Geology topics

James M. Long

Publications and source records attributed to James M. Long.

At least 19 recordsLinked to original sources

USGS2026

Variation in diet and lipid content of age-0 sturgeon (Scaphirhynchus sp.) in the lower Missouri River basin

Shovelnose sturgeon ( Scaphirhynchus platorynchus ) and related endangered pallid sturgeon ( S. albus ) are species of interest in the highly modified Missouri River. Scaphirhynchus sturgeon require long distances of riverine habitat for the development of drifting free embryos along with suitable foraging habitat during the subsequent transition to exogenous feeding. Working with specimens collected by the US Army Corps of Engineers and Nebraska Game and Parks Commission, we examined diet composition of age-0 (<12 cm) sturgeon at four reaches in the lower Missouri River to examine the potential role of prey acquisition at this vulnerable life stage. In general, Ephemeroptera were more represented at reaches further upstream in the lower Missouri River, whereas Diptera larvae were the dominant prey item in reaches downstream. Body condition, as measured by total lipid content and length‒weight regressions, exhibited spatial differences in 2016 but not in 2017. Even with differences in prey frequencies and numbers consumed, percent consumption regardless of prey type remained consistent among reaches within years, but was overall higher in 2016 when river discharge was greater. Although temporal and spatial differences were observed in condition, comparisons using previous data from 2014 and 2015 suggest that these condition results were not driven by the longitudinal variability in prey composition as the reaches below Kansas city yielded relatively high and low lipid values despite the limited consumption of ephemeropteran prey relative to upstream reaches. Although it is unknown if any of the observed differences affected survival, our results, coupled with previous work, suggest that age-0 sturgeon can opportunistically forage in the lower Missouri River.

Missouri River↗

USGS2025

Summary of first daily ring formation in otoliths of freshwater fishes in the continental United States

Daily ring counts in young-of-the-year fishes are important for estimating important vital rates, such as growth, mortality, and timing of hatch. To accurately estimate some of these rates, the timing of the first daily ring must be estimated accurately. Variation in the timing of the first daily ring can be attributed to many factors, including biology of the species and experience of laboratory personnel. The amount of variation and the degree of differences, however, have not been quantified, hindering the utility of daily ring information to provide accurate estimates of spawning and hatching times. We conducted a review of studies for freshwater fishes in the continental United States to quantify variation in daily ring validation studies as it relates to timing of the first ring. We found 40 studies representing 12 orders, 15 families, and 35 species. Most studies investigated rings in the sagittae, although the lapilli and asterisci were also used for a few species. Variation in the timing of the first ring formation was evident, but not consistent among otolith types or groups of fishes. The first daily ring in sagittae varied from 31 d before hatch to 150 d after hatch. First daily ring formation in lapilli was consistent within families but formed before hatch in some families of fish and after hatch in other families. The first daily ring in asterisci were near universally formed after hatch, with the exception of one species of sturgeon (family Acipenseridae). Only three of the nine species where replicate studies existed were found to exhibit consistent first ring formation timing. Such findings suggest that differences among laboratories and personnel may play a larger role than differences among species or populations when inconsistent first ring formation timing results occur. For most species, error surrounding differences in timing formation is about 1 week, except for Salmoniformes, where error was up to a 150-d difference. Incorporating species biology along with uncertainty in temporal estimates based on otolith chronology would aid interpretation of results in field situations.

continental United States↗

USGS2025

The effect of turbidity on foraging by prerostrum juvenile Paddlefish

Objective A previous study evaluating restoration success of Paddlefish Polyodon spathula suggested that excessive turbidity in lakes and rivers may inhibit foraging by juveniles prior to the development of the rostrum. Although a Paddlefish's rostrum, which contains electroreceptors, helps the fish to locate zooplankton prey, the prerostrum stage lacks many of these electroreceptors, potentially affecting foraging in highly turbid waters. To evaluate this hypothesis, we conducted a series of laboratory experiments in small aquaria by varying the level of turbidity measured as Secchi tube depth: >95 (clear tap water), 40, 20, 10, or 5 cm. Methods For each foraging trial, approximately 300 zooplankton were added to the aquaria, followed by three postlarval Paddlefish, which were allowed to feed on the zooplankton for approximately 18 h. After the 18-h period, Paddlefish were removed and dissected and the zooplankton in the gut were counted to quantify foraging success. Results From three experimental trials, we observed statistically significant nonlinear relationships for two trials, which included the largest fish tested. The smallest Paddlefish size-class showed no significant trend in foraging among turbidity treatments. However, the subsequent trials, which contained larger Paddlefish, both showed unimodal responses, with the highest foraging observed at moderate (30–50-cm Secchi tube depth) turbidity levels. Conclusions High turbidity and excessively clear water both appear to affect foraging by juvenile Paddlefish before the rostrum is fully developed, depending on fish size. Understanding this relationship can further influence management and restoration projects directed at this species.

