Rock River Research Articles

Identification of endangered Alabama lampmussel (Lampsilis virescens) specimens collected in the Emory river, Tennessee, USA via DNA barcoding

The federally endangered Alabama lampmussel (Lampsilis virescens) has been presumed extirpated in the Emory river, TN for almost four decades. In the fall of 2011, three specimens that were morphologically identified as L. virescens (based on external shell morphology) were collected from the Emory river. The significance of such a find led biologists to take a noninvasive tissue sample from each individual for genetic confirmation. Approximately 400 nucleotides of the mtDNA COI gene were sequenced for each individual along with two samples of L. virescens from the Paint Rock river. DNA sequence data was also obtained from Genbank for other Lampsilis sp. Maximum parsimony and Bayesian phylogenetic methods revealed strong support for a clade consisting of putative Emory river L. virescens and known L. virescens (Paint Rock river origin) that was sister to all other taxa. These results indicated that the individuals collected from the Emory river were indeed L. virescens.

Soil and landscape influences on native riparian phosphorus availability in three Lake Champlain Basin stream corridors

The ability to rank riparian soils by native phosphorus (P) concentration could help prioritize riparian management practices aimed at reducing P loading from streambank erosion. The objective of this study was to explore the relationship between riparian soil variability and native P availability in three riparian corridors in northwestern Vermont. In the first study, two sites along tributaries of Lake Champlain were remapped at a high resolution (1:5000) by the USDA Natural Resources Conservation Service in 2006. After the remapping, multiple profile samples were taken from each series and were analyzed for total P (TP) and Modified Morgan extractable P. In a second study, 27 soil characterization pedons were sampled along three riparian corridors (Lewis Creek, Rugg Brook, and Rock River) to capture a broader range of parent material and P content. These samples were analyzed for particle size separates (sand, silt, and clay content), TP, and oxalate extractable P. Results showed a strong relationship between soil series variation (e.g., texture and drainage differences) and native P concentration. The first study revealed that both Modified Morgan extractable P and TP were lower in the coarser-textured, well drained soil series compared to the finer-textured soils. In the second study, native P concentrations (TP and oxalate extractable P) were also significantly greater in the finer-textured soils. The ratio of oxalate extractable P to TP decreased strongly with increasing sand content (r2 = 0.69), indicating that the finer-textured soils had a greater fraction of potentially desorbable P. Texture was a good indicator of native P concentrations across a wide range of soil properties, suggesting that accurate soil maps will be an important tool for indexing the native P status along riparian corridors in the Lake Champlain Basin region.

SWAT Model Application to Assess the Impact of Intensive Corn-farming on Runoff, Sediments and Phosphorous loss from an Agricultural Watershed in Wisconsin

The potential future increase in corn-based biofuel may be expected to have a negative impact on water quality in streams and lakes of the Midwestern US due to increased agricultural chemicals usage. This study used the SWAT model to assess the impact of continuous-corn farming on sediment and phosphorus loading in Upper Rock River watershed in Wisconsin. It was assumed that farmers in the area where corn was rotated with soybean would progressively skip soybean for continuous corn as corn became more profitable. Simulations using SWAT indicated that conversion of corn-soybean to corn-corn-soybean would cause 11% and 2% increase in sediment yield and TP loss, respectively. The conversion of corn-soybean to continuous corn caused 55% and 35% increase in sediment yield and TP loss, respectively. However, this increase could be mitigated by applying various BMPs and/or conservation practices such as conservation tillage, fertilizer management and vegetative buffer strips. The conversion to continuous corn tilled with conservation tillage reduced sediment yield by 2% and did not change TP loss. Increase in P fertilizer amount was roughly proportional to increase in TP loss and 11% more TP was lost when fertilizer was applied four months before planting. Vegetative buffer strips, 15 to 30 m wide, around corn farms reduced sediment yield by 51 to 70% and TP loss by 41 to 63%.

