Willapa Bay: a historical perspective and a rationale for research
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FWS/OBS↗
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Core OL-92 from Owens Lake, southeast California
The drilling project at Owens Lake commenced in April, 1991. This Open-File Report represents an effort to make available to other researchers our preliminary data collected during the first year of study following completion of the core-drilling phase. Nineteen data collections and preliminary interpretations are presented in the following sections. They are the work of fifteen first-authors and their numerous co-authors. Broadly, their topics include a field log of the core (1 contribution), sedimentological analyses (1), clay- mineral identification (1), geochemical analyses (5), dating and age estimates of the cored sediments (4), and identifications of fossil materials (7).
California↗
National climate assessment technical report on the impacts of climate and land use and land cover change
This technical report responds to the recognition by the U.S. Global Change Research Program (USGCRP) and the National Climate Assessment (NCA) of the importance of understanding how land use and land cover (LULC) affects weather and climate variability and change and how that variability and change affects LULC. Current published, peer-reviewed, scientific literature and supporting data from both existing and original sources forms the basis for this report's assessment of the current state of knowledge regarding land change and climate interactions. The synthesis presented herein documents how current and future land change may alter environment processes and in turn, how those conditions may affect both land cover and land use by specifically investigating, * The primary contemporary trends in land use and land cover, * The land-use and land-cover sectors and regions which are most affected by weather and climate variability,* How land-use practices are adapting to climate change, * How land-use and land-cover patterns and conditions are affecting weather and climate, and * The key elements of an ongoing Land Resources assessment. These findings present information that can be used to better assess land change and climate interactions in order to better assess land management and adaptation strategies for future environmental change and to assist in the development of a framework for an ongoing national assessment.
Open-File Report↗
Selected environmental and geohydrologic reports for the Fort Wainwright and Fairbanks areas, Alaska as of July 1995
As part of its effort to help collect data and gather information for geohydrologic investigations, the U.S. Geological Survey (USGS) collects and reviews environmental and technical reports relating to geology, hydrology, and geohydrology. The USGS investigation efforts are coordinated with ongoing technical investigations by the Water Research Center of the University of Alaska Fairbanks and the U.S. Army Cold Regions Research and Engineering Laboratory. One project objective for Fort Wainwright includes maintaining a library of report references for USGS project use and for use by the U.S. Army, Alaska (USARAK), USARAK contractors, and other Federal and State agencies. This report presents an annotated bibliography of reports relating to the project study area or geohydrologic processes important to investigations in the study area.
Open-File Report↗
Critical stakeholder engagement: The road to actionable science Is paved with scientists’ good intentions
To help stakeholders such as planners, resource managers, policymakers, and decision makers address environmental challenges in the Anthropocene, scientists are increasingly creating actionable science—science that is useful, usable, and used. Critical physical geography encourages the engagement of stakeholders in the creation of scientific knowledge to conduct actionable science and produce outputs that are directly relevant to stakeholder plans, decisions, or actions. Many scientists, however, lack formal training in how to partner with stakeholders using effective and ethical practices. In this article, we use the core principles for ethical research of respect for persons, beneficence, and justice from the Belmont Report (1979) as a suggested framework to examine the perspectives of stakeholders engaged in climate adaptation science projects. We argue that this framework aligns with the principles of critical physical geography and provides guidance for scientists to make their research more actionable while placing necessary emphasis on ethical considerations. We also challenge scientists to consider the broader ethical implications of engaging with these partners.
