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At least 811 records · Page 45Linked to original sources

USGS2006

Hydroacoustic separation of rainbow smelt (Osmerus mordax) age groups in Lake Champlain

Separate assessment of young-of-year (YOY) and yearling-and-older (YAO) fish is desirable from both ecological and management perspectives. Acoustic assessments provide information on fish population size structure in the target strength (TS) distribution, but interpretation of TS distributions must be done carefully, as single age groups can produce multiple TS modes. We assessed the ability of in situ TS distributions to identify Lake Champlain rainbow smelt (Osmerus mordax) age groups in June, July, and September of 2001 using mobile and stationary surveys, knowledge of vertical distribution preferences, and predicted TS from trawl catches. YAO rainbow smelt (93-179 mm total length) had wide TS distributions between -60 and -35 dB in all 3 months with two modes at approximately -50 and -40 dB. Most stationary survey single-fish tracks attributed to YAO had targets in both TS modes and a wide TS range often over 15 dB. Between June and September, YOY rainbow smelt TS increased, but single-fish tracks were unimodal, and the TS range was smaller (6 dB). Overlap in TS attributed to YOY and YAO increased from no overlap in June (YOY TS -76 to -61 dB, 15-25 mm) to moderate overlap in July (-76 to -50 dB, 25-63 mm) to considerable overlap in September (-68 to -45 dB, 33-80 mm). In June and July, the TS distribution changed abruptly at the thermocline, indicating almost complete separation of the two groups. A more gradual TS transition was evident in September, indicating substantial overlap between YOY and YAO. Separate estimates can be obtained in September by decomposing TS overlap into components attributed to YOY and YAO rainbow smelt. However, this decomposition introduces additional uncertainty and an assessment in July or possibly August is preferable to obtain separate abundance estimates of YOY and YAO. ?? 2006 Elsevier B.V. All rights reserved.

Fisheries Research↗

USGS2022

Using carbon, nitrogen, and mercury isotope values to distinguish mercury sources to Alaskan lake trout

Lake trout ( Salvelinus namaycush ), collected from 13 remote lakes located in southwestern Alaska, were analyzed for carbon, nitrogen, and mercury (Hg) stable isotope values to assess the importance of migrating oceanic salmon, volcanic activity, and atmospheric deposition to fish Hg burden. Methylmercury (MeHg) bioaccumulation in phytoplankton (5.0–6.9 kg L –1 ) was also measured to quantify the basal uptake of MeHg to these aquatic food webs. Hg isotope values in lake trout revealed that while the extent of precipitation-delivered Hg was similar across the entire study area, volcanic Hg is likely an important additional source to lake trout in proximate lakes. In contrast, migratory salmon ( Oncorhynchus nerka ) deliver little MeHg to lake trout directly, although indirect delivery processes via decay could exist. A high level of variability in carbon, nitrogen, and Hg isotope values indicates niche partitioning in lake trout populations within each lake and that a complex suite of ecological interactions is occurring, complicating the conceptually linear assessment of the contaminant source to the receiving organism. Without connecting energy and contaminant isotope axes, we would not have understood why lake trout from these pristine lakes have highly variable Hg burdens despite consistently low water Hg and comparable age-length dynamics.

Alaska↗

USGS2020

Amphibian responses in the aftermath of extreme climate events

Climate change-induced extinctions are estimated to eliminate one in six known species by the end of the century. One major factor that will contribute to these extinctions is extreme climatic events. Here, we show the ecological impacts of recent record warm air temperatures and simultaneous peak drought conditions in California. From 2008–2016, the southern populations of a wide-ranging endemic amphibian (the California newt, Taricha torosa) showed a 20% reduction to mean body condition and significant losses to variation in body condition linked with extreme climate deviations. However, body condition in northern populations remained relatively unaffected during this period. Range-wide population estimates of change to body condition under future climate change scenarios within the next 50 years suggest that northern populations will mirror the loss of body condition recently observed in southern populations. This change is predicated on latter 21st century climate deviations that resemble recent conditions in Southern California. Thus, the ecological consequences of climate change have already occurred across the warmer, drier regions of Southern California, and our results suggest that predicted climate vulnerable regions in the more mesic northern range likely will not provide climate refuge for numerous amphibian communities.

