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USGS2020

Utilization of multiple microbial tools to evaluate efficacy of restoration strategies to improve recreational water quality at a Lake Michigan Beach (Racine, WI)

Hydro-meteorological conditions facilitate transport of fecal indicator bacteria (FIB) to the nearshore environment, affecting recreational water quality. North Beach (Racine, Wisconsin, United States), is an exemplar public beach site along Lake Michigan, where precipitation-mediated surface runoff, wave encroachment, stormwater and tributary outflow were demonstrated to contribute to beach advisories. Multiple restoration actions, including installation of a stormwater retention wetland, were successfully deployed to improve recreational water quality. Implementation of molecular methods (e.g. human microbial source tracking markers and Escherichia coli ( E. coli ) qPCR) assisted in identifying potential pollution sources and improving public health response time. However, periodic water quality failures still occur. As local beach managers reassess restoration measures in response to climatic changes, use of expanded microbial methods (including bacterial community profiling) may contribute to a better understanding of these dynamic environments. In this 2-year study (2015 and 2019), nearshore/offshore Lake Michigan, stormwater, and tributary samples were collected to determine if, 1) the constructed wetland (~50 m from the shoreline) continued to provide stormwater separation/retention and 2) mixing between onshore sources, Root River and Lake Michigan, was increasing due to rising precipitation/lake levels. Monthly rainfall totals were 1.5× higher in 2019 than 2015, coinciding with a 0.63 m lake-level rise. The prevalence of more intense, onshore winds also increased, facilitating interaction between potential reservoirs of FIB with nearshore water through wind driven waves and lake intrusion, e.g. beach sands and the adjacent Root River. While a strong relationship existed between wet weather wetland and North Beach nearshore E. coli concentrations (all sites), bacterial communities were strikingly different. Conversely, bacterial community overlap existed between the Root River mouth and nearshore/offshore sites. These results suggest the constructed wetland can accommodate the climate-related changes observed in this study. Future restoration activities could be directed towards upstream tributary sources in order to minimize microbial contaminants entering Lake Michigan.

Wisconsin↗

USGS2012

Elevated streamflows increase dam passage by juvenile coho salmon during winter: Implications of climate change in the Pacific Northwest

A 4-year evaluation was conducted to determine the proportion of juvenile coho salmon Oncorhynchus kisutch passing Cowlitz Falls Dam, on the Cowlitz River, Washington, during winter. River and reservoir populations of coho salmon parr were monitored using radiotelemetry to determine if streamflow increases resulted in increased downstream movement and dam passage. This was of interest because fish that pass downstream of Cowlitz Falls Dam become landlocked in Riffe Lake and are lost to the anadromous population. Higher proportions of reservoir-released fish (0.391-0.480) passed Cowlitz Falls Dam than did river-released fish (0.037-0.119). Event-time analyses demonstrated that streamflow increases were important predictors of dam passage rates during the study. The estimated effect of increasing streamflows on the risk of dam passage varied annually and ranged from 9% to 75% for every 28.3 m 3 /s increase in streamflow. These results have current management implications because they demonstrate the significance of dam passage by juvenile coho salmon during winter months when juvenile fish collection facilities are typically not operating. The results also have future management implications because climate change predictions suggest that peak streamflow timing for many watersheds in the Pacific Northwest will shift from late spring and early summer to winter. Increased occurrence of intense winter flood events is also expected. Our results demonstrate that juvenile coho salmon respond readily to streamflow increases and initiate downstream movements during winter months, which could result in increased passage at dams during these periods if climate change predictions are realized in the coming decades.

Washington↗

USGS2024

Effects of exploitation and emigration on apparent survival of Walleye in Lake Sharpe, South Dakota