Annals of the American Association of Geographers↗
In situ optical water-quality sensor networks - Workshop summary report
Advanced in situ optical water-quality sensors and new techniques for data analysis hold enormous promise for furthering scientific understanding of aquatic systems. These sensors measure important biogeochemical parameters for long deployments, enabling the capture of data at time scales over which they vary most meaningfully. The high-frequency, real-time water-quality data they generate provide opportunities for early warning of water-quality deterioration, trend detection, and science-based decision support. However, developing networks of optical sensors in freshwater systems that report reliable and comparable data across and between sites remains a challenge to the research and monitoring community. To address this, the U. S. Geological Survey (USGS) and the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) convened a joint 3-day workshop (June 8-10, 2011) at the National Conservation Training Center in Shepardstown, West Virginia, to explore ways to coordinate development of standards and applications for optical sensors, and improve handling, storing, and analyzing the continuous data they produce. The workshop brought together more than 60 scientists, program managers, and vendors from universities, government agencies, and the private sector. Several important outcomes emerged from the presentations and breakout sessions. There was general consensus that making intercalibrated measurements requires that both manufacturers and users better characterize and calibrate the sensors under field conditions. For example, the influence of suspended particles, highly colored water, and temperature on optical sensors remains poorly understood, but consistently accounting for these factors is critical to successful deployment and for interpreting results in different settings. This, in turn, highlights the lack of appropriate standards for sensor calibrations, field checks, and characterizing interferences, as well as methods for data validation, treatment, and analysis of resulting measurements. Participants discussed a wide range of logistical considerations for successful sensor deployments, including key physical infrastructure, data loggers, and remote-communication techniques. Tools to manage, assure, and control quality, and explore large streams of continuous water-quality data are being developed by the USGS, CUAHSI, and other organizations, and will be critical to making full use of these highfrequency data for research and monitoring.
Open-File Report↗
Long-term oceanographic observations in Massachusetts Bay, 1989-2006
This data report presents long-term oceanographic observations made in western Massachusetts Bay at long-term site A (LT-A) (42 deg 22.6' N., 70 deg 47.0' W.; nominal water depth 32 meters) from December 1989 through February 2006 and long-term site B (LT-B) (42 deg 9.8' N., 70 deg 38.4' W.; nominal water depth 22 meters) from October 1997 through February 2004 (fig. 1). The observations were collected as part of a U.S. Geological Survey (USGS) study designed to understand the transport and long-term fate of sediments and associated contaminants in Massachusetts Bay. The observations include time-series measurements of current, temperature, salinity, light transmission, pressure, oxygen, fluorescence, and sediment-trapping rate. About 160 separate mooring or tripod deployments were made on about 90 research cruises to collect these long-term observations. This report presents a description of the 16-year field program and the instrumentation used to make the measurements, an overview of the data set, more than 2,500 pages of statistics and plots that summarize the data, and the digital data in Network Common Data Form (NetCDF) format. This research was conducted by the USGS in cooperation with the Massachusetts Water Resources Authority and the U.S. Coast Guard.
Data Series↗
A nationwide evaluation of crowd-sourced ambient temperature data
Growing concerns about heat in urban areas paired with the sparsity of weather stations have resulted in individuals drawing on data from citizen science sensor networks to fill in data gaps. The PurpleAir are the most widely-used low-cost air quality sensors in the contiguous United States with 14,777 deployed between 1 Jan 2017 and 20 July 2021. Although the air quality data from PurpleAir sensors have been widely studied, less attention has been paid to reported temperature. We compare temperature metrics reported by PurpleAir sensors with a gridded temperature product, the North American Land Data Assimilation System (NLDAS)-2, which although not a gold-standard measure of temperature, is widely used in epidemiologic research. We evaluate the lag between indoor and outdoor PurpleAir temperatures. We report associations of the difference between outdoor PurpleAir temperatures and NLDAS-2 temperatures, an indicator of degradation, and the duration of sensor operation. Finally, based on the temperature range recorded by the outdoor PurpleAir sensors vis.a.vis NLDAS-2 temperatures, we provide a list of 271 (2.5%) sensors potentially misclassified as outdoor and likely located indoors. We observed that outdoor PurpleAir sensors agreed well with NLDAS-2 (R2 > 0.82). This association broke down under warm conditions (daily average NLDAS ≥ 21.1oC). Landcover and climate zone were significant modifiers of the association between PurpleAir and NLDAS-2 temperature metrics with the poorest PurpleAir- NLDAS-2 agreement in urban areas. Indoor PurpleAir temperatures lagged hourly NLDAS temperatures by two hours across almost all climate zones. The mean difference in hourly PurpleAir and NLDAS-2 temperatures increased by 0.57oC for every operational year, suggesting that careful attention must be paid to degradation. Overall, we find for use in epidemiological studies, that the PurpleAir sensor data is a reliable metric of daytime mean air temperature, but researchers should be aware of its limitations when examining extreme heat, or when aggregating sensor data across multiple years.
