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USGS2021

The impact of COVID-19 on freshwater fisheries fieldwork and data collection

COVID-19 has affected almost every aspect of society including freshwater fisheries fieldwork. Our study quantified the effects of the pandemic on fisheries fieldwork in the United States. We administered a survey to fisheries chiefs in all 50 states to assess the pandemic’s impact on fisheries fieldwork. Of the 37 participants, 91% reported the pandemic affected their fieldwork and 92% adapted their sampling methods in response to the pandemic. Common adaptation strategies included using Personal Protective Equipment (PPE; 100%), practicing social distancing (97%), using smaller crews (82%), and developing contingency plans (51%). Based on the survey results, we identified potential challenges to adaptations and offered strategies to improve them. Strategies we identified include adopting novel data collection techniques, finding new positions for temporary employees, and publicly sharing contingency plans. Ultimately, this paper offers novel guidance on how fisheries professionals can best move forward with fieldwork during a time of crisis.

Fisheries Magazine↗
USGS2021

Merging scientific silos: Integrating specialized approaches for thinking about and using spatial data that can provide new directions for persistent fisheries problems

By merging our specialization silos, fisheries professionals can expand the options that are available to them to address difficult fisheries and aquatic conservation problems, which require an understanding of spatial patterns in geographically large systems. Our purpose is to start a profession-wide conversation about additional ways to think about and use spatial data. We use case studies to illustrate how identifying and merging multiple specialized approaches (e.g., fish tracking, fish surveys, geomorphology, social science, jurisdictional viewpoints) can create an ensemble that has advantages over the use of any single approach alone. Thus, our perspective is not about solving a specific technical problem with a new tool, but about the benefits of identifying gaps in data from one specialized approach, and filling those gaps with data from other specialized approaches. If multiple approaches are coordinated through a larger, problem-specific planning strategy, the result can be better outcomes for difficult problems through creative integration. We encourage others to add constructive ideas to the views initiated here.

Fisheries Magazine↗
USGS2021

Climate change effects on North American fish and fisheries to inform adaptation strategies

Climate change is a global persistent threat to fish and fish habitats throughout North America. Climate-induced modification of environmental regimes, including changes in streamflow, water temperature, salinity, storm surges, and habitat connectivity can change fish physiology, disrupt spawning cues, cause fish extinctions and invasions, and alter fish community structure. Reducing greenhouse emissions remains the primary mechanism to slow the pace of climate change, but local and regional management agencies and stakeholders have developed an arsenal of adaptation strategies to help partially mitigate the effects of climate change on fish. We summarize common stressors posed by climate change in North America, including (1) increased water temperature, (2) changes in precipitation, (3) sea level rise, and (4) ocean acidification, and present potential adaptation strategies that fishery professionals may apply to help vulnerable fish and fisheries cope with a changing climate. Although our adaptation strategies are primarily from North America, they have broader geographic applicability to fish and aquatic biota in other jurisdictions. These strategies provide opportunities for managers to mitigate the effects of climate change on fish and fish habitat while needed global policies to reduce greenhouse gas emissions emerge, which may offer more lasting solutions.

Fisheries Magazine↗
USGS2021

The U.S. Inland Creel and Angler Survey Catalog (CreelCat): Development, applications, and opportunities

Inland recreational fishing, defined as primarily leisure-driven fishing in freshwaters, is a popular pastime in the USA. State natural resource agencies endeavor to provide high-quality and sustainable fishing opportunities for anglers. Managers often use creel and other angler survey data to inform state- and waterbody-level management efforts. Despite the broad implementation of angler surveys and their importance to fisheries management at state scales, regional and national coordination among these activities is minimal, limiting data applicability for larger-scale management practices and research. Here, we introduce the U.S. Inland Creel and Angler Survey Catalog (CreelCat), a first-of-its-kind, publicly available national database of angler survey data that establishes a baseline of national inland recreational fishing metrics. We highlight research and management applications to help support sustainable inland recreational fishing practices, consider cautions, and make recommendations for implementation.

