeling were derived from an existing fish database developed for a national fish habitat assessment in support of the National Fish Habitat Partnership (NFHP; http://assessment.fishhabitat.org/) and additional fish data collected in support of this project. Goals for collecting additional fish data were threefold. First, because NFHP fish data span the period 1990–2013, more recent data from 2014 to 2019 were needed to evaluate current conditions. Second, few western States were represented with fish data in the NFHP fish database, thus collection of fish data from data-poor regions was given a high priority to fill in spatial gaps in data availability. Third, whereas NFHP analyses required data that characterized the abundances of all species comprising assemblages, methods for creating SDMs used in this study required presence/absence data. Presence/absence data enabled use of datasets that included targeted samples of specific species or that reported species presence/absence compared to relative abundances. In total, 51 State, academic, and nonprofit sources were contacted, with a total of 14 institutions providing new fish data that could be used for this effort in addition to many datasets previously provided for NFHP. The models also included data from a Federal source (USGS BioData, https://apps.usgs.gov/biodata/; March 15. 2019), an existing consortium of State agency fish databases called Multistate Aquatic Resources Information System (USGS, 2013), and publicly available online State databases. All samples were georeferenced to stream reaches in the National Hydrography Dataset Plus Version 2.1, and the Latin species, genus, and family names used here were validated against and referenced by Integrated Taxonomic Information System taxonomic serial numbers for all records (Integrated Taxonomic Information System, 2019).

A tiered site-selection process based on sample species richness and year sampled was used to create the final fish dataset used in presence/absence modeling. This process ensured that a single, most recent, and species-rich sample was selected for stream reaches that had multiple sampling events. First, samples were assigned to one of six periods (1990–94, 1995–1999, 2000–4, 2005–9, 2010–14, and 2015–19). For each stream reach, the sample with the highest species richness within the most recent period was selected. When the most recent period for a given reach had multiple samples with the same species richness, the sample with the most recent sampling date was selected. This process resulted in the final selection of 35,918 fish samples spanning 1990–2019 for the conterminous United States (fig. 2).

The conterminous United States with dots representing locations of the 35,918 fish samples used in analyses
Figure 2.

Locations of the 35,918 fish samples for the conterminous United States spanning 1990–2019.

Fish Species Native Ranges

Fish species native range maps were used to constrain model input (fish presence/absence data) and output (projected model presence/absence). The USGS Nonindigenous Aquatic Species Program assisted in acquisition of USGS eight-digit hydrologic unit code (HUC8) -level range maps of 149 species, delineating their range status as native or introduced (Daniel and Neilson, 2020) (fig. 3; table 2). In these cases, use of these range maps ensured that SDMs were built with presence/absence data occurring within a species’ native range, excluding presence locations from introduced portions of the range. Species’ introduced ranges could represent novel environmental conditions, and therefore, affect model development and potentially limit utility of results intended to support native species conservation. Additionally, range maps were used to limit model projections to stream reaches located within a given species’ native range, ensuring that predicted presence/absence locations were not projected to areas where species are not known to be native.

Table 2.    

List of fluvial fish species analyzed.

