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At least 739 records · Page 41Linked to original sources
USGS2008

Hydrography and bottom boundary layer dynamics: Influence on inner shelf sediment mobility, Long Bay, North Carolina

This study examined the hydrography and bottom boundary-layer dynamics of two typical storm events affecting coastal North Carolina (NC); a hurricane and the passages of two small consecutive extratropical storms during November 2005. Two upward-looking 1200-kHz Acoustic Doppler Current Profilers (ADCP) were deployed on the inner shelf in northern Long Bay, NC at water depths of less than 15 m. Both instruments profiled the overlying water column in 0.35 in bins beginning at a height of 1.35 in above the bottom (mab). Simultaneous measurements of wind speed and direction, wave and current parameters, and acoustic backscatter were coupled with output from a bottom boundary layer (bbl) model to describe the hydrography and boundary layer conditions during each event. The bbl model also was used to quantify sediment transport in the boundary layer during each storm. Both study sites exhibited similar temporal variations in wave and current magnitude, however, wave heights during the November event were higher than waves associated with the hurricane. Near-bottom mean and subtidal currents, however, were of greater magnitude during the hurricane. Peak depth-integrated suspended sediment transport during the November event exceeded transport associated with the hurricane by 25-70%. Substantial spatial variations in sediment transport existed throughout both events. During both events, along-shelf sediment transport exceeded across-shelf transport and was related to the magnitude and direction of subtidal currents. Given the variations in sediment type across the bay, complex shoreline configuration, and local bathymetry, the sediment transport rates reported here are very site specific. However, the general hydrography associated with the two storms is representative of conditions across northern Long Bay. Since the beaches in the study area undergo frequent renourishment to counter the effects of beach erosion, the results of this study also are relevant to coastal management decision-making. Specifically, these issues include 1) identification of municipalities that should share the cost for renourishment given the likelihood for significant along-shelf sand movement and 2) appropriate timing of sand placement with respect to local climatology and sea-turtle nesting restrictions.

North Carolina↗
USGS2009

Geophysical investigation of seamounts near the Ogasawara fracture zone, western Pacific

This paper provides an analysis of multi-channel seismic data obtained during 2000-2001 on seamounts near the Ogasawara Fracture Zone (OFZ) northwest of the Marshall Islands in the western Pacific. The OFZ is unique in that it is a wide rift zone that includes many seamounts. Seven units are delineated on the basis of acoustic characteristics and depth: three units (I, II, and III) on the summit of seamounts and four units (IV, V, VI, and VII) in basins. Acoustic characteristics of layers on the summit of guyots and dredged samples indicate that the seamounts had been built above sea level by volcanism. This was followed by reef growth along the summit margin, which enabled deposition of shallow-water carbonates on the summit, and finally by subsidence of the edifices. The subsidence depth of the seamounts, estimated from the lower boundary of unit II, ranges between 1,550 and 2,040 m. The thick unit I of the southern seamounts is correlated with proximity to the equatorial high productivity zone, whereas local currents may have strongly affected the distribution of unit I on northern seamounts. A seismic profile in the basin around the Ita Mai Tai and OSM4 seamounts shows an unconformity between units IV and V, which is widespread from the East Mariana Basin to the Pigafetta Basin. Copyright ?? The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB.

Earth, Planets and Space↗
USGS2012

Preface

Telemetry provides a powerful and flexible tool for studying fish and other aquatic animals, and its use has become increasingly commonplace. However, telemetry is gear intensive and typically requires more specialized knowledge and training than many other field techniques. As with other scientific methods, collecting good data is dependent on an understanding of the underlying principles behind the approach, knowing how to use the equipment and techniques properly, and recognizing what to do with the data collected. This book provides a road map for using telemetry to study aquatic animals, and provides the basic information needed to plan, implement, and conduct a telemetry study under field conditions. Topics include acoustic or radio telemetry study design, tag implantation techniques, radio and acoustic telemetry principles and case studies, and data management and analysis.

Book chapter↗
USGS2014

Status and trends of pelagic prey fish in Lake Huron, 2013

The USGS Great Lakes Science Center (GLSC) conducted acoustic and midwater trawl surveys of Lake Huron during 1997 and annually during 2004-2013. The 2013 survey was conducted during September and October and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Pelagic fish density was 1,033 fish/ha in 2013 and increased 62% over the 2012 estimate. Total biomass in 2013 (6.07 kg/ha) was similar to the 2012 estimate (6.97 kg/ha). Mean numeric density of alewife Alosa pseudoharengus was substantially greater in 2013 than in 2012, but the 2013 estimate has low precision. Age-0 rainbow smelt Osmerus mordax abundance increased from 2012, whereas age-1+ rainbow smelt decreased. Age-0 bloater Coregonus hoyi abundance increased over 2012 estimates. Density and biomass of large bloater in 2013 was similar to 2012 levels. Emerald shiner Notropis atherinoides density and biomass increased during 2013. Two adult cisco Coregonus artedi were captured in Georgian Bay. Based on comparable biomass estimates during 2012 and 2013, prey fish availability during 2014 will likely be similar to 2013. Lake Huron has pelagic fish biomass similar to that observed in recent lake-wide acoustic surveys of Lake Michigan and Lake Superior, but species composition differs in the three lakes. There is an increasing gradient of diversity and native species occurrence from Lake Michigan to Lake Superior, with Lake Huron being intermediate in the prevalence of native fish species like coregonines and emerald shiner.