Fisheries Magazine↗
USGS2022

Native fish need a natural flow regime

Water development has threatened the ecological integrity of riverine ecosystems. Increasing water demand, persistent drought, and climate change exacerbate the effects of habitat degradation and loss in altered systems such as the Colorado River basin. Today, biologists are challenged to identify management actions that benefit native fishes while not hindering water development or management. Herein, we discuss the importance of the natural flow regime for functioning riverine ecosystems and provide examples from four tributaries to the Green River, a major headwater branch of the Colorado River. These tributaries represent a gradient of impacts ranging from water abstraction to the point of complete seasonal desiccation to a relatively natural flow regime, and consequently have maintained different levels of instream habitat complexity and native fish persistence. Despite decades of management, endangered species lack self-sustaining populations and other native species have been extirpated from over half their ranges, which begs the question: can water development and fish conservation be balanced under current water laws and climate change-driven declines in runoff? Given the continued decline in freshwater biodiversity and abundance occurring across the globe, we contend that immediate designation of rivers with natural flow regimes as freshwater conservation areas will enhance native species recovery.

Arizona, Colorado, Utah, Wyoming↗
USGS2022

Toward improved prediction of streamflow effects on freshwater fishes

Understanding the effects of hydrology on fish populations is essential to managing for native fish conservation. However, despite decades of research illustrating streamflow influences on fish habitat, reproduction and survival, biologists remain challenged when tasked with predicting how fish populations will respond to changes in flow regimes. This uncertainty stems from insufficient understanding of the context-dependent mechanisms underlying fish responses to, for example, periods of reduced flow or altered frequency of high-flow events. We aim to address this gap by drawing on previous research to hypothesize mechanisms by which low- and high-flows influence fish populations and communities, identifying challenges that stem from data limitations and ecological complexity, and outlining research directions that can advance an empirical basis for prediction. Focusing flow-ecology research on testing and refining mechanistic hypotheses can help narrow management uncertainties and better support species conservation in changing flow regimes.

Fisheries Magazine↗
USGS2022

How shall we meet? Embracing the opportunities of virtual conferencing

The SARS-CoV-2 (COVID-19) pandemic triggered dramatic shifts in the way that ecologists teach, research, and interact (e.g., Cooke et al. 2021 ). As the world now adjusts to a “new normal” era, there is notable and open discussion about the merits or desire to return to practices used prior to the pandemic (e.g., Roulson 2021 ). A dominant aspect of these discussions is when and how researchers can return to the practice of large, centralized, in-person conferences that have been the primary mode of professional interaction for decades. While questions of safety are naturally paramount and will guide decision making for some time, there remains the broader question of whether and how to implement virtual and hybrid formats in the future. Discussions about the return to in-person meetings and expressed resentment about the use of virtual formats (Stevens and Murphy 2021 ) that we routinely see circulated by professional organizations and on social media assume that the latter is a lesser-quality version of the former. However, we put forward that these sentiments neglect the diversity of opinions among scientists and evidence of prevalent, positive attitudes about the use of virtual (and possibly, as yet undeveloped) modes of conferences. For example, 74% of more than 900 researchers surveyed by the journal Nature during the initial phase of the pandemic expressed a desire for virtual conferences to remain in practice even when travel restrictions were eased (Remmel 2021 ). Other surveys have shown that scientists are highly interested in alternative conference formats due to concerns about climate change (Nursey-Bray et al. 2019 ; Haage 2020 ) and access (Niner and Wassermann 2021 ). These data indicate most researchers have personal circumstances or perspectives that recognize the value of a broader discussion about how conferences and interactions among researchers can be shaped.

Fisheries Magazine↗
USGS2022

A review of empirical evidence that examines the effectiveness of harvest regulation evaluations in freshwater systems: A systematic, standardized collaborative approach

Harvest regulations are important tools that fisheries professionals use to impact fish abundance, alter population size structure, and improve fishing opportunities. Fisheries professionals often assume that specialized harvest regulations will have specific effects on target fish populations, but these predictions are not always realized because theory and practice do not always match (literature indicates that predictions are not met in about half of the cases). To identify trends that can improve the future success of harvest regulations, we reviewed a representative sample of harvest regulation evaluations for inland sport fish (i.e., 62 evaluations from 41 studies). Our review revealed gaps related to quantitative predictions, evaluation duration, statistical design, researcher–manager collaboration, and data standardization. Fisheries professionals can benefit from shared and thoughtful data collection designs and protocol standardizations. These designs can transform assessment sampling into empirical regulation evaluations that provide generality across locations and time periods with similar effort and cost.

