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At least 1,063 records · Page 59Linked to original sources
USGS1980

Development of sea lamprey ( Petromyzon marinus ) larvicides

Larvicides are used to control sea lamprey ( Petromyzon marinus ) in the Great Lakes. These larvicides are useful because they are more toxic to sea lamprey than fish species found in the same habitat. The lampricides come from two classes of chemical compounds: (1) halonitrophenols, and (2) halonitrosalicylanilides. Selectivity of the larvicides appears to be based on the differences in the ability of sea lamprey larvae and fishes to detoxify and/or excrete the chemicals. Glucuronide conjugation is an important mechanism for detoxification of these larvicides by fish, and selectivity of larvicides may be due to differences in glucuronyl transferase activity between lamprey and fishes. If more detailed information were available on uptake, metabolism, excretion, and the biochemistry and physiology of lamprey as compared to fishes, it might be possible to design chemicals that would be more selective than those now in use.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1991

U.S. federal policies, legislation, and responsibilities related to importation of exotic fishes and other aquatic organisms

Within the Federal government, the U. S. Fish and Wildlife Service (Service) has primary responsibility for legal and policy responsibility for introduced exotic species. The Lacey Act of 1900 authorizes the Service to prohibit the importation of species that are potentially injurious to native fish and wildlife. However, regulations under authority of the Lacey Act cover only a few species. The Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 established a Task Force co-chaired by the Director of the Service and Under Secretary of Commerce for Oceans and Atmosphere. The Task Force consults with the Secretary of Transportation to develop regulations to prevent the importation and spread of aquatic nuisance species into the Great Lakes through exchange of ballast water. Federal agencies must comply with Presidential Executive Order 1198, Exotic Organisms, that prohibits Federal agencies or activities they fund or authorize from introducing exotic species. The Service conducts research and evaluation of exotic species to support Federal, State, and local efforts to prevent further importation of harmful species. Effective regulation will also depend on the full cooperation with Canada.

Canadian Journal of Fisheries and Aquatic Sciences↗
USGS1997

Woody debris decomposition in the Atchafalaya River Basin of Louisiana following hurricane disturbance

The contribution of woody debris to some biogeochemical functions of forested wetlands was examined in the Atchafalaya River Basin in Louisiana following disturbance by Hurricane Andrew. Woody debris decomposition processes were characterized in terms of mass, C, N, and P dynamics. These were compared between different diameters of debris, areas recieving different intensities of disturbance, and between different positions relative to the soil. Disturbance intensity (as defined by canopy closure) had little effect on decomposition processes when compared with soil orientation (i.e., whether in contact with or suspended above the soil). Rates of mass loss varied between 0.055 and 0.068 for suspended and ground-contact coarse woody debris, respectively. Fine woody debris rate coefficients averaged 0.060 and 0.085 for the same respective orientations. In general, woody debris displayed strong source activity for P but a greater tendency toward sink behavior for N. In terms of biogeochemical transformations, these data suggest that woody debris might act as a phosphate source during sheet flow events but could provide short-term retention of inorganic N associated with floodwaters.

Louisiana↗
USGS2013

UNLV’s environmentally friendly Science and Engineering Building is monitored for earthquake shaking

The University of Nevada Las Vegas’ (UNLV) Science and Engineering Building is at the cutting edge of environmentally friendly design. As the result of a recent effort by the U.S. Geological Survey’s National Strong Motion Project in cooperation with UNLV, the building is now also in the forefront of buildings installed with structural monitoring systems to measure response during earthquakes. This is particularly important because this is the first such building in Las Vegas. The seismic instrumentation will provide essential data to better understand the structural performance of buildings, especially in this seismically active region.

Nevada↗
USGS2022

Adaptation strategies and approaches for managing fire in a changing climate

As the effects of climate change accumulate and intensify, resource managers juggle existing goals and new mandates to operationalize adaptation. Fire managers contend with the direct effects of climate change on resources in addition to climate-induced disruptions to fire regimes and subsequent ecosystem effects. In systems stressed by warming and drying, increased fire activity amplifies the pace of change and scale of severe disturbance events, heightening the urgency for management action. Fire managers are asked to integrate information on climate impacts with their professional expertise to determine how to achieve management objectives in a changing climate with altered fire regimes. This is a difficult task, and managers need support as they incorporate climate adaptation into planning and operations. We present a list of adaptation strategies and approaches specific to fire and climate based on co-produced knowledge from a science–management partnership and pilot-tested in a two-day workshop with natural resource managers and regional stakeholders. This “menu” is a flexible and useful tool for fire managers who need to connect the dots between fire ecology, climate science, adaptation intent, and management implementation. It was created and tested as part of an adaptation framework used widely across the United States and should be applicable and useful in many fire-prone forest ecosystems.

