Crooked Lake Research Articles

Гидронимы севера Камчатки и их осмысление в устной традиции коряков

The etymology of the names of the largest rivers in the north of Kamchatka: Apuka, Essowejem, and Pakhacha cannot be identified in the context of the Koryak language. These names are apparently a linguistic relic of older tribes who had inhabited the north of Kamchatka before the arrival of the Koryaks. The Koryak language hydronyms have a stable and typical word-formation structure. The model includes the stem base gytgyn ‘lake’ or wejem ‘river’, supplemented by a dependent base according to the rules of left-handed incorporation: Gal’mogytgyn ‘a crooked lake.’ The article considers the hydronyms that directly characterize the natural features of the objects (Yynagytgyn ‘a foggy lake,’ Kujviwejem ‘an icy river’) or refer to a certain kind of trees growing along the river (Tyklawajam ‘a poplar river’). Also considered are metaphorically grounded hydronyms (Upupkin ‘under the nose river’). The analysis covers the hydonyms with warning semantics (Akakujul ‘a terrible swamp stream’, Wajampylka ‘a river where people drown’. The structure of a Koryak hydronym can refer to a particular animal species (Yajolwajam ‘a fox river’) or the hydronym may be rationally motivated (Echgynnywajam ‘white fish river’). It is also possible for hydronyms to have mythological origins. The article presents the fragments of the legends the mythological motifs of which may have provided the basis for the appearance of hydronyms Yil’ewejem ‘the river of the Evrazhka’ or Ev’jojnwajam ‘the river near the place where wolves were driven into a trap.’ In conclusion, hybrid hydronyms used in cartography to nominate tributaries are discussed.

An integrated machine learning-based approach to identifying controlling factors of unconventional shale productivity

The controlling factors of unconventional shale productivity by comprehensive analysis of mineralogy, petrophysics, geochemistry, and geomechanics have not been well understood. The comprehensive datasets from 1182 core samples of key wells from the Duvernay shale at Crooked Lake, Alberta, are gathered to evaluate the fundamental parameters controlling unconventional shale gas production. By integrating reservoir parameters and shale productivity, a machine learning-based approach is used to identify the fundamental elements that affect shale productivity. Four machine learning approaches are evaluated, where Extra Trees has led to the highest coefficient of determination R2 of 0.817. Factors that mostly contribute to shale productivity are found to be the production index, formation pressure, effective porosity, total organic carbon, gas saturation, and shale thickness. Case studies demonstrate that the average accordance rate between the predicted and actual production of three new wells reaches 92.3%, thereby shedding light on the site selection of hydraulic fracturing wells for the efficient development of unconventional resources.

An Integrated Method to Mitigate Hazards from Hydraulic Fracturing–Induced Earthquakes in the Duvernay Shale Play

Summary In recent decades, a remarkable increase in induced seismicity in the Western Canada Sedimentary Basin (WCSB) has been largely attributed to hydraulic fracturing (HF) operations in unconventional plays. However, a mitigation strategy concerning geological, geomechanical, and operational susceptibilities to HF-induced seismicity has not been well understood. This work proposes an integrated method to mitigate potential risks from HF-induced seismicity in the Duvernay play near Crooked Lake. The geological susceptibility to induced seismicity is evaluated first from site-specific formation pressure and a distance to the Precambrian basement. The regional in-situ stress and rock mechanical properties are then assessed to determine the geomechanical susceptibility to induced seismicity. Next, the operational factors are determined by comparing induced seismicity with operational parameters such as total injection fluids and proppant mass. It is found that regions with a low formation pressure (<60 MPa), a great distance from the base Duvernay to the Precambrian basement (>260 m), a low minimum principal stress (<70 MPa), and a low brittleness index (<0.45) tend to be induced-seismicity-quiescent regions. Finally, a multiple linear regression (MLR)-based approach is proposed by considering the relative importance of different parameters. The MLR analysis indicates that brittleness index, formation pressure, and total injection volume are the top three controlling factors. Three new horizontal wells are drilled and the MLR analysis of these wells using the three most important parameters is conducted. High-resolution monitoring results indicated that 95% of the induced events had a local magnitude of less than 2.0 during and after the HF operations (3-month time window and 5-km well-event distance), among which the maximum magnitude reached ML3.05 (<red light magnitude ML4.0). Therefore, the MLR-based approach was successfully validated, suggesting that this approach can be applied to mitigate potential seismicity risks in upcoming wells in the Fox Creek region. Such a workflow can also be applied to other regions to guide seismicity-free fracturing operations in unconventional plays.