Lake Huron↗
USGS1979

Multichannel seismic depth sections and interval velocities over outer continental shelf and upper continental slope between Cape Hatteras and Cape Cod: Rifted margins

Six computer-generated seismic depth sections over the outer continental shelf and upper slope reveal that subhorizontal Lower Cretaceous reflectors continue 20 to 30 km seaward of the present shelf edge. Extensive erosion on the continental slope has occurred primarily during the Tertiary, causing major unconformities and retreat of the shelf edge to its present position. The precise age and number of erosional events is not established, but at least one major erosional event is thought to be Oligocene and related to a marine regression in response to a worldwide eustatic lowering of sea level. Velocities derived from the multichannel data reveal distinctive ranges and lateral trends as functions of sediment age, depth of burial, and distance from the coastline. Seismic units beneath the shelf and slope of inferred Tertiary age range from 1.7 to 2.7 km/sec, increasing with age and depth of burial. Units interpreted as Upper Cretaceous rocks beneath the shelf range from 2.3 to 3.6 km/sec and show a distinct lateral increase across the shelf followed by a decrease beneath the present continental slope. Inferred Lower Cretaceous and Upper Jurassic rocks beneath the shelf increase from 3.7 to 4.8 km/sec from nearshore to offshore and indicate a change in facies from clastic units below the inner shelf to carbonate units beneath the outer shelf and upper continental slope. Both reflection and refraction data suggest that thin, high-velocity limestone units (5.0 km/sec) are present within the Lower Cretaceous and Upper Jurassic units beneath the outermost shelf edge, but that these change lithology or pinch out before reaching the middle shelf. Although lateral changes in velocity across the shelf and local velocity inversions appear, the interval velocities along the length of the margin show excellent continuity between Cape Hatteras and Cape Cod. The high-velocity horizons within the Lower Cretaceous and Upper Jurassic shelf-edge complex indicate the presence of a carbonate bank or reef. The continental shelf off New Jersey is underlain by a trough approximately 150 km wide with up to 12 km of sedimentary fill. The oceanic basement beneath the upper continental rise is usually at a depth of 10 to 11 km and is overlain by 6 to 8 km of sediments. The rise sediment trough is separated from the shelf trough by an acoustic basement ridge 25 to 75 km wide where penetration never exceeds 6 km beneath sea level, although faulting and carbonate bank or reef complexes frequently limit penetration to 3 to 4 km in this zone. The acoustic basement ridge coincides with the East Coast Magnetic Anomaly and is interpreted as thick oceanic crust formed during the initial phase of seafloor spreading between North America and Africa. Rapid differential subsidence occurred on opposite sides of the basement ridge during the Jurassic and Early Cretaceous. Differential subsidence beneath the shelf also occurred along the margins, with narrower and shallower shelf troughs occurring off platform areas such as Cape Cod and Cape Hatteras.

Cape Cod, Cape Hatteras↗
USGS2009

Snake River fall Chinook salmon life history investigation, annual report 2007

In 2007, we used radio and acoustic telemetry to evaluate the migratory behavior, survival, mortality, and delay of subyearling fall Chinook salmon in the Clearwater River and Lower Granite Reservoir. Monthly releases of radio-tagged fish (~95/month) were made from May through October and releases of 122-149/month acoustic-tagged fish per month were made from August through October. We compared the size at release of our tagged fish to that which could have been obtained at the same time from in-river, beach seine collections made by the Nez Perce Tribe. Had we relied on in-river collections to obtain our fish, we would have obtained very few in June from the free-flowing river but by late July and August over 90% of collected fish in the transition zone were large enough for tagging.

Idaho, Washington↗
USGS2006

Behavior of White Sturgeon near hydroprojects and fishways

During March 2004 through November 2005, white sturgeon movements were monitored at The Dalles Dam to characterize their distribution and movements in the immediate vicinity of the dam and to determine timing and routes of passage. A combination of radio and acoustic telemetry technologies were used to detect tagged fish within fishways and at strategic locations along the dam, the shorelines, and in the forebay. White sturgeon > 95 cm total length (TL) that were captured on baited setlines fished in the forebay and in the tailrace cul-de-sac received a surgically implanted transmitter that emitted radio and acoustic signals. During the course of this study, a total of 148 fish were tagged; 58 were captured and released in the forebay and 90 in the tailrace.