Climate↗
USGS2009

Earth science: lasting earthquake legacy

Earthquakes occur within continental tectonic plates as well as at plate boundaries. Do clusters of such mid-plate events constitute zones of continuing hazard, or are they aftershocks of long-past earthquakes? Early on the morning of 16 December 1811, an earthquake of about magnitude 7 shook the centre of the United States around a small town on the Mississippi called New Madrid. By 7 February 1812, it had triggered three more shocks of similar magnitude. The earthquakes broke a set of faults along the Arkansas, Missouri and Tennessee state boundaries, apparently reactivating an ancient rift in the interior of a continental tectonic plate. On 31 August 1886, a magnitude-7 shock struck Charleston, South Carolina; low-level activity continues there today. One view of seismic hazard is that large earthquakes will return to New Madrid and Charleston at intervals of about 500 years. With expected ground motions that would be stronger than average, that prospect produces estimates of earthquake hazard that rival those at the plate boundaries marked by the San Andreas fault and Cascadia subduction zone. The result is two large 'bull's-eyes' on the US National Seismic Hazard Maps — which, for example, influence regional building codes and perceptions of public safety.

Nature↗
USGS2015

Citizen science contributes to our knowledge of invasive plant species distributions

Citizen science is commonly cited as an effective approach to expand the scale of invasive species data collection and monitoring. However, researchers often hesitate to use these data due to concerns over data quality. In light of recent research on the quality of data collected by volunteers, we aimed to demonstrate the extent to which citizen science data can increase sampling coverage, fill gaps in species distributions, and improve habitat suitability models compared to professionally generated data sets used in isolation. We combined data sets from professionals and volunteers for five invasive plant species ( Alliaria petiolata , Berberis thunbergii , Cirsium palustre , Pastinaca sativa , Polygonum cuspidatum ) in portions of Wisconsin. Volunteers sampled counties not sampled by professionals for three of the five species. Volunteers also added presence locations within counties not included in professional data sets, especially in southern portions of the state where professional monitoring activities had been minimal. Volunteers made a significant contribution to the known distribution, environmental gradients sampled, and the habitat suitability of P. cuspidatum . Models generated with professional data sets for the other four species performed reasonably well according to AUC values (>0.76). The addition of volunteer data did not greatly change model performance (AUC > 0.79) but did change the suitability surface generated by the models, making them more realistic. Our findings underscore the need to merge data from multiple sources to improve knowledge of current species distributions, and to predict their movement under present and future environmental conditions. The efficiency and success of these approaches require that monitoring efforts involve multiple stakeholders in continuous collaboration via established monitoring networks.

Wisconsin↗
USGS2020

Catalogue of polar bear (Ursus maritimus) maternal den locations in the Beaufort and Chukchi Seas and nearby areas, 1910–2018

This report presents data on the approximate locations and methods of discovery of 530 polar bear ( Ursus maritimus ) maternal dens observed in the Beaufort and Chukchi Seas and neighboring areas from 1910 to 2018, and archived partly by the U.S. Geological Survey, Alaska Science Center, and partly by the U.S. Fish and Wildlife Service, Marine Mammals Management, in Anchorage, Alaska. A description of data collection methods and their associated biases, primary data collection time periods, and estimated position uncertainty are provided. Polar bears in the Beaufort and Chukchi Seas den on sea ice and land. Standardized very high frequency (VHF) aircraft surveys and satellite radio telemetry data provide a general understanding of where polar bears have denned in this region over the past 3 decades. Den observations made during other research activities and anecdotal reports from other government agencies, coastal residents, and industry personnel also are reported. These data on past polar bear maternal den locations are provided to inform decision making by natural resource agencies and for public use.

Alaska↗
USGS2003

Water-quality, bed-sediment, and biological data, for streams in the upper Prickly Pear Creek watershed, Montana, 2001