Determination of Critical Source Areas for Phosphorus Loss: Lake Champlain Basin, Vermont

Lake Champlain, located between Vermont, New York, and Quebec, exhibits eutrophication due to continuing phosphorus (P) inputs from upstream nonpoint-source areas. To address the effects of this eutrophication and as part of total maximum daily load (TMDL) requirements, state-level P reduction goals have been established by both the Vermont and New York Departments of Environmental Conservation. Unfortunately, remedial measures undertaken thus far have been mostly based on voluntary participation by the landowners and have not been guided by a systematic technique to implement remedial measures where they could provide the greatest P loss reduction. Consequently, P reduction goals have not been achieved in most segments of Lake Champlain. The main objective of this study was to identify and quantify critical source areas (CSAs) of P loss using a model-based approach. The Soil and Water Assessment Tool (SWAT) is used for this objective. This study focuses on the Rock River watershed, which is one of the highest contributors of P to Lake Champlain. Spread over 71 km2, the watershed is dominated by dairy agriculture and has fertile periglacial lacustrine and alluvial soils with an old tile drainage system. In this agriculture-dominated watershed, 80% of total P loss occurs from only 24% of the watershed area, signifying the need for focused remedial measures on CSAs of P loss. The identification of CSAs for P loss is expected to support the next phase of our project, which involves exploring cost-effective P management strategies with the highest potential for P loss reduction applicable to the study watershed and Lake Champlain basin.

Timing and origin for sand dunes in the Green River Lowland of Illinois, upper Mississippi River Valley, USA

The recent increase in dune studies in North America has been heavily focused in the Great Plains, while less attention has historically been given to the dune fields east of the Mississippi River. Here we report ages and suggest a potential sediment source for sand dunes in the Green River Lowland, Illinois, which may provide a better understanding of the dynamic interactions between eolian, glacial, lacustrine and fluvial processes that shaped the landscapes of the upper Midwest. Seven coherent optically stimulated luminescence ages (OSL, or optical ages) obtained from four sites suggest that major dune construction in the Green River Lowland occurred within a narrow time window around 17,500 ago. This implies either an enhanced aridity or an episodic increase of sediment supply at 17,500 years ago, or combination of the both. Contrary to previous assertions that dune sand was sourced from the deflation of the underlying outwash sand deposited when the Lake Michigan Lobe retreated from the area, we propose that Green River Lowland dunes sand originated from the Green Bay Lobe through the Rock River. Specifically, sediment supply increased in the Rock River valley during drainage of Glacial Lake Scuppernong, which formed between ∼18,000 and 17,000 years ago, when the Green Bay Lobe retreated from its terminal moraine. The lake drained catastrophically through the Rock River valley, providing glacial sediment and water to erode the preexisting sandy sediments. Throughout the remainder of the late Pleistocene, the Laurentide Ice Sheet drained into larger more northerly glacial lakes that in turn drained through other river valleys. Therefore, the dunes in the Green River Lowland formed only during the catastrophic drainage of Glacial Lake Scuppernong, but were stabilized through the remainder of the Pleistocene. This scenario explains the abrupt dune construction around 17,500 years ago, and explains the lack of later dune activity up to the Pleistocene–Holocene transition. OSL and radiocarbon ages also indicate that dunes were reactivated during the early, middle and late Holocene. Some eolian activation occurred within well-defined dry intervals in the upper Midwest, suggesting that increased aridity may have been the primary driver in mobilizing sand. However, many ages do not correspond to drier periods. In contrast to the relative coherency of the Pleistocene OSL ages from multiple study sites, the Holocene OSL ages do not overlap from one site to another, suggesting that increased aridity alone cannot explain the multiple phases of dune reactivation in the Holocene. Therefore, we conclude that the combined effect of localized disturbances and greater aridity acted in concert to increase eolian sand activity in the Holocene. The multiple periods of eolian activity during the Holocene suggest a high potential for future sand activation in the region, and these results are informative for environmental prediction and potential future mitigation.

Morphodynamics of a 1000‐year flood in the Kamp River, Austria, and impacts on floodplain morphology

AbstractThis paper investigates the impact of a 1000‐year flood in August 2002 on floodplains and valley morphology of an Austrian mixed alluvial bed rock river. Discharges with a recurrence interval between 500 and 2000 years caused distinctive overbank scouring and material deposition in the floodplains. After the 1000‐year flood, those morphologically affected areas were at random intervals documented over the whole longitudinal profile. In addition to overbank erosion in curved sections (cut‐offs), the river bed locally widened, floodplain stripping occurred and local overbank scours were documented along straight parts of the river. A hydrodynamic‐numerical model, combined with field measurements, was used to analyse the cause of these erosional landforms. Based on the modelled hydraulic conditions for a one‐year flood (30–78 m3 s–1) and the catastrophic 2002 event (700–800 m3 s–1), the numerical results allowed a cause‐effect study with 19 parameters. Deterministic and statistical analysis (ANOVA, discriminant analysis) showed that the morphodynamic effects of the 2002 flood were influenced by the variability of valley morphology of the Kamp River, which led partially to supercritical flow during flood constriction. These processes were in some cases also anthropogenically influenced. Lateral constriction and expansion of the valley geometry over short distances led to scouring and aggradation within the inundated areas during the event. These morphological features were therefore responsible for the elongated scour holes in the floodplains. Copyright © 2009 John Wiley & Sons, Ltd.