Objective In 2017, we began a 5-year mark–recapture study to estimate apparent survival of Walleye Sander vitreus and angler exploitation in Lake Sharpe, South Dakota, and inform management strategies for this fishery. The study revealed substantial downstream emigration of Walleye; therefore, we also examined the influence of emigration on apparent mortality. Methods We estimated Walleye apparent survival using the Seber parameterization of the dead recovery model. In our models, we included factors influencing voluntary fish release, as well as harvest restrictions, tagging location, and year. We used a multistate Markov model to estimate emigration in relation to Walleye total length, sex, and tagging location, as well as annual reservoir discharge. The exploitation and emigration estimates informed our interpretations of annual Walleye apparent survival. Result Apparent survival patterns were explained by an interaction between Walleye length and a minimum harvest length restriction. Apparent survival was lower during July and August, when the minimum harvest length limit was suspended, and results suggest that anglers were willing to release preferred sizes (≥508 mm) when able to harvest smaller (<381 mm) Walleye. Annual apparent survival, exploitation, and emigration estimates ranged between 15% and 47%, 8% and 25%, and 11% and 28%, respectively. Emigration was influenced by tagging location and annual discharge: increasing with proximity to Big Bend dam and during high annual flows. Although years with high exploitation or emigration corresponded to years with low apparent survival, estimates did not explain the magnitude of mortality or emigration indicated by survival models. Conclusion Our results revealed that harvest–release decisions by Walleye anglers in Lake Sharpe are primarily influenced by regulations, although exploitation was not a significant source of mortality. Annual patterns in apparent survival indicate high mortality or emigration. Continued investigations into immigration and emigration and sources of mortality of Lake Sharpe Walleye are warranted to better inform management strategies for the fishery.

South Dakota↗

USGS1987

Minimum tailwater flows in relation to habitat suitability and sport-fish harvest

The instream flow needs of four sport fishes (rainbow trout Salmo gairdneri , channel catfish Ictalurus punctatus , smallmouth bass Micropterus dolomieui , and white crappie Pomoxis annularis ) were evaluated in the tailwater below Green River Lake, Kentucky. The Newcombe method, a simple procedure developed in British Columbia that is based on the distribution of water depths and velocities at various flows, was used to predict usable habitat at seven flows. Predicted usable habitat was two to six times greater for rainbow trout than for any of the other species at all flows. Angler harvest corresponded to the predicted abundance for rainbow trout and smallmouth bass, but the catch of channel catfish and white crappies was seasonally greater than expected. The presence of the dam and reservoir apparently disrupted the normal movement and feeding patterns of these species and periodically overrode the relation between usable habitat and abundance assumed in the Newcombe method. The year-round minimum flow of 4.6 m 3/s recommended for the tailwater would generally increase the amount of habitat available in the tailwater from April through October, and the minimum flow of 2.4 m3/s recommended for periods of drought would allow the maintenance of a trout fishery.

Kentucky↗

USGS2024

Assessing factors related to Walleye stocking success in the Midwestern United States

Objective The objective of this study was to evaluate stocking success of Walleye Sander vitreus in lakes and reservoirs across the Midwestern United States to inform stocking practices for state agencies. Demand for Walleye stocking may increase if climate change limits the potential for natural recruitment in lakes. Consequently, the strategic distribution of Walleye stocking may maximize fishing opportunities. Methods We synthesized data from 2226 Walleye fry and fingerling stocking events on 653 lakes in the Midwestern United States and used random forest algorithms and mixed-effects linear models to identify abiotic and biotic factors related to Walleye stocking success. Result Latitude and year explained relatively little variation in stocking success compared to within-lake variation. Relative abundance of Largemouth Bass Micropterus nigricans was an important indicator of Walleye stocking success for fry and fingerlings, with stocking success generally decreasing with increased bass abundance. There was an interaction between lake surface area and growing degree-days, as large lakes (>2500 ha) seemed to be more conducive to Walleye stocking success regardless of growing degree-days. The models that we developed did not accurately predict exact levels of Walleye stocking success but were 92–94% accurate in predicting whether the stocking success of both fry and fingerlings would be at or above the 50th percentile. Conclusion These findings may help to inform the management and stocking allocation of Walleye and suggest that future increases in Largemouth Bass abundance and growing degree-days could limit the effectiveness of stocking in some lakes.

Illinois, Indiana, Iowa, Michigan, Minnesota, Nebr↗

USGS2005

Distribution and abundance of black bass in Skiatook Lake, Oklahoma, after introduction of smallmouth bass and a liberalized harvest regulation on spotted bass

