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At least 577 records · Page 32Linked to original sources
USGS2004

Preventing, controlling, and managing alien species introduction for the health of aquatic and marine ecosystems

The introduction and spread of invasive species is an emerging global problem. As economic and ecological impacts continue to grow, there will be an increasing need to develop innovative solutions and global partnerships to combat the increasing rate of invasions and their accompanying impacts. Threats to sustainable fisheries in North America associated with alien species come from many global directions and sources and can be deliberate or the unintended consequence of other actions. Decisions about the role of sustainable fisheries in protecting and restoring the health of aquatic ecosystems become even more complex when economic and social factors are considered along with environmental impacts, because many intentionally introduced species also have associated economic and community costs and benefits. Actions designed to prevent or control alien species in an aquatic ecosystem are often complicated by these nonenvironmental factors as well as public perception and opinion. Aquatic ecosystems are disturbed to varying degrees by alien species, including disease organisms. Prevention is the first and best line of defense. Determining likely pathways and effective countermeasures is more cost-effective than either eradication or control. Our ability to quickly identify new species and their associated risk to ecosystems is critical in designing and implementing effective control and management actions. Lack of infrastructure and necessary resources, clear-cut authority for regulation and action, and scientific information about the biology of alien species and effective control techniques are often limiting factors that prevent the needed action to protect aquatic ecosystems.

American Fisheries Society Symposium↗
USGS2025

Reevaluation of an adaptive management framework for invasive Grass Carp within Lake Erie

Objective Response efforts to control invasive species frequently require making decisions in the face of substantial uncertainty. Adaptive management, which emphasizes learning during the process of managing, can be useful in cases where uncertainty impedes the decision-making process. Here, we describe how technical and institutional learning led to reformulating decision-making elements, known as double-loop learning, and how uncertainty stemming from a lack of knowledge influenced the selection of alternative strategies in an ongoing adaptive management process for invasive Grass Carp Ctenopharyngodon idella in Lake Erie. Methods When response efforts began, little was known about the population dynamics, ecology, and biology of Grass Carp within the lake. The availability of funding for sustained response efforts was also unknown. A network population model was constructed that relied heavily on values and estimates from limited data to project adult Grass Carp abundance in Lake Erie and evaluate the ability of various response strategies to achieve the desired objectives. After this initial assessment, the collection of new information was emphasized as response efforts increased to aid future assessments. With this expanded knowledge and including additional input from stakeholders, we modified the population model, evaluated new response scenarios, refined objectives, and examined the influence of uncertainty (parameter and expert opinion) on Grass Carp response efforts. Results Under uncertainty of population model parameters and expert opinion, the value-of-information analysis revealed that uncertainties in spawning deterrent efficacy, survival, and the underlying stock–recruitment relationship were important and could change the preferred decision. The efficiency of spawning deterrents influenced the preferred decision outcome among alternative strategies, particularly when >80% of fish were allowed to pass and spawn, indicating that a deterrent may not be worth implementing if passing rates are above this threshold. Conclusions We thereby demonstrate the benefits for invasive species management programs of implementing learning and resolving uncertainties within an adaptive management framework to improve decision making.

Lake Erie↗
USGS2016

Vive la résistance: genome-wide selection against introduced alleles in invasive hybrid zones

Evolutionary and ecological consequences of hybridization between native and invasive species are notoriously complicated because patterns of selection acting on non-native alleles can vary throughout the genome and across environments. Rapid advances in genomics now make it feasible to assess locus-specific and genome-wide patterns of natural selection acting on invasive introgression within and among natural populations occupying diverse environments. We quantified genome-wide patterns of admixture across multiple independent hybrid zones of native westslope cutthroat trout and invasive rainbow trout, the world's most widely introduced fish, by genotyping 339 individuals from 21 populations using 9380 species-diagnostic loci. A significantly greater proportion of the genome appeared to be under selection favouring native cutthroat trout (rather than rainbow trout), and this pattern was pervasive across the genome (detected on most chromosomes). Furthermore, selection against invasive alleles was consistent across populations and environments, even in those where rainbow trout were predicted to have a selective advantage (warm environments). These data corroborate field studies showing that hybrids between these species have lower fitness than the native taxa, and show that these fitness differences are due to selection favouring many native genes distributed widely throughout the genome.