Oregon, Washington↗
USGS2019

North American Bat Monitoring Program regional protocol for surveying with stationary deployments of echolocation recording devices: Narrative version 1.0, Pacific Northwestern US

The outbreak of white-nose syndrome (WNS) and the growing awareness of the risks to bats from wind power generating facilities have driven radical changes to North American bat conservation. Over the last decade, formerly common species such as the little brown myotis (Myotis lucifugus) and hoary bat (Lasiurus cinereus) have experienced unprecedented mortality rates and are now facing non-trivial extinction risk. In response to this change, federal land management agencies such as the US National Park Service, US Fish and Wildlife Service, US Forest Service, US Bureau of Land Management and state wildlife management agencies such as the Oregon Department of Fish and Wildlife and Idaho Fish and Game have invested in collaborative, interagency bat monitoring to close the gap in information about bat welfare and to inform bat conservation strategies. Bats are notoriously difficult to track and study and there remains a paucity of fundamental information about the seasonal patterns of bat activity and habitat use and population distributions and abundances. Moreover, because bats are so highly mobile and difficult to survey (e.g., nocturnal flight), this information needs to be contextualized at broad regional (e.g., 10,000 km2) and range-wide extents. Delimiting bat populations at local scales (e.g., 100 km2) is very difficult and it is not clear, for example, how a declining trend in local (e.g., a small park unit) patterns of bat activity or relative abundance should be interpreted without broader context. In recognition of these challenges, a plan for coordinated continental-scale monitoring of bats, the North American Bat Monitoring Program (NABat) was developed (Loeb et al. 2015). The centerpiece of the plan is the use of a spatially-balanced randomized master sample of grid-cell sample units from a grid-based sampling frame to provide the architecture for collaboration and the statistical foundation for making inferences about bat populations across broad regions and entire bat geographic ranges. The plan outlines general goals, survey design, and field methods for both summertime acoustic surveys of bats as well as winter and summer counts of bats in hibernacula and maternity colonies but it does not provide field-level protocol and standard operating procedures for consistent and efficient implementation. This regional protocol provides these details for one component of NABat, the deployment of stationary acoustic detectors to record bats during summer, as is called for by the NABat plan. This protocol was written specifically to provide guidance and consistency across the Pacific Northwestern US (N. California [California Department of Fish and Wildlife Northern Region], Idaho, Washington, and Oregon; US Fish and Wildlife Service Region 1 and portion of Region 8 [in Northern California and Klamath Basin]; US Forest Service Region 6 and portions of Regions 1 and 5 in Idaho; and the Upper Columbia Basin, North Coast Cascades, and Klamath Networks of the National Park Service). This region has internal cohesion, sharing a distinct bat faunal assemblage of 15 species (with several additional species occurring on the southern periphery of the region), and a long history of collaborative bat monitoring beginning with the interagency Bat Grid Program which operated from 2003-2010 across Oregon and Washington (US Forest Service Region 6). This protocol will be coordinated and implemented by the Northwestern Bat Hub, on behalf of the collective interagency partnership. The Northwestern Bat Hub is housed on the Oregon State University-Cascades campus and leverages pooled partner funds and resources to maintain a small staff that coordinates and conducts monitoring, provides training and oversight, ensures high-quality data quality and control, and analyzes data and reports on results.