[ITIS TSN, Integrated Taxonomic Information System taxonomic serial number; SGCN, species of greatest conservation need identification; NAS, native range developed by U.S. Geological Survey Nonindigenous Aquatic Species Program; Y, yes for at least one State; N, no for every State; MSU, coarse range developed by Michigan State University]
Scientific name Common name ITIS TSN Presences Absences Prevalence Range map source Game fish SGCN
Acantharchus pomotis Mud sunfish 168095 124 1,509 0.0759 NAS Y Y
Acipenser fulvescens Lake sturgeon 161071 16 7,477 0.0021 NAS Y Y
Alosa aestivalis Blueback herring 161703 24 4,426 0.0054 NAS Y Y
Alosa chrysochloris Skipjack herring 161707 130 5,260 0.0241 NAS N Y
Alosa pseudoharengus Alewife 161706 39 4,942 0.0078 NAS Y Y
Alosa sapidissima American shad 161702 49 7,256 0.0067 NAS Y Y
Ambloplites ariommus Shadow bass 168099 252 1,236 0.1694 NAS Y N
Ambloplites cavifrons Roanoke bass 168098 17 370 0.0439 NAS Y Y
Ambloplites constellatus Ozark bass 168100 73 59 0.553 NAS Y N
Ambloplites rupestris Rock bass 168097 4,853 9,237 0.3444 NAS Y Y
Ameiurus brunneus Snail bullhead 164035 124 860 0.126 NAS N Y
Ameiurus catus White catfish 164037 92 6,486 0.014 NAS Y Y
Ameiurus melas Black bullhead 164039 2,310 17,055 0.1193 NAS Y Y
Ameiurus natalis Yellow bullhead 164041 6,280 15,963 0.2823 NAS Y Y
Ameiurus nebulosus Brown bullhead 164043 1,371 19,645 0.0652 NAS Y Y
Ameiurus platycephalus Flat bullhead 164045 278 1,407 0.165 MSU N Y
Amia calva Bowfin 161104 409 7,666 0.0507 NAS Y Y
Anguilla rostrata American eel 161127 2,189 18,916 0.1037 NAS Y Y
Apeltes quadracus Fourspine stickleback 166397 11 3,632 0.003 NAS N Y
Aphredoderus sayanus Pirate perch 164405 1,363 4,571 0.2297 NAS N Y
Aplodinotus grunniens Freshwater drum 169364 1,705 15,193 0.1009 NAS Y Y
Atractosteus spatula Alligator gar 201897 34 1,607 0.0207 NAS Y Y
Campostoma anomalum Central stoneroller 163508 9,931 8,224 0.547 NAS N Y
Campostoma oligolepis Largescale stoneroller 163509 803 3,447 0.1889 MSU N Y
Carpiodes carpio River carpsucker 163919 1,363 11,876 0.103 NAS N Y
Carpiodes cyprinus Quillback 163917 1,341 16,314 0.076 NAS N Y
Carpiodes velifer Highfin carpsucker 163920 224 10,368 0.0211 NAS N Y
Catostomus ardens Utah sucker 163899 39 208 0.1579 NAS N Y
Catostomus catostomus Longnose sucker 163894 558 7,142 0.0725 NAS N Y
Catostomus clarkii Desert sucker 163901 85 63 0.5743 NAS Y Y
Catostomus commersonii White sucker 553273 13,277 13,208 0.5013 NAS Y Y
Catostomus discobolus Bluehead sucker 163902 45 620 0.0677 MSU N Y
Catostomus insignis Sonora sucker 163905 72 73 0.4966 NAS N Y
Catostomus latipinnis Flannelmouth sucker 163906 80 447 0.1518 NAS N Y
Catostomus macrocheilus Largescale sucker 163896 217 2,226 0.0888 MSU N N
Catostomus occidentalis Sacramento sucker 163908 50 69 0.4202 NAS N N
Catostomus platyrhynchus Mountain sucker 163909 417 2,948 0.1239 MSU N Y
Catostomus tahoensis Tahoe sucker 163914 66 249 0.2095 NAS N N
Centrarchus macropterus Flier 168102 198 3,180 0.0586 NAS Y Y
Chrosomus eos Northern redbelly dace 913993 707 5,087 0.122 MSU N Y
Chrosomus erythrogaster Southern redbelly dace 913994 1,549 8,962 0.1474 MSU N Y
Chrosomus neogaeus Finescale dace 913995 211 3,352 0.0592 MSU N Y
Chrosomus oreas Mountain redbelly dace 913996 196 2,389 0.0758 MSU N Y
Clinostomus elongatus Redside dace 163373 468 7,162 0.0613 NAS N Y
Clinostomus funduloides Rosyside dace 163371 800 3,544 0.1842 MSU N Y
Cottus aleuticus Coastrange sculpin 167230 81 395 0.1702 NAS N Y
Cottus bairdii Mottled sculpin 167237 3,206 12,982 0.198 MSU N Y
Cottus beldingii Paiute sculpin 167238 141 1,080 0.1155 NAS N Y
Cottus carolinae Banded sculpin 167239 901 2,658 0.2532 MSU N Y
Cottus cognatus Slimy sculpin 167232 1,067 9,945 0.0969 NAS N Y
Cottus confusus Shorthead sculpin 167240 143 1,977 0.0675 MSU N N
Cottus hypselurus Ozark sculpin 167263 13 129 0.0915 NAS N N
Cottus rhotheus Torrent sculpin 167252 248 799 0.2369 MSU N Y
Couesius plumbeus Lake chub 163535 185 4,548 0.0391 NAS N Y
Culaea inconstans Brook stickleback 166399 1,622 8,675 0.1575 NAS N Y
Cycleptus elongatus Blue sucker 163953 150 6,290 0.0233 NAS N Y
Cyprinella analostana Satinfin shiner 163766 403 3,222 0.1112 MSU N N
Cyprinella camura Bluntface shiner 163776 237 1,156 0.1701 MSU N Y
Cyprinella galactura Whitetail shiner 163782 369 1,849 0.1664 MSU N Y
Cyprinella lutrensis Red shiner 163792 2,819 2,904 0.4926 NAS N Y
Cyprinella spiloptera Spotfin shiner 163803 3,941 12,708 0.2367 MSU N Y
Cyprinella venusta Blacktail shiner 163809 780 1,944 0.2863 MSU N Y
Cyprinella whipplei Steelcolor shiner 163811 452 7,548 0.0565 MSU N Y
Dorosoma cepedianum Gizzard shad 161737 2,561 17,397 0.1283 NAS Y N
Dorosoma petenense Threadfin shad 161738 136 716 0.1596 NAS N N
Elassoma zonatum Banded pygmy sunfish 168171 154 2,610 0.0557 NAS N Y
Enneacanthus chaetodon Blackbanded sunfish 168108 10 1,099 0.009 NAS N Y
Enneacanthus gloriosus Bluespotted sunfish 168113 289 2,439 0.1059 NAS N Y
Enneacanthus obesus Banded sunfish 168117 123 5,074 0.0237 NAS N Y
Entosphenus tridentatus Pacific lamprey 159699 73 992 0.0685 NAS Y Y
Erimystax dissimilis Streamline chub 163821 106 5,948 0.0175 NAS N Y
Erimystax x-punctatus Gravel chub 163824 153 6,865 0.0218 NAS N Y
Erimyzon oblongus Eastern creek chubsucker 163924 1,305 14,304 0.0836 MSU N Y
Erimyzon sucetta Lake chubsucker 163922 132 7,845 0.0165 MSU N Y
Esox americanus Redfin pickerel 162140 2,542 16,807 0.1314 NAS Y Y
Esox lucius Northern pike 162139 1,282 6,473 0.1653 NAS Y Y
Esox niger Chain pickerel 162143 1,126 13,551 0.0767 MSU Y Y
Etheostoma blennioides Greenside darter 168375 4,373 6,875 0.3888 MSU N Y
Etheostoma caeruleum Rainbow darter 168378 4,447 7,050 0.3868 MSU N Y
Etheostoma camurum Bluebreast darter 168379 118 6,502 0.0178 NAS N Y
Etheostoma cragini Arkansas darter 168386 150 715 0.1734 NAS N Y
Etheostoma exile Iowa darter 168393 421 8,128 0.0492 MSU N Y
Etheostoma flabellare Fantail darter 168394 5,415 9,525 0.3624 MSU N Y
Etheostoma fusiforme Swamp darter 168358 118 4,975 0.0232 MSU N Y
Etheostoma gracile Slough darter 168366 223 2,408 0.0848 MSU N Y
Etheostoma kennicotti Stripetail darter 168405 117 896 0.1155 MSU N Y
Etheostoma lynceum Brighteye darter 168456 76 615 0.11 NAS N Y
Etheostoma microperca Least darter 168411 75 8,376 0.0089 NAS N Y
Etheostoma nigrum Johnny darter 168369 7,774 10,643 0.4221 MSU N Y
Etheostoma olmstedi Tessellated darter 168360 2,710 6,743 0.2867 MSU N Y
Etheostoma punctulatum Stippled darter 168425 234 424 0.3556 MSU N Y
Etheostoma radiosum Orangebelly darter 168426 249 357 0.4109 MSU N Y
Etheostoma rufilineatum Redline darter 168428 191 1,091 0.149 MSU N Y
Etheostoma simoterum Snubnose darter 168431 204 1,166 0.1489 MSU N N
Etheostoma spectabile Orangethroat darter 168368 2,957 6,696 0.3063 MSU N Y
Etheostoma stigmaeum Speckled darter 168437 238 2,461 0.0882 MSU N Y
Etheostoma swaini Gulf darter 168439 202 1,166 0.1477 MSU N Y
Etheostoma variatum Variegate darter 168446 254 4,871 0.0496 MSU N Y
Etheostoma whipplei Redfin darter 168448 247 1,712 0.1261 MSU N Y
Etheostoma zonale Banded darter 168449 1,849 7,541 0.1969 NAS N Y
Exoglossum maxillingua Cutlip minnow 163356 852 2,773 0.235 NAS N Y
Fundulus catenatus Northern studfish 165660 562 2,769 0.1687 MSU N Y
Fundulus diaphanus Banded killifish 165646 282 11,938 0.0231 NAS N Y
Fundulus kansae Northern plains killifish 165654 249 1,880 0.117 MSU N Y
Fundulus notatus Blackstripe topminnow 165663 1,572 8,715 0.1528 MSU N Y
Fundulus olivaceus Blackspotted topminnow 165655 1,321 2,545 0.3417 MSU N N
Fundulus seminolis Seminole killifish 165667 34 101 0.2519 NAS N N
Fundulus zebrinus Plains killifish 165658 258 2,234 0.1035 MSU N N
Gambusia affinis Western mosquitofish 165878 3,068 10,477 0.2265 MSU N N
Gila robusta Roundtail chub 163558 55 496 0.0998 NAS Y Y
Hesperoleucus symmetricus California roach 163565 16 83 0.1616 NAS N N
Hiodon alosoides Goldeye 161905 240 8,240 0.0283 NAS N Y
Hiodon tergisus Mooneye 161906 134 8,789 0.015 NAS N Y
Hybognathus argyritis Western silvery minnow 163362 79 2,024 0.0376 NAS N Y
Hybognathus hankinsoni Brassy minnow 163363 921 5,673 0.1397 MSU N Y
Hybognathus nuchalis Mississippi silvery minnow 163360 185 5,416 0.033 MSU N Y
Hybognathus placitus Plains minnow 163361 225 4,337 0.0493 NAS N Y
Hybognathus regius Eastern silvery minnow 163359 119 4,045 0.0286 MSU N Y
Hybopsis amblops Bigeye chub 163476 567 10,796 0.0499 MSU N Y
Hybopsis amnis Pallid shiner 201917 14 2,340 0.0059 NAS N Y
Hybopsis dorsalis Bigmouth shiner 689231 109 814 0.1181 MSU N Y
Hybopsis winchelli Clear chub 201918 1,601 4,040 0.2838 MSU N Y
Hypentelium etowanum Alabama hog sucker 163950 147 792 0.1565 NAS N Y
Hypentelium nigricans Northern hog sucker 163949 112 154 0.4211 NAS N Y
Hypentelium roanokense Roanoke hog sucker 163951 6,064 9,113 0.3996 NAS N Y
Ichthyomyzon castaneus Chestnut lamprey 159725 62 117 0.3464 MSU N Y
Ichthyomyzon fossor Northern brook lamprey 159726 166 4,414 0.0362 NAS N Y
Ichthyomyzon gagei Southern brook lamprey 159727 64 3,181 0.0197 NAS N Y
Ichthyomyzon greeleyi Mountain brook lamprey 159728 169 2,168 0.0723 NAS N Y
Ictalurus furcatus Blue catfish 163997 111 1,449 0.0712 NAS Y Y
Ictalurus punctatus Channel catfish 163998 140 4,453 0.0305 NAS Y Y
Ictiobus bubalus Smallmouth buffalo 163955 3,544 16,874 0.1736 MSU Y Y
Ictiobus cyprinellus Bigmouth buffalo 163956 961 12,240 0.0728 MSU Y Y