A revision of the stratigraphic nomenclature of the Cambrian–Ordovician strata of the Philipsburg tectonic slice, southern Quebec

The Philipsburg tectonic slice is bounded to the west by a northeast–southwest-trending thrust fault (Logan’s Line) and preserves 10 formations of Middle (?) to Late Cambrian (Milton, Rock River, and Strites Pond formations), Early Ordovician (Wallace Creek, Morgan Corner, Hastings Creek, and Naylor Ledge formations), and early Middle Ordovician (Luke Hill, Solomons Corner, and Corey formations) age. The strata were previously assigned to the Philipsburg Group. Early correlations between the Philipsburg succession and coeval strata of the St. Lawrence Platform were mainly based on sparse macrofauna and inferred stratigraphic position. Unconformities at the Cambrian–Ordovician and Early Ordovician – Middle Ordovician boundaries occurring in autochthonous St. Lawrence Platform and the allochthonous Philipsburg succession (Philipsburg tectonic slice) highlight new stratigraphic interpretations between the inner-shelf (St. Lawrence Platform) and the outer-shelf (Philipsburg) successions. The succession in the Philipsburg tectonic slice is divided into three new groups. The Middle (?) to Upper Cambrian Missisquoi Group (new) includes the Milton, Rock River, and Strites Pond formations. The upper boundary of the Missisquoi Group is defined by the upper unconformable contact between the Upper Cambrian Strites Pond Formation and overlying Lower Ordovician Wallace Creek Formation. The Missisquoi Group correlates with the Potsdam Group of the St. Lawrence Platform. The Lower Ordovician School House Hill Group (new) includes the Wallace Creek, Morgan Corner, Hastings Creek, and Naylor Ledge formations. The upper boundary of this group is marked by a regionally extensive unconformity at the top of the Naylor Ledge Formation and correlates with the younger Beekmantown-topping unconformity. The School House Hill Group is correlative with the lower to upper part of the Beekmantown Group (Theresa Formation and the Ogdensburg Member of the Beauharnois Formation) of the St. Lawrence Platform. The Middle Ordovician Fox Hill Group (new) consists of the Luke Hill, Solomons Corner, and Corey formations. This group correlates with the uppermost part of the Beekmantown Group (Huntingdon Member of the Beauharnois Formation and the Carillon Formation).

Impacts of short-term acid and aluminum exposure on Atlantic salmon ( Salmo salar) physiology: A direct comparison of parr and smolts

Episodic acidification resulting in increased acidity and inorganic aluminum (Al i) is known to impact anadromous salmonids and has been identified as a possible cause of Atlantic salmon population decline. Sensitive life-stages such as smolts may be particularly vulnerable to impacts of short-term (days–week) acid/Al exposure, however the extent and mechanism(s) of this remain unknown. To determine if Atlantic salmon smolts are more sensitive than parr to short-term acid/Al, parr and smolts held in the same experimental tanks were exposed to control (pH 6.3–6.6, 11–37 μg l −1 Al i) and acid/Al (pH 5.0–5.4, 43–68 μg l −1 Al i) conditions in the lab, and impacts on ion regulation, stress response and gill Al accumulation were examined after 2 and 6 days. Parr and smolts were also held in cages for 2 and 6 days in a reference (Rock River, RR) and an acid/Al-impacted tributary (Ball Mountain Brook, BMB) of the West River in Southern Vermont. In the lab, losses in plasma Cl − levels occurred in both control parr and smolts as compared to fish sampled prior to the start of the study, however smolts exposed to acid/Al experienced additional losses in plasma Cl − levels (9–14 mM) after 2 and 6 days, and increases in plasma cortisol (4.3-fold) and glucose (2.9-fold) levels after 6 days, whereas these parameters were not significantly affected by acid/Al in parr. Gill Na +,K +-ATPase (NKA) activity was not affected by acid/Al in either life-stage. Both parr and smolts held at BMB (but not RR) exhibited declines in plasma Cl −, and increases in plasma cortisol and glucose levels; these differences were significantly greater in smolts after 2 days but similar in parr and smolts after 6 days. Gill NKA activity was reduced 45–54% in both life-stages held at BMB for 6 days compared to reference fish at RR. In both studies, exposure to acid/Al resulted in gill Al accumulation in parr and smolts, with parr exhibiting two-fold greater gill Al than smolts after 6 days. Our results indicate that smolts are more sensitive than parr to short-term acid/Al. Increased sensitivity of smolts appears to be independent of a reduction in gill NKA activity and greater gill Al accumulation. Instead, increased sensitivity of smolts is likely a result of both the acquisition of seawater tolerance while still in freshwater and heightened stress responsiveness in preparation for seawater entry and residence.