California, Idaho, Oregon, Washington↗
USGS2020

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2019

A comprehensive understanding of fish populations and their interactions is the cornerstone of modern fishery management and the basis for Fish Community Goals and Objectives for Lake Erie (Ryan et al. 2003). This report is responsive to U.S. Geological Survey (USGS) obligations via Memorandum of Understanding (MOU) with the Great Lakes Council of Lake Committees (CLC) to provide scientific information in support of fishery management. Goals for the USGS Great Lakes Deepwater Fish Assessment and Ecological Studies in 2019 were to monitor long-term changes in the fish community and population dynamics of key fishes of interest to management agencies. Specific to Lake Erie, expectations of this agreement were sustained investigations of native percids, forage (prey) fish populations, and Lake Trout. Our 2019 deepwater program operations began in April and concluded in December, and utilized trawl, gillnet, hydroacoustic, lower trophic sampling, and telemetry methods. This work resulted in 88 bottom trawls covering 65 ha of lake-bottom and catching 24,140 fish totaling 3,622 kg during three separate trawl surveys in the West and Central basins of Lake Erie. Overnight gillnet sets (n=44) for cold water species were performed at 42 unique locations in the West and East basins of Lake Erie. A total of 8.0 km of gillnet was deployed during these surveys, which caught 286 fish, 114 of which were native coldwater species: Lake Trout, Burbot, and Lake Whitefish. USGS hydroacoustic surveys in 2019 produced 240 km of transects, and lower trophic sampling provided data from zooplankton samples (n=21) and water quality profiles (n=21) to populate a database maintained by the Ontario Ministry of Natural Resources and Forestry (OMNRF), Ohio Division of Natural Resources (ODNR), Michigan Division of Natural Resources (MDNR), Pennsylvania Fish and Boat Commission (PFBC), and New York State Department of Environmental Conservation (NYSDEC). USGS also assisted CLC member agencies with deployment and maintenance of the Great Lakes Acoustic Telemetry Observation System (GLATOS) throughout all three Lake Erie sub-basins, supporting multiple coordinated telemetry investigations. In 2019, Lake Trout investigations included annual gill net surveys and acoustic telemetry of spawning migration and habitat use in coordination with OMNRF, NYSDEC, and PFBC. Results from Lake Trout investigations were reported in the Coldwater Task Group annual report to the Great Lakes Fishery Commission (GLFC) and the CLC (Coldwater Task Group 2020). Likewise, interagency forage fish assessments conducted with hydroacoustics were summarized and reported in the Forage Task Group annual report (Forage Task Group 2020). This report presents biomass-based summaries of fish communities in western Lake Erie derived from USGS bottom trawl surveys conducted from 2013 to 2019 during June and September. The survey design provided temporal and spatial coverage that did not exist in the historic interagency trawl database, and thus complemented the August ODNR-OMNRF effort to reinforce stock assessments with more robust data. Analyses herein evaluated trends in: total biomass, abundance of dominant predator and forage species, non-native species composition, biodiversity and community structure. Data from this effort can be explored interactively online (https://lebs.shinyapps.io/western-basin/), and are accessible for download (https://doi.org/10.5066/P9LL6YOR, Keretz et al. 2020). Annual survey data are added to these sources as the data become available.

Lake Erie↗
USGS2022

Status and trends of the Lake Huron prey fish community, 1976-2020

The USGS Great Lakes Science Center (GLSC) has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October and an acoustics-midwater trawl survey conducted in September-October. In 2020, USGS-GLSC vessels were not permitted to cross into Canada due to the COVID-19 pandemic, so prey fish surveys sampled only sites in U.S. (Michigan) waters of Lake Huron. This prevented USGS from providing information about the current status and trends of prey fish communities in Georgian Bay and the North Channel. Prey fish biomass in U.S. waters of Lake Huron in 2020 remained below levels observed prior to community-wide declines that began in the early to mid-1990s. Fish community biomass was dominated by two species, Bloater (Coregonus hoyi) and Rainbow Smelt (Osmerus mordax). While both surveys found Bloater biomass in the main basin had declined from levels observed in 2019, Bloater still comprised over three-quarters of prey fish biomass in Lake Huron in 2020. Biomass and abundance for other prey fish species were within the range observed over the past five years. Current low biomass of invasive species like Alewife (Alosa pseudoharengus) and Rainbow Smelt is consistent with fish community objectives focused on restoration of native fish communities. Reduced lake productivity, predation by a recovering piscivore community, and shifts in food web dynamics that favor fish production in nearshore environments may prevent prey fish biomass in offshore areas from returning to levels observed prior to the early 1990’s. However, the dominance of Bloater in bottom trawl catches and acoustic surveys suggests that current lake conditions are conducive to the recovery of some native species.

Lake Huron↗
USGS2023

Status and trends of the Lake Huron prey fish community, 1976-2021

The U.S. Geological Survey Great Lakes Science Center has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October of each year and an acoustics-midwater trawl survey, which began in 2004 and is conducted in September-October. Due to weather delays and continued travel restrictions during 2021, there were no bottom trawl samples off the port of Goderich, Ontario and two acoustic transects were cancelled in Georgian Bay. Prey fish biomass in Lake Huron in 2021 was dominated by two species, Bloater (Coregonus hoyi) and Rainbow Smelt (Osmerus mordax). In the main basin, prey fish biomass remained below levels observed prior to community-wide declines that began in the early to mid 1990s. Bloater was the most abundant prey fish species in the main basin, whereas Rainbow Smelt was the most abundant prey species in the North Channel and in Georgian Bay. Both surveys suggested that Bloater biomass is increasing in the main basin. Low biomass of invasive species like Alewife (Alosa pseudoharengus) and Rainbow Smelt is consistent with fish community objectives focused on restoration of native fish communities. Abundance of invasive Round Goby (Neogobius melanostomus) increased in 2021 relative to 2019-2020. Biomass of the native Cisco (Coregonus artedi) increased in the North Channel in 2021 but remained low in Georgian Bay, possibly as an artifact of reduced sampling. Biomass of Slimy Sculpin (Cottus cognatus) and Deepwater Sculpin (Myoxocephalus thompsoni) in 2021 remained low but within the range observed over the past decade. Reduced lake productivity, predation by a recovering piscivore community, and shifts in food web dynamics that favor fish production in nearshore environments may prevent prey fish biomass in offshore areas from returning to levels observed prior to the early 1990s. However, increased biomass of Bloater and Cisco suggests that lake conditions may favor recovery of native corgonines.