Ictiobus niger Black buffalo 163957 515 10,849 0.0453 MSU N Y
Labidesthes sicculus Brook silverside 166016 273 7,852 0.0336 NAS N Y
Lampetra aepyptera Least brook lamprey 159705 1,467 13,856 0.0957 MSU N Y
Lampetra richardsoni Western brook lamprey 159707 490 6,097 0.0744 NAS N Y
Lepisosteus oculatus Spotted gar 161095 28 687 0.0392 NAS N Y
Lepisosteus osseus Longnose gar 161094 432 5,417 0.0739 NAS N Y
Lepisosteus platostomus Shortnose gar 161096 1,063 17,549 0.0571 NAS N Y
Lepisosteus platyrhincus Florida gar 161098 359 6,157 0.0551 NAS N Y
Lepomis auritus Redbreast sunfish 168131 76 218 0.2585 NAS Y Y
Lepomis cyanellus Green sunfish 168132 1,970 6,304 0.2381 NAS Y N
Lepomis gibbosus Pumpkinseed 168144 10,914 6,315 0.6335 NAS Y Y
Lepomis humilis Orangespotted sunfish 168151 1,762 14,669 0.1072 NAS Y Y
Lepomis macrochirus Bluegill 168141 1,821 10,191 0.1516 NAS Y N
Lepomis marginatus Dollar sunfish 168152 9,943 8,599 0.5362 NAS N Y
Lepomis megalotis Longear sunfish 168153 310 2,139 0.1266 NAS Y Y
Lepomis microlophus Redear sunfish 168154 5,587 5,063 0.5246 NAS Y N
Lepomis miniatus Redspotted sunfish 168157 589 2,914 0.1681 NAS N Y
Lepomis punctatus Spotted sunfish 168155 306 2,275 0.1186 NAS Y Y
Lepomis symmetricus Bantam sunfish 168156 374 458 0.4495 NAS N Y
Lethenteron appendix American brook lamprey 914061 25 924 0.0263 MSU N Y
Lota lota Burbot 164725 442 8,886 0.0474 NAS Y Y
Luxilus albeolus White shiner 163826 518 8,031 0.0606 MSU N N
Luxilus cardinalis Cardinal shiner 163828 254 825 0.2354 MSU N Y
Luxilus cerasinus Crescent shiner 163830 190 386 0.3299 MSU N N
Luxilus chrysocephalus Striped shiner 163832 150 903 0.1425 MSU N Y
Luxilus coccogenis Warpaint shiner 163834 4,907 7,753 0.3876 NAS N Y
Luxilus cornutus Common shiner 163836 269 474 0.362 NAS N Y
Luxilus zonatus Bleeding shiner 163840 4,482 12,384 0.2657 MSU N N
Lythrurus ardens Rosefin shiner 163847 215 410 0.344 MSU N Y
Lythrurus fasciolaris Scarlet shiner 201928 166 4,968 0.0323 MSU N Y
Lythrurus fumeus Ribbon shiner 163853 1,185 3,627 0.2463 MSU N Y
Lythrurus snelsoni Ouachita shiner 163859 165 1,828 0.0828 NAS N Y
Lythrurus umbratilis Redfin shiner 163861 45 111 0.2885 MSU N Y
Macrhybopsis storeriana Silver chub 163870 1,732 10,098 0.1464 MSU N Y
Margariscus margarita Allegheny Pearl Dace 163873 232 10,436 0.0217 NAS N Y
Menidia beryllina Inland silverside 165993 76 1,882 0.0388 MSU N Y
Micropterus cataractae Shoal bass 564610 203 4,350 0.0446 NAS Y Y
Micropterus coosae Redeye bass 168163 17 64 0.2099 MSU Y Y
Micropterus dolomieu Smallmouth bass 550562 91 833 0.0985 NAS Y Y
Micropterus punctulatus Spotted bass 168161 4,035 10,099 0.2855 NAS Y Y
Micropterus salmoides Largemouth bass 168160 1,908 6,343 0.2312 NAS Y Y
Minytrema melanops Spotted sucker 163959 7,089 12,364 0.3644 MSU N Y
Morone americana White perch 167678 1,167 11,600 0.0914 NAS Y N
Morone chrysops White bass 167682 69 3,663 0.0185 NAS Y N
Morone mississippiensis Yellow bass 167683 399 9,191 0.0416 NAS Y Y
Morone saxatilis Striped bass 167680 28 1,657 0.0166 NAS Y Y
Moxostoma anisurum Silver redhorse 163933 53 4,331 0.0121 MSU N Y
Moxostoma breviceps Smallmouth redhorse 163929 1,157 12,953 0.082 NAS N N
Moxostoma carinatum River redhorse 163936 404 5,257 0.0714 NAS N Y
Moxostoma collapsum Notchlip redhorse 201946 245 8,392 0.0284 MSU N Y
Moxostoma congestum Gray redhorse 163931 154 1,388 0.0999 NAS N Y
Moxostoma duquesnii Black redhorse 553274 35 116 0.2318 MSU N Y
Moxostoma erythrurum Golden redhorse 163939 1,498 9,783 0.1328 MSU N Y
Moxostoma macrolepidotum Shorthead redhorse 163928 3,946 12,611 0.2383 NAS N Y
Moxostoma poecilurum Blacktail redhorse 163932 1,517 9,614 0.1363 MSU N Y
Moxostoma rupiscartes Striped jumprock 163946 252 1,176 0.1765 MSU N N
Moxostoma valenciennesi Greater redhorse 163947 168 915 0.1551 NAS N Y
Mugil cephalus Striped mullet 170335 168 4,099 0.0394 MSU N Y
Nocomis biguttatus Hornyhead chub 163395 164 1,857 0.0811 NAS N Y
Nocomis leptocephalus Bluehead chub 163393 1,410 9,375 0.1307 MSU N Y
Nocomis micropogon River chub 163392 1,023 1,971 0.3417 MSU N Y
Notemigonus crysoleucas Golden shiner 163368 1,027 9,186 0.1006 MSU N Y
Notropis amabilis Texas shiner 163410 2,899 25,193 0.1032 NAS N N
Notropis atherinoides Emerald shiner 163412 37 85 0.3033 MSU N Y
Notropis blennius River shiner 163429 1,652 17,354 0.0869 MSU N Y
Notropis boops Bigeye shiner 163430 154 7,945 0.019 MSU N Y
Notropis buccatus Silverjaw minnow 163478 620 5,157 0.1073 MSU N Y
Notropis chiliticus Redlip shiner 163435 2,774 6,427 0.3015 MSU N Y
Notropis cummingsae Dusky shiner 163438 201 419 0.3242 MSU N Y
Notropis girardi Arkansas River shiner 163442 17 1,036 0.0161 NAS N Y
Notropis heterolepis Blacknose shiner 163446 263 8,626 0.0296 MSU N Y
Notropis hudsonius Spottail shiner 163404 871 13,936 0.0588 MSU N Y
Notropis leuciodus Tennessee shiner 163451 239 1,190 0.1672 MSU N Y
Notropis longirostris Longnose shiner 163452 177 684 0.2056 MSU N N
Notropis lutipinnis Yellowfin shiner 163453 88 599 0.1281 MSU N Y
Notropis nubilus Ozark minnow 163456 378 1,116 0.253 NAS N Y
Notropis percobromus Carmine shiner 689522 374 3,771 0.0902 MSU N N
Notropis petersoni Coastal shiner 163460 125 997 0.1114 MSU N N
Notropis photogenis Silver shiner 163461 1,020 7,449 0.1204 MSU N Y
Notropis procne Swallowtail shiner 163407 351 2,873 0.1089 MSU N Y
Notropis rubellus Rosyface shiner 163409 1,212 13,840 0.0805 MSU N Y
Notropis stramineus Sand shiner 163419 4,843 12,834 0.274 MSU N Y
Notropis telescopus Telescope shiner 163470 294 1,891 0.1346 MSU N N
Notropis texanus Weed shiner 163420 359 2,670 0.1185 NAS N Y
Notropis topeka Topeka shiner 163471 27 2,152 0.0124 NAS N Y
Notropis volucellus Mimic shiner 163421 1,081 16,167 0.0627 MSU N Y
Noturus albater Ozark madtom 164006 47 172 0.2146 NAS N N
Noturus exilis Slender madtom 164010 654 1,913 0.2548 NAS N Y
Noturus flavus Stonecat 164013 1,756 15,529 0.1016 NAS N Y
Noturus gyrinus Tadpole madtom 164003 983 20,262 0.0463 NAS N Y
Noturus insignis Margined madtom 164004 917 2,028 0.3114 NAS N Y
Noturus leptacanthus Speckled madtom 164019 298 997 0.2301 MSU N N
Noturus miurus Brindled madtom 164020 322 9,573 0.0325 NAS N Y
Noturus nocturnus Freckled madtom 164005 337 3,546 0.0868 MSU N Y
Oncorhynchus clarkii Cutthroat trout 161983 2,907 1,945 0.5991 NAS Y Y
Oncorhynchus kisutch Coho salmon 161977 206 503 0.2906 NAS Y Y
Oncorhynchus mykiss Rainbow trout 161989 659 510 0.5637 NAS Y Y
Oncorhynchus tshawytscha Chinook salmon 161980 30 405 0.069 NAS Y Y
Opsopoeodus emiliae Pugnose minnow 163876 192 6,576 0.0284 MSU N Y
Perca flavescens Yellow perch 168469 1,807 18,000 0.0912 NAS Y Y
Percina caprodes Logperch 168472 3,219 14,114 0.1857 MSU N Y
Percina evides Gilt darter 168483 169 3,930 0.0412 NAS N Y
Percina maculata Blackside darter 168488 2,659 11,986 0.1816 NAS N Y
Percina nigrofasciata Blackbanded darter 168490 572 867 0.3975 MSU N Y
Percina peltata Shield darter 168474 191 1,947 0.0893 MSU N Y
Percina phoxocephala Slenderhead darter 168494 685 8,152 0.0775 MSU N Y
Percina roanoka Roanoke darter 168496 179 698 0.2041 MSU N N
Percina sciera Dusky darter 168475 547 5,712 0.0874 MSU N Y
Percopsis omiscomaycus Trout-perch 164409 421 9,802 0.0412 MSU N Y
Petromyzon marinus Sea lamprey 159722 197 5,203 0.0365 NAS N Y
Phenacobius mirabilis Suckermouth minnow 163502 1,960 10,250 0.1605 NAS N Y
Pimephales notatus Bluntnose minnow 163516 10,143 12,332 0.4513 MSU N Y
Pimephales promelas Fathead minnow 163517 4,873 21,247 0.1866 MSU N N
Pimephales vigilax Bullhead minnow 163518 1,334 10,333 0.1143 MSU N Y
Platygobio gracilis Flathead chub 163882 245 2,867 0.0787 NAS N Y
Polyodon spathula Paddlefish 161088 22 7,511 0.0029 NAS Y Y
Pomoxis annularis White crappie 168166 1,332 14,622 0.0835 NAS Y N
Pomoxis nigromaculatus Black crappie 168167 1,362 16,632 0.0757 NAS Y Y
Prosopium williamsoni Mountain whitefish 162009 476 4,154 0.1028 NAS Y Y
Ptychocheilus grandis Sacramento pikeminnow 163524 26 66 0.2826 NAS N N
Ptychocheilus oregonensis Northern pikeminnow 163523 117 2,315 0.0481 NAS Y N
Pylodictis olivaris Flathead catfish 164029 1,238 11,045 0.1008 NAS Y Y
Rhinichthys atratulus Blacknose dace 163382 5,872 15,446 0.2754 MSU N Y
Rhinichthys cataractae Longnose dace 163384 4,136 14,805 0.2184 MSU N Y
Rhinichthys obtusus Western blacknose dace 689949 3,146 9,545 0.2479 MSU N Y
Rhinichthys osculus Speckled dace 163387 654 1,627 0.2867 MSU N Y
Richardsonius balteatus Redside shiner 163528 310 3,133 0.09 MSU N Y
Salmo salar Atlantic salmon 161996 223 3,753 0.0561 NAS N Y
Salvelinus confluentus Bull trout 162004 511 1,887 0.2131 NAS Y Y
Salvelinus fontinalis Brook trout 162003 3,019 7,630 0.2835 NAS Y Y
Sander canadensis Sauger 650171 451 9,942 0.0434 NAS Y Y
Sander vitreus Walleye 650173 795 13,325 0.0563 NAS Y Y
Scaphirhynchus platorynchus Shovelnose sturgeon 161082 50 4,286 0.0115 NAS Y Y
Semotilus atromaculatus Creek chub 163376 13,586 13,198 0.5072 MSU N Y
Semotilus corporalis Fallfish 163375 1,512 6,137 0.1977 NAS N Y
Thoburnia rhothoeca Torrent sucker 553276 86 358 0.1937 MSU N Y
Umbra limi Central mudminnow 162153 2,088 7,187 0.2251 NAS N Y
Umbra pygmaea Eastern mudminnow 162148 412 1,639 0.2009 MSU N Y
Table 2.    List of fluvial fish species analyzed.
The conterminous United States with color-coded polygons depicting an example of native compared to introduced species ranges
Figure 3.