Proceedings of the Royal Society B: Biological Sci↗
USGS2017

Development of a coastal drought index using salinity data

A critical aspect of the uniqueness of coastal drought is the effects on the salinity dynamics of creeks, rivers, and estuaries. The location of the freshwater–saltwater interface along the coast is an important factor in the ecological and socioeconomic dynamics of coastal communities. Salinity is a critical response variable that integrates hydrologic and coastal dynamics including sea level, tides, winds, precipitation, streamflow, and tropical storms. The position of the interface determines the composition of freshwater and saltwater aquatic communities as well as the freshwater availability for water intakes. Many definitions of drought have been proposed, with most describing a decline in precipitation having negative impacts on the water supply. Indices have been developed incorporating data such as rainfall, streamflow, soil moisture, and groundwater levels. These water-availability drought indices were developed for upland areas and may not be ideal for characterizing coastal drought. The availability of real-time and historical salinity datasets provides an opportunity for the development of a salinity-based coastal drought index. An approach similar to the standardized precipitation index (SPI) was modified and applied to salinity data obtained from sites in South Carolina and Georgia. Using the SPI approach, the index becomes a coastal salinity index (CSI) that characterizes coastal salinity conditions with respect to drought periods of higher-saline conditions and wet periods of higher-freshwater conditions. Evaluation of the CSI indicates that it provides additional coastal response information as compared to the SPI and the Palmer hydrologic drought index, and the CSI can be used for different estuary types and for comparison of conditions along coastlines.

Bulletin of the American Meteorological Society↗
USGS2021

Eastward expansion of Round Goby in New York: Assessment of detection methods and current range

The Round Goby Neogobius melanostomus has spread rapidly around the Great Lakes region since its introduction to North America in 1990. In 2014, a specimen was captured in the New York State Canal System west of Utica, prompting concerns that Round Goby would soon reach the ecologically and economically valuable watersheds of Lake Champlain and the Hudson River estuary. The establishment of Round Goby populations elsewhere has been linked to a number of negative ecological consequences, yet methods for monitoring the invasion front of this species remain limited. The objectives of this study were to assess the current distribution of Round Goby in central New York and to determine the most effective methods for monitoring the invasion front. This was achieved by concurrently using benthic trawling, seining, minnow traps, and environmental DNA (eDNA) twice annually from 2016 to 2019 at 12 sites on the canal system between Oneida Lake and the Hudson River. Of the three traditional gear types, benthic trawling was the most effective method and captured Round Goby as far east as Utica by 2019. This finding suggests only minimal eastward expansion of Round Goby occurred between 2014 and 2019. Round Goby DNA was detected in water samples during all surveys in which individuals were captured with trawling, and the estimated concentration of DNA explained 69% of the variability in trawl catch. At multiple study sites, Round Goby DNA was identified during consecutive surveys before Round Goby were first captured with trawling. This suggests that in lotic waters, eDNA has the potential to forecast or serve as a sentinel for the expansion of Round Goby to new locations. Our results demonstrate the importance of using eDNA in a repeated sampling framework and supplementing eDNA sampling with some level of effort with traditional sampling methods.

Great Lakes↗
USGS2022

Herbaceous production lost to tree encroachment in United States rangelands

Rangelands of the United States provide ecosystem services that benefit society and rural economies. Native tree encroachment is often overlooked as a primary threat to rangelands due to the slow pace of tree cover expansion and the positive public perception of trees. Still, tree encroachment fragments these landscapes and reduces herbaceous production, thereby threatening habitat quality for grassland wildlife and the economic sustainability of animal agriculture. Recent innovations in satellite remote sensing permit the tracking of tree encroachment and the corresponding impact on herbaceous production. We analysed tree cover change and herbaceous production across the western United States from 1990 to 2019. We show that tree encroachment is widespread in US rangelands; absolute tree cover has increased by 50% (77,323 km 2 ) over 30 years, with more than 25% (684,852 km 2 ) of US rangeland area experiencing tree cover expansion. Since 1990, 302 ± 30 Tg of herbaceous biomass have been lost. Accounting for variability in livestock biomass utilization and forage value reveals that this lost production is valued at between $4.1–$5.6 billion US dollars. Synthesis and applications . The magnitude of impact of tree encroachment on rangeland loss is similar to conversion to cropland, another well-known and primary mechanism of rangeland loss in the US Prioritizing conservation efforts to prevent tree encroachment can bolster ecosystem and economic sustainability, particularly among privately-owned lands threatened by land-use conversion.