The upper Prickly Pear Creek watershed encompasses the upstream 15 miles of Prickly Pear Creek, south of Helena, Montana (fig. 1). The headwaters of Prickly Pear Creek and its tributaries (Beavertown Creek, Clancy Creek, Dutchman Creek, Golconda Creek, Lump Gulch, Spring Creek, and Warm Springs Creek) are primarily in the Helena National Forest, whereas the central part of the watershed primarily is within either Bureau of Land Management (BLM) or privately owned property. Three mining districts are present in the upper Prickly Pear Creek watershed: Alhambra, Clancy, and Colorado. Numerous prospects, adits, tailings piles, mills, dredge piles, and mines (mostly inactive) are located throughout the watershed. These districts contain polymetallic (Ag, Au, Cu, Pb, Zn) vein deposits and precious-metal (Au-Ag) vein and disseminated deposits that were exploited beginning in the 1860’s. Placer Au deposits in the major streams were extensively mined in the late 1800’s and early 1900’s. As part of a cooperative effort with Federal land management agencies, the U.S. Geological Survey (USGS) is currently using an integrated approach to investigate two mining impacted watersheds in the western United States (the Animas River in Colorado and the Boulder River in Montana). These studies provide the USDA Forest Service and BLM scientific data for implementing informed land-management decisions regarding cleanup of abandoned mine lands within each watershed. A similar integrated-science approach will be used to characterize the upper Prickly Pear Creek watershed with respect to water and streambed sediment chemistry, aquatic biota, and geologic framework. This integrated database presents data that will be used to identify important pathways of metals movement and biological impacts, thereby guiding resource management decisions of land-managers in several publications that are in preparation. Watershed-level characterization in terms of water quality, streambed sediment chemistry, and fish health will facilitate determinations of whether removal of contaminated materials or other cleanup activities are necessary, planning of short- and long-term restoration efforts, and development of a monitoring plan to document cleanup effectiveness.

Montana↗
USGS2022

Flood-inundation maps for Schoharie Creek in North Blenheim, New York

Digital flood-inundation maps for a 2.4-mile reach of the Schoharie Creek in North Blenheim, New York, were created by the U.S. Geological Survey (USGS) in cooperation with the New York Power Authority. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://fim.wim.usgs.gov/fim/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Schoharie Creek near North Blenheim, N.Y. (station number 01350212). Near-real-time stage at this streamgage may be obtained on the internet from the USGS National Water Information System at https://waterdata.usgs.gov/ . Flood profiles were computed for the stream reach by means of a two-dimensional implicit finite-volume hydraulic model. The model was calibrated by using the active (as of April 2021) stage-discharge ratings at the USGS streamgages on the Schoharie Creek near North Blenheim (station number 01350212) and at North Blenheim (station number 01350180) and documented high-water marks in the study reach from the floods of August 28, 2011; January 19, 1996; and April 4, 1987. The hydraulic model was used to compute 13 water-surface profiles for flood stages at 1-foot intervals referenced to the datum at the streamgage on the Schoharie Creek near North Blenheim, N.Y. (01350212). These profiles range from 14 feet, or near bankfull, to 26 feet, which is the highest whole-foot increment on the stage-discharge rating for the streamgage. The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.52-foot vertical accuracy and 3.3-foot [1-meter] horizontal resolution) to delineate the area flooded at each stage. Flood inundation maps, along with near-real-time stage data from USGS streamgages, can provide emergency management personnel and residents with information critical for flood-response activities, such as evacuations and road closures, as well as for postflood recovery efforts.

New York↗
USGS2023

Elevated road segment (ERS) passage design may provide enhanced connectivity for amphibians, reptiles, and small mammals

Introduction: Designs for safe and effective road crossing structures for small animals are typically under-road microtunnels and culverts which have varying levels of effectiveness reported in the scientific literature. Many species, particularly migratory amphibians, may have limited ability to find and use passages if they are too far apart, resulting in substantial barrier effects. Methods: We designed a novel open elevated passage (elevated road segment: ERS), similar to a low terrestrial bridge, that could theoretically be built to any length based upon species needs and movement characteristics. A 30 m length prototype ERS was installed along a forest road with a history of amphibian road mortality in Sierra National Forest, Fresno County, CA, USA. From 2018 to 2021, we monitored small animal activity under the ERS in relation to surrounding roadside and forest habitats using active infrared cameras. Results: We documented a total of 8,815 unique use events, using species specific independence criteria, across 22 species of amphibians (3), reptiles (4), and small mammals (15). Poisson regression modeling of taxonomic group activity under the ERS, roadside and forest, showed that amphibian activity was highest in the forest habitat, no differences were observed for reptiles, and small mammal activity was highest under the ERS. However, mean activity estimates under the ERS were equal to or greater than the open roadside habitat for all 22 species, suggesting that adding cover objects, such as downed logs and vegetation may further enhance passage use. Discussion: Overall, results showed that the design of the ERS crossing has potential to provide high connectivity for a wide range of amphibian, reptile, and small mammal species while reducing road mortality. ERS systems can also be used in areas with challenging terrain and other hydrological and environmental constraints. Incorporating current road ecology science, we provide supplemental ERS concept designs for secondary roads, primary roads and highways to help increase the options available for road mitigation planning for small animals.