Frontiers of Environmental Science and Engineering↗
U.S. Geological Survey activities related to American Indians and Alaska Natives: Fiscal years 2009 and 2010
The U.S. Geological Survey is the earth and natural science bureau within the U.S. Department of the Interior. The U.S. Geological Survey provides impartial information on the health of our ecosystems and environment, the natural hazards that threaten us, the natural resources we rely on, the negative effects of climate and land-use change, and the core science systems that help us provide timely, relevant, and usable information. The U.S. Geological Survey is not responsible for regulations or land management. In the late 1800s, John Wesley Powell the second director of the U.S. Geological Survey, followed his interest in the Tribes of the Great Basin and Colorado Plateau and studied their cultures, languages, and surroundings. From that early time, the U.S. Geological Survey has recognized the importance of Native knowledge as a complement to the U.S. Geological Survey mission to better understand the Earth and its systems. Collaboration allows the U.S. Geological Survey and Native American governments, organizations, and peoples to increase their mutual understanding of the increasing challenges facing our natural world. Although this report uses the term “resources,” the U.S. Geological Survey, through its interdisciplinary research, acknowledges the interconnectedness of the Earth and all the life forms that live upon it.
Circular↗
Sackung at Bald Eagle ridge, central Colorado: An updated interpretation of ridge-spreading movement, structures, and mechanisms from 50 years (1975–2025) of U.S. Geological Survey research
Slow gravitational failures of mountain peaks and ridges are poorly understood. Herein, we report on 50 years of studies at a slowly spreading castellate ridge in the Sawatch Range in central Colorado. The orientations of geomorphic-structural features indicate that the fractured Precambrian granitic rock underlying the ridge has extended and spread northwestward toward the formerly glacier-covered Busk Creek valley. Results from surveying, field-based geomorphic-structural mapping using lidar, rock mass quality measurements, a passive seismic survey, and satellite radar provide a major update to research started by U.S. Geological Survey researchers in the 1970s and 1980s. New insights include a recognition that the entire ridge has slowly moved by concurrent sliding along an inferred northwest dipping, compound basal-slip surface (or zone), and through the formation of multiple grabens by normal faulting and flexural toppling along sets of pre-existing fractures that dip moderately (∼45°) to the southeast. We were unable to distinguish the presence of a sudden and strong contrast in seismic velocity across the inferred slip surface. Movement during the 50-year study period has been episodic and gradually decreasing, in correspondence with decreasing cumulative annual precipitation and increasing mean annual air temperatures. The fastest moving area, just upslope from the glacier trimline, had an average horizontal velocity of 3 – 4 mm/yr. Evidence suggests that movement started as a paraglacial response mechanism, but because of the site’s proximity to the Rio Grande Rift, we cannot exclude earthquake shaking as a mechanism for initiation or enhancement of slope movement. An estimate of longer-term horizontal movement from the exposed basal-slip surface at the uphill side of the ridgetop graben is ∼1.1 mm/yr for the 13 – 14 ky post-glacial period. Broad implications of our work are that: (1) long-term measurements (decades or longer) of slope movement can add insights into how sackungen form and evolve through time; (2) the identification of thrust faults and toes in zones of compression near valley bottoms can be crucial for interpreting sackung failure mechanisms, and (3) the use of passive-seismic techniques to identify the depth to a slip surface may not be successful in granitic terrain dominated by planar fractures and subtle changes in rock-mass characteristics.