California↗

USGS2021

Insect pathogenic fungi for biocontrol of plague vector fleas: A review

Bubonic plague is a lethal bacterial disease of great historical importance. The plague organism, Yersinia pestis , is primarily transmitted by fleas (Siphonaptera). In natural settings, where its range expands, Y. pestis resides in association with wild rodents and their fleas (sylvatic plague). While chemical insecticides are used against plague vector fleas, biological approaches have not been as critically evaluated. Benign and cost-effective control methods are sorely needed, particularly where imperiled species are at risk. Here we explore the potential of two representative insect pathogenic fungi, Beauveria bassiana Vuillemin 1912 (Hypocreales: Cordycipitaceae) and Metarhizium anisopliae Metschnikoff 1879 (Hypocreales: Clavicipitaceae), each already used commercially worldwide in large-scale agricultural applications, as candidate biopesticides for application against fleas. We review the life cycles, flea virulence, commercial production, and field application of these fungi, and ecological and safety considerations. Pathogenic fungi infections among natural flea populations suggest that conditions within at least some rodent burrows are favorable, and laboratory studies demonstrate lethality of these fungi to at least some representative flea species. Continued study and advancements with these fungi, under appropriate safety measures, may allow for effective biocontrol of plague vector fleas to protect imperiled species, decrease plague outbreaks in key rodent species, and limit plague in humans.

Journal of Integrated Pest Management↗

USGS2026

Epigenetics in captivity: Restoring wild phenotypes in captive-reared salmonids

Captive rearing is a common practice for the stocking, conservation, and supplementation of fish species worldwide, but captive-reared fish can exhibit altered phenotypes leading to reduced fitness in nature compared to wild conspecifics. In salmonids, certain studies have found limited genetic differentiation between wild and captive-reared fish. However, documented changes in gene expression in hatchery fish have led scientists to investigate epigenetic mechanisms, such as DNA methylation, as a source of these differences. In this binational collaborative piece, we synthesize the knowledge and efforts of academics and government scientists to highlight how interactions between captive rearing and the epigenome elicit parallel phenotypic changes across salmonid species. We examine the known and potential links between DNA methylation and the phenotypic effects of captive rearing including changes in behavior, color, gut microbiomes, and developmental abnormalities. We review efforts to minimize these phenotypic and epigenetic effects including attempts to modify the hatchery environment and rearing protocols. We provide a framework to integrate epigenetic considerations into hatchery rearing protocols by weighing the heritable nature of DNA methylation with the goals of different captive rearing programs and explore whether minimizing the phenotypic and epigenetic effects of captive rearing is worthwhile. We examine heritability and persistence of epigenetic effects, and we propose the exploitation of heritable bet-hedging as an epigenetic buffer to increase post-release survival. We also suggest novel applications of epigenomic biomarkers as a non-lethal method for post-release monitoring. Ultimately, collaborative multi-disciplinary research across species is needed to understand the comprehensive effects of captive rearing, reduce the ecological impacts of captive fish in the wild, and increase population resilience. Integrating epigenetics into fish hatchery management will provide new opportunities for optimizing and improving captive rearing.

Evolutionary Applications↗

USGS2022

Genetic analyses provide new insight on the mating strategies of the American Black Swift (Cypseloides niger)

Avian mating strategies play a vital role in the demographic and genetic dynamics of a species and understanding avian reproductive tactics is important to conservation, population management and restoration. Classifications of avian mating strategies have historically been based on direct physical observations and tend to be rigid population-level generalizations that overlook the variations inherent in most ecological systems. Based on limited empirical field observations, the American Black Swift Cypseloides niger borealis is considered to be a socially monogamous species with pair bonds lasting for many years. To test this hypothesis, we collected genomic DNA samples from banded swifts from six American Black Swift colonies in the western United States from 2004 to 2019 and isolated and developed primers for highly polymorphic microsatellite loci and used them to genotype our samples. Our parentage analysis revealed that sampled females never mated with the same male in subsequent years, suggesting that they are not sexually monogamous with a single partner for many years as previously hypothesized.