Physics Northwest: An Academic Alliance

It's a weekday in mid-October, late at night and with another teaching assignment not far below the horizon. Yet 40 teachers are laughing, joking, and sharing in the fun that is associated with physics teaching. The event: a Physics Northwest (PNW) meeting, an organization that is in its 20th year and thriving. “Physics Northwest meetings are not only interesting, educational, and a source of great ideas for physics demonstrations, they are also Phun,” says David Thiessen. David's response appears to be universal among PNW members and he continues to attend PNW meetings even though he is into his ninth year of retirement. Patti Sievert of Northern Illinois University tells us, “I'm here tonight to learn how to form a Physics Northwest in the Rock River Valley,” and immediately three people from PNW volunteer to be there to help with her first meeting. Yes, this happened and continues to happen monthly in many northwest Illinois suburban high schools. The history of this prosperous organization and its sister organization, the Illinois State Physics Project (ISPP),1 can be gleaned from the website in Ref. 2.

Biostratigraphy of Late Maastrichtian larger foraminifers in Jamaica and the importance of <i>Chubbina</i> as a Late Maastrichtian index fossil

Abstract. The succession of larger foraminifers from the White Rock River Bridge section of the Guinea Corn Formation (Late Maastrichtian) in Jamaica, West Indies, contains: Sulcoperculina dickersoni (Palmer), Ayalaina rutteni (Palmer), Orbitoides cf. megaloformis Papp & Küpper, Vaughania cubensis Palmer and Chubbina cardenasensis (Barker & Grimsdale). A. rutteni occurs in the lower beds and C. cardenasensis occurs in the upper beds. The orbitoid foraminifer Or. cf. megaloformis is restricted to the middle beds. The White Rock River Bridge Section can be correlated to the standard Guinea Corn successions using lithological/biostratigraphic markers and rudist marker beds, and linked ages derived from Sr-isotope values. This indicates that Or. cf. megaloformis occurs in the last 1.3 Ma of the Cretaceous in the Caribbean and that its evolution was retrograde compared to coeval populations in Europe. The first appearance of Chubbina represents a valuable datum since the genus occurs in various different biofacies (both with and without orbitoid foraminifers) and allows correlation in the Caribbean, Central America and Florida.

Structure analysis of montmorillonite crystallites by convergent-beam electron diffraction

AbstractThe small particle size and the random stacking of layers has previously hindered systematic structure investigations of montmorillonite. By applying the convergent-beam electron diffraction mode (CBED) of a transmission electron microscope (TEM) with a beam spot of ~800 Å we were able to examine undisturbed areas of montmorillonite crystallites.Because montmorillonite crystallites are mostly thin particles, kinematic theory can be applied and the CBED patterns can be interpreted directly, provided that the particle thickness remains below the critical value of 350 Å. An average thickness of ~90 Å was calculated here for montmorillonite of bulk samples from X-ray diffraction analysis and lattice-fringe images. However, satisfactory diffraction intensity patterns for quantitative evaluation were obtained only from crystallites with a thickness above the average, which yielded a sufficient scattering volume. These patterns could be described in terms of the kinematic theory and therefore these crystallites were <350 Å thick. Yet, crystallites of adequate thickness were extremely rare in the three samples investigated (Clay Spur, Rock River and Upton, all in Wyoming, USA).The diffraction intensities from theabplane of single montmorillonite crystallites of the various origins fit the three structural models for atrans-vacancy distribution, acis-vacancy distribution or a random-cation distribution within the octahedral sheets. The configuration of the diffraction patterns also shows a 1Msymmetry of the layer. Due to the limited data set of CBED patterns, a refinement of the structure could not be achieved. However, energy dispersive X-ray spectroscopy data and computation of the cation–anion distances and valences using the ‘distance valence least square’ program permitted a refinement of the models.