Lake Huron↗
USGS2022

Status and trends of pelagic and benthic prey fish populations in Lake Michigan, 2021

Lake wide acoustic (AC) and bottom trawl (BT) surveys are conducted annually to generate indices of pelagic and benthic prey fish densities in Lake Michigan. The BT survey has been conducted each fall since 1973 using 12-m trawls at depths ranging from 9 to 110 m and includes 70 fixed locations distributed across seven transects; this survey estimates densities of seven prey fish species [i.e., alewife ( Alosa pseudoharengus ), bloater ( Coregonus hoyi ), rainbow smelt ( Osmerus mordax ), deepwater sculpin ( Myoxocephalus thompsonii ), slimy sculpin ( Cottus cognatus ), round goby ( Neogobius melanostomus ), ninespine stickleback ( Pungitius pungitius )] as well as for age-0 yellow perch ( Perca flavescens ) and large (> 350 mm) burbot ( Lota lota ). The AC survey has been conducted each late summer/early fall since 2004, and the 2021 survey consisted of 25 transects [507 km total (315 miles)] covering bottom depths ranging from 15 to 235 m and 42 midwater trawl tows covering bottom depths ranging 13 to 215 m; this survey estimates densities of three prey fish species (i.e., alewife, bloater, and rainbow smelt). The data generated from these surveys are used to estimate various population parameters that are, in turn, used by state and tribal agencies in managing Lake Michigan fish stocks. For the BT survey, total biomass density of prey fish equaled only 2.4 kg/ha, the 5th lowest estimate of the time series and well below the long-term average total biomass of 34.28 kg/ha. For the AC survey, total biomass density of prey fish equaled 6.61 kg/ha, 50% higher than the longterm average total biomass of 4.28 kg/ha. The AC survey reported bloater to be the dominant species (by biomass) among prey fishes, while the BT survey reported co-dominance of alewife, bloater, and round goby. Mean biomass of yearling and older (YAO) alewives in 2021 was 1.71 kg/ha in the AC survey and 0.504 kg/ha in the BT survey. Catchability of YAO alewives continues to be substantially lower for the BT survey since 2014. Comparing the acoustic estimate to previous years, YAO alewife biomass was 10% higher than the 2019 estimate and less than the average from 2004-2019. Numeric density of age-0 alewife from the AC survey was 352 fish/ha in 2021, which is 71% of the long-term mean of 499 fish/ha. The alewife age distribution remained truncated, with age-0 fish and age-1 fish dominating the population. Biomass density of YAO bloater was 3.7 kg/ha in the AC survey and 0.43 kg/ha in the BT survey- each at least an order of magnitude lower than what was estimated by the BT survey between 1981 and 1998. Numeric density of age-0 bloater was the highest ever measured for the AC survey at 1,037 fish/ha while for the BT survey, it was 20 fish/ha. Biomass density of YAO rainbow smelt was 0.13 kg/ha in the AC survey and 0.005 kg/ha in the BT survey, continuing the trend of low rainbow smelt biomass that has been observed since 2001. Numeric density of age-0 rainbow smelt was 84 fish/ha in the AC survey and 1.9 fish/ha in the BT survey, indicating a weak year-class. All four prey fish species sampled only by the BT survey indicated below average biomass densities. Deepwater sculpin was estimated at 0.45 kg/ha, which makes 11 of the past 12 years when biomass was <1 kg/ha. Slimy sculpin was estimated at 0.05 kg/ha, the sixth lowest density ever measured. Round goby was estimated at 0.63 kg/ha, which was below the average biomass of 0.84 kg/ha since 2008. Ninespine stickleback density was < 1 fish/ha. Burbot biomass remained near record low levels, and only three age-0 yellow perch were caught in all trawls, indicating a weak yellow perch year-class in 2021.