Colorado, Idaho, New Mexico↗

USGS2010

Modelling detection probabilities to evaluate management and control tools for an invasive species

For most ecologists, detection probability (p) is a nuisance variable that must be modelled to estimate the state variable of interest (i.e. survival, abundance, or occupancy). However, in the realm of invasive species control, the rate of detection and removal is the rate-limiting step for management of this pervasive environmental problem. For strategic planning of an eradication (removal of every individual), one must identify the least likely individual to be removed, and determine the probability of removing it. To evaluate visual searching as a control tool for populations of the invasive brown treesnake Boiga irregularis, we designed a mark-recapture study to evaluate detection probability as a function of time, gender, size, body condition, recent detection history, residency status, searcher team and environmental covariates. We evaluated these factors using 654 captures resulting from visual detections of 117 snakes residing in a 5-ha semi-forested enclosure on Guam, fenced to prevent immigration and emigration of snakes but not their prey. Visual detection probability was low overall (= 0??07 per occasion) but reached 0??18 under optimal circumstances. Our results supported sex-specific differences in detectability that were a quadratic function of size, with both small and large females having lower detection probabilities than males of those sizes. There was strong evidence for individual periodic changes in detectability of a few days duration, roughly doubling detection probability (comparing peak to non-elevated detections). Snakes in poor body condition had estimated mean detection probabilities greater than snakes with high body condition. Search teams with high average detection rates exhibited detection probabilities about twice that of search teams with low average detection rates. Surveys conducted with bright moonlight and strong wind gusts exhibited moderately decreased probabilities of detecting snakes. Synthesis and applications. By emphasizing and modelling detection probabilities, we now know: (i) that eradication of this species by searching is possible, (ii) how much searching effort would be required, (iii) under what environmental conditions searching would be most efficient, and (iv) several factors that are likely to modulate this quantification when searching is applied to new areas. The same approach can be use for evaluation of any control technology or population monitoring programme. ?? 2009 The Authors. Journal compilation ?? 2009 British Ecological Society.

Journal of Applied Ecology↗

USGS2011

Could residual oil from the Exxon Valdez spill create a long-term population "sink" for sea otters in Alaska?

Over 20 years ago, the Exxon Valdez oil tanker spilled 42 million L of crude oil into the waters of Prince William Sound, Alaska, USA. At the time of the spill, the sea otter (Enhydra lutris) population inhabiting the spill area suffered substantial acute injuries and loss. Subsequent research has resulted in one of the best-studied species responses to an oil spill in history. However, the question remains: Is the spill still influencing the Prince William Sound sea otter population? Here we fit time-varying population models to data for the sea otter population of western Prince William Sound to quantify the duration and extent of mortality effects from the spill. We hypothesize that the patchy nature of residual oil left in the environment has created a source-sink population dynamic. We fit models using the age distributions of both living and dying animals and estimates of sea otter population size to predict the number of sea otters in the hypothesized sink population and the number lost to this sink due to chronic exposure to residual oil. Our results suggest that the sink population has remained at just over 900 individuals (95% CI: 606-960) between 1990 and 2009, during which time prime-age survival remained 2-6% below pre-spill levels. This reduced survival led to chronic losses of ???900 animals over the past two decades, which is similar in magnitude to the number of sea otter deaths documented in western Prince William Sound during the acute phase of the spill. However, the unaffected source population appears to be counterbalancing these losses, with the model indicating that the sea otter population increased from ???2150 individuals in 1990 to nearly 3000 in 2009. The most optimistic interpretation of our results suggests that mortality effects dissipated between 2005 and 2007. Our results suggest that residual oil can affect wildlife populations on time scales much longer than previously believed and that cumulative chronic effects can be as significant as acute effects. Further, source-sink population dynamics can explain the slow recovery observed in the spill-affected western Prince William Sound sea otter population and are consistent with available data. ??2011 by the Ecological Society of America.

Ecological Applications↗

USGS2002

Environmental setting and water-quality issues of the Mobile River Basin, Alabama, Georgia, Mississippi, and Tennessee