Transaction of the American Fisheries Society↗

USGS2025

Impoundments facilitate upstream invasion and introgression: Case studies of fluvial black basses (Micropterus spp.) in the southeastern USA

Impoundment construction has resulted in the alternation and loss of fluvial habitats, threatening the persistence of many native fishes. Compounding this threat, non-native species stocked into impoundments often invade interconnected fluvial habitats, where they may negatively affect native species. Black basses (genus Micropteru s) are popular sportfishes with divergent ecologies: some taxa are tolerant of impoundments and widely stocked to create fishing opportunities, whereas others are endemic fluvial specialists that are threatened by introgression with non-native congeneric taxa. We investigated whether impoundments facilitate non-native invasion and introgression in two case study systems: Lake Lanier, Georgia, and Lake Tenkiller, Oklahoma. In both case studies, native fluvial taxa inhabited upstream tributaries and a non-native was established within the downstream impoundment. Results from longitudinal surveys of upstream tributaries provided clear evidence that non-natives invaded upstream from impoundments, and in some cases, extensive introgression with native taxa also occurred. Variation in spatial trends of invasion and directionalities of introgression across case studies provided insights into eco-evolutionary drivers. Within the riverscapes studied, proximity to impoundment appeared to influence invasion and introgression dynamics, and in one case, stream size was also influential. Introgression rates also varied markedly across the species pairs studied–from very little introgression to the onset of hybrid swarming–illustrating the importance of underlying eco-evolutionary mechanisms such as habitat alteration, propagule pressure, and reproductive isolation. Our results underscore the need to consider the upstream influences of impoundments, and the non-natives that invade from them, to create more holistic riverscape conservation plans for fluvial fishes, including native black basses.

Arkansas, Georgia↗

USGS2025

New distributional record of the federally threatened Rabbitsfoot Mussel (Theliderma cylindrica) in Oklahoma

Sampling conducted from May to August of 2024 yielded new distributional records for the federally threatened Theliderma cylindrica (Rabbitsfoot) in the Caney River, OK. We found 4 live individuals, representing at least 2 age classes, ∼7 km upstream of the confluence with the Verdigris River. This report is the first documentation of live Rabbitsfoot in the Caney River, where the species was previously known only from weathered shells. This finding extends the known distribution of Rabbitsfoot into a system previously unrecognized as part of its range.

Oklahoma↗

USGS2024

Using down-scan capabilities from recreational-grade side-scan sonar systems to sample paddlefish and evaluate depth use in a reservoir

Recreational-grade side-scan sonar (SSS) has only recently been applied to estimate abundance of Paddlefish Polyodon spathula , a large pelagic planktivore, in reservoirs. Current recreational-grade SSS units also have a dedicated down-scan channel, which may be useful for detecting Paddlefish in reservoirs because the range of depths they inhabit. We investigated the utility of down-scan images using SSS data from a previously published study of Paddlefish in Keystone Lake, Oklahoma. Two readers counted Paddlefish and estimated the depth of each fish and the water column. We used proximity functions in a geographic information system to find individual Paddlefish that were common between the readers. We further used proximity functions to identify common fish observed from the SSS survey conducted previously as an aid to compare and refine down-scan estimates. Depth of Paddlefish averaged approximately 7 m, but fish were deeper when water was deeper. Density estimates from down-scan were comparable to side-scan, but only after utilizing the side-scan data to adjust for detection-by-distance in a dual-gear approach. Down-scan data thus appear to be useful for not only estimating density of Paddlefish, but also for incorporating depth use, creating a three-dimensional database of locations that can inform managers of optimal depths for sampling gear (e.g., gill nets), improve monitoring efficiency, and facilitate better management of reservoir populations.

Oklahoma↗

USGS2024

Updated distribution for two freshwater mussel species of conservation concern in Oklahoma

Qualitative and quantitative sampling efforts in the Verdigris River, OK (upstream of Lake Oologah), yielded new distributional records of 2 freshwater mussel species of conservation need: Cyprogenia aberti (Western Fanshell) and Ptychobranchus occidentalis (Ouachita Kidneyshell). The Ouachita Kidneyshell has not been documented alive during a scientific survey in the Oklahoma portion of the Verdigris River in nearly 100 years. Our observations extend the known distribution for the Western Fanshell further downstream into Oklahoma by ∼36 river km. These findings indicate an expansion in the known range and potential improvement in the populations of 2 imperiled mussel species, contrary to the prevailing global trend of mussel population decline.