We conducted a 3-year study to examine the trends in abundance and distribution of three sympatric black bass species ( Micropterus ) in an Oklahoma reservoir after implementation of a differential harvest regulation to reduce the abundance of spotted bass M. punctulatus and after stocking nonnative smallmouth bass M. dolomieu . Largemouth bass M. salmoides were stocked in Skiatook Lake, Oklahoma, immediately after its creation in 1984 to supplement the existing population in the watershed. Nonnative smallmouth bass were stocked in 1990, and their abundance and distribution have increased ever since. Native spotted bass, which have less fishery value than the other two black bass species, increased fivefold in abundance in 1994, became the predominant black bass species by at least 1996, and appeared to displace largemouth bass from many habitats. From boat-mounted electrofishing sampling conducted in April and May 1997–1999, we found that spotted bass abundance (proportion and catch per hour) had decreased while smallmouth bass abundance and distribution within the reservoir steadily increased. Largemouth bass abundance did not change among years. Throughout our study period, spotted bass was always the most abundant black bass species where differences in abundance were found. Our results suggest that the continually expanding smallmouth bass population is displacing spotted bass from many of their formerly used habitats, much like spotted bass had displaced largemouth bass by 1996.

Oklahoma↗

USGS2022

Differences in population characteristics and modeled response to harvest regulations in reestablished Appalachian Walleye populations

Historically, the Monongahela, Tygart, and Cheat River watersheds in West Virginia were impaired by acidification from acid mine drainage and Walleye Sander vitreus were extirpated from these watersheds by the 1940s. Walleye were reestablished after water quality improvements following passage of environmental legislation and subsequent reintroduction efforts. We compared population characteristics, with emphasis on growth, of Walleye and used modeling to predict the potential effects of harvest regulations in the Monongahela River and two main-stem reservoirs in the Cheat River and Tygart River watersheds. Statistical comparisons of von Bertalanffy growth curves and relative growth indices indicated that Walleye growth significantly differed across all water bodies. Relative growth index results suggested that Walleye growth was above average in Cheat Lake, average in the Monongahela River, and below average in Tygart Lake relative to other North American populations. Growth was negatively correlated with Walleye relative abundance and positively correlated with estimates of productivity (total phosphorus, chlorophyll a ). Walleye diets significantly differed across all water bodies, with diets dominated by Yellow Perch Perca flavescens and Gizzard Shad Dorosoma cepedianum in Cheat Lake, where growth was fastest. Population modeling suggested that effects of exploitation on yield, spawning potential, and size structure were similar under regulations of no length limit and a minimum length limit (381 mm). Models suggested that removing length limits in Tygart Lake could increase angler harvest opportunities and pose minimal threat to the fishery. Models suggested that a protected slot limit could provide increased protection to the spawning potential of Cheat Lake and the Monongahela River populations. Additionally, models predicted that a protected slot limit could increase the number of large (>630-mm) Walleye in these waters. Our findings demonstrate the different characteristics that Walleye populations can develop after reestablishment based on abiotic and biotic conditions and the need for watershed-specific management.

West Virginia↗

USGS2014

Population dynamics of bowfin in a south Georgia reservoir: latitudinal comparisons of population structure, growth, and mortality

The objectives of this study were to evaluate the population dynamics of bowfin (Amia calva) in Lake Lindsay Grace, Georgia, and to compare those dynamics to other bowfin populations. Relative abundance of bowfin sampled in 2010 in Lake Lindsay Grace was low and variable (mean±SD; 2.7±4.7 fish per hour of electrofishing). Total length (TL) of bowfin collected in Lake Lindsay Grace varied from 233–683 mm. Age of bowfin in Lake Lindsay Grace varied from 0–5 yr. Total annual mortality (A) was estimated at 68%. Both sexes appeared to be fully mature by age 2 with gonadosomatic index values above 8 for females and close to 1 for males. The majority of females were older, longer, and heavier than males. Bowfin in Lake Lindsay Grace had fast growth up to age 4 and higher total annual mortality than the other populations examined in this study. A chi-square test indicated that size structure of bowfin from Lake Lindsay Grace was different than those of a Louisiana population and two bowfin populations from the upper Mississippi River. To further assess bowfin size structure, we proposed standard length (i.e., TL) categories: stock (200 mm, 8 inches), quality (350 mm, 14 inches), preferred (460 mm, 18 inches), memorable (560 mm, 22, inches), and trophy (710 mm, 28 inches). Because our knowledge of bowfin ecology is limited, additional understanding of bowfin population dynamics provides important insight that can be used in management of bowfin across their distribution.