Mitigating risks from hydraulic fracturing-induced seismicity in unconventional reservoirs: case study

The recent remarkable increase in induced seismicity in Western Canada has been largely attributed to hydraulic fracturing in unconventional reservoirs. The nucleation of large magnitude events has been demonstrated to be closely linked to site-specific geological and operational factors. A mitigation strategy of fracturing-induced seismicity concerning both factors has not been well investigated. In this paper, a comprehensive investigation of risk mitigations from induced seismicity is conducted based on the formation overpressure, distance to Precambrian basement, proximity to faults, fracturing job size and safe hydraulic fracture-fault distance. It is found that the middle-south region near Crooked Lake is an optimal region for fracturing operations with low formation pressure, a great distance to the basement and relatively fewer pre-existing faults. A field case study suggests that fracturing operations of three new horizontal wells are successful with low magnitude induced events and with high production performance, demonstrating the applicability of a comprehensive approach of seismicity risk mitigations. Such an approach can be applied to other field cases to mitigate the potential fracturing-induced seismicity in unconventional reservoirs.

Investigation on Two Mw 3.6 and Mw 4.1 Earthquakes Triggered by Poroelastic Effects of Hydraulic Fracturing Operations Near Crooked Lake, Alberta

AbstractA coupled approach of fluid flow and geomechanics is proposed in this study to quantitatively understand the hydraulic fracturing‐induced poroelastic effects that activate pre‐existing faults and trigger earthquake swarms near Crooked Lake, Alberta. The 3D poroelastic simulation of the seismogenic fault zone is then conducted to characterize the pressure diffusion and stress perturbation that led to fault activation. Results show that the poroelastic effects on the high‐permeable damage zones of a conductive‐barrier fault triggered the sequential activation of the seismogenic fault in the basement and Winterburn Formation. In addition, the high‐permeable damage zones act as conduits for pore pressure diffusion along the fault, whereas the fault core functions as a barrier to prevent crossing flow. The poroelastic effects in terms of pressure diffusion and stress perturbation in response to fluid injection facilitated the fault slip and hence triggered the Mw 3.6 earthquake in the basement formation 40 days after the fracturing operations. Moreover, the mainshock created negative Coulomb failure stress changes, inhibiting further fault slip in the basement formation. Subsequently, the stimulation of another well facilitated poroelastic effects on the fault damage zone in top Winterburn Formation, reactivating the same fault with an Mw 4.1 earthquake 8 days after the initiation of treatments. It is essential to optimize the injection site selection near the existing faults to reduce risks of the induced earthquakes near Crooked Lake.

Walleye Population Responses to Experimental Exploitation in a Northern Wisconsin Lake

AbstractUnderstanding how fish populations respond to exploitation is critical for sustainable fisheries management. Walleye Sander vitreus have been exploited by tribal spear and angling fisheries in the Ceded Territory of Wisconsin (CTWI) since 1985, and harvest in individual lakes has been regulated using a 35% adult exploitation limit reference point since 1990. We conducted a 35% annual adult Walleye exploitation experiment (1993–1997: baseline exploitation at ~13%; 1998–2008: 35% exploitation) on Big Crooked Lake, Wisconsin, to test for responses in adult, male, female, age‐0, and age‐1 density and sex‐specific mean length at age and proportional size distribution (PSD) indices. Adjacent Wolf Lake was used as the reference system. Adult Walleye density in Big Crooked Lake declined significantly between exploitation periods and was due to the experiment. Adult Walleye density declined from about 16 to 10 fish/ha and was about 7 fish/ha during 2001–2008. Male density declined significantly between exploitation periods, whereas female density did not change. Age‐0 and age‐1 density did not change as a result of the experiment. Male and female mean length at age across several age‐classes increased significantly over time. The PSD indices did not change over time for males, but female PSD‐Quality and PSD‐Preferred increased significantly. Our results suggest that sustained 35% annual exploitation on the Big Crooked Lake Walleye population led to an undesirable adult density (≤7.4/ha) but improved growth. Walleye recruitment did not change in Big Crooked Lake under sustained exploitation; however, we caution that other CTWI populations may respond differently to this level of targeted exploitation. Based on our results, long‐term declines in CTWI Walleye natural recruitment and productivity, and as suggested by other independent studies, we recommend that the limit reference point be lowered to reduce exploitation and be protective of all Walleye populations in the CTWI.