lake Michigan↗
USGS2023

Status and trends in the Lake Superior fish community, 2022

In 2022, the Lake Superior fish community was sampled with daytime bottom and surface trawls at 71 nearshore locations in May-June and 35 offshore locations in July, and at 51 Coordinated Science and Monitoring Initiative (CSMI) locations in July-October with bottom trawls, surface trawls, mid-water trawls and acoustics that were previously sampled in 2011 and 2016. Nearshore bottom trawls collected 11,603 fish from 25 species or morphotypes. Nearshore mean biomass was 1.6 kg per ha which was one of the lowest biomass estimates over survey’s 45-year history. Offshore bottom trawls collected 13,876 fish from 11 species or morphotypes. Offshore mean biomass was 5.1 kg per ha, which was less than the annual average since 2011 of 6.5 kg per ha. Recruitment, as measured by age-1 densities, was near zero for Bloater ( Coregonus hoyi ), Cisco ( C. artedi ), and Kiyi ( C. kiyi ), 2 age-1 fish per ha for Lake Whitefish ( C. clupeaformis ) and 77 age-1 fish for Rainbow Smelt ( Osmerus mordax ). All were less than the long-term averages. Sampling at the CSMI locations collected 26 species and morphotypes. The most abundant species’ lakewide were Deepwater Sculpin (all years), young-of-year ciscoe (Bloater, Cisco, and Kiyi, 2022), and Rainbow Smelt (2011 and 2016). Cisco had the highest estimated lakewide biomass in 2011 and 2022 and siscowet Lake Trout had the highest estimated lakewide biomass in 2016. Native species were more abundant than invasive species by numbers (80, 65, and 92%) and biomass (94, 93, 96%) in 2011, 2016, and 2022, respectively. Total lakewide benthic fish biomass declined from 47 thousand metric tons in 2011 to 29 thousand metric tons in 2016 and increased to 33 thousand metric tons in 2022. Total lakewide pelagic fish biomass declined from 61 thousand metric tons in 2011 to 25 thousand metric tons in 2016 and increased to 54 thousand metric tons in 2022. The most unexpected result from our sampling in 2022 was the 2 billion age-0 ciscoe estimate from the mid-water trawl and acoustic sampling in August-October. These fish were broadly distributed across the lake, being collected at 53 of the 54 locations, and their population estimates were highest in the depths >100 m. The factors underlying the survival of these ciscoes into late summer in 2022 as compared to previous years have not been identified, but our annual population surveys of larval ciscoes suggests that lake conditions in June and July may have differed from previous years and enhanced survival. In 2022, ciscoe larval densities in May were lower than average (likely due to a cold winter and spring that delayed hatching), June densities were similar to previous years, and July density estimates were more than double that of any previous year’s estimate.

Lake Superior↗
USGS2023

Status and trends of the Lake Huron prey fish community, 1976-2022

The United States Geological Survey-Great Lakes Science Center has monitored annual changes in the offshore prey fish community of Lake Huron since 1973. Monitoring of prey fish populations in Lake Huron is based on a bottom trawl survey that targets demersal (benthic) species and an acoustic-midwater trawl survey that targets pelagic species and life stages. Status of the main basin prey fish community in 2022 was considered ‘Fair’ due to sustained improvements in native species status but species diversity that remains below desired levels. Current lake conditions, characterized by ongoing oligotrophication, seem to favor native coregonines like Bloater ( Coregonus artedi ), which in the main basin has exhibited signs of population growth and strong recruitment in recent years, and Cisco ( Coregonus artedi ), whose biomass in the North Channel increased for the second consecutive year in 2022. In contrast, conditions in the main basin are less favorable for exotic prey fish such as Alewife ( Alosa pseudoharengus ), whose population collapsed in 2014 and has not recovered, and Rainbow Smelt ( Osmerus mordax ), which remains the second-most abundant prey species in the main basin but has produced multiple weak year classes over the past decade including in 2022. Status of benthic prey fish in the main basin in 2022 depended on species. As in prior years, the native sculpin community in 2022 consisted primarily of Deepwater Sculpin ( Myoxocephalus thompsoni ) because Slimy Sculpin ( Cottus cognatus ) has become exceedingly rare. In contrast, biomass of the ecologically similar Round Goby ( Neogobius melanostomus ), an exotic species, reached an all-time high in 2022. Use of complementary surveys (bottom trawl, acoustics) remains important for evaluating prey fish status in Lake Huron, where prey fish community dynamics vary by basin and prey fish responses to changing environmental conditions depend on species and/or habitat.

Lake Huron↗
USGS2023

Status and trends of pelagic and benthic prey fish populations in Lake Michigan, 2022