California↗
USGS2009

Quaternary science reviews Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths that range from 40 to 80 km, maximum thicknesses of 400–800 m, and maximum widths of 10–40 km. We also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse, at four locations (Makushin, Cleveland, Seguam and Yunaska SW volcanoes), which represent large to moderate sized events in this region. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model, which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large local tsunamis as well as large transoceanic tsunamis. These waves may be several meters in elevation at distal locations, such as Japan, Hawaii, and along the North and South American coastlines where they would constitute significant hazards.

Alaska↗
USGS2019

Machine learning classifiers for attributing tephra to source volcanoes: An evaluation of methods for Alaska tephras

Glass composition-based correlations of volcanic ash (tephra) traditionally rely on extensive manual plotting. Many previous statistical methods for testing correlations are limited by using geochemical means, masking diagnostic variability. We suggest that machine learning classifiers can expedite correlation, quickly narrowing the list of likely candidates using well-trained models. Eruptives from Alaska's Aleutian Arc-Alaska Peninsula and Wrangell volcanic field were used as a test environment for 11 supervised classification algorithms, trained on nearly 2000 electron probe microanalysis measurements of glass major oxides, representing 10 volcanic sources. Artificial neural networks and random forests were consistently among the top-performing learners (accuracy and kappa > 0.96). Their combination as an average ensemble effectively improves their performance. Using this combined model on tephras from Eklutna Lake, south-central Alaska, showed that predictions match traditional methods and can speed correlation. Although classifiers are useful tools, they should aid expert analysis, not replace it. The Eklutna Lake tephras are mostly from Redoubt Volcano. Besides tephras from known Holocene-active sources, Holocene tephra geochemically consistent with Pleistocene Emmons Lake Volcanic Center (Dawson tephra), but from a yet unknown source, is evident. These tephras are mostly anchored by a highly resolved varved chronology and represent new important regional stratigraphic markers.

Journal of Quaternary Science↗
USGS2012

Titan's fluvial valleys: Morphology, distribution, and spectral properties

Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan's geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200 km and widths of up to 10 km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan's atmospheric windows, as most of them are located on Titan's bright ‘continents’. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at 1.3 μ m "> 1.3μm in a VIMS false color RGB composite with R: 1.59 / 1.27 μ m "> 1.59/1.27μm , G: 2.03 / 1.27 μ m "> 2.03/1.27μm , and B: 1.27 / 1.08 μ m "> 1.27/1.08μm ; the channels either dissect pure bluish surface units or they are carved into terrain with a mixed spectral signature between bright and bluish surface materials. The global picture of fluvial flows clearly indicates a high diversity of parameters controlling fluvial erosion, such as climatic processes, as well as surface and bedrock types. Recent fluvial activity is very likely in the north polar region in contrast to more arid conditions at lower latitudes and at the south pole of Titan. This divergence is probably an indication of seasonal climatic asymmetries between the hemispheres. However, traces of previous fluvial activity are scattered over all latitudes of Titan, which is indicative of previous climatic conditions with at least episodic rainfall.

Planetary and Space Science↗
USGS2018

Pharmaceutical manufacturing facility discharges can substantially increase the pharmaceutical load to U.S. wastewaters

Discharges from pharmaceutical manufacturing facilities (PMFs) previously have been identified as important sources of pharmaceuticals to the environment. Yet few studies are available to establish the influence of PMFs on the pharmaceutical source contribution to wastewater treatment plants (WWTPs) and waterways at the national scale. Consequently, a national network of 13 WWTPs receiving PMF discharges, six WWTPs with no PMF input, and one WWTP that transitioned through a PMF closure were selected from across the United States to assess the influence of PMF inputs on pharmaceutical loading to WWTPs. Effluent samples were analyzed for 120 pharmaceuticals and pharmaceutical degradates. Of these, 33 pharmaceuticals had concentrations substantially higher in PMF-influenced effluent (maximum 555,000 ng/L) compared to effluent from control sites (maximum 175 ng/L). Concentrations in WWTP receiving PMF input are variable, as discharges from PMFs are episodic, indicating that production activities can vary substantially over relatively short (several months) periods and have the potential to rapidly transition to other pharmaceutical products. Results show that PMFs are an important, national-scale source of pharmaceuticals to the environment.