Georgia↗

USGS2026

Gerrard strain Rainbow Trout are not piscivorous in a shallow, polymictic reservoir

Objective Georgetown Lake (Montana, USA) is renowned for its multispecies salmonid fishery. Although many anglers target kokanee Oncorhynchus nerka in Georgetown Lake, the body length of kokanee has typically been considered unsatisfactory. To reduce the density of kokanee and increase the average size, Montana Fish, Wildlife & Parks began stocking the piscivorous Gerrard strain of Rainbow Trout O. mykiss (hereafter “Gerrard”) in 2015 to consume kokanee. In 2020, preliminary evidence suggested that the average length of kokanee greater than 200 mm increased by almost 40 mm. Methods To assess the efficacy of biocontrol through the introduction of a piscivore to predate on kokanee, we examined the diet composition of all potential predators (three strains of Rainbow Trout and Brook Trout Salvelinus fontinalis ) to determine the amount of predation on kokanee and to understand the feeding ecology of all potential predators. Results There was little evidence of piscivory in any predator and no evidence of Gerrards consuming kokanee. Gerrards exhibited a generalist feeding strategy, and there was dietary overlap and no difference in trophic position among Gerrards and other predators. Conclusions From a biological-control perspective, there is no benefit in continuing to stock Gerrards to reduce kokanee densities in Georgetown Lake. These findings underscore the challenge of predicting predator–prey relationships, as diet plasticity can lead to unexpected dynamics based on resource availability and habitat structure within aquatic ecosystems, highlighting the importance of evaluating management interventions, such as biocontrols, in different ecosystems.

Montana↗

USGS2010

Dispersal of smallmouth bass from a simulated tournament weigh-in site

Simulated smallmouth bass Micropterus dolomieu fishing tournaments were staged in Dale Hollow Lake, a 12,400-ha reservoir in Tennessee, between March 2004 and February 2005 to investigate posttournament dispersal. Smallmouth bass (n = 54) were captured with conventional hook-and-line tackle and artificial lures, placed in live wells, and subjected to a weigh-in procedure before being externally tagged with an ultrasonic transmitter and released. Water temperatures ranged from 7.4°C to 29.3°C (mean [SE] = 17.6°C [2.5]), fish ranged in total length from 330 to 572 mm (mean = 452 [8.3]), and no fish were dead at the weigh-ins. Smallmouth bass dispersed rapidly away from the release site, which was located at the head of a 68-ha embayment. After 3-5d, survivors (n = 44) traversed an average distance of 1,475 m [213]. Most (72%) fish swam uplake and out of the 385-ha study area after 6 d. The rapid dispersal of smallmouth bass may be relevant in systems that experience heavy tournament activity. The smallmouth bass caught and subjected to simulated tournament conditions on Dale Hollow Lake did not stockpile near the release site.

North American Journal of Fisheries Management↗

USGS2017

Carbon dioxide enhanced oil recovery performance according to the literature

Introduction The need to increase the efficiency of oil recovery and environmental concerns are bringing to prominence the use of carbon dioxide (CO 2 ) as a tertiary recovery agent. Assessment of the impact of flooding with CO 2 all eligible reservoirs in the United States not yet undergoing enhanced oil recovery (EOR) requires making the best possible use of the experience gained in 40 years of applications. Review of the publicly available literature has located relevant CO 2 -EOR information for 53 units (fields, reservoirs, pilot areas) in the United States and 17 abroad. As the world simultaneously faces an increasing concentration of CO 2 in the atmosphere and a higher demand for fossil fuels, the CO 2 -EOR process continues to gain popularity for its efficiency as a tertiary recovery agent and for the potential for having some CO 2 trapped in the subsurface as an unintended consequence of the enhanced production (Advanced Resources International and Melzer Consulting, 2009). More extensive application of CO 2 -EOR worldwide, however, is not making it significantly easier to predict the exact outcome of the CO 2 flooding in new reservoirs. The standard approach to examine and manage risks is to analyze the intended target by conducting laboratory work, running simulation models, and, finally, gaining field experience with a pilot test. This approach, though, is not always possible. For example, assessment of the potential of CO 2 -EOR at the national level in a vast country such as the United States requires making forecasts based on information already available. Although many studies are proprietary, the published literature has provided reviews of CO 2 -EOR projects. Yet, there is always interest in updating reports and analyzing the information under new perspectives. Brock and Bryan (1989) described results obtained during the earlier days of CO 2 -EOR from 1972 to 1987. Most of the recovery predictions, however, were based on intended injections of 30 percent the size of the reservoir’s hydrocarbon pore volume (HCPV), and the predictions in most cases badly missed the actual recoveries because of the embryonic state of tertiary recovery in general and CO 2 flooding in particular at the time. Brock and Bryan (1989), for example, reported for the Weber Sandstone in the Rangely oil field in Colorado, an expected recovery of 7.5 percent of the original oil in place (OOIP) after injecting a volume of CO 2 equivalent to 30 percent of the HCPV, but Clark (2012) reported that after injecting a volume of CO 2 equivalent to 46 percent of the HCPV, the actual recovery was 4.8 percent of the OOIP. Decades later, the numbers by Brock and Bryan (1989) continue to be cited as part of expanded reviews, such as the one by Kuuskraa and Koperna (2006). Other comprehensive reviews including recovery factors are those of Christensen and others (2001) and Lake and Walsh (2008). The Oil and Gas Journal (O&GJ) periodically reports on active CO 2 -EOR operations worldwide, but those releases do not include recovery factors. The monograph by Jarrell and others (2002) remains the most technically comprehensive publication on CO 2 flooding, but it does not cover recovery factors either. This chapter is a review of the literature found in a search for information about CO 2 -EOR. It has been prepared as part of a project by the U.S. Geological Survey (USGS) to assess the incremental oil production that would be technically feasible by CO 2 flooding of all suitable oil reservoirs in the country not yet undergoing tertiary recovery.