Fall bottom trawl (fall BT) and lakewide acoustic (AC) surveys are conducted annually to generate indices of pelagic and benthic prey fish densities in Lake Michigan. The fall BT survey has been conducted each fall since 1973 using 12-m trawls at depths ranging from 9 to 110 m at fixed locations distributed across seven transects; this survey estimates densities of seven prey fish species [i.e., Alewife (Alosa pseudoharengus), Bloater ( Coregonus hoyi ), Rainbow Smelt ( Osmerus mordax ), Deepwater Sculpin ( Myoxocephalus thompsonii ), Slimy Sculpin ( Cottus cognatus ), Round Goby ( Neogobius melanostomus ), Ninespine Stickleback ( Pungitius pungitius )] as well as age-0 Yellow Perch ( Perca flavescens ) and large (> 350 mm) Burbot ( Lota lota ). The AC survey has been conducted each late summer/early fall since 2004, and the 2022 survey consisted of 26 transects [570 km total (354 miles)] covering bottom depths ranging from 5 to 255 m and 37 midwater trawl tows above bottom depths ranging 5 to 232 m; this survey estimates densities of three prey fish species (i.e., Alewife, Bloater, and Rainbow Smelt). The data generated from these surveys are used to estimate various population parameters that are, in turn, used by state and tribal agencies in managing Lake Michigan fish stocks. In spring of 2022, an additional spring bottom trawl survey (spring BT) was implemented across six of the transects sampled in the fall and sites ranged in depth from 9 to 236 m. The goal of the spring BT was to explore seasonal differences in biomass density and distributions of key prey species, mostly notably Alewife. Total prey fish biomass density from the spring BT was 2.1 kg/ha. For the AC survey, total biomass density of prey fish equaled 6.2 kg/ha, 37% higher than the long-term average (2004-2021) of 4.5 kg/ha and 0.43 kg/ha higher than the 2021 estimate. For the fall BT, total biomass density of prey fish equaled 8.7 kg/ha, the highest value since 2013 and 21% higher than average value from 20042021 (6.8 kg/ha). The 2022 fall BT biomass density was still well below the average over the entirety of the time series (1973-2021; 34.3 kg/ha). Over the period both surveys have been conducted (2004-2021), total biomass density has trended downward in the fall BT (despite a high 2022 estimate) and remained relatively stable in the AC survey. Bloater was the dominant species (by biomass) among prey fishes in both the spring and fall BT, while the AC survey reported co-dominance of Bloater and Alewife. Mean biomass of yearling and older (YAO) Alewife was 0.38 kg/ha in the spring BT, 3.0 kg/ha in the AC survey, and 0.10 in the fall BT. Alewife were aggregated in deepwater habitats in the spring of 2022 (> 110 m). Since 2014, catchability of YAO Alewives for the fall BT has been substantially lower than the AC survey. Results of the 2022 spring BT do not suggest that catchability is substantially higher in the spring than the fall. Comparing the acoustic estimate to previous years, YAO Alewife biomass was 40% higher than the average from 2004-2021. An age-7 fish was recorded for the first time since 2009. Despite the rare catches of older fish, the Alewife age distribution still appears truncated, with age-1 fish as the most represented age class in all three surveys. Numeric density of age-0 Alewife from the AC survey was 7 fish/ha in 2022, which is the third lowest in the time series and well below the longterm mean of 452 fish/ha. Biomass density of large (≥120 mm) Bloater was 2.7 kg/ha in the AC survey and 4.4 kg/ha in the fall BT - each at least an order of magnitude lower than what was estimated by the fall BT between 1981 and 1998. Following a record high year in 2021 (1,037 fish/ha), the numeric density of small (<120 mm) Bloater was only 15 fish/ha in the AC survey. Meanwhile, small Bloater density estimated in the fall BT was 261 fish/ha, the highest value since 1990 and likely partially reflective of a large 2021 year-class. Biomass density of large Rainbow Smelt (≥90 mm) was 0.29 kg/ha in the AC survey and 0.12 kg/ha in the fall BT survey, continuing the trend of low Rainbow Smelt biomass that has been observed since 2001. Numeric density of small (<90 mm) Rainbow Smelt was 21 fish/ha in the AC survey and 2.7 fish/ha in the fall BT, indicating a weak year-class. All four prey fish species sampled only by the fall BT indicated below average biomass densities. Deepwater Sculpin biomass density was estimated at 0.41 kg/ha, which makes 12 of the past 13 years when biomass was <1 kg/ha. Slimy Sculpin was estimated at 0.10 kg/ha, the highest estimate since 2016 but still only 25% of the long-term average. Round Goby was estimated at 1.3 kg/ha, above the average biomass of 0.82 kg/ha since 2008 but similar to intermittent high values observed throughout the dataset. Ninespine Stickleback density was 1.5 fish/ha. Burbot biomass remained near record low levels, and no age-0 Yellow Perch were caught, indicating a weak Yellow Perch year-class in 2022.

Lake Michigan↗
USGS2024

Seasonal activity patterns of northern long-eared bats on the coastal Mid-Atlantic

Conservation of bats declining from white-nose syndrome (WNS) impacts requires an understanding of both temporal and landscape-level habitat relationships. Traditionally, much of the research on bat ecology has focused on behavior of summer maternity colonies within species’ distribution cores, including that of the endangered northern long-eared bat ( Myotis septentrionalis ). To further our knowledge of this species, we evaluated multi-season activity patterns in eastern North Carolina and Virginia, including areas where populations were recently discovered. We used passive acoustic monitoring to assess relative and probable activity of northern long-eared bats from October 2016 to August 2021. Northern long-eared bat relative activity was greatest in areas containing greater proportions of woody wetlands and upland pine-dominated evergreen forests. However, the likelihood of recording northern long-eared bats was associated with smaller proportions of woody wetlands and open water resources. Furthermore, we observed a higher probability of recording northern long-eared bats during non-winter seasons. Probable activity was greatest at temperatures between 10 and 25 C, potentially highlighting an optimal thermoneutral zone for the species regionally. Relative activity of northern long-eared bats on the Coastal Plain of Virginia and North Carolina was primarily driven by cover features, whereas probable activity was driven by a combination of cover features, seasonality, and temperature. Therefore, acoustical surveys for this species may be most effective when targeting woody wetlands adjacent to upland forests, particularly upland pine-dominated evergreen stands, during moderate temperatures of non-winter seasons (1 April–15 November). Moreover, conservation of a diverse mosaic of woody wetlands juxtaposed by upland forests may promote both roosting and overwintering habitat, thereby enhancing overwintering survival, maternity colony establishment, and ultimately, successful reproduction of northern long-eared bats.