Example U.S. Geological Survey Nonindigenous Aquatic Species range map depicting native compared to introduced eight-digit hydrologic unit code (HUC8) origin status for Salvelinus fontinalis (Mitchill, 1814) (brook trout).

For an additional 122 species lacking detailed native and introduced range maps, HUC8 range maps were developed using all known occurrences (noted as Michigan State University, or MSU, in table 2). These range maps were derived from four data sources: point occurrences from the Aquatic GAP fish database (previously described), point occurrences from the IchthyMaps dataset (Frimpong and others, 2015), point occurrences from Global Biodiversity Information Facility (2020), and HUC8 level range maps developed by NatureServe (NatureServe, 2020) (fig. 4). For Global Biodiversity Information Facility, or GBIF, data, the following data filters were applied to ensure accuracy of both species identification and observation locations: (1) observations were limited to the United States only, (2) observation coordinate uncertainty was less than or equal to 1,000 meters, and (3) observations were made by collectors from Federal, State, or academic institutions (observations based on citizen science were excluded). While these range maps do not include native compared to introduced range status, they do provide geographic boundaries from which to constrain model input/output data and are based on a large set of known occurrences and ranges.

Five map tiles of the eastern United States with polygons highlighting known fish occurrences from four sources, one tile represents the combination of the other four
Figure 4.

Example range map development for Umbra pygmaea (DeKay, 1842) (eastern mudminnow) using all known occurrences from A, the Aquatic Gap Analysis Project fish database, B, IchthyMaps, C, Global Biodiversity Information Facility, and D, NatureServe to produce E, a final range map used to constrain model input/output for this species.

Species Distribution Modeling with Boosted Regression Trees

Previous analyses by the USGS Aquatic GAP tested multiple species distribution modeling techniques for fluvial fishes, including logistic regression, BRT, classification and regression trees, and MaxEnt (A. Ostroff, U.S. Geological Survey, written commun., 2013). Based on results of these analyses and feedback from Aquatic GAP steering committee members, the BRT approach was selected for Aquatic GAP species distribution modeling efforts. BRT differs significantly from regression-based approaches by adaptively combining simple tree models using a boosting technique to improve predictive ability (Elith and others, 2008). Boosting is a sequentially stagewise procedure to link simple trees by emphasizing observations underrepresented in simpler models. Like other machine learning models, regularization is required for BRT to avoid overfitting in the training dataset. Three regularization parameters are commonly used in BRT: learning rate, tree complexity, and bag fraction. Learning rate is used to shrink the contribution of each individual tree in BRT. Tree complexity, ranging from 1 to 5, determines the number of nodes in each tree in the model. If the tree complexity equals 1, interaction effects are not analyzed in the BRT model. If the tree complexity equals 2, BRT models are fit with up to two-way interactions and so on (Elith and others, 2008). Finally, bag fraction is defined as the proportion of training data that are selected in each iteration, which introduces randomness into boosting. A preliminary study evaluated different value combinations of learning rate, tree complexity, and bag fraction (Cooper and others, 2019). Based on results of Cooper and others (2019), an initial learning rate of 0.05 for species with many occurrences (greater than 100) and a learning rate of 0.01 for species with few occurrences (less than or equal to 100) was used in this study. A tree complexity of 5 and bag fraction of 0.75 were used in each model. To ensure a minimum of 1,000 trees in the final model, the learning rate was divided by 2 in each iteration with the maximum number of trees capped at 10,000 to avoid overfitting. All the models were developed using the dismo package (Species Distribution Modeling Version 1.3-3R; Hijmans and others, 2020).

BRT models were evaluated using a tenfold cross-validation procedure in which the entire dataset was split into 10 nonoverlapping subsets and the BRT model was run 10 times. Each time, one of the 10 subsets was used as a test set while the remaining formed a training set for model fitting. The predicted values of all 10 test sets were then used to calculate diagnostic metrics for evaluating the BRT models.