Colorado↗
Trends of Abutment-Scour Prediction Equations Applied to 144 Field Sites in South Carolina
The U.S. Geological Survey conducted a study in cooperation with the Federal Highway Administration in which predicted abutment-scour depths computed with selected predictive equations were compared with field measurements of abutment-scour depth made at 144 bridges in South Carolina. The assessment used five equations published in the Fourth Edition of 'Evaluating Scour at Bridges,' (Hydraulic Engineering Circular 18), including the original Froehlich, the modified Froehlich, the Sturm, the Maryland, and the HIRE equations. An additional unpublished equation also was assessed. Comparisons between predicted and observed scour depths are intended to illustrate general trends and order-of-magnitude differences for the prediction equations. Field measurements were taken during non-flood conditions when the hydraulic conditions that caused the scour generally are unknown. The predicted scour depths are based on hydraulic conditions associated with the 100-year flow at all sites and the flood of record for 35 sites. Comparisons showed that predicted scour depths frequently overpredict observed scour and at times were excessive. The comparison also showed that underprediction occurred, but with less frequency. The performance of these equations indicates that they are poor predictors of abutment-scour depth in South Carolina, and it is probable that poor performance will occur when the equations are applied in other geographic regions. Extensive data and graphs used to compare predicted and observed scour depths in this study were compiled into spreadsheets and are included in digital format with this report. In addition to the equation-comparison data, Water-Surface Profile Model tube-velocity data, soil-boring data, and selected abutment-scour data are included in digital format with this report. The digital database was developed as a resource for future researchers and is especially valuable for evaluating the reasonableness of future equations that may be developed.
South Carolina↗
Extreme ground motions and Yucca Mountain
Yucca Mountain is the designated site of the underground repository for the United States' high-level radioactive waste (HLW), consisting of commercial and military spent nuclear fuel, HLW derived from reprocessing of uranium and plutonium, surplus plutonium, and other nuclear-weapons materials. Yucca Mountain straddles the western boundary of the Nevada Test Site, where the United States has tested nuclear devices since the 1950s, and is situated in an arid, remote, and thinly populated region of Nevada, ~100 miles northwest of Las Vegas. Yucca Mountain was originally considered as a potential underground repository of HLW because of its thick units of unsaturated rocks, with the repository horizon being not only ~300 m above the water table but also ~300 m below the Yucca Mountain crest. The fundamental rationale for a geologic (underground) repository for HLW is to securely isolate these materials from the environment and its inhabitants to the greatest extent possible and for very long periods of time. Given the present climate conditions and what is known about the current hydrologic system and conditions around and in the mountain itself, one would anticipate that the rates of infiltration, corrosion, and transport would be very low—except for the possibility that repository integrity might be compromised by low-probability disruptive events, which include earthquakes, strong ground motion, and (or) a repository-piercing volcanic intrusion/eruption. Extreme ground motions (ExGM), as we use the phrase in this report, refer to the extremely large amplitudes of earthquake ground motion that arise at extremely low probabilities of exceedance (hazard). They first came to our attention when the 1998 probabilistic seismic hazard analysis for Yucca Mountain was extended to a hazard level of 10 -8 /yr (a 10-4/yr probability for a 10 4 -year repository “lifetime”). The primary purpose of this report is to summarize the principal results of the ExGM research program as they have developed over the past 5 years; what follows will be focused on Yucca Mountain, but not restricted to it.