North Carolina, Virginia↗
USGS2024

Seasonal activity patterns of northern long-eared bats at hibernacula in western Virginia

Understanding the relationships of biotic and abiotic factors to seasonal activity at hibernacula is important for the conservation of bats impacted by white-nose syndrome (WNS). Research on the relative and probable activity patterns of the federally endangered northern long-eared bat ( Myotis septentrionalis ) primarily has focused on summer maternity colonies, whereas surveys at hibernacula have traditionally relied on external capture and internal counts. We used passive acoustic monitoring to assess the relative and probable activity of northern long-eared bats at 13 hibernacula in western Virginia, from August 2020 to May 2022. Northern long-eared bats were most active near hibernacula during warmer weeks of the fall swarm and spring emergence, when rainfall was low. Similarly, the probability of northern long-eared bat activity was highest near hibernacula during the spring/summer season. However, unlike relative activity, the likelihood of recording northern long-eared bats was associated with more heterogeneous, interior forests. Our results suggest that northern long-eared bat activity largely follows the described pre-WNS hibernation phenology of the species. Therefore, acoustical surveys to monitor northern long-eared bat populations at hibernacula should focus on entrances during peak activity periods (mid-April and early September), rather than the nearby landscape. Finally, management to promote resource-rich foraging habitat adjacent to hibernacula for use during swarming and emergence may increase survival during hibernation, fitness for spring migration, and ultimately, improve the reproductive success of northern long-eared bats in western Virginia.

Virginia↗
USGS2024

Lake Ontario April prey fish survey results and Alewife assessment, 2024

The Lake Ontario April bottom trawl survey assesses pelagic prey fish populations, in particular Alewife Alosa pseudoharengus , which are the primary prey supporting the lake’s sport fish populations. The 2024 survey included 234 trawls in the main lake and embayments and sampled depths from 3.9 to 245 m (13 – 809 ft). The survey captured 441,942 fish from 28 species with a total weight of 10,519 kg (23,142 lbs.). Alewife were 89% of the total catch by number while Deepwater Sculpin Myoxocephalus thompsonii , Round Goby Neogobius melanostomus , and Rainbow Smelt Osmerus mordax , comprised 4%, 3%, and 2% of the catch respectively. The estimated Alewife biomass increases slightly from 2023 to 2024 (83.9 to 84.2 kg·ha-1) and was the largest biomass value since whole lake sampling began in 2016. Adult Alewife abundance increased in 2024 as predicted in 2023, and most of the total Alewife biomass was comprised of adult fish (97%), predominantly from the 2020 and 2022 year classes. In contrast, Age-1 Alewife biomass (2.2 kg·ha-1) was the lowest estimated since whole lake sampling began in 2016 (previous range: 2.7 – 26.7 kg·ha-1), indicating reproductive success was poor in 2023. Adult Alewife biomass is predicted to remain relatively high but decline slightly in 2025 and 2026, due to the smaller year classes produced in 2021 and 2023. Alewife condition as measured by the weight of a standard length fish (165 mm; ~6.5 inches), was 32.8 g, which was within of the range of previously observed values (28.0 – 35.9 g, 1997 – 2023). Acoustic-based prey fish densities, in the water above the bottom trawl, were similar to observations from 2021 – 2023 and were orders of magnitude lower than bottom trawl densities. These acoustic results support the seasonal timing of the April survey, when the majority of Alewife and other pelagic prey fishes are near the lake bottom and susceptible to capture with bottom trawls. The trawl survey also provides information on the status of other pelagic prey fishes and native fish restorations. In 2024, biomass indices for Rainbow Smelt, Emerald Shiner Notropis atherinoides , and Threespine Stickleback Gasterosteus aculeatus , were similar to 2023 values while the index for Cisco Coregonus artedi declined. The density index for naturally reproduced, juvenile Lake Trout Salvelinus namaycush declined relative to 2023. Density estimates of Lake Whitefish Coregonus clupeaformis continue to be orders of magnitude lower in U.S. waters relative to Canadian waters. A single purported Bloater Coregonus hoyi (total length = 148 mm, sampling depth = 105 m) was captured near Rochester, NY during the 2024 survey. This is the eighth Bloater recaptured during this survey since restoration stocking began in 2012.

Lake Ontario↗