Source characteristics and geological implications of the January 2016 induced earthquake swarm near Crooked Lake, Alberta

On 2016 January 12, an intraplate earthquake with an initial reported local magnitude (ML) of 4.8 shook the town of Fox Creek, Alberta. While there were no reported damages, this earthquake was widely felt by the local residents and suspected to be induced by the nearby hydraulic-fracturing (HF) operations. In this study, we determine the earthquake source parameters using moment tensor inversions, and then detect and locate the associated swarm using a waveform cross-correlation based method. The broad-band seismic recordings from regional arrays suggest a moment magnitude (M) 4.1 for this event, which is the largest in Alberta in the past decade. Similar to other recent M ∼ 3 earthquakes near Fox Creek, the 2016 January 12 earthquake exhibits a dominant strike-slip (strike = 184°) mechanism with limited non-double-couple components (∼22 per cent). This resolved focal mechanism, which is also supported by forward modelling and P-wave first motion analysis, indicates an NE–SW oriented compressional axis consistent with the maximum compressive horizontal stress orientations delineated from borehole breakouts. Further detection analysis on industry-contributed recordings unveils 1108 smaller events within 3 km radius of the epicentre of the main event, showing a close spatial-temporal relation to a nearby HF well. The majority of the detected events are located above the basement, comparable to the injection depth (3.5 km) on the Duvernay shale Formation. The spatial distribution of this earthquake cluster further suggests that (1) the source of the sequence is an N–S-striking fault system and (2) these earthquakes were induced by an HF well close to but different from the well that triggered a previous (January 2015) earthquake swarm. Reactivation of pre-existing, N−S oriented faults analogous to the Pine Creek fault zone, which was reported by earlier studies of active source seismic and aeromagnetic data, are likely responsible for the occurrence of the January 2016 earthquake swarm and other recent events in the Crooked Lake area.

Poroelastic stress triggering of the December 2013 Crooked Lake, Alberta, induced seismicity sequence

AbstractThe Crooked Lake area in Central Alberta, Canada, became seismically active in December 2013 with a sequence of earthquakes Mw 2.0 and higher. The earthquakes are suspected to be induced by hydraulic fracturing in nearby horizontal wells due to their strong spatiotemporal correlation. To investigate the physical mechanism of the induced seismicity near Crooked Lake, we calculate stress and pore pressure perturbations resulting from high‐rate multistage fluid injection in the framework of linear poroelasticity. The calculated perturbations are used for seismic risk analysis based on the Coulomb failure criterion. Results show that most seismicity is within a positive Coulomb stress change regime, indicating that failure is promoted by injection of fluid. By comparing Coulomb stress results for different parameter settings, we show that elastic response of the solid matrix, instead of fluid diffusion, is more likely the dominant factor for the induced earthquakes shortly after fluid injection.

Stress drop estimates and hypocenter relocations of induced seismicity near Crooked Lake, Alberta

AbstractWe use a sequence of induced earthquakes near Crooked Lake, Alberta, to investigate the physical differences between induced and tectonic earthquakes. Starting with the Natural Resources Canada earthquake catalogue, we use a spectral ratio method to calculate the static stress drops of a group of relocated earthquakes ranging from December 2013 to June 2015. We find that stress drops fall within the high side of the typical reported range of tectonic events and show no correlation with earthquake magnitude, depth, or distance from the well. The stress drops appear roughly constant for events with Mw 3 to 4. Relocated hypocenters cluster both spatially and temporally around corresponding injection wells and appear to migrate deeper with increasing time from injection. Fine‐scale lineations apparent in relocated hypocenters could indicate the presence and orientation of fault planes, consistent with the published focal mechanism solutions of M 4+ events in the area.