Oklahoma↗

USGS2023

Factors associated with Paddlefish (Polyodon spathula) restoration success in Oklahoma

The Paddlefish ( Polyodon spathula) has been extirpated from portions of its native range due to anthropogenic habitat degradation and fragmentation, most notably the impoundment of rivers. To mitigate some of these losses in Oklahoma, Paddlefish have been stocked into reservoirs throughout the state, with variable success in establishing self-sustaining populations. Two factors thought to contribute to success of Paddlefish stocking are spawning substrate and prey availability, which were quantified in six reservoirs and nine reservoir tributaries. Side-scan sonar and supervised classification of aerial imagery were used to classify 4517-ha of river substrate upstream of the river-reservoir interface in reservoir tributaries. Zooplankton community structure, water clarity, and nutrient availability were also assessed in the same reservoirs and tributaries. One tributary had suitable spawning substrate (>40%), and the rest had minimal (<1.5%), which suggested that availability of suitable spawning substrate was not directly correlated with Paddlefish stocking success. Reservoirs with self-sustaining Paddlefish populations had higher abundance of large zooplankton (copepods and cladocerans) than reservoirs without a reproducing population. Notably, tributaries associated with Lake Texoma, the one known example of failed restoration, were much more turbid than other rivers. We conclude that abiotic factors such as water clarity may contribute more to variable recruitment than spawning substrate or zooplankton abundance by mediating foraging success of Paddlefish post-larvae.

Oklahoma↗

USGS2023

Assessing potential spawning locations of Silver Chub in Lake Erie

Objective Silver Chub Macrhybopsis storeriana , a predominately riverine species throughout its native range, exists within Lake Erie as the only known lake population. Its population declined in the 1950s and never fully recovered. Canada has listed Silver Chub in the Great Lakes–St. Lawrence River as endangered and has initiated a recovery plan that recognized the identification of spawning areas as a critical component to inform Silver Chub's recovery potential. Methods We investigated potential spawning locations of Silver Chub using capture records, otolith microchemistry, and daily age analysis. Lapillus otolith Sr:Ca ratios from 27 age-0 Silver Chub were used to identify potential spawning areas. Daily ages estimated from lapilli were used to calculate hatch dates, which then were compared with capture data of adults and river flows to further inform potential spawning areas. Result The Detroit River (and its nearshore area) was all but ruled out as a potential spawning location. The Maumee, Portage, and Sandusky rivers or their nearshore areas were all possible spawning locations. Projected hatch dates spanned the end of May through the end of June and occurred across a wide range of flows, although some peaks in hatch dates corresponded to flow peaks, indicating recruitment is potentially enhanced by high flows. Conclusion Silver Chub spawning period and hypothesized spawning rivers or lacustuaries overlap those of invasive Grass Carp Ctenopharyngodon idella , creating a need to jointly consider Grass Carp control efforts with conservation of Silver Chub when assessing management alternatives. Further research on spawning guild and the use of rivers themselves or nearshore areas influenced by rivers as spawning areas are required to maximize potential for conservation and recovery of Silver Chub.

Lake Erie↗

USGS2023

Limited hybridisation and introgression despite stocking among endemic Interior Highlands black basses (Centrarchidae: Micropterus)

