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Results for “Journal of Lake and Reservoir Management”

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At least 37 records · Page 2Linked to original sources
USGS2019

Understanding fish assemblage structure in lentic ecosystems: Relative effects of abiotic factors and management legacies

We investigated associations of fish assemblages and habitat characteristics (e.g., morphology and water chemistry) from 45 natural lakes and reservoirs in Iowa to determine whether species or trophic guild composition and environmental correlations were concordant between waterbodies of different origins. Overall, fish assemblage composition between natural lakes and reservoirs was consistently dissimilar based on a permutational multivariate ANOVA. Species composition from nonmetric multidimensional scaling ordinations for reservoirs was correlated with a variety of limnological and physical characteristics, whereas species composition and trophic composition of natural lakes were weakly associated with habitat characteristics. Species richness was positively related to waterbody and watershed size for reservoirs but not for natural lakes. Conversely, species richness was negatively correlated with increasing eutrophic conditions in natural lakes but not in reservoirs. Overall, distinct differences in assemblage composition were observed between natural and artificial lentic ecosystems and may have resulted from underlying differences in limnological, physical, and anthropogenic influences between systems. Dissimilar management legacies between waterbody types, such as limited or no stocking of nonrecreationally important species and the use of piscicides, may have additionally had overriding effects on the observed assemblage–environmental relationships. For instance, lower trophic richness and species richness in reservoirs appeared to have resulted from replacement of a diversity of small-bodied native species by relatively few commonly stocked sport fishes. Our results emphasize the need to consider waterbody origin and the potential influence of historical or current management strategies on fish assemblage characterization and subsequent inferences made from environmental correlations.

Iowa↗
USGS2023

When are environmental DNA early detections of invasive species actionable?

Environmental DNA (eDNA) sampling provides sensitive early detection capabilities for recently introduced taxa. However, natural resource managers struggle with how to integrate eDNA results into an early detection rapid response program because positive eDNA detections are not always indicative of an eventual infestation. We used a structured decision making (SDM) framework to evaluate appropriate response actions to hypothetical eDNA early detections of an introduced aquatic plant in Sebago Lake (Maine, USA). The results were juxtaposed to a recent study that used a similar SDM approach to evaluate response actions to hypothetical eDNA early detections of introduced mussels in Jordanelle Reservoir (Utah, USA). We found that eDNA early detections were not actionable in Sebago Lake because the plant's invasion potential was spatially constrained and the current management activities provided acceptable levels of mitigation. In Jordanelle Reservoir, eDNA detections were actionable due to high invasion potential and analyses supported management actions to contain the invasion. The divergent outcomes of the two case studies are related to the unique attributes of the habitats and species, highlighting the utility of the SDM approach when considering an eDNA monitoring program. We use these two case studies to present a general SDM framework and a set of heuristics that can be efficiently applied to eDNA early detection rapid response scenarios and other instances associated with indeterminant eDNA detections, especially when there is an imperative to make decisions as quickly as possible.

Maine↗
USGS2018

Population characteristics of Yellow Perch in a central Appalachia hydropower reservoir

Estimates of population characteristics of sport fishes inform fisheries management decisions and provide feedback on management strategies. Cheat Lake provides an unusual fishery in West Virginia because the hydropower reservoir supports a Yellow Perch Perca flavescens population. We estimated age structure, size structure, condition, total instantaneous mortality, growth, and summer diet for Cheat Lake Yellow Perch based on electrofishing collections in 2012. From 302 individuals, we observed a maximum age of 9 y. Maximum age, average size, and growth of females in the sample exceeded those of males. Cheat Lake Yellow Perch scored low on the relative weight index, but generally exhibited faster growth than other populations, even when compared by sex. Estimated annual survival was 0.63 (95% CI = 0.51–0.78), which is comparable to other exploited populations. These data support the presence of an ontogenetic diet shift from consumption of zooplankton to macroinvertebrates and fishes as Yellow Perch age. This study is the first evaluation we are aware of on Yellow Perch population characteristics in West Virginia, providing baseline data to enhance management decisions and direct future studies.

