Migrations are a key component of the life histories of many highly mobile animals. Potamodromous migrations occurring within large lakes are poorly understood for most species. This lack of understanding hampers restoration efforts and adaptive management because the movement of species and underlying patterns and mechanisms help scientists identify key habitats and quantify species’ role in the ecosystem

The Northern Snakehead Channa argus, a species originating from Asia, was illegally introduced into ponds of Maryland in 2002. Later discovered in tidal freshwater of the Potomac River, the species has become successfully established in many Maryland rivers. The magnitude of impact on preferred prey of Northern Snakehead in North American ecosystems has not been widely studied, leaving unresolved whether

Populations of Burbot Lota lota across the Holarctic ecozone are facing imperilment from environmental warming, particularly in ecosystems impacted by hydropower and climate change. We conducted a series of laboratory experiments to evaluate the tolerance of Burbot embryos to various thermal regimes. Both cyclical and constant warming between 4.0°C and 5.5°C during the initial 25 degree-days of embryo

The Pacific Lamprey Entosphenus tridentatus is an important species both ecologically and culturally, but their population numbers and range have declined severely in the past several decades in the Columbia Basin. In freshwater ecosystems, larval lampreys are candidate prey species for many fish predators, but little is known regarding the magnitude of predation they currently experience. Predation

Understanding biological parameters such as growth patterns, condition, and energy reserves is important for a better understanding of the environmental constraints exerted on fish populations. This is especially true for exploited fish stocks in the current context of climate change. Using biological data collected from 2006 to 2009 during bottom trawl research surveys by Fisheries and Oceans Canada

Density-dependent (DD) and density-independent (DI) effects play an important role in shaping fish growth rates, an attribute that correlates with many life-history traits in fishes. Consequently, understanding the extent to which DD and DI effects influence growth rates is valuable for fisheries assessments because it can inform managers how populations may respond as environmental conditions continue

The body conductivity of fish (Cf; µS/cm) and the power density causing threshold immobilization (Dm; µW/cm3) play a critical role in determining electrofishing success. My aim was to compare two methods for estimating Cf and Dm: the response-threshold method using live Rainbow Trout Oncorhynchus mykiss (12–15 cm TL) and the direct-measure method using the carcasses of the same fish. The estimates

The ability of native fish to establish self-sustaining populations when reintroduced to vacant habitats is variable. We evaluated factors potentially affecting reintroduction success of juvenile Colorado River Cutthroat Trout (Oncorhynchus clarkii pleuriticus) reintroduced to an isolated watershed experiencing sub-optimal survival and recruitment. We conducted a three-year mark-recapture study to

Pike Killifish Belonesox belizanus is an established non-native fish species that was first documented in south Florida, U.S.A., in 1957 and secondarily in Tampa Bay tidal tributaries in 1994. Decreased abundance and altered size structure in small-bodied fish populations have been linked to Pike Killifish introductions in both of these regions. Increases in the range and abundance of Pike Killifish

Imaging sonars, such as the Adaptive Resolution Imaging Sonar (ARIS), provide high-resolution sonar data that is used in fisheries research and management. While sonar methods have enormous potential for making population estimates, species identification via sonar remains an unresolved challenge. One method that may overcome this challenge involves measuring tailbeat frequencies to guide species differentiation

Movement, delays, and survival of hatchery Atlantic Salmon Salmo salar smolts were evaluated through the Piscataquis River, a tributary of the Penobscot River in Maine, USA. We explored the effects of the river’s four dams (Guilford, Dover, Browns Mill, and Howland dams) from 2005 to 2019. During this period, the downstream-most dam (Howland Dam) transitioned from full hydropower generation to seasonal

American Shad Alosa sapidissima is an anadromous species with populations ranging along the U.S. Atlantic coast. Past American Shad stock assessments have been data limited and estimating system-specific growth parameters or instantaneous natural mortality (M) was not possible. This precluded system-specific stock assessment and management due to reliance on these parameters for estimating other population

Larval Atlantic croakers (Micropogonias undulatus) ingress into estuaries from offshore spawning sites during fall and winter. Larvae and early juveniles migrate up‐estuary to oligohaline nurseries where they reside for several months before emigrating seaward. We examined ontogenetic changes in behavioral salinity preference and avoidance as potential contributors to these movement patterns along

The timing of life history events in many plants and animals depends on the seasonal fluctuations of specific environmental conditions. Climate change is altering environmental regimes and disrupting natural cycles and patterns across communities. Anadromous fishes that migrate between marine and freshwater habitats to spawn are particularly sensitive to shifting environmental conditions and thus are

As a prolific invasive species, Blue Catfish Ictalurus furcatus threaten native organisms in numerous estuarine and tidal freshwaters along the Atlantic coast of the United States. However, no published estimates of consumption rates are available for Blue Catfish in the scientific literature. This information is critical for development of bioenergetics models or estimation of population-level impacts