Aim: Smallmouth Bass ( Micropterus dolomieu ; SMB) are globally popular among anglers and have been widely introduced (i.e. stocked) for population management and sportfishing. Importantly, stocking was prevalent before cryptic diversity within the SMB complex was known, which now includes three newly elevated species: Neosho Bass ( M. velox ; NB), Little River Bass ( M. sp. cf. dolomieu Little River; LRB) and Ouachita Bass ( M. sp. cf. dolomieu Ouachita River; OB). We sought to quantify population structure and hybridisation and introgression in these three recently described species. Location: Species-level diversity, particularly in the basin-restricted LRB and OB in the Ouachita Mountains within the Central Interior Highlands (CIH), North America, suggests the presence of distinct genetic variation that could be eroded by introgression. Methods: We estimated interspecific introgression and intraspecific population differentiation in the Smallmouth Bass species complex (SMB-C) using 472 specimens comprising SMB, NB, LRB and OB, including the naturally sympatric Spotted Bass ( M. punctulatus ; SPB). Genomic samples were genotyped on a SNP panel of 192 loci designed to detect allele-sharing on multiple hierarchical levels. Results: We found low range-wide hybridisation between species in the SMB-C and SPB (mostly SMB-C backcrosses), and interspecific heterozygosity varied, indicating differential introgression. Range-wide hybridisation between species in the CIH and SMB was similar overall (but mostly F 2 and CIH backcrosses) and was observed in streams with known SMB stocking in connected reservoirs. Interspecific heterozygosity in SMB hybrids was also generally lower, indicating later-generation backcrosses. We found strong population structure in the Ouachita Mountains (LRB and OB). Main conclusions: Despite isolated incidences of natural (SPB) and human-mediated (SMB) introgression, genomic identity appears intact in endemic LRB and OB, suggesting potential ecological or behavioural isolating mechanisms preventing cross-species reproduction. Our findings reveal that genetic variation remains in cryptic, basin-restricted species in the Ouachita Mountains ecoregion that may be managed for long-term conservation.

Arkansas, Missouri, Oklahoma↗

USGS2023

Global status of non-native Largemouth Bass (Micropterus Salmoides, Centrachidae) and Smallmouth Bass (Micropterus Dolomieu, Centrarchidae): Disparate views as beloved sportfish and feared invader

Largemouth Bass ( Micropterus salmoides , LMB) and Smallmouth Bass ( Micropterus dolomieu , SMB) are among the most highly invasive species across the globe, but are simultaneously among the most highly sought-after game fish. To explain these disparate views, data on invasive status and angling participation of these two species were compiled at the country level. Largemouth Bass were found established in 62 countries on five continents, whereas SMB were found established in only nine countries on the same five continents. Invasive risk assessments were disparate between the species, with more for SMB ( N = 29) than LMB ( N = 27). In every instance save one (Finland), SMB were considered “invasive” compared to LMB, which were “invasive” in only 74% of assessments. Twenty-eight countries with non-native black bass have groups that participate in high-profile fishing tournament such the Black Bass World Championship, BASS (Bass Anglers Sportsmans Society) Nation, and Major League Fishing. Most countries with fishing tournaments occur in countries with established LMB populations than in countries with established SMB populations, suggesting a greater economic importance on LMB fishing. The struggle between conserving biodiversity and relying upon economic benefits from fishing for introduced species is a wicked problem likely to continue into the future.

Reviews in Fisheries Science & Aquaculture↗

USGS2023

Validation and comparison of age estimates for Smallmouth Buffalo in Oklahoma based on otoliths, pectoral fin rays, and opercula

With an increased interest in nongame fishes such as buffalofishes (Catostomidae, Ictiobus ), there is a need for better foundational data on their life history. Bigmouth Buffalo I. cyprinellus , for example, have been found to live for more than a century. Age estimates for other sucker species have similarly suggested long life spans, but validation studies as reference points are often lacking. We conducted a 3-year study on Smallmouth Buffalo I. bubalus in Oklahoma to validate annual increments on three hard part structures (otoliths [lapilli], pectoral fin rays, and opercula) typically used for age estimation. We marked wild fish with oxytetracycline (OTC) injection and stocked those fish into a hatchery pond to create a population of fish with known times since marking. Furthermore, reproduction in the pond allowed us to validate annulus formation in young fish. We analyzed 117 fish and found that otoliths were more reliable, precise, and accurate than the other two structures for detecting OTC marks and counting annuli. Age estimates, from 1 to 61 years, were greatest when otoliths were used, with 99% of estimates corresponding to known time since marking or known age. Otoliths appear to be the only reliable structure for accurately estimating the age of Smallmouth Buffalo within 1 year of actual age, and their use indicates that this species can live for more than six decades in Oklahoma.