Nevada↗
Updates to models of streamflow and water temperature for 2011, 2015, and 2016 in rivers of the Willamette River Basin, Oregon
Mechanistic river models capable of simulating hydrodynamics and stream temperature are valuable tools for investigating thermal conditions and their relation to streamflow in river basins where upstream water storage and management decisions have an important influence on river reaches with threatened fish populations. In the Willamette River Basin in northwestern Oregon, a two-dimensional, hydrodynamic water-quality model (CE ‑ QUAL ‑ W2) has been used to investigate the downstream effects of dam operations and other anthropogenic influences on stream temperature. By simulating the managed releases of water and various temperatures from the large Willamette Valley Project dams upstream of the modeling domain, these models can be used to investigate riverine temperature conditions and their relation to streamflow to determine where and when conditions are most challenging for threatened fish populations and how dam operations and flow management can affect and optimize thermal conditions in the river. The original models were initially developed to simulate conditions in spring–autumn of 2001 and 2002. This report documents (1) the upgrade of the river models to CE‑QUAL‑W2 version 4.2 and (2) the update of those models to simulate conditions that occurred from March through October of 2011, 2015, and 2016. These years were selected to represent a range of climatic and hydrologic conditions in the Willamette River Basin, including a “cool, wet” year (2011), a “hot, dry” year (2015), and a “normal” year (2016). Six submodels comprise the modeling system updated in this report; each submodel can be run independently or run with the others as a system. These models include the Coast Fork and Middle Fork Willamette River submodel, which includes the Coast Fork and Middle Fork Willamette Rivers, the Row River, and Fall Creek; the McKenzie River submodel, which includes the South Fork McKenzie River downstream of Cougar Dam and the McKenzie River from its confluence with the South Fork McKenzie River to its mouth; the South Santiam River submodel, which comprises the South Santiam River from Foster Dam to the Santiam River; the North Santiam and Santiam River submodel, which includes the Santiam River and the North Santiam River downstream of Big Cliff Dam; the Upper Willamette River submodel, which includes the Willamette River from Eugene to Salem; and the Middle Willamette River submodel, which includes the Willamette River from Salem to Willamette Falls near Oregon City. The models included in this report were originally developed, calibrated, and documented by other researchers. As part of the model updates described here, some model parameters were adjusted to improve stability and decrease runtime. Boundary conditions including meteorological, hydrologic, and thermal parameters were developed and updated for model years 2011, 2015, and 2016. In many cases, the data sources used to drive the 2001 and 2002 models were no longer available, which required the use of new data sources, the determination of a proxy record, or the development of appropriate estimation techniques. Goodness-of-fit statistics for the updated models show a good model fit, with the models simulating subdaily water temperatures at most comparable locations with a mean absolute error of generally less than 1 °C and often nearing 0.5 °C, depending on the individual submodel, and a reasonably low bias. The subdaily mean error for the South Santiam River submodel produced the highest bias of any of the submodels. Goodness-of-fit statistics indicate that the results may be biased cool (ranging from -0.43 °C in 2016 to -0.80 °C in 2011 for subdaily results), but the only water temperature data available for comparison on the South Santiam River is itself estimated, and those estimates are known to be too high in summer. Depending on future modeling needs, that submodel may warrant further refinement, along with additional data collection to properly define and minimize any model bias.
Oregon↗
Cooperative Fish and Wildlife Research Units Program—2017 year in review
The Cooperative Fish and Wildlife Research Units Program was involved in a number of notable events during 2017, many concerning our personnel. Dr. Barry Grand left his position as Leader of the Alabama Cooperative Fish and Wildlife Research Unit to become the Cooperative Units Program Supervisor for the South, replacing Dr. Kevin Whalen who took over as Supervisor for the West. We welcomed Dr. Sarah Converse who left the Patuxent Wildlife Research Center to become Leader of the Washington Cooperative Fish and Wildlife Research Unit. Dr. Amanda Rosenberger joined the Tennessee Cooperative Fishery Research Unit as Assistant Leader, transferring from the Missouri Cooperative Unit. Dr. Scott Carleton left his position as Assistant Unit Leader in New Mexico to become Chief of the Region 2 Migratory Bird Program of the U.S. Fish and Wildlife Service. We said farewell to many colleagues who retired. Their departure is bittersweet as we wish them health, happiness, and wellness in retirement. We will miss their companionship and the extraordinary contributions they have made to the Cooperative Fish and Wildlife Research Units Program and conservation. The Cooperative Fish and Wildlife Research Units Program has a record high number of vacant scientist positions due to a combination of retirements and base funding short-falls. These issues are affecting our ability to meet cooperator needs. Yet, we remain highly productive. For example, this year we released a report ( https://doi.org/10.3133/cir1427 ) containing abstracts of nearly 600 of our research projects, covering thematic areas ranging from advanced technologies to wildlife diseases. We provided highly competent, trained scientists and natural resource managers for our cooperators’ workforce. We delivered technical training and guidance to professional practitioners. We provided critical information to cooperators for decisions on species status assessments and management of species of greatest conservation need. This year we had an active presence at major national meetings, including the North American Wildlife and Natural Resources Conference where we co-sponsored a workshop on continuing education as a means to bridge the gap between science and management. During the coming year, with support from the U.S. Geological Survey and our cooperators, we intend to reduce the number of vacancies in the program. It will take time and active support of our cooperators to get back to full strength, but I am committed to this goal and encouraged by the resolve of our partners. We look forward to an even more productive year in 2018!