Journal of Applied Ecology↗
USGS1968

Structure of the New England herring gull population

Measurements of the rates of population increase, reproduction, and mortality together with an observed age ratio, were used to analyze the population of the Herring Gull in New England. Data from sporadic censuses prior to this study, aerial censuses by the authors, and National Audubon Society Christmas Bird Count indicated that the New England breeding population has been doubling every 12 to 15 years since the early 1900's. This increase has involved founding new colonies and expanding the breeding range There is evidence that 15 to 30% of the adults do not breed in any given year. Sixty—one productivity measurements on 43 islands from 1963 through 1966, involving almost 13,000 nests, showed that from 0.8 to 1.4 young/breeding pair/year is the usual range of rate of production. The age distribution in the population was determined by classifying Herring Gulls by plumage category on an aerial census of the coast from Tampico, Mexico, to Cape Sable, Nova Scotia. Of the 622,000 gulls observed, 68% were adults, 17% were second— and third—year birds, and 15% were first—year birds. Mortality rates derived from band recovery data were too high to be consistent with the observed rate of population growth, productivity, and age structure. Loss of bands increasing to the rate of about 20%/year 5 years after banding eliminates most of the discrepancy. The age structure and rate of population increase indicate a mortality rate of 4 to 9% for gulls 2 years old or older, compared with the 25 to 30% indicated by band recoveries. The population structure we have developed fits everything we have observed about Herring Gull population dynamics, except mortality based on band recoveries.

Ecology↗
USGS2021

Broadening the ecology of fear: Non-lethal effects arise from diverse responses to predation and parasitism

Research on the ‘ecology of fear’ posits that defensive prey responses to avoid predation can cause non-lethal effects across ecological scales. Parasites also elicit defensive responses in hosts with associated non-lethal effects, which raises the longstanding, yet unresolved question of how non-lethal effects of parasites compare with those of predators. We developed a framework for systematically answering this question for all types of predator–prey and host–parasite systems. Our framework reveals likely differences in non-lethal effects not only between predators and parasites, but also between different types of predators and parasites. Trait responses should be strongest towards predators, parasitoids and parasitic castrators, but more numerous and perhaps more frequent for parasites than for predators. In a case study of larval amphibians, whose trait responses to both predators and parasites have been relatively well studied, existing data indicate that individuals generally respond more strongly and proactively to short-term predation risks than to parasitism. Apart from studies using amphibians, there have been few direct comparisons of responses to predation and parasitism, and none have incorporated responses to micropredators, parasitoids or parasitic castrators, or examined their long-term consequences. Addressing these and other data gaps highlighted by our framework can advance the field towards understanding how non-lethal effects impact prey/host population dynamics and shape food webs that contain multiple predator and parasite species.

Proceedings of the Royal Society B↗
USGS1997

Fish assemblages and environmental correlates in least-disturbed streams of the upper Snake River basin

Fish assemblages and environmental variables were evaluated from 37 least‐disturbed, 1st‐ through 6th‐order streams and springs in the upper Snake River basin, western USA. Data were collected as part of the efforts by the U.S. Geological Survey National Water Quality Assessment Program and the Idaho State University Stream Ecology Center to characterize aquatic biota and associated habitats in least‐disturbed coldwater streams. Geographically, the basin comprises four ecoregions. Environmental variables constituting various spatial scales, from watershed characteristics to instream habitat measures, were used to examine distribution patterns in fish assemblages. Nineteen fish species in the families Salmonidae, Cottidae, Cyprinidae, and Catostomidae were collected. Multivariate analyses showed high overlap in stream fish assemblages among the ecoregions. Major environmental factors determining species distributions in the basin were stream gradient, watershed size, conductivity, and percentage of the watershed covered by forest. Lowland streams (below 1,600 m in elevation), located mostly in the Snake River Basin/High Desert ecoregion, displayed different fish assemblages than upland streams (above 2,000 m elevation) in the Northern Rockies, Middle Rockies, and Northern Basin and Range ecoregions. For example, cottids were not found in streams above 2,000 m in elevation. In addition, distinct fish assemblages were found in tributaries upstream and downstream from the large waterfall, Shoshone Falls, on the Snake River. Fish metrics explaining most of the variation among sites included the total number of species, number of native species, number of salmonid species, percent introduced species, percent cottids, and percent salmonids. Springs also exhibited different habitat conditions and fish assemblages than streams. The data suggest that the evolutionary consequences of geographic features and fish species introductions transcend the importance of ecoregion boundaries on fish distributions in the upper Snake River basin.