The Mobile River Basin is one of over 50 river basins and aquifer systems being investigated as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. This basin is the sixth largest river basin in the United States, and fourth largest in terms of streamflow, encompassing parts of Alabama, Georgia, Mississippi, and Tennessee. Almost two-thirds of the 44,000-square-mile basin is located in Alabama. Extensive water resources of the Mobile River Basin are influenced by an array of natural and cultural factors. These factors impart unique and variable qualities to the streams, rivers, and aquifers providing abundant habitat to sustain the diverse aquatic life in the basin. Data from Federal, State, and local agencies provide a description of the environmental setting of the Mobile River Basin. Environmental data include natural factors such as physiography, geology, soils, climate, hydrology, ecoregions, and aquatic ecology, and human factors such as reservoirs, land use and population change, water use, and water-quality issues. Characterization of the environmental setting is useful for understanding the physical, chemical, and biological characteristics of surface and ground water in the Mobile River Basin and the possible implications of that environmental setting for water quality. The Mobile River Basin encompasses parts of five physiographic provinces. Fifty-six percent of the basin lies within the East Gulf section of the Coastal Plain Physiographic Province. The remaining northeastern part of the basin lies, from west to east, within the Cumberland Plateau section of the Appalachian Plateaus Physiographic Province, the Valley and Ridge Physiographic Province, the Piedmont Physiographic Province, and the Blue Ridge Physiographic Province. Based on the 1991 land-use data, about 70 percent of the basin is forested, while agriculture, including livestock (poultry, cattle, and swine), row crops (cotton, corn, soybeans, sorghum, and wheat), and pasture land accounts for about 26 percent of the study unit. Agricultural land use is concentrated along the Black Prairie Belt district of the Coastal Plain. Urban areas account for only 3 percent of the total land use; however, the areal extent of the metropolitan statistical areas (MSA) may indicate more urban influences. The MSAs include urban areas outside of the city boundaries and can include adjacent counties. Seven MSAs are delineated in the Mobile River Basin, including Montgomery, Mobile, Tuscaloosa, Birmingham, Gadsden, Anniston, and Atlanta. The total population for the Mobile River Basin was about 3,673,100 in 1990. State water-quality agencies have identified numerous causes and sources of water-body impairment in the Mobile River Basin. In 1996, organic enrichment, dissolved oxygen depletion, elevated nutrient concentrations, and siltation were the most frequently cited causes of impairment, affecting the greatest number of river miles. Bacteria, acidic pH, and elevated metal concentrations also were identified as causes of impairment. The sources for impairment varied among river basins, were largely a function of land use, and were attributed primarily to municipal and industrial sources, mining, and agricultural activities.

Water-Resources Investigations Report↗

USGS2019

Evaluation of an acoustic fish deterrent system in shallow water application at the Emiquon Preserve, Lewistown, IL.

Expansion of non-native fish have caused ecological and economic damage and can negatively impact native fish populations. Current research on deterrent technologies for bighead Hypophthalmichthys nobilis and silver carp H. molitrix have primarily focused on reducing upstream movement in large river lock approaches. However, there is also interest in excluding carp from smaller-scale locations. A water control structure at Emiquon Preserve, Lewistown, Illinois, USA reconnected the Preserve’s wetland lakes to the Illinois River, and is a pinch point that site managers seek to deter immigration of non-native fishes without restricting native fish movement. One possible deterrent strategy that was evaluated within the water control structure in 2017 was the use of a 100 hp boat motor acoustic stimulus. Two underwater speakers were installed in each of two culverts to discourage fish movement though the water control structure. Fish passage was monitored using a series of passive integrated transponder (PIT) antennas in a confined study area. A combination of 176 fish consisting of seven different species (native and non-native) were implanted with PIT tags and relocated downstream of the water control structure. Over 2 days of periodic playback of the acoustic stimulus, 29% of tagged silver carp that were detected crossed though the active underwater speaker array. The acoustic treatment did not significantly reduce silver carp or native centrarchid passage through the culverts. However, numerous silver carp were observed jumping out of the acoustically active culvert at the onset of the stimulus. The acoustic stimulus, especially the frequencies to which silver carp are most sensitive to (< 2000 Hz), rapidly attenuated in the water control structure (water depth 0.55–0.38 m). Depth related attenuation observed in and around the water control structure may have reduced the efficacy of the acoustic fish deterrent system at this location.