Scientific Investigations Report↗

USGS2018

Featured collection introduction: Connectivity of streams and wetlands to downstream waters

Connectivity is a fundamental but highly dynamic property of watersheds. Variability in the types and degrees of aquatic ecosystem connectivity presents challenges for researchers and managers seeking to accurately quantify its effects on critical hydrologic, biogeochemical, and biological processes. However, protecting natural gradients of connectivity is key to protecting the range of ecosystem services that aquatic ecosystems provide. In this featured collection, we review the available evidence on connections and functions by which streams and wetlands affect the integrity of downstream waters such as large rivers, lakes, reservoirs, and estuaries. The reviews in this collection focus on the types of waters whose protections under the U.S. Clean Water Act have been called into question by U.S. Supreme Court cases. We synthesize 40+ years of research on longitudinal, lateral, and vertical fluxes of energy, material, and biota between aquatic ecosystems included within the Act's frame of reference. Many questions about the roles of streams and wetlands in sustaining downstream water integrity can be answered from currently available literature, and emerging research is rapidly closing data gaps with exciting new insights into aquatic connectivity and function at local, watershed, and regional scales. Synthesis of foundational and emerging research is needed to support science‐based efforts to provide safe, reliable sources of fresh water for present and future generations.

Journal of the American Water Resources Associatio↗

USGS2016

Impacts of Northern Pike on stocked Rainbow Trout in Pactola Reservoir, South Dakota

Establishment of nonnative Northern Pike Esox lucius in Pactola Reservoir, South Dakota, has prompted concern among biologists about the influence of this species on the lake’s intensively managed salmonid fisheries. Ancedotal information suggests that catch rates of Rainbow Trout Oncorhynchus mykiss have declined while mean size and abundance of Northern Pike has increased, although quantitative information on diet and growth of the Northern Pike population is lacking. To address potential interactions between Northern Pike and Rainbow Trout, we assessed size-dependent predation by Northern Pike on Rainbow Trout and determined the relative energetic contribution of stocked Rainbow Trout to Northern Pike growth using bioenergetics modeling. Stable isotopes combined with traditional diet analyses revealed that smaller Northern Pike (<600 mm TL) consumed primarily centrarchids and Rainbow Smelt Osmerus mordax , and Rainbow Trout contributed less than 10% to their annual energy consumption. In contrast, larger Northern Pike (≥600 mm TL) consumed primarily Rainbow Trout, which accounted for 56% of their annual energy consumption. Combining estimates of Northern Pike predation with production costs of catchable-size Rainbow Trout revealed that annual economic losses ranged from US$15,259 to $24,801 per year. Over its lifespan, an age-10 Northern Pike was estimated to consume ~117 Rainbow Trout worth approximately $340. Thus, Northern Pike predation substantially influences salmonid management initiatives and is likely a primary factor contributing to reduced Rainbow Trout abundance and return to anglers in Pactola Reservoir. Strategies for reducing Northern Pike predation on Rainbow Trout include increasing the size of stocked fish or altering the timing and spatial distribution of stocking events.