Idaho, Oregon, Washington, Wyoming↗
USGS2013

Location-only and use-availability data: analysis methods converge

This Special Feature arose from a session on a topic of the same name that took place during The Wildlife Society meeting in Kona, Hawaii, from 5 to 10 November, 2011. The purpose of that session and this Special Feature is to compare methods for predictive modelling of species geographical distributions and the modelling of habitat (resource) selection by animals. The predictive modelling of species geographical distributions and the modelling of habitat selection based on the environmental conditions at sites where animals are known to occur are essentially the same problem. Presence-only and used-available data both consist of a sample of locations with known presence of a species or an individual. A separate sample of locations from a study area, with unknown presence (pseudo-absence), is also assumed to exist. The probability or relative probability of presence of a species or individual is modelled and estimated across a certain time implicitly defined by the sampling mechanism, for example, by the time period during which museum specimens or radiotelemetry data were collected. A number of modelling methods have appeared in the literature over the last couple of decades. Many of these methods were made feasible by the availability of geographical information systems (GIS), global positioning system (GPS) radiotelemetry and public online data access initiatives (e.g. global biodiversity information facility). The papers in this Special Feature are intended to present the state of the methodological art in their subject area, with particular attention paid to contrasting the advantages and disadvantages of alternative methods of analysis for data.

Journal of Animal Ecology↗
USGS2012

Partly cloudy with a chance of migration: Weather, radars, and aeroecology

Aeroecology is an emerging scientific discipline that integrates atmospheric science, Earth science, geography, ecology, computer science, computational biology, and engineering to further the understanding of biological patterns and processes. The unifying concept underlying this new transdisciplinary field of study is a focus on the planetary boundary layer and lower free atmosphere (i.e., the aerosphere), and the diversity of airborne organisms that inhabit and depend on the aerosphere for their existence. Here, we focus on the role of radars and radar networks in aeroecological studies. Radar systems scanning the atmosphere are primarily used to monitor weather conditions and track the location and movements of aircraft. However, radar echoes regularly contain signals from other sources, such as airborne birds, bats, and arthropods. We briefly discuss how radar observations can be and have been used to study a variety of airborne organisms and examine some of the many potential benefits likely to arise from radar aeroecology for meteorological and biological research over a wide range of spatial and temporal scales. Radar systems are becoming increasingly sophisticated with the advent of innovative signal processing and dual-polarimetric capabilities. These capabilities should be better harnessed to promote both meteorological and aeroecological research and to explore the interface between these two broad disciplines. We strongly encourage close collaboration among meteorologists, radar scientists, biologists, and others toward developing radar products that will contribute to a better understanding of airborne fauna.

Bulletin of the American Meteorological Society↗
USGS2026

A novel method for quantifying streambed penetrability to inform benthic habitat assessment

Objective Penetrability of streambed sediments is important for the ecological functioning of many benthic organisms, yet there is ambiguity in terminology associated with this concept and there is no standardized method of penetrability measurement available to scientists and resource managers. The goal of our study was to better define the terms of compaction and penetrability as they relate to streambed substrate and to advance the measurement techniques for assessing penetrability of bed sediments in gravel-bed streams. Methods We tested the performance of a modified penetrometer method in 12 different substrate configurations in the laboratory and used the data to determine the relationship between penetration depth and substrate characteristics. We then simulated additional sampling effort and used bootstrapping methods to provide guidance on the number of samples required to achieve consistent results. Finally, we tested the device in a field setting to validate our laboratory and simulation results. Results Depth of penetration was negatively related to increasing substrate particle diameter and number of particle size-classes in both laboratory and field tests. Mean depth of penetration and CV stabilized after five samples, but variation remained high in scenarios containing large-grained particles. Conclusions Our results show that the device has application in gravel-bed streams but may require high amounts of sampling effort to capture variation in streams dominated by large substrate. We discuss the uses and limitations of this method for estimating substrate penetrability and provide guidance on interpretation of the estimates that it produces.

Transaction of the American Fisheries Society↗
USGS2017

Reproductive ecology, spawning behavior, and juvenile distribution of Mountain Whitefish in the Madison River, Montana