Focal Mechanisms of Some Inferred Induced Earthquakes in Alberta, Canada

Although it has long been understood that injection of fluids into the subsurface can activate slip on a fault (e.g., Healy et al. , 1968), seismicity induced by fluid injection associated with oil and gas operations has recently come into sharper focus (Ellsworth, 2013; Keranen et al. , 2013; Schultz et al. , 2014). Since December 2013, anomalous seismicity of magnitude up to M L 4.4 has occurred episodically in parts of Alberta, Canada. In the Crooked Lake (CL) area of west‐central Alberta, induced seismicity appears to be spatially and temporally correlated with hydraulic fracturing, a process of injecting fracturing fluids into a rock formation at a force exceeding the fracture pressure of the rock, thus inducing a network of fractures through which oil or natural gas can flow to the wellbore (CCA, 2014). Farther south, an M w 3.8 earthquake on 9 August 2014 occurred within the Rocky Mountain House (RMH) cluster, an area where persistent seismic activity since the late 1970s has been interpreted to be triggered by poroelastic stress changes from the production of hydrocarbons (Baranova et al. , 1999). This recent earthquake is the largest event that has occurred to date within this cluster (Stern et al. , 2013), representing a significant departure from a trend of declining seismicity for the past three decades. In this article, we investigate focal mechanisms for some events that have occurred in Alberta since December 2013. These focal solutions were obtained using the polarity of P ‐wave first motions registered on regional seismograms. This investigation was facilitated by the installation of numerous seismograph stations in Alberta during the past few years (Schultz et al. , 2015), including the Regional Alberta Observatory for Earthquake Studies Network (RAVEN). For the purpose of this study, a crustal velocity model was developed based on sonic log data from …

Hydraulic fracturing and the Crooked Lake Sequences: Insights gleaned from regional seismic networks

AbstractWithin central Alberta, Canada, a new sequence of earthquakes has been recognized as of 1 December 2013 in a region of previous seismic quiescence near Crooked Lake, ~30 km west of the town of Fox Creek. We utilize a cross‐correlation detection algorithm to detect more than 160 events to the end of 2014, which is temporally distinguished into five subsequences. This observation is corroborated by the uniqueness of waveforms clustered by subsequence. The Crooked Lake Sequences have come under scrutiny due to its strong temporal correlation (>99.99%) to the timing of hydraulic fracturing operations in the Duvernay Formation. We assert that individual subsequences are related to fracturing stimulation and, despite adverse initial station geometry, double‐difference techniques allow us to spatially relate each cluster back to a unique horizontal well. Overall, we find that seismicity in the Crooked Lake Sequences is consistent with first‐order observations of hydraulic fracturing induced seismicity.

Influence of wind, wave, and water level dynamics on walleye eggs in a north temperate lake

Walleye (Sander vitreus) populations are cyclic because of biotic and abiotic factors, and wind activity, wave energy, and water levels may be influential given walleye spawn close to shore. We installed an anemometer and tridirectional velocimeter on a spawning reef in Big Crooked Lake, Wisconsin, in 2005 to determine wind–wave relationships and wave energy exceedance of critical velocities of both egg (affecting transport) and substrates (affecting abrasion or burial). To evaluate egg movement, we delineated egg locations at adhesive, postspawn, and black-eyed stages and surveyed on-shore for stranded eggs. We monitored water level with a staff gauge. Wind and wave velocities were significantly (p < 0.01) correlated, and wave velocities were significantly higher (p < 0.01) nearshore (2.0 m) than further from shore (4.6 m). Mean nearshore wave velocities were often sufficient to initiate movement of nonadhesive eggs (45% of records) and fine sand (39%) during egg incubation. Surveys indicated waves moved eggs closer to shore and some onto shore. Water level fluctuations (range = 2.4 cm) likely did not strand or desiccate eggs. We documented that wind and wave activity transports eggs and substrates and should be considered a critical factor in annual walleye egg survival and year-class strength.

Quantity, Structure, and Habitat Selection of Natural Spawning Reefs by Walleyes in a North Temperate Lake: A Multiscale Analysis

AbstractSpawning habitat, the cornerstone of self‐sustaining, naturally reproducing walleye Sander vitreus populations, has received limited quantitative research. Our goal was to quantitatively describe the structure and quantity of natural walleye spawning habitat and evaluate potential selection of habitat in Big Crooked Lake, Wisconsin. In 2004 and 2005, we located and delineated walleye egg deposition polygons through visual snorkel and scuba surveys. We also delineated recently deposited, adhesive egg patches daily along one spawning reef in 2005. To determine habitat selection, we quantified and compared spawning and lakewide available habitat at different scales. In both years, walleyes used similar spawning habitat, including three geomorphic types: linear shorelines, a point bar, and an island. Walleyes used only 14% of the entire lake shoreline and 39% of the shoreline comprised of gravel (6.4–76.0 mm), cobble (76.1–149.9 mm), or coarser substrates for spawning in 2005, indicating selection of specific spawning habitat. Lakewide, walleyes spawned close to shore (outer egg deposition polygon boundary mean distance = 2.7 m), in shallow water (outer egg deposition polygon boundary mean depth = 0.3 m), and over gravel substrate (percent coverage mean = 64.3) having low embeddedness (mean = 1.30). Our best nearshore (0–13‐m) resource selection function predicted an increase in the relative probability of egg deposition with the increasing abundance of gravel, cobble, and rubble (150.0–303.9‐mm) substrates and a decrease with increasing distance from shore and water depth (89.9% overall correct classification). Adhesive egg patches confirmed that walleyes actively chose nearshore, shallow‐water, and coarse‐substrate spawning habitat. The quantitative habitat information and predictive models will assist biologists in developing walleye spawning reef protection strategies and potentially aid in designing and evaluating artificial spawning reefs.