Fisheries Magazine↗
USGS2022

Abundance-occupancy patterns of black bass in an impounded river

A positive relationship has been documented for a wide diversity of taxa between the percentage of transects sampled in which a species is recorded (i.e., occupancy) and the average abundance of the species at transects where recorded. This positive relationship implies that abundance increases faster than occupancy, so populations that occupy more sites also tend to occupy them at higher abundances. Plainly, there is a limit to the sites available for a species to occupy, so as the population expands numerically, abundance at a site must also increase. The pattern may differ across species and geography depending on aspects such as species vital rates, resource use, and resource availability. I investigated abundance–occupancy patterns of three black basses Micropterus spp. in reservoirs of the mainstem Tennessee River, USA. The data set included relative abundance estimates made at 7,237 sites in nine reservoirs sampled during 1997–2018, for 43,243 black bass, including 67% Largemouth Bass Micropterus salmoides , 14% Smallmouth Bass M. dolomieu , and 19% Spotted Bass M. punctulatus . As relative abundance increased due to natural annual population fluctuations, occupancy also increased, but faster for Largemouth Bass and more slowly for Smallmouth Bass and Spotted Bass. Largemouth Bass spread abundance more thinly over many sites, and Smallmouth Bass and Spotted Bass spread abundance more thickly over fewer sites. The recognition that black bass populations that decline in occupancy face the additional burden of disproportionally larger decreases in abundance per site, or that black bass that decline in abundance per site face decreases in occupancy, has various conservation and habitat management implications.

Alabama, Georgia, Kentucky, Mississippi, North Car↗
USGS2022

Decades of global sturgeon conservation efforts are threatened by an expanding captive culture industry

After centuries of overexploitation and habitat loss, many of the world's sturgeon (Acipenseridae) populations are at the brink of extinction. Although significant resources are invested into the conservation and restoration of imperiled sturgeons, the burgeoning commercial culture industry poses an imminent threat to the persistence of many populations. In the past decade, the number and distribution of captive sturgeon facilities has grown exponentially and now encompasses diverse interest groups ranging from hobby aquarists to industrial-scale commercial facilities. Expansion of sturgeon captive culture has largely fallen outside the purview of existing regulatory frameworks, raising concerns that continued growth of this industry has real potential to jeopardize conservation of global sturgeon populations. Here, we highlight some of the most significant threats commercial culture poses to wild populations, with particular emphasis on how releases can accelerate wild population declines through mechanisms such as hybridization, introgression, competition, and disease transmission. We also note that in some circumstances, commercial captive culture has continued to motivate harvest of wild populations, potentially accelerating species' declines. Given the prevalence and trajectory of sturgeon captive culture programs, we comment on modifications to regulatory frameworks that could improve the ability of captive culture to support wild sturgeon conservation.

Fisheries Magazine↗
USGS2023

Synthesizing professional opinion and published science to build a conceptual model of Walleye recruitment

Understanding and predicting recruitment, longstanding goals in fisheries science and ecology, are complicated by variation in the importance of environmental drivers coupled with the dynamic nature of individual ecosystems. Developing an understanding of recruitment from well-monitored stocks offers an opportunity to overcome these complexities. We used a systematic literature review, a survey, and a workshop attended by professionals with expertise in recruitment of Walleye Sander vitreus to identify common environmental drivers of Walleye recruitment and additional sources of variation (i.e., context dependencies) among populations. The importance of individual environmental drivers, as well as the direction of their influence, differed as a function of geographic region, lake surface area, and Walleye life stage. The literature suggested abiotic conditions (e.g., temperature) during the first year of life were influential in determining recruitment. Professional opinion noted the importance of biotic factors, with prey availability and predation risk having the most consistent relationships with recruitment. We synthesized this information to propose a conceptual model that illustrates the suite of characteristics that shape Walleye recruitment over large spatial and temporal scales. Our findings emphasize the importance of first-year growth and system-specific contextual factors, which can alter the relative importance of the environmental drivers of recruitment.