Mountain Whitefish Prosopium williamsoni were historically common throughout much of the U.S. Intermountain West. However, within the last decade Mountain Whitefish have exhibited population-level declines in some rivers. In the Madison River, Montana, anecdotal evidence indicates Mountain Whitefish abundance has declined and the population is skewed toward larger individuals, which is typically symptomatic of recruitment problems. Describing reproductive development, spawning behavior, and juvenile distribution will form a foundation for investigating mechanisms influencing recruitment. We collected otoliths and gonadal samples from fish of all size-classes to characterize fecundity, age at maturity, and spawning periodicity. We implanted radio tags in mature Mountain Whitefish and relocated tagged fish in autumn 2012–2014. Timing of spawning was determined from spawning status of captured females and from density of eggs collected on egg mats. In spring 2014, we seined backwater and channel sites to describe age-0 whitefish distribution. Mountain Whitefish were highly fecund (18,454 eggs/kg body weight) annual spawners, and age at 50% maturity was 2.0 years for males and 2.6 years for females. In 2013 and 2014, spawning occurred between the third week of October and first week of November. During spawning, spawning adults and collected embryos were concentrated in the downstream 26 km of the study site, a reach characterized by a complex, braided channel. This reach had the highest CPUE of age-0 Mountain Whitefish, and the percentage of spawning adults in the 25 km upstream from a sampling site was positively associated with juvenile CPUE. Within this reach, age-0 Mountain Whitefish were associated with silt-laden backwater and eddy habitats. Future investigations on mechanisms influencing recruitment should be focused on the embryological phase and age-0 fish.

Montana↗
USGS2002

An index of biological integrity for northern Mid-Atlantic Slope drainages

An index of biological integrity (IBI) was developed for streams in the Hudson, Delaware, and Susquehanna River drainages in the northeastern United States based on fish assemblage data from the Mohawk River drainage of New York. The original IBI, developed for streams in the U.S. Midwest, was modified to reflect the assemblage composition and structure present in Mid-Atlantic Slope drainages. We replaced several of the Midwestern IBI metrics and criteria scores because fishes common to the Midwest are absent from or poorly represented in the Northeast and because stream fish assemblages in the Northeast are less rich than those in the Midwest. For all replacement metrics we followed the ecology-based rationale used in the development of each of the metrics of the Midwestern IBI so that the basic theoretical underpinnings of the IBI remained unchanged. The validity of this modified IBI is demonstrated by examining the quality of streams in the Hudson, Delaware, and lower Susquehanna River basins. The relationships between the IBI and other indicators of environmental quality are examined using data on assemblages of fish and benthic macroinvertebrates and on chemical and physical stream characteristics obtained during 1993-2000 by the U.S. Geological Survey's National Water Quality Assessment Program in these three river basins. A principal components analysis (PCA) of chemical and physical variables from 27 sites resulted in an environmental quality gradient as the primary PCA axis (eigenvalue, 0.41 ). Principal components analysis site scores were significantly correlated with such benthic macroinvertebrate metrics as the percentage of Ephemeroptera, Plecoptera, and Trichoptera taxa (Spearman R = -0.66, P < 0.001). Index of biological integrity scores for sites in these three river basins were significantly correlated with this environmental quality gradient (Spearman R = -0.78, P = 0.0001). The northern Mid-Atlantic Slope IBI appears to be sensitive to environmental degradation in all three of the river basins addressed in this study. Adjustment of metric scoring criteria may be warranted, depending on composition of fish species in streams in the study area and on the relative effort used in the collection of fish assemblage data.

Transactions of the American Fisheries Society↗
USGS2019

New insights into the ecology of adfluvial Bull Trout and the population response to the Endangered Species Act in the North Fork Lewis River, Washington

Like many other salmonids, Bull Trout Salvelinus confluentus migratory life-history expressions are becoming increasingly rare. A critical step in effectively refining management and conservation strategies is a robust assessment of the effectiveness of such strategies and key biological information used in monitoring and recovery planning. To address this need, we integrated a variety of methods to evaluate the population demographics (abundance), vital rates (survival), and life-history characteristics (ageing, growth, spawning migrations and iteroparity) of an adfluvial Bull Trout population. We also employed our mark-recapture data to quantify if recruitment or adult survival had a greater contribution to population trends from year to year. Our results indicated Bull Trout spawning migrations vary with body size, as a considerable portion of smaller adults (<650 mm) did not spawn each year. Additionally, most spawning individuals made only one spawning migration, while <13% made three or more spawning migrations. Our abundance and survival data, which extends to the early 1990s, illustrated positive responses in survival and abundance following the protection of Bull Trout under the Endangered Species Act (1998). Over this period, we found high interannual variability in both survival and abundance, and adult survival (average = 0.45, SE = 0.04) was surprisingly lower than subadult individuals (average = 0.66, SE = 0.04), suggesting limitations at this important life stage. Our mark-recapture data also suggested the attributes driving the Bull Trout population trend (i.e., recruitment to the adult stage or adult survival) has varied through time, with declining trends in the relative contribution of recruitment. Our results provide new insights into the life-history patterns of adfluvial Bull Trout and can serve as a template to consider factors potentially limiting this and other native trout populations.