Seasonal Viral Loop Dynamics in Two Large Ultraoligotrophic Antarctic Freshwater Lakes

The effect of viruses on the microbial loop, with particular emphasis on bacteria, was investigated over an annual cycle in 2003-2004 in Lake Druzhby and Crooked Lake, two large ultraoligotrophic freshwater lakes in the Vestfold Hills, Eastern Antarctica. Viral abundance ranged from 0.16 to 1.56 x 10(9) particles L-1 and bacterial abundances ranged from 0.10 to 0.24 x 10(9) cells L-1, with the lowest bacterial abundances noted in the winter months. Virus-to-bacteria ratios (VBR) were consistently low in both lakes throughout the season, ranging from 1.2 to 8.4. lysogenic bacteria, determined by induction with mitomycin C, were detected on three sampling occasions out of 10 in both lakes. In Lake Druzhby and Crooked Lake, lysogenic bacteria made up between 18% and 73% of the total bacteria population during the lysogenic events. Bacterial production ranged from 8.2 to 304.9 x 10(6) cells L-1 day-1 and lytic viral production ranged from 47.5 to 718.4 x 10(6) viruslike particles L-1 day-1. When only considering primary production, heterotrophic nanoflagellate (HNF) grazing and viral lysis as the major contributors to the DOC pool (i.e., autochthonous sources), we estimated a high contribution from viruses during the winter months when >60% of the carbon supplied to the DOC pool originated from viral lysis. In contrast, during the summer <20% originated from viral lysis. Our study shows that viral process in ultraoligotrophic Antarctic lakes may be of quantitative significance with respect to carbon flow especially during the dark winter period.

Late Archaean granulite facies metamorphism in the Vestfold Hills, East Antarctica

Granulites of the Vestfold Hills record a pulsed end-Archaean to early Palaeoproterozoic M1–M2 evolution that is distinct from other Archaean areas in East Antarctica and cratonic domains placed adjacent to East Antarctica in Gondwana reconstructions. Pressure and temperature conditions of the end-Archaean to earliest Palaeoproterozoic (2501–2496 Ma) M1 granulite facies metamorphism in the Vestfold Hills have been constrained from mineral assemblages and thermobarometry of Fe-rich paragneisses. Reintegrated compositions of exsolved subcalcic clinopyroxenes and pigeonites in a metaironstone yield temperatures of 895 ± 35 °C, whilst reintegrated compositions of perthitic feldspars in semipelitic paragneisses give minimum estimates of 860 ± 30 °C. These results rule out the extreme ultrahigh temperature (UHT) conditions previously proposed for M1 in the Vestfold Hills. Pressures of metamorphism during M1 are estimated as 8.1 ± 0.9 kb at 850 ± 40 °C from hercynite + sillimanite + almandine + corundum and retrieved Fe–Mg–Al relations in orthopyroxene coexisting with garnet. A second metamorphic event, M2, occurred at 600–660 °C and 6–8 kb based on thermometry of recrystallised pyroxene neoblasts and thermobarometry applied to M2 garnet–quartz symplectites formed on orthopyroxene and garnet. The intervening emplacement of the magmatic Crooked Lake Gneiss Group precursors occurred at similar or shallower pressures prior to D2–M2, an event that caused tectonic interleaving and reactivation of the Vestfold Hills basement at mid-crustal depths in the earliest Palaeoproterozoic, prior to its unroofing to shallower levels (3–5 kb) by 2470 Ma. The lack of correlative Archaean histories in areas that were formerly adjacent in Gondwanan reconstructions is consistent with the Vestfold Hills region either being exotic to the East Antarctic Shield until the final (Neoproterozoic to Cambrian) amalgamation of Gondwana, or being accreted to part of East Antarctica in a Proterozoic event distinct from the Rayner–Eastern Ghats tectonism that united much of India with Antarctica at 1000–900 Ma.