Circular↗
Environmental DNA pilot monitoring program for invasive species and biodiversity assessments on Santa Cruz Island: Interim report, September 2025
The U.S. Geological Survey (USGS) and Southern California Coastal Water Research Project supported Channel Islands National Park, The Nature Conservancy’s (TNC) Santa Cruz Island Preserve, and University of California San Diego (UCSD) researchers in using environmental DNA sampling to monitor for invasive Argentine ant ( Linepithema humile ) and to describe spatial biodiversity patterns in a freshwater stream on Santa Cruz Island that is colloquially known as Cañada del Puerto Creek (hydrologic unit code 12 number 180600140201). An eDNA autosampler was deployed May 27–June 02, 2025, which filtered and preserved four 2-L water samples every 12 hours (n = 48 samples). These samples were extracted by USGS and shipped to UCSD for targeted eDNA analyses of Argentine ant. Environmental DNA sampling kits were used to filter and preserve water samples at four sites along the creek spanning ~ 5 km of stream distance. Six 1-L samples were collected at each site May 27–28 and samples were analyzed for eDNA metabarcoding using a comprehensive panel, which encompasses species across the tree of life. In these samples, eDNA from 2,134 unique taxa spanning 30 taxonomic groups (e.g., amoebas, insects, plants) were found. These sampling efforts demonstrated how eDNA autonomous and manual sampling approaches can be applied by National Park Service, TNC, and partners at scale to provide otherwise difficult and expensive to acquire information about biological threats and biodiversity.
California↗
Allostratigraphy of the U.S. middle Atlantic continental margin; characteristics, distribution, and depositional history of principal unconformity-bounded upper Cretaceous and Cenozoic sedimentary units
Publication of Volumes 93 and 95 ('The New Jersey Transect') of the Deep Sea Drilling Project's Initial Reports completed a major phase of geological and geophysical research along the middle segment of the U. S. Atlantic continental margin. Relying heavily on data from these and related published records, we have integrated outcrop, borehole, and seismic-reflection data from this large area (500,000 km^2 ) to define the regional allostratigraphic framework for Upper Cretaceous and Cenozoic sedimentary rocks. The framework consists of 12 alloformations, which record the Late Cretaceous and Cenozoic depositional history of the contiguous Baltimore Canyon trough (including its onshore margin) and Hatteras basin (northern part). We propose stratotype sections for each alloformation and present a regional allostratigraphic reference section, which crosses these basins from the inner edge of the coastal plain to the inner edge of the abyssal plain. Selected supplementary reference sections on the coastal plain allow observation of the alloformations and their bounding unconformities in outcrop. Our analyses show that sediment supply and its initial dispersal on the middle segment of the U. S. Atlantic margin have been governed, in large part, by hinterland tectonism and subsequently have been modified by paleoclimate, sea-level changes, and oceanic current systems. Notable events in the Late Cretaceous to Holocene sedimentary evolution of this margin include (1) development of continental-rise depocenters in the northern part of the Hatteras basin during the Late Cretaceous; (2) the appear ance of a dual shelf-edge system, a marked decline in siliciclastic sediment accumulation rates, and widespread acceleration of carbonate production during high sea levels of the Paleogene; (3) rapid deposition and progradation of thick terrigenous delta complexes and development of abyssal depocenters during the middle Miocene to Quaternary interval; and (4) deep incision of the shelf edge by submarine canyons, especially during the Pleistocene. Massive downslope gravity flows have dominated both the depositional and erosional history of the middle segment of the U. S. Atlantic Continental Slope and Rise during most of the last 84 million years. The importance of periodic widespread erosion is recorded by well-documented unconformities, many of which can be traced from coastal-plain outcrops to coreholes on the continental slope and lower continental rise. These unconformities form the boundaries of the 12 allostratigraphic units we formally propose herein. Seven of the unconformities correlate with supercycle boundaries (sequence boundaries) that characterize the Exxon sequence-stratigraphy model.