Washington↗
USGS2024

Feeding habits and ecological implications of the invasive Flathead Catfish in the Susquehanna River basin, Pennsylvania

Objective Flathead Catfish Pylodictis olivaris are a widespread aquatic invasive species within the United States and a recent invader in the Susquehanna River basin, Pennsylvania. Flathead Catfish are piscivores known to consume native and recreationally important fish species. In the mid-Atlantic United States, it is unknown how this invader is impacting food webs and which species may be at greatest predation risk. To address this knowledge gap, we DNA barcoded stomach contents collected from Flathead Catfish to identify prey species and elucidate potential predatory impacts of Flathead Catfish in the Susquehanna River. Methods We used a Bayesian hierarchical multivariate probit model to investigate if the probability of prey species occurrence in the diets of Flathead Catfish varied seasonally or was a function of Flathead Catfish length. Result A total of 576 Flathead Catfish were collected during 2020–2021, with 241 individuals having recoverable stomach contents. In all, we identified 47 different prey species. The most common prey species were rusty crayfish Faxonius rusticus , Margined Madtom Noturus insignis , and shiners Notropis spp . While frequency of occurrence of prey species differed across Flathead Catfish length classes (<300 mm, 301–600 mm, 601–900 mm TL), rusty crayfish were commonly found (33.7–44.0% of diets) in stomachs of all size-classes. Conclusion We found that Flathead Catfish length and seasonality did influence occurrence probability differentially for several prey species. For example, Channel Catfish Ictalurus punctatus were more likely to appear in shorter Flathead Catfish while Smallmouth Bass Micropterus dolomieu appeared in larger Flathead Catfish. We demonstrate significant variation in Flathead Catfish predation, increasing our understanding of predator–prey dynamics, which is necessary to better manage and identify future impacts to aquatic communities in the Susquehanna River basin.

Pennsylvania↗
USGS2018

Spatial variability and macro‐scale drivers of growth for native and introduced Flathead Catfish populations

Quantifying spatial variability in fish growth and identifying large‐scale drivers of growth are fundamental to many conservation and management decisions. Although fish growth studies often focus on a single population, it is becoming increasingly clear that large‐scale studies are likely needed for addressing transboundary management needs. This is particularly true for species with high recreational value and for those with negative ecological consequences when introduced outside of their native range, such as the Flathead Catfish Pylodictis olivaris . This study quantified growth variability of the Flathead Catfish across a large portion of its contemporary range to determine whether growth differences existed between habitat types (i.e., reservoirs and rivers) and between native and introduced populations. Additionally, we investigated whether growth parameters varied as a function of latitude and time since introduction (for introduced populations). Length‐at‐age data from 26 populations across 11 states in the USA were modeled using a Bayesian hierarchical von Bertalanffy growth model. Population‐specific growth trajectories revealed large variation in Flathead Catfish growth and relatively high uncertainty in growth parameters for some populations. Relatively high uncertainty was also evident when comparing populations and when quantifying large‐scale patterns. Growth parameters (Brody growth coefficient [ K ] and theoretical maximum average length [ L ∞ ]) were not different (based on overlapping 90% credible intervals) between habitat types or between native and introduced populations. For populations within the introduced range of Flathead Catfish, latitude was negatively correlated with K . For native populations, we estimated an 85% probability that L ∞ estimates were negatively correlated with latitude. Contrary to predictions, time since introduction was not correlated with growth parameters in introduced populations of Flathead Catfish. Results of this study suggest that Flathead Catfish growth patterns are likely shaped more strongly by finer‐scale processes (e.g., exploitation or prey abundances) as opposed to macro‐scale drivers.

Transactions of the American Fisheries Society↗
USGS2011

Effects of hypoxia on consumption, growth, and RNA:DNA ratios of young Yellow Perch

As in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie’s central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end, we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic growth, and RNA:DNA ratios (an index of short-term growth) of young yellow perch and (2) explored the effects of bottom hypoxia on young yellow perch growth in Lake Erie’s central basin by collecting individuals in hypoxic and normoxic regions of the lake and quantifying their RNA:DNA ratios. Yellow perch consumption and growth in our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA:DNA ratios responded strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding ration. We did, however, observe a positive correlation between yellow perch growth and RNA:DNA ratios at low temperatures (11◦C). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA:DNA ratios. Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA:DNA ratios of yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.

Transactions of the American Fisheries Society↗