North American Journal of Fisheries Management↗

USGS2023

Dietary comparison of age-0 sturgeon (Scaphirhynchus sp.) between upper and lower Missouri River basins

Understanding potential limiting factors affecting population growth of the endangered pallid sturgeon, Scaphirhynchus albus, is important in the upper (UMOR) and lower Missouri River (LMOR) basins. The UMOR is upstream of several reservoirs and generally has more natural habitat features, whereas the LMOR is downstream of these reservoirs and has been channelized to support navigation. In both sections, pallid sturgeon recruitment to age-1 is a concern, but hypothesized for different reasons. One hypothesis in the LMOR centers on food limitation for age-0 fish, which is not considered an issue in the UMOR, but evaluating this hypothesis is challenging given the rarity of age-0 pallid sturgeon. As a result, the related, more abundant shovelnose sturgeon ( S. platorhynchus ) has been considered as a potential surrogate to assess food-related hypotheses. Thus, the purpose of our study was to compare diets of age-0 sturgeon captured in 2016 from three reaches in the LMOR (Copeland, Langdon, and Lexington) with individuals captured from a reach in the UMOR (Williston) during the same year to provide additional context regarding potential food limitation in the LMOR. Consumption percentage (prey weight in the gut as a percentage of body weight) was similar among all reaches, but diet composition was different for the most downstream reach in the LMOR. Age-0 sturgeon in the UMOR reach as well as the two upstream LMOR reaches primarily consumed Diptera larvae along with Ephemeroptera nymphs. In contrast, age-0 sturgeon in the most downstream LMOR reach (Lexington) almost exclusively consumed Diptera larvae. These results may provide information on relative differences in prey availability between Lexington and the other upstream reaches but the similarity in consumption percentage values across all reaches provide further evidence that age-0 sturgeon are not food limited in the LMOR.

Upper and lower Missouri River basins↗

USGS2023

Viability of side-scan sonar to enumerate Paddlefish, a large pelagic freshwater fish, in rivers and reservoirs

Recreational-grade side-scan sonar (SSS) has become an invaluable tool for inland fisheries, particularly when characterizing underwater habitat, but it is being increasingly used for enumerating large-bodied (> 1 m total length [TL]) aquatic fauna. We used SSS in river and reservoir environments to evaluate methods for identifying and counting Paddlefish Polyodon spathula , a large pelagic planktivore of recreational and economic importance that can exceed 2 m in length and weigh over 70 kg. We assessed accuracy and precision among readers to identify Paddlefish by assigning confidence scores (1–3; with 3 being more confident) to sonar images of a ballistics-gel filled fiberglass replica Paddlefish. Readers varied in their confidence scores for the replica Paddlefish and no reader could identify the target beyond 25 m from the transducer. Afterwards, we used SSS to survey several kilometers of a reservoir during summer residency and a large river during springtime spawning migrations. Two readers counted Paddlefish images in the SSS recordings and we estimated population size in the surveyed area with distance sampling. In the reservoir, the number of Paddlefish counted ranged from 172 to 184. In the river, the number of Paddlefish counted ranged from 165 to 617. The exponential model of distance was most-supported for detection in both environments, except there was support for a half-norm distribution for one reader in the river. In the reservoir, abundance estimates were statistically similar between readers at approximately 1500 (7/ha) in the total scanned area. In the river, similar abundance estimates were obtained with the half-norm model from one reader compared to the exponential model of the other reader, resulting in approximately 1500 individuals (30/ha) in the surveyed area. The application of SSS to count Paddlefish has some clear advantages to traditional methods, such as gill netting, and can be done at multiple times of the year. Distance sampling methods compensated for differences in counts among readers, indicating distance sampling can produce similar abundance estimates even when variation in counts exists among readers.

Oklahoma↗

USGS2022

Genomic divergence, local adaptation, and complex demographic history may inform management of a popular sportfish species complex

The Neosho Bass ( Micropterus velox ), a former subspecies of the keystone top-predator and globally popular Smallmouth Bass ( M. dolomieu ), is endemic and narrowly restricted to small, clear streams of the Arkansas River Basin in the Central Interior Highlands (CIH) ecoregion, USA. Previous studies have detected some morphological, genetic, and genomic differentiation between the Neosho and Smallmouth Basses; however, the extent of neutral and adaptive divergence and patterns of intraspecific diversity are poorly understood. Furthermore, lineage diversification has likely been impacted by gene flow in some Neosho populations, which may be due to a combination of natural biogeographic processes and anthropogenic introductions. We assessed: (1) lineage divergence, (2) local directional selection (adaptive divergence), and (3) demographic history among Smallmouth Bass populations in the CIH using population genomic analyses of 50,828 single-nucleotide polymorphisms (SNPs) obtained through ddRAD-seq. Neosho and Smallmouth Bass formed monophyletic clades with 100% bootstrap support. We identified two major lineages within each species. We discovered six Neosho Bass populations (two nonadmixed and four admixed) and three nonadmixed Smallmouth Bass populations. We detected 29 SNPs putatively under directional selection in the Neosho range, suggesting populations may be locally adapted. Two populations were admixed via recent asymmetric secondary contact, perhaps after anthropogenic introduction. Two other populations were likely admixed via combinations of ancient and recent processes. These species comprise independently evolving lineages, some having experienced historical and natural admixture. These results may be critical for management of Neosho Bass as a distinct species and may aid in the conservation of other species with complex biogeographic histories.