Model Evaluation

Five diagnostic metrics were used to evaluate model performance in this study, including four fundamental measures often used in SDM evaluation: proportion of deviance explained (Elith and others, 2008), sensitivity, specificity, AUC, and True Skill Statistic (TSS) (Allouche and others, 2006). AUC is a threshold-independent metric that avoids the subjective selection of presence/absence cutoff values to develop a confusion matrix for model evaluation. AUC values range between 0 and 1, with larger values indicating better predictive ability. An AUC of 0.5 means that the prediction capability of the model is no better than random, and values greater than 0.7 are considered adequate for modeling species distributions (Swets, 1988). TSS is equal to the sum of sensitivity and specificity minus 1 (Fielding and Bell, 1997). In this study, predicted presences and absences for each fish species were separated by a threshold value that equals the observed prevalence of each sample species, where prevalence represents the proportion of sites in which the species was recorded present.

Predictor Relative Importance

The relative importance (or percent contribution) of each predictor variable was calculated for each species as follows:

R I i = 100 % × 1 M ∑ m = 1 M I i 2 T m
(1)
where

R I i

stands for the relative importance of the ith predictor variable,

M

is the number of trees, and

I i 2 T m

is the squared improvement of each predictor weighted by the number of times it was chosen as the splitting variable in tree m (Hastie and others, 2009).

The relative importance of each predictor variable was scaled so that the sum was equal to 100 percent (Elith and others, 2008). Relative importance of all predictor variables in the BRT model was calculated for each species, providing insights into the major natural and anthropogenic factors controlling species distributions.

Results

We modeled the distributions of 271 species out of a set of 298 total fluvial fish species (table 2). For 27 species, lack of occurrences resulted in either the inability to attempt model development due to low number of occurrences (less than 10) or an inability of the BRT approach to create a stable model due to lack of model convergence (see table 1.1 in app. 1). For modeled species, the range in number of presences, number of absences, and prevalence was large (figs. 5 and 6). In total, 263 species were considered to have low to moderate prevalence (less than 0.5), while 10 species had high prevalence (greater than 0.5). Species prevalence ranged from 0.0021 (Acipenser fulvescens, lake sturgeon) to 0.6335 (Lepomis gibbosus, pumpkinseed), with a mean of all the prevalence values plus or minus (±) standard error of 0.1566 ± 0.0082. The proportion of deviance explained by the BRT model also varied considerably across fish species (table 3; fig. 7), ranging from 0.0562 (Moxostoma congestum, gray redhorse) to 0.7198 (Micropterus cataractae, shoal bass) with a mean of 0.3442 ± 0.0065. The model predictive performance evaluation metrics calculated from tenfold cross validation varied across models (table 3; fig. 7). In total, 270 of 271 models were considered acceptable based on AUC values (greater than or equal to 0.7).

Table 3.    

Proportion of boosted regression tree model deviance and performance statistics for fluvial fish species distribution models.