The habitat associations of three species of black bass Micropterus spp. were examined in six habitat types (i.e., sediment, gravel, rock, riprap, brush, and aquatic plants) along a cascade of 10 reservoirs in the Tennessee River. We tested whether habitat selection differed among the three species and whether species’ co-occurrence depended on habitat type. We found that some species occurred in some

Salmonid populations of the Central Valley of California have been in decline for decades, making hatchery practices that combine conservation strategies with targeted research essential to optimize recruitment to adulthood. Hatchery populations generally exhibit a higher incidence of precocious male maturation than in natural populations. However, optimal hatchery management practices as they pertain

Lahontan Cutthroat Trout (LCT) Oncorhynchus clarkii henshawi have experienced some of the most marked reductions in abundance and distribution among Cutthroat Trout subspecies. The population of LCT in Pyramid Lake, Nevada has returned from the brink of extirpation, and although it is highly managed via stocking, the population is thriving and has recently started to reproduce naturally. Our objectives

Species‐specific target strength (TS)‐to‐length (L) and TS‐to‐weight (W) equations can reduce bias in biomass estimates from hydroacoustic surveys, yet these equations do not exist for most fishes. Equations specific to the Gizzard Shad Dorosoma cepedianum, a wide‐ranging and often highly abundant prey fish in North American reservoirs and rivers, do not exist. Herein, we sought to develop TS–L and

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

Fishery managers have struggled for decades to rebuild stocks of Atlantic Cod Gadus morhua in the northwestern Atlantic Ocean, and the resolution of current fine-scale population structure will surely help those efforts. Using double digest restriction-site associated DNA sequencing, we analyzed 248 adult and 215 juvenile Atlantic Cod collected from areas bordering the Canada–USA boundary in 2017–2018

The Blue Sucker Cycleptus elongatus is an imperiled North American catostomid in need of management and protection. No hard structures are validated for aging this species, but past studies focused on somatic structures such as fin rays and scales. Calculated parameters (mortality, recruitment, growth) that inform management decisions are directly influenced by the accuracy and precision of the hard

The Hudson River currently supports the largest population of Atlantic Sturgeon Acipenser oxyrinchus in the United States despite currently supporting less than 1% of historic abundance. Federally listed as endangered throughout much of their range, Atlantic Sturgeon are still impacted by multiple threats, resulting in habitat destruction or direct mortality that has inhibited the rebuilding of populations

Piscivorous fishes attack and consume a variety of prey; however, few studies have examined interactions of multiple predators with multiple prey species. The situational complexity of foraging at different times of day was explored by examining the interactions of paired native predators (Burbot Lota lota or Smallmouth Bass Micropterus dolomieu) with either native (Mottled Sculpin Cottus bairdii)

In recent decades, fisheries research has benefited from the use of various forms of electroimmobilization to facilitate fish handling through rapid induction and recovery times, capacity to allow immediate release, and other advantages not shared by pharmaceuticals. However, as electroimmobilization becomes increasingly prevalent, it is expected that animal care committees may require electroimmobilized

Stream-dwelling Brook Trout Salvelinus fontinalis rely heavily on terrestrial invertebrates, especially when aquatic prey is limited. We examined the effects of an experimental harvest of riparian timber on the diet and condition of Brook Trout in late summer. We evaluated the effects of two riparian harvest intensities (50% and 90% of the basal area harvest) in each of two streams on the diet, consumption

Translocation has been used to conserve imperiled fishes and create new fisheries. One species for which translocation has played a significant role is the Sacramento Perch Archoplites interruptus. Extirpated from its native range, the Sacramento Perch has been introduced throughout California and Nevada through multiple translocation events, though historical records are incomplete. Recent assessments

Fish populations at the fringe of their geographic range often inhabit marginal habitats and are vulnerable to ecological disturbances, such as species invasion, land cover conversion, and climate change. The Driftless Area of northeastern Iowa, USA represents the southwestern edge of the native range of Brook Trout Salvelinus fontinalis, where endemic populations have been greatly reduced due to habitat

The lack of safe, timely, and effective fish passage at dams remains a major impediment to the restoration of diadromous fish species to their historic range and abundance. Because fish passage facilities are often ineffective, dam removal has increasingly been used to restore diadromous species. However, few quantitative studies have assessed the response of fishes to dam removal. This paper documents

When barriers to migration are removed, anadromous fishes from other rivers may colonize newly accessible habitat or landlocked forms of the species may resume anadromy if conditions allow. For example, two large hydroelectric dams on the Elwha River, Washington, were removed between 2011 and 2014 to restore populations of Pacific salmon Oncorhynchus spp. after a century of isolation. Immediately prior