West Virginia↗
USGS2014

Small reservoir distribution, rate of construction, and uses in the upper and middle Chattahoochee basins of the Georgia Piedmont, USA, 1950-2010

Construction of small reservoirs affects ecosystem processes in numerous ways including fragmenting stream habitat, altering hydrology, and modifying water chemistry. While the upper and middle Chattahoochee River basins within the Southeastern United States Piedmont contain few natural lakes, they have a high density of small reservoirs (more than 7500 small reservoirs in the nearly 12,000 km2 basin). Policymakers and water managers in the region have little information about small reservoir distribution, uses, or the cumulative inundation of land cover caused by small reservoir construction. Examination of aerial photography reveals the spatiotemporal patterns and extent of small reservoir construction from 1950 to 2010. Over that 60 year timeframe, the area inundated by water increased nearly six fold (from 19 reservoirs covering 0.16% of the study area in 1950 to 329 reservoirs covering 0.95% of the study area in 2010). While agricultural practices were associated with reservoir creation from 1950 to 1970, the highest rates of reservoir construction occurred during subsequent suburban development between 1980 and 1990. Land cover adjacent to individual reservoirs transitioned over time through agricultural abandonment, land reforestation, and conversion to development during suburban expansion. The prolific rate of ongoing small reservoir creation, particularly in newly urbanizing regions and developing counties, necessitates additional attention from watershed managers and continued scientific research into cumulative environmental impacts at the watershed scale.

Georgia↗
USGS2021

Adult sockeye salmon responses to transplanting upstream of an impassable dam

The Yakama Nation manages a program for reintroducing Sockeye Salmon Oncorhynchus nerka upstream of Cle Elum Dam in the Yakima River basin. The program involves transplanting of a mix of adult Sockeye Salmon from two middle Columbia River donor stocks, Lake Wenatchee (WEN) and Osoyoos Lake (OSO), with the goal of establishing a self-sustaining population in the basin. In 2017, a subset of the transplanted population was radio-tagged and monitored to assess stock-specific responses to transplanting, including downstream entrainment at Cle Elum Dam (“fallback”) and prespawn mortality. Tagged fish were active during the first two weeks after release: some fish moved upstream into the Cle Elum River and then returned to the reservoir; other fish moved downstream and passed Cle Elum Dam. Movement within the study area diminished during August but increased in September when fish began migrating up the Cle Elum River for spawning. A greater proportion of WEN fish (76.3%) were detected entering the river compared to OSO fish (53.9%). The hazard ratio from a multistate analysis of fish behavior indicated that WEN fish were nine times more likely to enter the river than OSO fish. The WEN fish also initiated upstream movement three weeks earlier than OSO fish. We found that 27.0% of all tagged fish were lost to the spawning population through fallback (20.7%) and prespawn mortality (6.3%). Fallback and pre-spawn mortality occurred for a greater percentage of OSO fish (26.9% and 7.7%) than WEN fish (15.3% and 5.1%) but these differences were not statistically different. These results provide foundational information from the early phase of a reintroduction effort. Continued monitoring will be required as Sockeye Salmon evolve to conditions upstream of Cle Elum Dam, and results from these efforts will provide valuable insights for this reintroduction effort and others in river systems with similar characteristics.

Washington↗
USGS2011

Source and delivery of nutrients to receiving waters in the Northeastern and Mid-Atlantic regions of the United States

This study investigates nutrient sources and transport to receiving waters, in order to provide spatially detailed information to aid water-resources managers concerned with eutrophication and nutrient management strategies. SPAtially Referenced Regressions On Watershed attributes (SPARROW) nutrient models were developed for the Northeastern and Mid-Atlantic (NE US) regions of the United States to represent source conditions for the year 2002. The model developed to examine the source and delivery of nitrogen to the estuaries of nine large rivers along the NE US Seaboard indicated that agricultural sources contribute the largest percentage (37%) of the total nitrogen load delivered to the estuaries. Point sources account for 28% while atmospheric deposition accounts for 20%. A second SPARROW model was used to examine the sources and delivery of phosphorus to lakes and reservoirs throughout the NE US. The greatest attenuation of phosphorus occurred in lakes that were large relative to the size of their watershed. Model results show that, within the NE US, aquatic decay of nutrients is quite limited on an annual basis and that we especially cannot rely on natural attenuation to remove nutrients within the larger rivers nor within lakes with large watersheds relative to the size of the lake.