Late Maastrichtian rudist and coral assemblages from the Central Inlier, Jamaica: towards an event stratigraphy for shallow-water Caribbean limestones

The lithological succession of the Guinea Corn Formation in the Slippery Rock River, central Jamaica, comprises 91 m of limestones and subsidiary mudstones. The biostratigraphic distribution of rudist bivalves and corals demonstrates that the succession of biostratigraphic markers is consistent with the previously documented standard Guinea Corn Formation succession in the Rio Minho between Grantham and Guinea Corn, central Jamaica. Additionally, the Slippery Rock River succession shows the boundary between the Chiapasella radiolitiformis and C. trechmanni zones that has not previously been documented. The marker horizons are also consistent with major facies changes within both sections, demonstrating that both lithological changes and biostratigraphic markers are synchronous within the limestone successions of central Jamaica. This may prove to be a valuable tool for stratigraphic correlation elsewhere in Jamaica and within the Antillean region.

Avant-Gardist in the Forest

Lorine Niedecker inhabited a periphery, as a manual laborer and poet, in an unplumbed cabin she built on a peninsula beside the Rock River in Wisconsin. People find places of refuge where they might be secure, say cultural geographers; the margins provide hybrid vigor; they produce the most interesting lateral thinking. She was drawn to threshold states, to boundaries between the familiar and the alien, between the facilitating contours of syntax and an alien content, writes Jenny Penberthy, the Canadian professor who has devoted a life of scholarship to Niedecker, and on the centenary of the poet's birth, edited the Collected Works. I'm very happy to have spent all this time working on a poet who is so decent and so good and so good-humored.

Agreement Among Observers Classifying Larval Sea Lamprey ( Petromyzon marinus) Habitat

Estimates of larval sea lamprey ( Petromyzon marinus) abundance are used to rank Great Lakes tributaries for lampricide treatment. Observers subjectively stratify habitat into three categories: type I = preferred, type II = acceptable, type III = unacceptable. Agreement was evaluated among eight observers classifying habitats in small discrete plots in two Lake Superior tributaries, the Rock and Chocolay rivers, and among four observers classifying and measuring the amount of each habitat type along random transects in the Rock River. Agreement among the eight observers classifying habitat plots was high (Chocolay, κ = 0.742 and Rock, κ = 0.785). The amounts of types I, II, and III habitat estimated were statistically different among observers. However, the amount of variability found in the classification and measurement of habitat by observers had little effect on the ranking of 51 streams considered for lampricide treatment.

PREDICTING SEDIMENT AND PHOSPHORUS LOADS IN THE ROCK RIVER BASIN USING SWAT

The Rock River is considered degraded from excessive amounts of phosphorus. Individual programs are ongoing to reduce phosphorus from point and nonpoint sources. However, a comprehensive phosphorus management approach may prove more cost effective and beneficial. To be successful, such an approach must take into consideration phosphorus from all sources and seek geographically targeted, cost–effective, and holistic solutions. This study utilized the SWAT (Soil and Water Assessment Tool) model to quantify phosphorus sources throughout the basin and quantify impacts from the application of basin–wide BMPs. Results of this study indicate that, under existing land use and management conditions, an average annual phosphorus load of approximately 764,000 kg enters the Rock River and it tributaries. Point sources account for 41% of this value, and nonpoint sources account for 59%. Model results show that, under existing conditions, approximately 160,000 tons of sediment is delivered to the streams and surface water bodies on an average annual basis. Modeling results indicate that implementation of improved tillage practices (predominantly conservation tillage) can reduce sediment yields by almost 20%.