Illinois↗

USGS2024

Northern Mexican gartersnake demographics and movement ecology

The northern Mexican gartersnake ( Thamnophis eques ; hereafter NMGS) is a federally threatened species occurring in riparian areas in central and southeast Arizona and west-central New Mexico. While previous studies have examined the ecology of this species in central Arizona, less is known about NMGS ecology in grassland landscapes of southeast Arizona. This project continues a long-term mark-recapture study of NMGS in the upper Santa Cruz River in the San Rafael Valley of southeast Arizona. We analyzed mark-recapture data collected by Arizona Game and Fish Department from 2008–2019 and included data we collected during 2022 and 2023. We also studied NMGS movement ecology using a combination of externally attached GPS transmitters and surgically implanted VHF transmitters. We had 517 NMGS captures over 26 survey sessions across the entire study, 186 of which were captures of previously marked snakes. Most of our captures were females and evidence of a statistically significant female-biased sex ratio was present on three survey sessions. Trapping success was generally highest June-September and catch-per-unit-effort (CPUE) was strongly correlated with the number of individuals captured. We used mark-recapture data from 288 individuals to estimate annual apparent survival and session-specific recapture probabilities. Annual apparent survival was higher for females (0.72, 95% highest posterior density intervals [HPDI] = 0.630.81) than for males (0.58, 95% HPDI = 0.44–0.72). Session-specific recapture probabilities were similar for males and females and were highly correlated with CPUE. During 2023, we monitored the movements of 13 adult females using GPS transmitters, two adult males using VHF transmitters, and one adult female using a GPS transmitter followed by a VHF transmitter. GPS transmitters were deployed from 7-18 days at a time as limited by battery life. After filtering out low-quality GPS locations, we obtained a total of 1,688 hourly GPS locations. Mean and maximum distances moved per hour ranged from 5.54–10.92 m and 15.24–135.71 m, respectively, across GPS transmitter attachment periods. Space use estimates from 100% minimum convex polygons ranged from 0.04–1.16 ha across GPS transmitter attachment periods. All documented NMGS movements during 2023 were relatively close (< 100 m) to the Santa Cruz River. These results continue to build upon our knowledge of NMGS ecology and suggest the continued presence of a relatively robust population within the upper Santa Cruz River.

Arizona↗

USGS2014

Fatal paralytic shellfish poisoning in Kittlitz's Murrelet ( Brachyramphus brevirostris ) nestlings, Alaska, USA

Paralytic shellfish poisoning (PSP) is an acute toxic illness in humans resulting from ingestion of shellfish contaminated with a suite of neurotoxins (saxitoxins) produced by marine dinoflagellates, most commonly in the genus Alexandrium . Poisoning also has been sporadically suspected and, less often, documented in marine wildlife, often in association with an outbreak in humans. Kittlitz's Murrelet ( Brachyramphus brevirostris ) is a small, rare seabird of the Northern Pacific with a declining population. From 2008 to 2012, as part of a breeding ecology study, multiple Kittlitz's Murrelet nests on Kodiak Island, Alaska, were monitored by remote cameras. During the 2011 and 2012 breeding seasons, nestlings from several sites died during mild weather conditions. Remote camera observations revealed that the nestlings died shortly after consuming sand lance ( Ammodytes hexapterus ), a fish species known to biomagnify saxitoxin. High levels of saxitoxin were subsequently documented in crop content in 87% of nestling carcasses. Marine bird deaths from PSP may be underreported.

Alaska↗

USGS2003

Amphibian decline: An integrated analysis of multiple stressor effects

Capturing the attention and imagination of the public and the scientific community alike, the mysterious decline in amphibian populations drew scientists and resource managers from ecotoxicology and chemistry, ecology and field biology, conservation biology, and natural resource policy to a SETAC–Johnson Foundation workshop. Facilitating environmental stewardship, increasing capacity of the sciences to explain complex stressors, and educating the public on relationships among communities of all types motivated these experts to address amphibian decline and the role of various stressors in these losses.

Book↗

USGS2014

Survival of female white-cheeked pintails during brood rearing in Puerto Rico

Anas bahamensis (White-cheeked Pintail) is widely distributed across the Caribbean islands and South America. The species is classified as threatened in Puerto Rico and a species of least concern across most of its range. Little demographic data exist for the species, particularly during the breeding season. During 2000-2002, we radiomarked 31 incubating females at the Humacao Nature Reserve (Humacao) in southeastern Puerto Rico and estimated daily and interval survival rates of females during brood rearing. Only one of 31 birds died; the average ± 95% CI daily survival rate of pintails was 0.998 ± 0.989-0.999 for all years, and interval survival was 0.913 ± 0.527-0.987 for a 60-day brood-rearing period. High survival of females suggests their mortality during brood rearing does not influence White-cheeked Pintail populations at Humacao, but further studies of reproductive and annual ecology are needed.

Puerto Rico↗

USGS2026

Avoiding common pitfalls in the implementation of adaptive forest wildlife management

Forest management planning requires the evaluation of tradeoffs in proposed management actions to meet multiple objectives, including providing the habitat required to sustain wildlife populations. However, various species-specific life history strategies and ecological uncertainties complicate our understanding of the responses of wildlife to disturbances, such as wildfires and forest management. We believe that adaptive management processes, applied through the close collaboration of researchers and managers (e.g., coproduction), will be valuable in this effort. Although adaptive management programs have been touted in the past, we stress that many of these programs have fallen short of the requisite steps to complete the learning cycles of this process (i.e., single- and double-loop learning). Thus, we provide guidance on what we believe to be the missing components of these efforts in hopes to guide future coordination of local and regional adaptive management programs for forest wildlife.