Fisheries Magazine↗
USGS2023

Climate change risks to freshwater subsistence fisheries in Arctic Alaska: Insights and uncertainty from broad whitefish Coregonus nasus

Arctic freshwater ecosystems and fish populations are largely shaped by seasonal and long-term watershed hydrology. In this paper, we hypothesize how changing air temperature and precipitation will alter freeze and thaw processes, hydrology, and instream habitat to assess potential indirect effects, such as the change to the foraging and behavioral ecology, on Arctic fishes, using Broad Whitefish Coregonus nasus as an indicator species. Climate change is expected to continue to alter hydrologic pathways, flow regimes, and, therefore, habitat suitability, connectivity, and availability for fishes. Warming and lengthening of the growing season will likely increase fish growth rates; however, the exceedance of threshold stream temperatures will likely increase physiological stress and alter life histories. We expect these changes to have mixed effects on Arctic subsistence fishes and fisheries. Management and conservation approaches focused on preserving the processes that create heterogeneity in aquatic habitats, genes, and communities will help maintain the resilience of Broad Whitefish and other important subsistence fisheries. Long-term effects are uncertain, so filling scientific knowledge gaps, such as identifying important habitats or increasing knowledge of abiotic variables in priority watersheds, is key to understanding and potentially mitigating likely impacts to Arctic fishes in a rapidly changing landscape.

Alaska↗
USGS2023

Assembling the right pieces: Developing an interdisciplinary team to study disease, decline, and recovery of a world-class Smallmouth Bass fishery

Managing and understanding fisheries dynamics are becoming more complex as new and seemingly more complicated environmental factors are identified. Often management requires resources beyond that of any one entity and calls for collaboration among partners with differing priorities and backgrounds to account for the complexity of factors influencing fisheries. We present a collaborative case study from the Susquehanna River basin, Pennsylvania, where Smallmouth Bass Micropterus dolomieu have faced population declines, mortality events, and notable signs of disease in recent years. Collaboration was required to study many facets of the fishery and the environment simultaneously to better understand risk factors and underlying relationships influencing Smallmouth Bass health. The outcomes from this interdisciplinary collaboration allowed for identification of contributing risk factors, led to the development of products and analytical techniques that were mutually beneficial to all partners involved, and provided knowledge that was integrated into fish health and fisheries management.

Maryland, New York, Pennsylvania↗
USGS2023

Influence of electrofishing boat operation and driving techniques on reservoir fish catches

We compared three methods of boat driving and pedal operation using 600-s transects: these were the parallel continuous (PC), parallel intermittent (PI), and arc-intermittent (AI) methods for surveying warmwater fishes in reservoirs. We tested differences in total time and distance per transect, CPUE (fish/h, fish/m), and length frequencies of captured fish among methods. The PC method took the least amount of time, while the AI method took the least amount of distance to complete a transect. The AI method provided slightly higher CPUE (fish/h, fish/m) for Bluegill Lepomis macrochirus and Yellow Bass Morone mississippiensis and higher CPUE (fish/m) for Common Carp Cyprinus carpio , Green Sunfish L. cyanellus , and Largemouth Bass Micropterus salmoides . Each method caught similar size ranges of fish; however, there were slight differences in proportions of sizes for Gizzard Shad Dorosoma cepedianum , Largemouth Bass, and Bluegill. Overall, the AI method performed slightly better for a few species; however, difference in the methods were minor. Any technique should work well for monitoring reservoir fish populations when fish/h is the effort metric.

Fisheries Magazine↗
USGS2023

Aging, climate, and invasions threaten reservoirs in the Mississippi basin

Reservoirs in the Mississippi River basin are facing three momentous threats. The first two, aging and climate change, are relatively slow moving and their signal can be hard to discern given their stretched temporal scales. The third, species invasions, is faster paced and discernable within shorter temporal scales and restricted spatial scales. Aging and climate directly affect reservoir environments and indirectly affect their biotic communities. Climate change is expected to interact with aging to speed up and, in some instances, slow down aging. Conversely, invasions primarily imperil biotic communities but can also impact environmental elements. This triple jeopardy is expected to transform reservoir environs and their biotic assemblages in various, often uncertain, ways. I take a broad view of these threats within the Mississippi River basin. A basin-scale perspective, in contrast to a single reservoir or regional scale, may enhance awareness of reservoirs at a larger level and produce understanding less evident at local levels, hence possibly offering a wider range of choices for confronting threats. My aim is to (1) provide a synopsis of the assemblage of reservoirs and their attributes over the Mississippi River basin, (2) describe the issues related to aging, climate change, and invasions, and (3) consider a conservation framework for confronting these pressures. Given the overlapping temporal, spatial, and ecological effects of these threats, it is essential to address their effects simultaneously.