South Dakota↗

USGS2015

Agonistic behavior among three stocked trout species in a novel reservoir fish community

The popularity of reservoirs to support sport fisheries has led to the stocking of species that did not co-evolve, creating novel reservoir fish communities. In Utah, the Bear Lake strain of Bonneville Cutthroat Trout Oncorhynchus clarkii utah and tiger trout (female Brown Trout Salmo trutta × male Brook Trout Salvelinus fontinalis ) are being more frequently added to a traditional stocking regimen consisting primarily of Rainbow Trout O. mykiss . Interactions between these three predatory species are not well understood, and studies evaluating community interactions have raised concern for an overall decrease of trout condition. To evaluate the potential for negative interactions among these species, we tested aggression in laboratory aquaria using three-species and pairwise combinations at three densities. Treatments were replicated before and after feeding. During the three-species trials Rainbow Trout initiated 24.8 times more aggressive interactions than Cutthroat Trout and 10.2 times more aggressive interactions than tiger trout, and tiger trout exhibited slightly (1.9 times) more aggressive initiations than Cutthroat Trout. There was no significant difference in behavior before versus after feeding for any species, and no indication of increased aggression at higher densities. Although Rainbow Trout in aquaria may benefit from their bold, aggressive behavior, given observations of decreased relative survival in the field, these benefits may be outweighed in reservoirs, possibly through unnecessary energy expenditure and exposure to predators.

North American Journal of Fisheries Management↗

USGS2023

Environmental correlates of walleye spawning movements in an Appalachian hydropower reservoir

Understanding walleye ( Sander vitreus ) spawning behavior is important for managing walleye fisheries, but such information is limited for Appalachian reservoirs. We assessed spawning movements and spawning locations for a reestablished walleye population in Cheat Lake, West Virginia. We tagged fifty-two walleye with acoustic telemetry transmitters to evaluate environmental correlates associated with pre-spawn movements and to deter- mine spawning locations. Using an information-theoretic approach, we compared candidate logistic regression models to determine which environmental variables best explained upstream movements to spawning areas. The two models with the most support both included additive effects of year and water temperature, with sex also included in the second of these models. Water temperature had a significant positive relationship with pre-spawn movements in each model. Other environmental covariates such as river discharge and water elevation were not significant predictors of upstream pre-spawn move- ments. Walleye made pre-spawn upstream movements in late winter/early spring to spawning areas in the headwaters of Cheat Lake during periods of el- evated water temperatures (75 % of movement events occurred at water temperatures >4.1 C) where spawning occurred in shallow (<1.5 m), rocky habitat. Male walleye generally made upstream pre-spawn movements earlier than females. Our results also suggested the timing of walleye spawning with respect to water-level fluctuations could influence reproductive success due to stranding of eggs or reducing suitable spawning habitat. Knowledge of pre-spawn movement patterns and spawning locations could aid management of this recovering population. Benefits to management may include the prediction of spawning timing and locations for broodstock surveys and influences of water-level fluctuations and other environmental stressors on spawning success.

Pennsylvania, West Virginia↗

USGS2017

Comparison of American Fisheries Society (AFS) standard fish sampling techniques and environmental DNA for characterizing fish communities in a large reservoir

Recently, methods involving examination of environmental DNA (eDNA) have shown promise for characterizing fish species presence and distribution in waterbodies. We evaluated the use of eDNA for standard fish monitoring surveys in a large reservoir. Specifically, we compared the presence, relative abundance, biomass, and relative percent composition of Largemouth Bass Micropterus salmoides and Gizzard Shad Dorosoma cepedianum measured through eDNA methods and established American Fisheries Society standard sampling methods for Theodore Roosevelt Lake, Arizona. Catches at electrofishing and gillnetting sites were compared with eDNA water samples at sites, within spatial strata, and over the entire reservoir. Gizzard Shad were detected at a higher percentage of sites with eDNA methods than with boat electrofishing in both spring and fall. In contrast, spring and fall gillnetting detected Gizzard Shad at more sites than eDNA. Boat electrofishing and gillnetting detected Largemouth Bass at more sites than eDNA; the exception was fall gillnetting, for which the number of sites of Largemouth Bass detection was equal to that for eDNA. We observed no relationship between relative abundance and biomass of Largemouth Bass and Gizzard Shad measured by established methods and eDNA copies at individual sites or lake sections. Reservoirwide catch composition for Largemouth Bass and Gizzard Shad (numbers and total weight [g] of fish) as determined through a combination of gear types (boat electrofishing plus gillnetting) was similar to the proportion of total eDNA copies from each species in spring and fall field sampling. However, no similarity existed between proportions of fish caught via spring and fall boat electrofishing and the proportion of total eDNA copies from each species. Our study suggests that eDNA field sampling protocols, filtration, DNA extraction, primer design, and DNA sequencing methods need further refinement and testing before incorporation into standard fish sampling surveys.