Ecology and Evolution↗

USGS2022

Factors affecting interannual variation in diet and body lipid content of age-0 Scaphirhynchus sturgeon in the lower Missouri River, USA

The ability of young fish to find and consume food during early life history is an important factor affecting survival and recruitment. While dietary assessments for age-0 Scaphirhynchus sturgeon (shovelnose sturgeon and pallid sturgeon) in the Missouri River, USA have received increased attention over the last 15 years, there is currently limited information available to evaluate long-term trends in prey consumption and body condition. To better understand interannual factors during early-life history, we examined foraging and body condition of age-0 (<12.0 cm) Scaphirhynchus in relation to discharge and the availability of hypothesized foraging and food-producing habitats at a single reach (Lexington) of the Missouri River over a span of five years (2014–2018). Relatively high discharge in 2015 led to concomitant maxima in foraging and lipid levels for age-0 sturgeon. However, lower water levels in 2014 did not see declines in lipid content as would be expected given the low level of foraging observed that year. Additionally, the availability of hypothesized foraging and food-producing habitats had little effect on age-0 sturgeon prey consumption and condition in the Lexington Reach. Our results suggest that other factors in addition to river discharge may affect age-0 sturgeon foraging and condition and more research focused on understanding the flow-habitat relationships would be critical.

Missouri↗

USGS2021

Modern reporting methods for angler tag-return studies:Trends in data quality, choice of method, and future considerations

Angler tag-return studies are a cornerstone of fisheries research, providing insights into individual movements and estimates of exploitation, among many other applications. However, the data generated from these studies is dependent upon effective communication between anglers and scientists. As technological advances are adopted by anglers, little research has been directed at the potential benefits of incorporating modern tag reporting methods. We tagged stream-dwelling black bass Micropterus spp. and provided anglers a choice of reporting methods (telephone, email, iNaturalist app, or a “mixed-mode” combination thereof). Our objectives were to examine the fate of reported fish, quantify trends in data quality across reporting methods, and explore how geographic location and angler avidity may influence use of reporting methods. Ninety-four percent of tag reports involved the release of the fish with the tag still intact, creating opportunities for longer-term data collection. Telephone was the most commonly used reporting method; however, this method had significantly lower completeness scores (e.g., lack of photographs or specifying fate of fish) and less precise location information than other methods. In contrast, iNaturalist had the highest completeness and most precise location information but was seldom used and had increased lag times in reporting. We found no significant differences in the proportion of reporting methods used across stream locations in our study, and avid anglers appeared to be individualistic in their choice of method. Overall, our study suggests that the adoption of modern reporting methods, like email and smartphone apps, could benefit data collection efforts of angler tag-return studies. Fisheries scientists may wish to consider which reporting methods align with their specific study objectives and with the angling public of a given study area.

Arkansas, Oklahoma↗

USGS2021

Environmental conditions associated with occurrences of the threatened Yaqui Catfish in the Yaqui River Basin, Mexico

The Yaqui Catfish Ictalurus pricei is an understudied species, with limited information available on its ecology, distribution, and local habitat use. Native to the southwestern United States and northwestern Mexico, Yaqui Catfish populations are declining, which has prompted listing of the species as threatened in the United States and as a species of concern in Mexico. Water overallocation, habitat degradation, invasive species introductions, and hybridization with nonnative Channel Catfish I . punctatus have caused the populations in Mexico to decline. The United States population collapsed after years of low recruitment. To better focus conservation efforts as well as define habitat associated with Yaqui Catfish occurrences, we assessed the distribution in the Yaqui River basin of Mexico by using historical data at a landscape scale. Yaqui Catfish were historically found across the watershed among a diversity of environments but were most frequently associated with small, intermittent streams. Basin land cover was dominated by forest, shrubland, and grassland, and Yaqui Catfish generally occurred in stream segments at similar proportions. However, a small number of Yaqui Catfish occurrences were associated with urban and cropland land cover types in proportions greater than the availability of those categories on the landscape. With the species facing declines in the region, this work will help to inform future conservation efforts aimed at securing the Yaqui Catfish, protecting suitable habitat, and better defining its current status in Mexico.

Yaqui River Basin↗