Journal of the American Water Resources Associatio↗
USGS2013

High-density grass carp stocking effects on a reservoir invasive plant and water quality

Stocking grass carp [Ctenopharyngodon idella (Valenciennes)] is a commonly applied technique to control nuisance aquatic vegetation in reservoirs. Factors that influence the degree of aquatic vegetation control are fish stocking density, regional climate, abundance and species composition of the aquatic plant community, and relative grass carp feeding preferences for plant species. We evaluated high-density grass carp stocking in a southeastern U.S. reservoir for control of parrot-feather [Myriophyllum aquaticum (Vell) Verdc.], an invasive aquatic plant that is not preferentially consumed by grass carp and the associated effects on water quality. Lookout Shoals Lake, a 528-ha piedmont North Carolina reservoir, was stocked with triploid grass carp at a density of 100 fish per vegetated hectare. Parrot-feather biomass in the lake was significantly reduced three months after grass carp stocking, compared to biomass in in-situ exclosures. During the second year after grass carp stocking, parrot-feather biomass in the lake compared to biomass in in-situ exclosures indicated continued control, but unexplained lack of growth within most experimental exclosures precluded biomass analyses. Increases in ambient water chlorophyll a, reactive phosphorus, and nitrate-nitrite concentrations were measured after grass carp stocking. The biological significance of observed changes in water chemistry and long-term effects on lake biota remain undetermined. Our results demonstrate that intensive grass carp stocking can control an invasive aquatic plant that is not preferentially consumed by grass carp and reveal associated changes in water quality.

North Carolina↗
USGS1985

Chronology of migration by American coots in Oklahoma

American coots ( Fulica americana ) were studied on large reservoirs in north-central Oklahoma in 1979-1982 to determine chronologies of migrations by age- and sex class. Coots began migrating into Oklahoma in mid-September, numbers peaked in early to mid-October, and few birds were seen after 1 November. Some late migrants appeared in mid-December. In spring, coots began migrating in late February, numbers peaked in mid-April, and the last birds were seen in mid-May. Generally, adult and juvenile males and juvenile female coots migrated simultaneously in autumn, but adult females completed migration by 1 November. A few juveniles and adult males migrated in December. Adult coots preceded yearlings in spring. Despite annual and between-lake differences in chronology of autumn migration, most coots migrated before waterfowl hunting season in Oklahoma. Coot hunting seasons in mid-latitude states should commence before the general waterfowl season where management goals are to increase hunter interest and the harvest of birds.

Oklahoma↗
USGS2005

Temporal and spatial variation in relative abundance and length structure of salmonids in reservoirs: Implications for monitoring

Spatial and temporal variations in salmonid catch per unit effort (C/f) may affect monitoring efforts in lakes and reservoirs. This study evaluated the spatial and temporal variation in gill-net C/f and length structure of captured salmonids in nearshore (???7.6-m bottom depth) and offshore (>7.6-m bottom depth) areas of two Wyoming reservoirs. Floating experimental gill nets were set as nearshore and offshore pairs at 24 locations in both reservoirs during each of four sampling periods (spring, early summer, late summer, and fall). Salmonid C/f was significantly higher in nearshore areas than in offshore areas during all periods in one reservoir and during all periods except spring in the other reservoir. Mean C/f of rainbow trout Oncorhynchus mykiss was not significantly different between nearshore and offshore areas when water temperatures were 10-13??C in both reservoirs. Length structure of salmonids differed significantly between nearshore and offshore locations and among periods in both reservoirs. These patterns should be considered in both the design and analysis phases of monitoring efforts that use floating experimental gill nets and other sampling gears. ?? Copyright by the American Fisheries Society 2005.