Arizona↗

USGS2015

Status and conservation of interior Redband Trout in the western United States

In this article we describe the current status and conservation of interior (potamodromous) Redband Trout Oncorhynchus mykiss sspp. throughout its range in the western United States using extant data and expert opinion provided by fish managers. Redband Trout historically occupied 60,295 km of stream habitat and 152 natural lakes. Currently, Redband Trout occupy 25,417 km of stream habitat (42% of their historical range) and 124 lakes or reservoirs. Nonhybridized populations are assumed to occupy 11,695 km (46%) of currently occupied streams; however, fish from only 4,473 km (18%) have been genetically tested. Approximately 47% of the streams occupied by Redband Trout occur on private land, 45% on government lands, and 8% in protected areas. A total of 210 Redband Trout populations, occupying 15,252 km of stream habitat (60% of the current distribution) and 95,158 ha of lake habitat (52%), are being managed as “conservation populations.” Most conservation populations have been designated as weakly to strongly connected metapopulations (125; 60%) and occupy much more stream length (14,112 km; 93%) than isolated conservation populations (1,141 km; 7%). The primary threats to Redband Trout include invasive species, habitat degradation and fragmentation, and climate change. Although the historical distribution of interior Redband Trout has declined dramatically, we conclude that the species is not currently at imminent risk of extinction because it is still widely distributed with many populations isolated by physical barriers and active conservation efforts are occurring for many populations. However, the hybridization status of many populations has not been well quantified, and introgression may be more prevalent than documented here. We recommend (1) collecting additional genetic data and estimating distribution and abundance by means of a more rigorous spatial sampling design to reduce uncertainties, (2) collecting additional information to assess and predict the impacts of climate on populations, and (3) continuing to use this database to evaluate the status of Redband Trout and inform conservation efforts through time.

North American Journal of Fisheries Management↗

USGS2019

Age and growth of Freshwater Drum and Gizzard Shad occupying two reservoir-river complexes with different groundwater contributions

Restoring groundwater flow is a management option that improves water temperature regimes and benefits fishes. Although this strategy applies more readily to river systems, the thermal character of reservoirs is heavily influenced by inflowing rivers. We examined differences in age, structure, and growth of both Freshwater Drum Aplodinotus grunniens and Gizzard Shad Dorosoma cepedianum that occupy catchments with varying groundwater contributions in the south‐central United States. Seepage run data indicated that the Kiamichi River was losing surface water to groundwater in summer 2016, whereas groundwater inflows were apparent in the Elk River basin. Summer 2016 data showed that the Elk River had cooler water temperatures than the Kiamichi River and Grand Lake O’ the Cherokees water temperatures were similar to those in the incoming Elk River. We found higher densities of older Freshwater Drum and Gizzard Shad (maximums of 32 and 8 years old, respectively) in samples from the Grand basin than among fish that were sampled from the Kiamichi River basin (21 and 6 years old, respectively). Freshwater Drum grew at similar rates in both basins even though they reached larger maximum lengths in the Grand basin (649 mm TL) than in the Kiamichi River basin (600 mm). The average asymptotic length was greater for the Kiamichi population ( L ∞ = 613 mm) than for the Grand population ( L ∞ = 557 mm). Gizzard Shad from the Grand basin were larger than those from the Kiamichi River basin, though the latter population grew faster initially (Brody growth coefficient: K = 0.787 versus K = 0.179, respectively), but they had smaller asymptotic length ( L ∞ = 206 mm versus L ∞ = 343 mm). The role that groundwater plays in temperature regulation in these basins partially explains the observed differences. Our results suggest that the metabolic theory of ecology can be applied to fisheries management at a finer spatial scale.

Oklahoma↗