Density Dependence of Walleye Maturity and Fecundity in Big Crooked Lake, Wisconsin, 1997–2003

AbstractDensity is an important factor regulating age at maturity and fecundity of fish populations, so we evaluated the effect of the population density of adult walleyes Sander vitreus on age at 50% maturity and length‐specific fecundity in Big Crooked Lake, Wisconsin, during 1997–2003. Abundance of adult walleyes from mark–recapture surveys ranged from 2,046 fish (3 per acre) to 4,901 fish (7 per acre). Age at 50% maturity ranged from 3.89 to 4.88 years, length of walleye sampled for fecundity ranged from 13.0 to 24.7 in, and average fecundity of a 17‐in walleye ranged from 41,061 to 53,009 eggs. Age at 50% maturity increased significantly as adult walleye population density increased, whereas average fecundity of a 17‐in walleye did not change significantly with density. We conclude that age at 50% maturity could be used as an indicator of population density and exploitation stress and thus could be used to set desired levels of harvest.

A preliminary survey of aquatic macroinvertebrates collected from Crooked Lake Fen Nature Sanctuary in southeastern Saskatchewan

A preliminary survey of aquatic macroinvertebrates collected from Crooked Lake Fen Nature Sanctuary in southeastern Saskatchewan

Bacterioplankton production in freshwater Antarctic lakes

Summary1. Bacterioplankton production was measured in the water columns of two ultra‐oligotrophic, freshwater Antarctic lakes (Crooked Lake and Lake Druzhby) during an annual cycle. In both lakes bacterial production, measured by the incorporation of [3H] thymidine, continued in winter and showed a cycle over the year. The range of production was between 0 and 479 ng C L−1 h−1 in Crooked Lake and 0–354 ng L−1 h−1 in Lake Druzhby.2. Abundance and mean cell volume both varied, producing marked changes in biomass during the year, with highest biomass occurring in the winter and early spring. Biomass showed similar seasonal trends in both lakes.3. For most of the year inorganic forms of nitrogen and phosphorus were detectable in the water columns of the lakes and were unlikely to have limited bacterial production. Dissolved organic carbon (DOC) was below 3000 μg L−1. Dissolved amino acids and carbohydrates contributed 5–25% of the DOC pool in Crooked Lake and 5–64% in Lake Druzhby. Dissolved carbohydrates were consistently low, suggesting that this may have been the preferred carbon substrate for bacterioplankton.4. Aggregate associated bacteria had higher mean cell volume, abundances and production than freely suspended bacteria in Lake Druzhby, while in Crooked Lake aggregate associated bacteria consistently had higher mean cell volumes than free bacteria, but abundance and production were on occasion higher in free bacteria compared with aggregate associated communities.5. The data indicated that production is limited by continuous low temperatures and the limited availability of suitable DOC substrate. However, the bacterioplankton functions year round, responding to factors other than temperature.

Diet Overlap and Predation between Smallmouth Bass and Walleye in a North Temperate Lake

ABSTRACT Walleye (Stizostedion vitreum vitreum) and smallmouth bass (Micropterus dolomieu) diets from Big Crooked Lake, Wisconsin were examined to assess the degree of diet overlap and predation occurring between these species in an attempt to determine whether walleye influence smallmouth bass recruitment, which is consistently low compared to proximal lakes that do not have walleye. Of 389 adult walleye stomachs examined from June 1999 through March 2000, a total of 879 prey fish was found, but only one was identified as a smallmouth bass. In 303 smallmouth bass stomachs examined, 55 prey fish were found and no cannibalism was evident, nor were walleye preyed upon. Dietary overlap using the Schoener resource overlap index was 0.416, 0.293 and 0.205 for the months June, July and August 1999, respectively, indicating that there was not a significant dietary overlap during summer months. Because neither diet overlap nor predation appeared substantial in Big Crooked Lake, additional research on interactions among younger age classes of walleye, interactions at other times of the year, and interactions with other species are needed to elucidate limitations to smallmouth bass recruitment in this system.

Lichen inventory of the crooked lake fen nature sanctuary

Lichen inventory of the crooked lake fen nature sanctuary