[ITIS TSN, Integrated Taxonomic Information System taxonomic serial number; dev exp, deviance explained; AUC, area under the receiver operating characteristic curve; TSS, True Skill Statistic]
Scientific name ITIS TSN Dev exp AUC Sensitivity Specificity TSS
Acantharchus pomotis 168095 0.273455 0.882752 0.311644 0.975391 0.287035
Acipenser fulvescens 161071 0.380867 0.983065 0.083333 0.999321 0.082654
Alosa aestivalis 161703 0.242115 0.895504 0.059908 0.997401 0.057309
Alosa chrysochloris 161707 0.545646 0.969485 0.193929 0.996873 0.190802
Alosa pseudoharengus 161706 0.267295 0.942352 0.104167 0.998082 0.102249
Alosa sapidissima 161702 0.399099 0.962159 0.111413 0.998847 0.11026
Ambloplites ariommus 168099 0.206497 0.808224 0.395238 0.919476 0.314714
Ambloplites cavifrons 168098 0.270639 0.859777 0.243243 0.977143 0.220386
Ambloplites constellatus 168100 0.237221 0.820525 0.756757 0.706897 0.463653
Ambloplites rupestris 168097 0.378368 0.887134 0.68987 0.884575 0.574445
Ameiurus brunneus 164035 0.166562 0.767076 0.297297 0.935172 0.23247
Ameiurus catus 164037 0.321094 0.916765 0.100775 0.995449 0.096224
Ameiurus melas 164039 0.253209 0.84792 0.333595 0.957128 0.290723
Ameiurus natalis 164041 0.263703 0.834591 0.533159 0.894028 0.427187
Ameiurus nebulosus 164043 0.171372 0.813339 0.173433 0.974221 0.147654
Ameiurus platycephalus 164045 0.305727 0.878176 0.459746 0.949711 0.409457
Amia calva 161104 0.302421 0.893271 0.214386 0.984227 0.198614
Anguilla rostrata 161127 0.579605 0.966524 0.550324 0.986502 0.536826
Apeltes quadracus 166397 0.196631 0.759999 0.048276 0.998856 0.047132
Aphredoderus sayanus 164405 0.300667 0.863348 0.524964 0.927667 0.452631
Aplodinotus grunniens 169364 0.464044 0.934777 0.450032 0.978223 0.428255
Atractosteus spatula 201897 0.327291 0.879983 0.147651 0.991957 0.139608
Campostoma anomalum 163508 0.342746 0.866148 0.805279 0.764584 0.569863
Campostoma oligolepis 163509 0.403592 0.899819 0.573357 0.947117 0.520474
Carpiodes carpio 163919 0.459579 0.935917 0.424972 0.979507 0.404479
Carpiodes cyprinus 163917 0.409888 0.9248 0.345358 0.983411 0.328768
Carpiodes velifer 163920 0.43299 0.950289 0.178704 0.996741 0.175445
Catostomus ardens 163899 0.200186 0.815582 0.4 0.937853 0.337853
Catostomus catostomus 163894 0.364336 0.915454 0.328879 0.981898 0.310777
Catostomus clarkii 163901 0.120928 0.736508 0.725 0.602941 0.327941
Catostomus commersonii 553273 0.321196 0.856125 0.766613 0.780173 0.546786
Catostomus discobolus 163902 0.235354 0.855448 0.237288 0.968921 0.20621
Catostomus insignis 163905 0.342594 0.872527 0.794521 0.805556 0.600076
Catostomus latipinnis 163906 0.389564 0.918205 0.52381 0.965087 0.488897
Catostomus macrocheilus 163896 0.517104 0.947363 0.487936 0.983092 0.471027
Catostomus occidentalis 163908 0.371764 0.87913 0.769231 0.850746 0.619977
Catostomus platyrhynchus 163909 0.29378 0.878014 0.395503 0.954772 0.350275
Catostomus tahoensis 163914 0.231306 0.843252 0.534091 0.9163 0.45039
Centrarchus macropterus 168102 0.233491 0.843705 0.222772 0.977273 0.200045
Chrosomus eos 913993 0.275081 0.864422 0.35894 0.961485 0.320425
Chrosomus erythrogaster 913994 0.378826 0.903724 0.476281 0.962671 0.438952
Chrosomus neogaeus 913995 0.281555 0.882181 0.265472 0.983723 0.249196
Chrosomus oreas 913996 0.483888 0.95252 0.444444 0.987313 0.431758
Clinostomus elongatus 163373 0.378014 0.917223 0.332413 0.983649 0.316062
Clinostomus funduloides 163371 0.367426 0.890425 0.535004 0.943207 0.478211
Cottus aleuticus 167230 0.268905 0.867042 0.458333 0.926966 0.3853
Cottus bairdii 167237 0.341741 0.882146 0.530996 0.941915 0.47291
Cottus beldingii 167238 0.278707 0.864263 0.391473 0.958463 0.349936
Cottus carolinae 167239 0.461566 0.922751 0.685845 0.939123 0.624968
Cottus cognatus 167232 0.336628 0.888504 0.380466 0.968282 0.348749
Cottus confusus 167240 0.327649 0.913739 0.332344 0.982614 0.314958
Cottus hypselurus 167263 0.132454 0.771616 0.257143 0.962617 0.21976
Cottus rhotheus 167252 0.360038 0.885416 0.592262 0.931083 0.523345
Couesius plumbeus 163535 0.329156 0.911532 0.233333 0.987509 0.220842
Culaea inconstans 166399 0.367101 0.899351 0.467277 0.960563 0.42784
Cycleptus elongatus 163953 0.564445 0.978974 0.277344 0.99865 0.275994
Cyprinella analostana 163766 0.3326 0.891468 0.37851 0.966857 0.345367
Cyprinella camura 163776 0.396511 0.895493 0.545455 0.946378 0.491833
Cyprinella galactura 163782 0.355755 0.888902 0.504488 0.94702 0.451508
Cyprinella lutrensis 163792 0.474995 0.917167 0.824633 0.856017 0.68065
Cyprinella spiloptera 163803 0.441616 0.911478 0.630769 0.932669 0.563438
Cyprinella venusta 163809 0.300041 0.856279 0.603109 0.887436 0.490545
Cyprinella whipplei 163811 0.364136 0.914407 0.272167 0.98523 0.257397
Dorosoma cepedianum 161737 0.399987 0.908105 0.449346 0.96543 0.414776
Dorosoma petenense 161738 0.531808 0.951579 0.642458 0.968796 0.611255
Elassoma zonatum 168171 0.171764 0.834891 0.169935 0.976766 0.1467
Enneacanthus chaetodon 168108 0.333239 0.776934 0.175 0.997194 0.172194
Enneacanthus gloriosus 168113 0.35339 0.903757 0.395797 0.970793 0.36659
Enneacanthus obesus 168117 0.174368 0.858816 0.120357 0.990716 0.111073
Entosphenus tridentatus 159699 0.234519 0.871133 0.236111 0.974087 0.210198
Erimystax dissimilis 163821 0.4782 0.953587 0.206074 0.998033 0.204107
Erimystax x-punctatus 163824 0.552337 0.962424 0.319249 0.997421 0.31667
Erimyzon oblongus 163924 0.374934 0.910549 0.365091 0.978274 0.343365
Erimyzon sucetta 163922 0.436181 0.917359 0.140351 0.99613 0.136481
Esox americanus 162140 0.298854 0.871009 0.386146 0.957976 0.344122
Esox lucius 162139 0.348532 0.890135 0.463292 0.952175 0.415468
Esox niger 162143 0.269458 0.868757 0.251335 0.975325 0.22666
Etheostoma blennioides 168375 0.350333 0.872518 0.71538 0.857098 0.572478
Etheostoma caeruleum 168378 0.375941 0.884101 0.71934 0.871946 0.591286
Etheostoma camurum 168379 0.423671 0.944408 0.195021 0.99609 0.191111
Etheostoma cragini 168386 0.451713 0.925967 0.610577 0.964992 0.575569
Etheostoma exile 168393 0.218983 0.853443 0.145529 0.983955 0.129484
Etheostoma flabellare 168394 0.331533 0.865184 0.678233 0.86311 0.541343
Etheostoma fusiforme 168358 0.154425 0.838969 0.0887 0.989461 0.078161
Etheostoma gracile 168366 0.253753 0.873763 0.299639 0.972557 0.272196
Etheostoma kennicotti 168405 0.306356 0.868208 0.438776 0.962056 0.400832
Etheostoma lynceum 168456 0.228591 0.828477 0.322368 0.949907 0.272276
Etheostoma microperca 168411 0.284231 0.915993 0.093805 0.99721 0.091016
Etheostoma nigrum 168369 0.365097 0.877913 0.734528 0.858158 0.592686
Etheostoma olmstedi 168360 0.348808 0.878421 0.62068 0.907206 0.527886
Etheostoma punctulatum 168425 0.241885 0.819787 0.614286 0.835979 0.450265
Etheostoma radiosum 168426 0.442236 0.904717 0.775 0.90184 0.67684
Etheostoma rufilineatum 168428 0.308594 0.87293 0.463816 0.948875 0.412691
Etheostoma simoterum 168431 0.344841 0.888377 0.489933 0.945896 0.435828
Etheostoma spectabile 168368 0.354747 0.878778 0.65017 0.892431 0.542601
Etheostoma stigmaeum 168437 0.223362 0.831639 0.291429 0.960902 0.25233
Etheostoma swaini 168439 0.168828 0.797301 0.348168 0.93002 0.278188
Etheostoma variatum 168446 0.430444 0.948479 0.363636 0.989897 0.353533
Etheostoma whipplei 168448 0.278742 0.868433 0.423611 0.958088 0.381699
Etheostoma zonale 168449 0.369557 0.890777 0.544737 0.940565 0.485301
Exoglossum maxillingua 163356 0.350654 0.882804 0.584381 0.919952 0.504333
Fundulus catenatus 165660 0.395186 0.909642 0.554591 0.954455 0.509046
Fundulus diaphanus 165646 0.27785 0.883571 0.132161 0.992606 0.124767
Fundulus kansae 165654 0.433229 0.93005 0.484848 0.975882 0.460731
Fundulus notatus 165663 0.278731 0.857791 0.421846 0.943842 0.365689
Fundulus olivaceus 165655 0.325018 0.863321 0.646739 0.886878 0.533617
Fundulus seminolis 165667 0.236318 0.825568 0.555556 0.9 0.455556
Fundulus zebrinus 165658 0.281646 0.870353 0.322064 0.960104 0.282168
Gambusia affinis 165878 0.377076 0.893437 0.553506 0.942045 0.495551
Gila robusta 163558 0.466019 0.94813 0.511111 0.980477 0.491588
Hesperoleucus symmetricus 163565 0.14175 0.823042 0.4 0.918919 0.318919
Hiodon alosoides 161905 0.588814 0.974619 0.337079 0.996182 0.33326
Hiodon tergisus 161906 0.44664 0.965409 0.138826 0.998631 0.137458
Hybognathus argyritis 163362 0.238133 0.880773 0.188356 0.986748 0.175104
Hybognathus hankinsoni 163363 0.246744 0.848015 0.366331 0.951328 0.31766
Hybognathus nuchalis 163360 0.321884 0.914528 0.181481 0.992068 0.17355
Hybognathus placitus 163361 0.439618 0.92743 0.319343 0.987544 0.306887
Hybognathus regius 163359 0.220832 0.847169 0.109489 0.987353 0.096842
Hybopsis amblops 163476 0.371916 0.928704 0.31295 0.986764 0.299714
Hybopsis amnis 201917 0.08879 0.745147 0.038462 0.99636 0.034822
Hybopsis dorsalis 689231 0.383778 0.892119 0.63499 0.916969 0.551959
Hybopsis winchelli 201918 0.175267 0.800587 0.364964 0.929323 0.294287
Hypentelium etowanum 163950 0.290853 0.845199 0.72807 0.809211 0.537281
Hypentelium nigricans 163949 0.388501 0.888279 0.732438 0.863905 0.596343
Hypentelium roanokense 163951 0.248472 0.824097 0.630137 0.849057 0.479194
Ichthyomyzon castaneus 159725 0.303727 0.900949 0.204583 0.98967 0.194253
Ichthyomyzon fossor 159726 0.161049 0.839015 0.074919 0.993158 0.068077
Ichthyomyzon gagei 159727 0.234432 0.851544 0.251716 0.968947 0.220664
Ichthyomyzon greeleyi 159728 0.45405 0.947214 0.405172 0.987199 0.392371
Ictalurus furcatus 163997 0.552636 0.973566 0.351955 0.996694 0.34865
Ictalurus punctatus 163998 0.458865 0.927934 0.557011 0.964995 0.522006
Ictiobus bubalus 163955 0.475484 0.945477 0.388703 0.986591 0.375294
Ictiobus cyprinellus 163956 0.305864 0.899528 0.198404 0.985027 0.183432
Ictiobus niger 163957 0.401452 0.944709 0.20342 0.993299 0.196719
Labidesthes sicculus 166016 0.287671 0.869851 0.309819 0.967004 0.276823
Lampetra aepyptera 159705 0.278189 0.875435 0.29381 0.971875 0.265685