Creating a diverse and inclusive fisheries profession requires telling new stories. While we revere the well‐known pioneers in our profession, we must expand beyond them. New stories, like those in my book, Nature’s Allies, show that conservationists come from all walks of life, proving that anyone and everyone can be a member and leader in our field. For example, the life of Billy Frank Jr., a Native

Floodplains provide multiple benefits to both resident and migratory fish species, including juvenile Chinook Salmon Oncorhynchus tshawytscha, but direct comparisons of survival during migration through a floodplain versus riverine routes are scarce. The Yolo Bypass is a broad floodplain of the Sacramento River that floods in about 30% of years in response to large, uncontrolled runoff events. We analyzed

The construction and operation of dams represents one of the most significant anthropogenic impacts to the aquatic environment of freshwater ecosystems and includes changes in flow, temperature, water chemistry, sedimentation, and nutrient delivery. Despite the substantial changes caused by dams, we have a limited understanding of how dams influence important rate functions of fish, including growth

The Gulf Sturgeon Acipenser oxyrinchus desotoi is an anadromous species that inhabits Gulf of Mexico coastal waters from Louisiana to Florida and is listed as threatened under the U.S. Endangered Species Act. Seasonal cues (e.g., freshwater discharge) determine the timing of spawning and migration and may influence the availability of critical habitat during winter months in six estuaries. Large information

Predation of juvenile salmonids within California’s Sacramento–San Joaquin Delta (the Delta) has been identified as a contributing factor to low survival during out‐migration through the system. Artificial lighting at night (ALAN) may contribute to increased levels of salmonid predation by attracting predators and prey, increasing predator reaction distance, and boosting foraging success. To assess

Delineation of management units across broad spatial scales can help to visualize population structuring and identify conservation opportunities. Geographical information system (GIS) approaches can be useful for developing broad‐scale management units, especially when paired with field data that can validate the GIS‐based delineations. Genetic data can be useful for evaluating whether management units

The movement patterns of native migratory fishes may reflect different selection pressures in different environments that are associated with predictable patterns of temperature and discharge. Spatial and temporal variability in the movement patterns of adult Coho Salmon Oncorhynchus kisutch were explored with data that were collected from the Umpqua River basin, Oregon, focusing on two points in their

Environmental changes caused by hydrological shifts between wet and dry seasons in the tropics drive variation in resource availability and feeding interactions for riverine fish assemblages, but studies of trophic structure typically take place over short time scales that do not adequately capture this variation. In this study, we used analysis of stable isotopes (δ13C and δ15N) to assess seasonal

Maximum densities of juvenile river herring (Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis) vary among freshwater lakes, likely due to densities of adult spawners. Differences in habitat availability and lake water quality may also contribute to variation in juvenile river herring productivity between populations, yet these relationships have not been tested across a large geographic

Salmonids adaptively select when in the daily light cycle to feed, and they use different habitat at different times of day; however, the data and methods used to evaluate management actions like instream flows and restoration projects typically consider daytime only. Our new model, inSTREAM 7, lets us investigate how management decisions might change if we consider the full daily light cycle. The

Allowing reproductive individuals to colonize novel habitat or recolonize previously occupied habitat is increasingly being considered as a tool for recovery of depleted populations of anadromous salmon. Successful application of these techniques requires thorough understanding of how adults use the riverscape during colonization to ensure that programs achieve desired outcomes. We examined the movements

The management of Snake River spring/summer Chinook Salmon and Snake River steelhead is a major concern for several federal, state, and tribal agencies. A primary issue is the effect of the Federal Columbia River Power System (FCRPS), composed of eight dams and reservoirs in the Snake and Columbia rivers, on adult return rate. Management decisions have been influenced by the hypothesis that the passage

Faulkner et al. (2019) presents data and analyses to support a hypothesis that bypass encounters by juvenile Chinook Salmon and steelhead at hydropower dams are not harmful (e.g., “Our results suggest that after fish leave the hydropower system, bypass passage history has little effect on mortality”), and any difference in life‐cycle survival among bypassed and non‐bypassed fish is largely an artifact

The Red Snapper Lutjanus campechanus is a structure‐associated species occurring across a wide depth range in the northern Gulf of Mexico. We used the random forest machine learning algorithm to understand which habitat and individual fish characteristics could predict reproductive parameters of female Red Snapper. We evaluated fish captured from 2016 to 2018 on three artificial structure types with

We highlight the uncertainty that exists around estimating productivity and survival for one population of threatened steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) with the goal of strengthening our understanding of the well‐documented poor marine survival of Puget Sound steelhead. We evaluated how sensitive estimates of productivity and survival were to the uncertainty associated with smolt

Removal of two dams in the Elwha River basin, Washington, started one of the largest river restoration projects ever attempted in the Pacific Northwest. These dams had eliminated Pacific Lamprey Entosphenus tridentatus populations upstream. After the dam removals, larval production increased in the upper watershed, but the sources and numbers of new adult spawners were unknown. We applied genetic stock