Professional Paper↗
Estimating recruitment of Largemouth Bass to exceptional weights using angler-reported catches
ABSTRACT Objective Although most facets of Largemouth Bass Micropterus nigricans ecology have been researched, the upper tiers of weight distributions (i.e., ≥3.6 kg; herein, “lunkers”) have received little attention due to the challenges of collecting sufficient sample sizes. Our aim was to estimate Largemouth Bass recruitment to higher weights after reaching 3.6 kg and to identify factors correlated with such recruitment. Methods We used an online database of angler-reported catches to investigate recruitment of Largemouth Bass after reaching lunker size and to identify associated factors. Recruitment was indexed by the slopes of the reversed cumulative counts relative to increasing weights, with gentler negative slopes indicating higher recruitment. The influence of environmental variables on these slopes identified the factors associated with recruitment. Results An average of 20% (minimum = 4%; maximum = 45%) of lunker bass were estimated to recruit after reaching 3.6 kg. When expanded, these estimates revealed that recruitment from 3.6 to 4.5 kg averaged 23.5% and recruitment from 3.6 to 5.9 kg averaged 2.5%. The observed recruitment was positively correlated with the frequency of Florida Bass M. salmoides alleles in the population and was inversely correlated with human population densities in the vicinity of the reservoir and with chlorophyll- a concentrations in the environment. Conclusions Recruitment of Largemouth Bass after reaching 3.6 kg appears to require a nuanced equilibrium enabled by a higher frequency of Florida Bass alleles, a remote location of the fishery, and a reservoir trophic state that balances adequate environmental conditions and food supply.
North American Journal of Fisheries Management↗
Are changes in lower trophic levels limiting prey-fish biomass and production in Lake Michigan?
To improve understanding of how recent changes in lower trophic levels in Lake Michigan could be affecting prey-fish biomass and production, the Lake Michigan Committee (LMC) convened a Lower Trophic Level Task Group and provided several charges that are responded to in this report. First, we compiled a comprehensive summary of lower trophiclevel data in Lake Michigan, separating out nearshore versus offshore trends over time. Declining trends were prevalent in offshore time series for phosphorus, chlorophyll a, biomass of total crustacean zooplankton, biomass of herbivorous cladocerans, and density of Diporeia spp. In the nearshore, declining trends were evident only for biomass of cyclopoid copepods and density of Diporeia spp. Second, we hypothesized specific mechanisms by which changes in lower trophic levels could affect prey-fish biomass and production and described the degree of empirical support for each mechanism. The best-supported hypothesis was that declining invertebrate prey (especially Diporeia spp.) was responsible for declining growth of prey fish, especially over the last decade when competition for prey resources should otherwise have been lessened due to declining prey-fish densities. As a result, declining growth potentially limits the prey-fish biomass that could have been attained had growth been maintained at the levels that were achieved in the 1980s and earlier. Third, we prioritized several lower trophic-level indicators that fishery managers could use to better inform decision making. The top-ranked indicator was annual reporting of Alewife (Alosa pseudoharengus) condition. Fourth, we prioritized the key monitoring and research gaps that limit our current understanding of how lower trophic levels influence fish production. The highest-priority monitoring gap was coordinated sampling of the nearshore, which, if accomplished, would complement annual reporting on offshore sampling. The top-ranked knowledge gap was identifying bottlenecks that regulate fish recruitment, given that recent changes in zooplankton distribution and abundance could be suppressing survival of larval fish and, ultimately, the biomass and production of prey fish. We provided three specific recommendations for the LMC to consider as they seek to better incorporate lower trophiclevel changes into their management decision process: (1) implement a coordinated and standardized nearshore monitoring program, (2) encourage funding agencies to use our prioritized lists in their decision processes, and (3) foster the already improved dialogue between those researching lower trophic levels and those researching fisheries.
Miscellaneous Publication↗