Lampetra richardsoni 159707 0.131325 0.829278 0.120301 0.979381 0.099682
Lepisosteus oculatus 161095 0.367696 0.914641 0.308318 0.980814 0.289132
Lepisosteus osseus 161094 0.370234 0.921974 0.266767 0.988237 0.255004
Lepisosteus platostomus 161096 0.344437 0.913221 0.269652 0.984032 0.253684
Lepisosteus platyrhincus 161098 0.415719 0.915319 0.693182 0.927184 0.620366
Lepomis auritus 168131 0.518801 0.938533 0.679472 0.9529 0.632372
Lepomis cyanellus 168132 0.229812 0.803475 0.806313 0.633304 0.439617
Lepomis gibbosus 168144 0.199398 0.80448 0.395651 0.915091 0.310742
Lepomis humilis 168151 0.310882 0.87573 0.425221 0.951312 0.376533
Lepomis macrochirus 168141 0.230955 0.804429 0.74223 0.72647 0.4687
Lepomis marginatus 168152 0.131248 0.765104 0.270833 0.927968 0.198802
Lepomis megalotis 168153 0.363044 0.872829 0.788885 0.79289 0.581775
Lepomis microlophus 168154 0.356235 0.877753 0.501742 0.940575 0.442317
Lepomis miniatus 168157 0.231595 0.841551 0.353448 0.949525 0.302974
Lepomis punctatus 168155 0.339714 0.866976 0.742268 0.806306 0.548574
Lepomis symmetricus 168156 0.079916 0.742381 0.085271 0.982927 0.068198
Lethenteron appendix 914061 0.264976 0.869286 0.221477 0.981845 0.203322
Lota lota 164725 0.386684 0.917286 0.310239 0.984138 0.294377
Luxilus albeolus 163826 0.357005 0.885674 0.605341 0.932615 0.537956
Luxilus cardinalis 163828 0.536089 0.941192 0.779343 0.933884 0.713227
Luxilus cerasinus 163830 0.391633 0.915836 0.531818 0.960384 0.492202
Luxilus chrysocephalus 163832 0.383179 0.88682 0.724564 0.871576 0.59614
Luxilus coccogenis 163834 0.324137 0.864438 0.66358 0.871122 0.534702
Luxilus cornutus 163836 0.334214 0.870555 0.580661 0.910411 0.491072
Luxilus zonatus 163840 0.630723 0.959716 0.834025 0.963542 0.797567
Lythrurus ardens 163847 0.381091 0.904683 0.238095 0.991104 0.2292
Lythrurus fasciolaris 201928 0.314831 0.865969 0.564229 0.91617 0.480398
Lythrurus fumeus 163853 0.178327 0.790839 0.22449 0.957474 0.181964
Lythrurus snelsoni 163859 0.357568 0.893694 0.62963 0.892157 0.521786
Lythrurus umbratilis 163861 0.364313 0.901866 0.475762 0.959964 0.435726
Macrhybopsis storeriana 163870 0.397959 0.944315 0.148618 0.996463 0.145081
Margariscus margarita 163873 0.11199 0.785377 0.127946 0.977122 0.105068
Menidia beryllina 165993 0.430607 0.930711 0.293286 0.99072 0.284006
Micropterus cataractae 564610 0.719817 0.976103 0.761905 0.983333 0.745238
Micropterus coosae 168163 0.419146 0.929699 0.474359 0.977865 0.452224
Micropterus dolomieu 550562 0.406161 0.896394 0.665835 0.91067 0.576505
Micropterus punctulatus 168161 0.284807 0.848611 0.524554 0.91048 0.435034
Micropterus salmoides 168160 0.183469 0.779072 0.572891 0.811039 0.383929
Minytrema melanops 163959 0.244046 0.847497 0.270626 0.966432 0.237058
Morone americana 167678 0.241679 0.881963 0.131443 0.994617 0.126061
Morone chrysops 167682 0.484609 0.950607 0.281488 0.992149 0.273637
Morone mississippiensis 167683 0.253758 0.908117 0.092308 0.993289 0.085596
Morone saxatilis 167680 0.306549 0.948822 0.105405 0.996512 0.101918
Moxostoma anisurum 163933 0.488505 0.941345 0.421702 0.985884 0.407586
Moxostoma breviceps 163929 0.629815 0.971759 0.529235 0.989788 0.519023
Moxostoma carinatum 163936 0.40987 0.940826 0.184188 0.995592 0.179779
Moxostoma collapsum 201946 0.218316 0.845831 0.292754 0.955723 0.248476
Moxostoma congestum 163931 0.056148 0.667734 0.404255 0.846154 0.250409
Moxostoma duquesnii 553274 0.349293 0.884616 0.432018 0.957324 0.389342
Moxostoma erythrurum 163939 0.375291 0.887747 0.580737 0.92266 0.503397
Moxostoma macrolepidotum 163928 0.507037 0.941914 0.548833 0.971986 0.520819
Moxostoma poecilurum 163932 0.244767 0.830327 0.432763 0.926398 0.359161
Moxostoma rupiscartes 163946 0.477555 0.944223 0.59919 0.976077 0.575267
Moxostoma valenciennesi 163947 0.333957 0.902576 0.207381 0.986479 0.193861
Mugil cephalus 170335 0.473984 0.946311 0.42284 0.98409 0.406929
Nocomis biguttatus 163395 0.428904 0.921717 0.507389 0.96761 0.474999
Nocomis leptocephalus 163393 0.52548 0.936905 0.76652 0.917698 0.684218
Nocomis micropogon 163392 0.410779 0.916047 0.44986 0.973422 0.423282
Notemigonus crysoleucas 163368 0.148159 0.77747 0.220037 0.952815 0.172852
Notropis amabilis 163410 0.349889 0.881717 0.690476 0.9 0.590476
Notropis atherinoides 163412 0.407726 0.91198 0.394856 0.977899 0.372756
Notropis blennius 163429 0.469311 0.940281 0.16771 0.99726 0.16497
Notropis boops 163430 0.446315 0.933524 0.456093 0.976185 0.432279
Notropis buccatus 163478 0.268151 0.837997 0.57448 0.878176 0.452656
Notropis chiliticus 163435 0.45368 0.913036 0.708155 0.906977 0.615131
Notropis cummingsae 163438 0.427514 0.921365 0.468421 0.972715 0.441136
Notropis girardi 689231 0.583401 0.98819 0.571429 0.999024 0.570453
Notropis heterolepis 163442 0.344755 0.921033 0.157703 0.993877 0.151581
Notropis hudsonius 163446 0.337654 0.903722 0.266983 0.984114 0.251097
Notropis leuciodus 163404 0.367799 0.894715 0.529586 0.945005 0.47459
Notropis longirostris 163451 0.223025 0.821563 0.465385 0.906822 0.372207
Notropis lutipinnis 163452 0.480297 0.938344 0.601695 0.970123 0.571818
Notropis nubilus 163453 0.453838 0.920279 0.66951 0.937561 0.607071
Notropis percobromus 163456 0.325086 0.890405 0.359335 0.972346 0.331681
Notropis petersoni 163460 0.206225 0.824851 0.334694 0.950969 0.285663
Notropis photogenis 163461 0.39533 0.910658 0.462457 0.969155 0.431612
Notropis procne 163407 0.372988 0.909449 0.414097 0.972867 0.386964
Notropis rubellus 163409 0.358354 0.899983 0.351249 0.977115 0.328364
Notropis stramineus 163419 0.395401 0.896293 0.628526 0.919472 0.547998
Notropis telescopus 163470 0.315882 0.881918 0.449064 0.954225 0.40329
Notropis texanus 163420 0.477143 0.93912 0.49359 0.978794 0.472384
Notropis topeka 163471 0.28941 0.894568 0.15 0.997057 0.147057
Notropis volucellus 163421 0.304347 0.887732 0.24728 0.982668 0.229948
Noturus albater 164006 0.170003 0.779193 0.414286 0.879195 0.29348
Noturus exilis 164010 0.399989 0.901661 0.650852 0.931805 0.582657
Noturus flavus 164013 0.31892 0.887501 0.353198 0.97155 0.324748
Noturus gyrinus 164003 0.298364 0.893476 0.203385 0.986463 0.189849
Noturus insignis 164004 0.297257 0.852559 0.617958 0.88115 0.499108
Noturus leptacanthus 164019 0.303465 0.864779 0.513453 0.918728 0.432181
Noturus miurus 164020 0.301551 0.895617 0.181458 0.989227 0.170685
Noturus nocturnus 164005 0.27884 0.873358 0.329562 0.967254 0.296816
Oncorhynchus clarkii 161983 0.378698 0.884544 0.847158 0.748886 0.596044
Oncorhynchus kisutch 161977 0.382641 0.88724 0.675676 0.931111 0.606787
Oncorhynchus mykiss 161989 0.257544 0.829257 0.809524 0.723562 0.533086
Oncorhynchus tshawytscha 161980 0.251126 0.855556 0.35 0.976 0.326
Opsopoeodus emiliae 163876 0.281799 0.899119 0.119841 0.992556 0.112398
Perca flavescens 168469 0.284847 0.863506 0.292748 0.968166 0.260914
Percina caprodes 168472 0.321559 0.874191 0.488583 0.939851 0.428434
Percina evides 168483 0.501329 0.961432 0.348894 0.992687 0.341581
Percina maculata 168488 0.347941 0.884012 0.508547 0.940377 0.448924
Percina nigrofasciata 168490 0.412658 0.897335 0.735385 0.880862 0.616246
Percina peltata 168474 0.363216 0.912057 0.39267 0.976651 0.369322
Percina phoxocephala 168494 0.470636 0.942591 0.399734 0.988413 0.388147
Percina roanoka 168496 0.361015 0.898049 0.580913 0.938679 0.519592
Percina sciera 168475 0.335449 0.898903 0.325653 0.975187 0.300839
Percopsis omiscomaycus 164409 0.338242 0.911788 0.238532 0.987773 0.226306
Petromyzon marinus 159722 0.288921 0.905082 0.203704 0.988506 0.192209
Phenacobius mirabilis 163502 0.342045 0.891119 0.476966 0.954545 0.431511
Pimephales notatus 163516 0.472587 0.917364 0.804217 0.873249 0.677466
Pimephales promelas 163517 0.379183 0.896154 0.520965 0.947253 0.468217
Pimephales vigilax 163518 0.496734 0.944375 0.503537 0.979266 0.482803
Platygobio gracilis 163882 0.498321 0.947296 0.45977 0.98319 0.44296
Polyodon spathula 161088 0.248879 0.917067 0.048544 0.999031 0.047575
Pomoxis annularis 168166 0.245571 0.855397 0.253546 0.97243 0.225977
Pomoxis nigromaculatus 168167 0.247369 0.857795 0.232049 0.974719 0.206768
Prosopium williamsoni 162009 0.345543 0.900391 0.380902 0.969268 0.350171
Ptychocheilus grandis 163524 0.291792 0.86014 0.548387 0.852459 0.400846
Ptychocheilus oregonensis 163523 0.44812 0.959454 0.362007 0.992569 0.354576
Pylodictis olivaris 164029 0.455277 0.936639 0.417552 0.981831 0.399383
Rhinichthys atratulus 163382 0.402116 0.899928 0.631613 0.92721 0.558823
Rhinichthys cataractae 163384 0.327922 0.874088 0.51829 0.931649 0.449939
Rhinichthys obtusus 689949 0.429729 0.912374 0.620787 0.939394 0.560181
Rhinichthys osculus 163387 0.37346 0.88653 0.644156 0.895433 0.539589
Richardsonius balteatus 163528 0.358293 0.912851 0.348675 0.97799 0.326665
Salmo salar 161996 0.265759 0.87731 0.25 0.977568 0.227568
Salvelinus confluentus 162004 0.448997 0.923728 0.645706 0.948454 0.594159
Salvelinus fontinalis 162003 0.31771 0.859587 0.580209 0.889417 0.469626
Sander canadensis 650171 0.540302 0.965833 0.396 0.994145 0.390145
Sander vitreus 650173 0.47434 0.945396 0.376731 0.990662 0.367393
Scaphirhynchus platorynchus 161082 0.46423 0.970359 0.149007 0.998761 0.147767
Semotilus atromaculatus 163376 0.40266 0.891953 0.807999 0.806592 0.614591
Semotilus corporalis 163375 0.281146 0.85258 0.49385 0.921525 0.415375
Thoburnia rhothoeca 553276 0.383496 0.912758 0.596491 0.945455 0.541946
Umbra limi 162153 0.447939 0.918557 0.631502 0.944385 0.575887
Umbra pygmaea 162148 0.407484 0.909618 0.587189 0.944929 0.532118
Table 3.    Proportion of boosted regression tree model deviance and performance statistics for fluvial fish species distribution models.
Two boxplots with points representing count of samples and a box highlighting interquartile range. Boxplots separate samples by presence and absence
Figure 5.