General Technical Report↗

USGS2005

Host population persistence in the face of introduced vector-borne diseases: Hawaii amakihi and avian malaria

The past quarter century has seen an unprecedented increase in the number of new and emerging infectious diseases throughout the world, with serious implications for human and wildlife populations. We examined host persistence in the face of introduced vector-borne diseases in Hawaii, where introduced avian malaria and introduced vectors have had a negative impact on most populations of Hawaiian forest birds for nearly a century. We studied birds, parasites, and vectors in nine study areas from 0 to 1,800 m on Mauna Loa Volcano, Hawaii from January to October, 2002. Contrary to predictions of prior work, we found that Hawaii amakihi (Hemignathus virens), a native species susceptible to malaria, comprised from 24.5% to 51.9% of the avian community at three low-elevation forests (55-270 m). Amakihi were more abundant at low elevations than at disease-free high elevations, and were resident and breeding there. Infection rates were 24-40% by microscopy and 55-83% by serology, with most infected individuals experiencing low-intensity, chronic infections. Mosquito trapping and diagnostics provided strong evidence for year-round local transmission. Moreover, we present evidence that Hawaii amakihi have increased in low elevation habitats on south-eastern Hawaii Island over the past decade. The recent emergent phenomenon of recovering amakihi populations at low elevations, despite extremely high prevalence of avian malaria, suggests that ecological or evolutionary processes acting on hosts or parasites have allowed this species to recolonize low-elevation habitats. A better understanding of the mechanisms allowing coexistence of hosts and parasites may ultimately lead to tools for mitigating disease impacts on wildlife and human populations.

Proceedings of the National Academy of Sciences of↗

USGS2017

The gold tegu, Tupinambis teguixin (Linnaeus, 1758) sensu lato (Squamata: Teiidae): evidence for an established population in Florida

Gold tegus, Tupinambis teguixin (Linnaeus, 1758), are generalist predators from South America and are ecologically similar to Argentine black and white tegus ( Salvator merianae ), a successful invader in Florida. We trapped gold tegus in Broward and Miami-Dade counties, Florida, USA. In Miami-Dade County, collection occurred from 2008 through 2016. We combined new trapping records with previous literature records. Ten gold tegus of both sexes and multiple size classes over a nine year period indicate a reproducing population in Miami-Dade County. Tupinambis teguixin is the sixth established non-native teiid species in Florida. Additionally, we report Tupinambis teguixin from Sarasota and Lee counties, Florida, USA. Determining population status in those counties requires further study. It is critical to differentiate this species from Salvator merianae during removal efforts. The possibility of eradicating Tupinambis teguixin exists if proper identification enables reliable monitoring of the populations.

Florida↗

USGS2014

Extensive dispersal of Roanoke logperch ( Percina rex ) inferred from genetic marker data

The dispersal ecology of most stream fishes is poorly characterised, complicating conservation efforts for these species. We used microsatellite DNA marker data to characterise dispersal patterns and effective population size ( N e ) for a population of Roanoke logperch Percina rex , an endangered darter (Percidae). Juveniles and candidate parents were sampled for 2 years at sites throughout the Roanoke River watershed. Dispersal was inferred via genetic assignment tests (ATs), pedigree reconstruction (PR) and estimation of lifetime dispersal distance under a genetic isolation-by-distance model. Estimates of N e varied from 105 to 1218 individuals, depending on the estimation method. Based on PR, polygamy was frequent in parents of both sexes, with individuals spawning with an average of 2.4 mates. The sample contained 61 half-sibling pairs, but only one parent–offspring pair and no full-sib pairs, which limited our ability to discriminate natal dispersal of juveniles from breeding dispersal of their parents between spawning events. Nonetheless, all methods indicated extensive dispersal. The AT indicated unrestricted dispersal among sites ≤15 km apart, while siblings inferred by the PR were captured an average of 14 km and up to 55 km apart. Model-based estimates of median lifetime dispersal distance (6–24 km, depending on assumptions) bracketed AT and PR estimates, indicating that widely dispersed individuals do, on average, contribute to gene flow. Extensive dispersal of P. rex suggests that darters and other small benthic stream fishes may be unexpectedly mobile. Monitoring and management activities for such populations should encompass entire watersheds to fully capture population dynamics.

Ecology of Freshwater Fish↗