Science of the Total Environment↗
USGS2021

Small mammal shooting as a conduit for lead exposure in avian scavengers

Lead (Pb) exposure is a widespread wildlife conservation threat. Although commonly associated with Pb-based ammunition from big-game hunting, small mammals (e.g., ground squirrels) shot for recreational or pest-management purposes represent a potentially important Pb vector in agricultural regions. We measured the responses of avian scavengers to pest-shooting events and examined their Pb exposure through consumption of shot mammals. There were 3.4-fold more avian scavengers at shooting fields relative to those at fields with no recent shooting, and avian scavengers spent 1.8-fold more time feeding after recent shooting events. We isotopically labeled shot ground squirrels in the field with an enriched 15N isotope tracer; 6% of avian scavengers sampled within a 39 km radius reflected this tracer in their blood. However, 33% of the avian scavengers within the average foraging dispersal distance of nests (0.6−3.7 km) were labeled, demonstrating the importance of these shooting fields as a source of food for birds nesting in close proximity. Additionally, Pb concentrations in 48% of avian scavengers exceeded subclinical poisoning benchmarks for sensitive species (0.03−0.20 μg/g w/w), and those birds exhibited reduced δ-aminolevulinic acid dehydratase activity, indicating a biochemical effect of Pb. The use of shooting to manage small mammal pests is a common practice globally. Efforts that can reduce the use of Pb-based ammunition may lessen the negative physiological effects of Pb exposure on avian scavengers.

Oregon↗
USGS1991

Trondhjemitic, 1.35-1.31 Ga gneisses of the Mount Holly Complex of Vermont: evidence for an Elzevirian event in the Grenville Basement of the United States Appalachians

A newly recognized suite of trondhjemite–tonalite and dacitic gneiss forms a 10 km wide belt of rocks within the Mount Holly Complex in the central part of the Green Mountain massif of Vermont. Field relationships and chemistry indicate that these gneisses are calc-alkaline, volcanic, and hypabyssal plutonic rocks older than the Middle Proterozoic regional deformation that affected the Mount Holly Complex. U–Pb zircon dates indicate ages as great as 1.35 Ga for crystallization of the volcanic protoliths and for intrusion of crosscutting trondhjemite. Tonalitic plutonism continued until 1.31 Ga.Map-scale contacts between the trondhjemitic–tonalitic–dacitic gneisses and the paragneiss sequence of the Mount Holly Complex are sharp, suggesting that the volcanic rocks of the trondhjemite–tonalite suite underlie the paragneiss units and do not intrude them. These relationships suggest that the trondhjemite–tonalite suite is either considerably older than, and unconformable beneath, the paragneiss cover rocks or represents a volcanic edifice slightly older than the deposition of the sedimentary precursor to the paragneiss units. The paragneiss and tonalite–trondhjemite gneisses are both intruded by younger granitoids that were intruded at about 1.25 Ga during strong dynamothermal metamorphism.The trondhjemitic gneisses of the Mount Holly Complex of Vermont have high Al 2 O 3 and low Yb contents and light rare-earth element enrichment patterns that are more characteristic of continental than oceanic volcanic arcs. The Mount Holly intrusives and volcanics may have formed during 1.35–1.31 Ga ensialic volcanic-arc activity, contemporaneous with ensimatic arc activity during the early part of the Elzevirian phase of the Grenville orogeny. In Vermont, later deformation and granite intrusion at about 1.25 Ga coincide with the major pulse of the Elzevirian orogeny and associated trondhjemitic plutonism in the Central Metasedimentary Belt of eastern Canada.

Vermont↗
USGS2005

Evidence for cumulative temperature as an initiating and terminating factor in downstream migratory behavior of Atlantic salmon (Salmo salar) smolts

Temperature control of Atlantic salmon (Salmo salar) smolt migration was tested using a novel technique allowing nearly continuous monitoring of behavior with complete control over environmental conditions. Parr and presmolts were implanted with passive integrated transponder tags, placed in simulated streams, and monitored for upstream and downstream movements. Beginning 18 April, temperature was increased 1??C every third day (advanced), fourth day (ambient), and tenth day (delayed). Smolt downstream movements were initially low, peaked in mid-May, and subsequently declined under all conditions. Parr downstream movements were significantly lower than those of smolts in all treatments (0.8 ?? 0.5 movement??day-1 versus 26.5 ?? 4.5 movements??day-1, mean ?? SE) and showed no increase. At delayed temperatures, smolts sustained downstream movements through July; those under ambient and advanced conditions ceased activity by mid-June. Initiation and termination of downstream movements occurred at significantly different temperatures but at the same number of degree-days in all treatments. Physiological changes associated with smolting (gill Na+,K +-ATPase activity and plasma thyroxine) were coincident with behavioral changes. This is the first evidence of a behavioral component to the smolt window. We found that temperature experience over time is more relevant to initiation and termination of downstream movement than a temperature threshold. ?? 2005 NRC Canada.

Canadian Journal of Fisheries and Aquatic Sciences↗