Boxplots of presences and absences for the 271 fish species modeled. The left boxplot represents the distribution of presences of the 271 fish species, and the right boxplot represents the distribution of absences of the 271 fish species.

Histogram showing frequency of modeled fish species on y-axis for prevalence binned at 0.05 intervals on the x-axis
Figure 6.

Histogram of prevalence for the 271 fish species modeled.

five boxplots showing distribution of model evaluation metric values as a proportion on y-axis
Figure 7.

Boxplots of proportion of model deviance explained. Dev_exp, deviance explained; AUC, area under the receiver operating curve; TSS, True Skill Statistic.

The contributions of the predictor variables varied across species; however, network catchment area was consistently the most influential predictor, and overall, natural variables tended to have the greatest influence across species (fig. 8). The top three natural predictors, listed here with their variable names in order of mean relative importance, were network catchment area (N_areasqkm, 14.88 percent), local catchment mean annual air temperature (L_temp, 9.12 percent), and local catchment maximum elevation (L_maxelev, 6.70 percent). The top three anthropogenic predictors based on mean relative importance were downstream main stem dam density (DMD, 5.59 percent), distance to downstream main stem dam (DM2D_fishtail, 4.85 percent), and network catchment pasture and hay (N_nlcd82, 4.03 percent). There were seven predictors whose mean relative importance was less than 3 percent. These included upstream network dam density, network catchment mine density, degree of regulation, network catchment point source pollution density, network catchment human population density, network catchment urban land use, and stream network road crossing density. While average relative importance for these variables was low, influence of these variables was occasionally very high (greater than 20 percent) for certain species. These predictors could be reassessed for future modeling efforts, potentially dropping these predictors for some species or regions. Among climate-based predictors, mean annual air temperature played an important role in BRT models (relative importance greater than 10 percent) for 87 of 271 species modeled, while precipitation was less important with 37 of 271 species modeled meeting this cutoff. The influences of these climate variables pointed to 61 climate-sensitive fish species (having a sum relative importance of mean annual air temperature and precipitation greater than 20 percent) (table 4). Further, 40 fish species were responsive to anthropogenic stressors (having a sum relative importance of all anthropogenic variables greater than 50 percent) (table 5). The summaries in this section are based on 2 climate predictor variables and 13 anthropogenic predictor variables used to develop SDMs for each species.

Twenty-two boxplots each showing distribution of relative predictor contributions to fish distribution models for individual predictor variables
Figure 8.

Boxplots of relative importance of the predictor variables for fluvial fish species presence, absence, and prevalence. See table 1 for predictor variable explanations. EPA, Environmental Protection Agency.

Table 4.    

Fluvial fish species considered sensitive to climate influences in the conterminous United States.

[L_temp represents the relative importance of mean annual air temperature in percent, and N_precip represents the relative importance of mean annual precipitation in percent. Species with the sum of temperature and precipitation (sum) with variable importance greater than 20 percent are considered sensitive. ITIS TSN, Integrated Taxonomic Information System taxonomic serial number]
Scientific name ITIS TSN L_temp N_precip Sum
Erimyzon sucetta 163922 60.70 4.26 64.96
Lepisosteus platyrhincus 161098 55.17 0.60 55.78
Lepomis auritus 168131 43.63 1.91 45.54
Gambusia affinis 165878 29.69 12.19 41.88
Culaea inconstans 166399 14.36 25.39 39.75
Lythrurus snelsoni 163859 32.51 2.56 35.08
Pimephales vigilax 163518 16.48 16.28 32.76
Campostoma oligolepis 163509 22.21 10.01 32.22
Cyprinella lutrensis 163792 11.71 19.82 31.52
Umbra limi 162153 5.59 25.47 31.07
Notropis texanus 163420 23.87 6.98 30.85
Erimyzon oblongus 163924 22.84 5.81 28.64
Rhinichthys obtusus 689949 11.76 16.38 28.15
Esox lucius 162139 11.78 16.28 28.06
Phenacobius mirabilis 163502 13.05 14.62 27.66
Notropis heterolepis 163446 18.05 9.53 27.59
Micropterus coosae 168163 15.60 11.97 27.57
Notropis boops 163430 18.00 9.36 27.36
Enneacanthus gloriosus 168113 24.02 3.13 27.15
Percina nigrofasciata 168490 12.70 14.42 27.12
Etheostoma cragini 168386 24.40 2.62 27.03
Lepisosteus oculatus 161095 23.65 3.24 26.89
Oncorhynchus clarkii 161983 16.84 10.05 26.88