USING ROUND ROBINS AS A TOOL FOR EVALUATING LABORATORY QUALITY

USING ROUND ROBINS AS A TOOL FOR EVALUATING LABORATORY QUALITYThe Rock River Water Reclamation District monitors approximately 90 Significant Industrial Users, SIUs, for conventional and toxic pollutants. These industrial users may report the District's data to meet the self-monitoring requirements in the General Pretreatment Regulations, 40 CFR 403. In addition to using District data, about 20% of the SIUs also monitor their wastewater discharges at...Author(s)Mary JohnsonDennis PrieweSourceProceedings of the Water Environment FederationSubjectSession 37 - Plant Operations and Maintenance/Lab Practices: Laboratory Analysis—Regulatory and Environmental ImpactDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2002ISSN1938-6478SICI1938-6478(20020101)2002:14L.525;1-DOI10.2175/193864702784248494Volume / Issue2002 / 14Content sourceWEFTECFirst / last page(s)525 - 532Copyright2002Word count280

Food Use in Minnesota Populations of the Topeka Shiner (Notropis topeka)

ABSTRACT We examined gut contents of 65 Topeka shiners (Notropis topeka) collected from the Rock River drainage of southwestern Minnesota in 1997. Anecdotal and unpublished information regarding food habits have suggested that the Topeka shiner is largely a benthic or nektonic insectivore. Our results show that it is an omnivore that feeds opportunistically on immature aquatic insects, several kinds of microcrustaceans and other invertebrates, larval fish, algae, vascular plant matter, and detritus. The Topeka shiner functions both as a benthic and nektonic feeder and shows strong trophic similarities to its sister species, the sand shiner (N. ludibundis).

James Bryan Herrick.

Physician par excellence, scientist and humanist, James Bryan Herrick (Fig. 1 ) was born in Oak Park, Illinois, on August 1 1, 1861, the son of Origen White Herrick and Dora E. Kettlestrings. His mother’s father, an immigrant from England, had arrived in that area in acovered wagon and settled on a homestead which was later to be the site of the village known as Oak Park. The subsequent birth of Herrick’s mother in Oak Park gave her the distinction of being the oldest native daughter of that village.’ Herrick’s early education was confined to the local Oak Park High School and the Rock River Seminary at Mount Morris, Illinois. He then earned his Bachelor of Arts degree in 1882 from the University of Michigan, which imbued him with a firm background in the humanities. Apparently, Herrick had a penchant for literature even as a youngster, an interest that was nurtured during his stay at Michigan by Moises Coit Tyler, a professor of English literature. Above all, Tyler instilled in young Hemck an enduring fascination with Chaucer. Hemck was to reveal the extent of this fascination in an article he wrote on Chaucer more than five decades later, the article being the published version of an after-dinner speech that he had given at an annual meeting of the Association of American Physicians.2 It was quite evident from this long discourse that Henick had read everything that Chaucer ever wrote. This

Nocturnal habitat use of Atlantic salmon parr in winter

We completed 22 night snorkeling surveys between November and March 1995-1997 to quantify Atlantic salmon (Salmo salar) parr habitat use relative to habitat availability in the Rock River, Vermont, U.S.A. On average, post-young-of-the-year (PYOY) parr selected greater water depths in winter than young-of-the-year (YOY) parr, whereas YOY and PYOY parr both selected water velocities ([Formula: see text]19 cm/s) that were significantly lower than random measurements (46 cm/s). Maturity of PYOY parr had no significant influence on habitat selection. The majority of YOY and PYOY parr at night were found in contact with the stream bottom resting on silt-sand or gravel substrates in velocity dead-zone habitats created by the stream edge or depositional habitats created by midstream rocks and boulders. The strong selection that nocturnal Atlantic salmon parr exhibit for low water velocity areas in winter indicates the importance of maintaining large instream cover that provides refuges from high flows. The similarity that YOY and PYOY parr exhibited in many elements of habitat selection suggests that both stages may be similarly susceptible to habitat limitations in winter.

Nocturnal habitat use of Atlantic salmon parr in winter

We completed 22 night snorkeling surveys between November and March 1995-1997 to quantify Atlantic salmon (Salmo salar) parr habitat use relative to habitat availability in the Rock River, Vermont, U.S.A. On average, post-young-of-the-year (PYOY) parr selected greater water depths in winter than young-of-the-year (YOY) parr, whereas YOY and PYOY parr both selected water velocities (19 cm/s) that were significantly lower than random measurements (46 cm/s). Maturity of PYOY parr had no significant influence on habitat selection. The majority of YOY and PYOY parr at night were found in contact with the stream bottom resting on silt-sand or gravel substrates in velocity dead-zone habitats created by the stream edge or depositional habitats created by midstream rocks and boulders. The strong selection that nocturnal Atlantic salmon parr exhibit for low water velocity areas in winter indicates the importance of maintaining large instream cover that provides refuges from high flows. The similarity that YOY and PYOY parr exhibited in many elements of habitat selection suggests that both stages may be similarly susceptible to habitat limitations in winter.