North American Journal of Fisheries Management↗
USGS1983

Fish abundance and population stability in a reservoir tailwater and an unregulated headwater stream

Fish abundance and population stability were compared in the tailwater and in an unregulated tributary of Barren River Lake, a flood control reservoir in south central Kentucky. Fish abundance was greater in the tailwater near the dam and was dominated by three species common in the reservoir: gizzard shad ( Dorosoma cepedianum ), bluegills ( Lepomis macrochirus ), and white crappies ( Pomoxis annularis ). Three riverine suckers were less abundant in the tailwater than in the unregulated stream: northern hog suckers ( Hypentelium nigricans ), black redhorse ( Moxostoma duquesnei ), and golden redhorse ( Moxostoma erythrurum ). The fish populations in the tailwater, particularly common carp ( Cyprinus carpio ), northern hog suckers, black redhorse, and golden redhorse, were less stable than those in the unregulated stream. Population stability is defined as the extent to which fish remain in a stream section. This study suggests that the occurrence of reservoir species in the tailwater was the result of fish passage from the reservoir during high discharges in fall and winter. Reservoir operations (altered flow, low summer water temperature, and poor summer water quality) probably were responsible for the unstable populations of common carp and riverine suckers in the tailwater.

Kentucky↗
USGS2018

Monitoring algal blooms in drinking water reservoirs using the Landsat-8 Operational Land Imager

In this study, we demonstrated that the Landsat-8 Operational Land Imager (OLI) sensor is a powerful tool that can provide periodic and system-wide information on the condition of drinking water reservoirs. The OLI is a multispectral radiometer (30 m spatial resolution) that allows ecosystem observations at spatial and temporal scales that allow the environmental community and water managers another means to monitor changes in water quality not feasible with field-based monitoring. Using the provisional Land Surface Reflectance product and field-collected chlorophyll- a (chl- a ) concentrations from drinking water monitoring programs in North Carolina and Rhode Island, we compared five established approaches for estimating chl- a concentrations using spectral data. We found that using the three band reflectance approach with a combination of OLI spectral bands 1, 3, and 5 produced the most promising results for accurately estimating chl- a concentrations in lakes ( R 2 value of 0.66; root mean square error value of 8.9 µg l −1 ). Using this model, we forecast the spatial and temporal variability of chl- a for Jordan Lake, a recreational and drinking water source in piedmont North Carolina and several small ponds that supply drinking water in southeastern Rhode Island.

North Carolina↗
USGS2010

Interactions between walleyes and smallmouth bass in a Missouri River reservoir with consideration of the influence of temperature and prey

Walleyes Sander vitreus are the most popular fish among South Dakota anglers, but smallmouth bass Micropterus dolomieu were introduced to provide new angling opportunities. Some walleye anglers have reported reductions in the quality of walleye fisheries since the introduction of smallmouth bass and attribute this to the consumption of young walleyes by smallmouth bass and competition for shared prey resources. We quantified the diets of walleyes and smallmouth bass in the lower reaches of Lake Sharpe (a Missouri River reservoir), calculated the diet overlap between the two predators, and determined whether they partitioned shared prey based on size. We also quantified walleye diets in the upper reach of the reservoir, which has a different prey base and allowed us to compare the growth rates of walleyes within Lake Sharpe. Age-0 gizzard shad Dorosoma cepedianum composed a substantial proportion of the diets of both predators, regardless of location, for most of the growing season; the patterns in shad vulnerability appeared to drive the observed patterns in diet overlap. Smallmouth bass appeared to consume a smaller size range of gizzard shad than did walleyes, which consumed a wide range. Smallmouth bass consumed Sander spp. in some months, but in very low quantities. Given that global climate change is expected to alter the population and community dynamics in Great Plains reservoirs, we also used a bioenergetics approach to predict the potential effects of limiting prey availability (specifically, the absence of gizzard shad and rainbow smelt Osmerus mordax ) and increased water temperatures (as projected from global climate change models) on walleye and smallmouth bass growth. The models indicated that the absence of rainbow smelt from the diets of walleyes in upper Lake Sharpe would reduce growth but that the absence of gizzard shad would have a more marked negative effect on both predators at both locations. The models also indicated that higher water temperatures would have an even greater negative influence on walleye growth; however, smallmouth bass growth was predicted to increase with higher temperatures. Fisheries managers should consider strategies to enhance the prey base or mitigate the effects of increased water temperatures that may occur in the future as a result of global climate change. Such proactive actions may alleviate potential future competition between walleyes and smallmouth bass resulting from changes in the fish community.

North American Journal of Fisheries Management↗
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&ndash;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↗