The introduction of additional forage fish species to enhance sport fisheries is a common management strategy in lakes and reservoirs. However, illegal introductions occur without consideration of all potential ecological consequences. Introduction of Blueback Herring Alosa aestivalis as a forage fish to enhance recreational fisheries has been controversial, with several illegal introductions documented

Hypoxia induced by eutrophication and high summer temperatures is common in most Midwestern reservoirs, with uncertain effects on resident fishes. To evaluate the potential influence of low dissolved oxygen (DO) and high‐temperature conditions on habitat quality for three common sport fishes (Largemouth Bass Micropterus salmoides, saugeye [Walleye Sander vitreus × Sauger S. canadensis], and White Crappie

In aquatic systems, refuge habitats increase resistance to drying events and maintain populations in disturbed environments. However, reduced water availability and altered flow regimes threaten the function of these habitats. We conducted a capture–mark–recapture study, integrating angler citizen science. Our objectives were to quantify variation in survival of Florida Largemouth Bass Micropterus

Pacific salmon spawning and rearing habitats result from dynamic interactions among geomorphic processes, natural disturbances, and hydro‐climatological factors acting across a range of spatial and temporal scales. We used a 21‐year record of redd locations in a wilderness river network in central Idaho, USA, to examine which covariates best predict the spawning occurrence of Chinook Salmon Oncorhynchus

The upper Columbia River in Washington State (main‐stem and tributary habitat between McNary and Chief Joseph dams) is inhabited by two major lineages of Chinook Salmon Oncorhynchus tshawytscha: endangered spring Chinook Salmon and summer Chinook Salmon, which are not Endangered Species Act (ESA) listed. The lineages are highly genetically divergent from one another, and historically, spatial and temporal

Recruitment is one of the driving forces determining the population dynamics of a stock, and knowledge about recruitment is crucial in providing reliable results in modern stock assessment. The population of the American Eel Anguilla rostra is at risk, and the fisheries on the elvers are one threat for its persistence. We applied a generalized depletion model on the catch and effort data of the elver

The Smith River is a popular recreational sport fishery in western Montana, but salmonid abundances there are thought to be artificially limited by riparian land‐use alterations, irrigation water withdrawals, and high summer water temperatures. We used integrated networks of temperature loggers, PIT tag antenna stations, and in situ temperature mapping to investigate the thermal hydrodynamics and associated

Light can modify orientation and locomotory behaviors in fish and has been applied to attract or repel migrant fish by inducing positive or negative phototaxis. Here, recently metamorphosed downstream‐migrating Sea Lamprey Petromyzon marinus were exposed to light cues in several orientations and intensities at night under controlled flowing‐water conditions in a laboratory flume. Behaviors and rates

Recent stock assessments of Atlantic Halibut Hippoglossus hippoglossus in the United States have been unable to determine stock status. Although there are several fishery‐independent surveys available in the region, few Atlantic Halibut are typically encountered, the survey indices are highly variable, and a reliable index of abundance is not available for this stock. In the absence of reliable fishery‐independent

The Cisco Coregonus artedi is a planktivorous fish that is widely distributed in lakes across glaciated areas of North America. With retreat of Laurentide ice, Cisco dispersed from refugia into a vast network of meltwater (proglacial) lakes that eventually receded, stranding populations in depressions—today’s lakes. Refugial populations also colonized lakes that fell outside of the footprint of a proglacial

Lake Sturgeon Acipenser fulvescens, once widespread throughout North America, are now considered endangered in much of their natural range. However, recreational catch‐and‐release (C&R) fisheries targeting the Lake Sturgeon have developed in areas with strong populations. Here, we evaluated physiological and behavioral impairment of Lake Sturgeon after C&R angling. Fish were angled from the Winnipeg

It is essential for fish to respond appropriately when faced with a threatening situation. Accordingly, fish are able to reduce predation risk through learning. In addition to privately learned experiences, fish can acquire social information about a threat by observing the response of conspecifics and use such public information to adapt future behavior through learning. It is unclear if social learning

The St. Louis River estuary is a designated area of concern by the U.S. Environmental Protection Agency due to severe environmental degradation. The spatial ecology of Muskellunge Esox masquinongy, an indicator species, is uncertain within the estuary and the large, connected water body, Lake Superior. We collected genetic samples and used passive acoustic telemetry to track 60 adult Muskellunge in

Overwintering Pacific salmon Oncorhynchus spp. are vulnerable to mortality. Ecosystem degradation exacerbates salmonid vulnerability to mortality; thus, knowledge of winter movement dynamics is essential for guiding holistic management and restoration to safeguard population viability. In northeast Oregon, long‐term population performance metrics (e.g., survival) exist for parr of two neighboring Chinook