Mississippi River basin↗
USGS2023

Yellowstone Cutthroat Trout recovery in Yellowstone Lake: Complex interactions among invasive species suppression, disease, and climate change

In Yellowstone Lake, Wyoming, the largest inland population of nonhybridized Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri , hereafter Cutthroat Trout, declined throughout the 2000s because of predation from invasive Lake Trout Salvelinus namaycush , drought, and whirling disease Myxobolus cerebralis . To maintain ecosystem function and conserve Cutthroat Trout, a Lake Trout gill netting suppression program was established in 1995, decreasing Lake Trout abundance and biomass. Yet, the response of Cutthroat Trout to varying Lake Trout suppression levels, collectively with the influence of disease and climate, is unknown. We developed an ecosystem model (calibrated to historical data) to forecast (2020–2050) whether Cutthroat Trout would achieve recovery benchmarks given disease, varying suppression effort, and climate change. Lake Trout suppression influenced Cutthroat Trout recovery; current suppression effort levels resulted in Cutthroat Trout recovering from historical lows in the early 2000s. However, Cutthroat Trout did not achieve conservation benchmarks when incorporating the influence of disease and climate. Therefore, the National Park Service intends to incorporate age-specific abundance, spawner biomass, or both in conservation benchmarks to provide better indication of how management actions and environmental conditions influence Cutthroat Trout. Our results illustrate how complex interactions within an ecosystem must be simultaneously considered to establish and achieve realistic benchmarks for species of conservation concern.

Wyoming↗
USGS2023

The incredible HALK: borrowing data for age assignment

Understanding age and growth are important for fisheries science and management; however, age data are not routinely collected for many populations. We propose and test a method of borrowing age–length data across increasingly broader spatiotemporal levels to create a hierarchical age–length key (HALK). We assessed this method by comparing growth and mortality metrics to those estimated from lake–year age–length keys ages using seven common freshwater fish species across the upper Midwestern United States. Levels used for data borrowing began most specifically by borrowing within lake across time and increased in breadth to include data within the Hydrologic Unit Code (HUC) 10 watershed, HUC8 watershed, Level III Ecoregion, and finally a species-wide data ALK using all available data with our study for a species. Median deviation in mean length of age-3 fish was within 1 cm for the most specific HALK levels, and median deviation in total annual mortality was close to 0 for most species when borrowing occurred within HUC10 and HUC8 watersheds. Percent error in growth curves increased with data borrowing, but plateaued—or even decreased—for some species when data borrowing expanded across spatial levels. We present the HALK as a method for gaining age information about a fishery when age data are unavailable.

Illinois, Indiana, Iowa, Michigan, Minnesota, Sout↗
USGS2023

Environmental DNA as a tool for better understanding the distribution, abundance, and health of Atlantic and Pacific salmon

The development and application of approaches to detect and quantify environmental DNA (eDNA) have potential to improve our understanding of the distribution, abundance, and health of Atlantic Salmon Salmo salar and Pacific salmon Oncorhynchus spp. Here, we review 61 articles focusing on eDNA applications pertaining to salmon occupying natural habitat and aquaculture facilities in the context of advances, opportunities, and challenges. Given recent advances, eDNA now serves as a useful tool for detecting Atlantic Salmon and Pacific salmon and understanding threats to the health of fish and their habitats. Opportunities exist to apply sensitive and minimally invasive eDNA approaches to detect fish and assess fish habitat, assess range expansions of salmon and salmon pathogens, and detect invasive species that may threaten salmon health and abundance. Near real-time eDNA detection and quantification approaches to inform fisheries management may be on the horizon. Challenges limiting the widespread application of eDNA approaches for informing salmon management include accounting for the many factors affecting detection and quantification of eDNA, limits of data for deriving inference, and expense. Through continued development and refinement, eDNA approaches are anticipated to become increasingly available to, and utilized by, managers of Atlantic Salmon and Pacific salmon fisheries.

Fisheries Magazine↗