Environmental flows and recruitment of walleye (Sander vitreus) in the Peace–Athabasca Delta

2013 ◽  
Vol 70 (2) ◽  
pp. 307-315 ◽  
Author(s):  
Andrew J. Paul
Keyword(s):  
River Discharge ◽  
Positive Relationship ◽  
Environmental Flows ◽  
A Priori ◽  
Null Model ◽  
Open Water ◽  
Sander Vitreus ◽  
Theoretic Approach ◽  
Nutrient Inputs ◽  
Athabasca River

Age composition data from a commercial walleye (Sander vitreus) fishery in the Peace–Athabasca Delta were used to test the hypotheses that recruitment varied interannually and that recruitment was related to local hydrological conditions. Variable interannual recruitment was strongly supported over a null model of constant annual recruitment. Assuming recruitment strength was established in a walleye's first year of life, several a priori hypotheses relating recruitment to river discharge or lake levels were tested using an information–theoretic approach. The data best supported the hypothesis of a positive relationship between walleye recruitment and mean discharge in the Athabasca River during the fry rearing period (weeks 18–43). Approximately 25% of observed variability in annual recruitment could be explained by mean discharge during the fry period. However, the data could not fully rule out the alternate hypotheses that recruitment was related to mean discharge in the Athabasca River over the entire year or during winter. Several mechanisms are hypothesized to explain the positive relationship, including increased space in preferred open-water habitat or greater food production from nutrient inputs or wetted area. The observed correlation between river discharge and walleye recruitment can be used to help us understand water management planning on the Athabasca River.

scholarly journals Landscape condition influences energetics, reproduction, and stress biomarkers in grizzly bears

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Abbey E. Wilson ◽  
Dan Wismer ◽  
Gordon Stenhouse ◽  
Nicholas C. Coops ◽  
David M. Janz
Keyword(s):  
Protein Expression ◽  
Physiological Function ◽  
A Priori ◽  
Food Resources ◽  
Information Criteria ◽  
Complement C3 ◽  
Grizzly Bears ◽  
Theoretic Approach ◽  
Protein Food ◽  
The Impact

AbstractEnvironmental change has been shown to influence mammalian distribution, habitat use, and behavior; however, few studies have investigated the impact on physiological function. This study aimed to determine the influence of landscape condition on the expression of target proteins related to energetics, reproduction, and stress in grizzly bears. We hypothesized that changes in landscape condition explains protein expression. Skin biopsies were collected from free-ranging grizzly bears in Alberta, Canada from 2013–2019 (n = 86 individuals). We used an information theoretic approach to develop 11 a priori candidate generalized linear mixed models to explain protein expression. We compared models using Akaike Information Criteria (AICc) weights and averaged models with ΔAICc < 2 for each protein. Food resources, represented by increased distance to coal mines and decreased crown closure, positively influenced energetic proteins (adiponectin and alpha-1-acid glycoprotein). Proteins related to reproduction (ceruloplasmin and serpin B5) were positively associated with increased wetland and upland food resources in addition to movement, but negatively associated with increased distance to roads. One stress related protein, complement C3, was positively influenced by increased percent conifer. Given the need to detect emerging threats to wildlife, we suggest the assessment of physiological function will lead to improved monitoring of species in rapidly changing landscapes.

scholarly journals Hydrology influences breeding time in the white-throated dipper

BMC Ecology ◽  
2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Anna L. K. Nilsson ◽  
Thomas Skaugen ◽  
Trond Reitan ◽  
Jan Henning L’Abée-Lund ◽  
Marlène Gamelon ◽  
...  
Keyword(s):  
Climate Change ◽  
River Discharge ◽  
Large Scale ◽  
Time Window ◽  
River System ◽  
Open Water ◽  
Local Conditions ◽  
Environmental Indices ◽  
Groundwater Levels ◽  
Breeding Time

Abstract Background Earlier breeding is one of the strongest responses to global change in birds and is a key factor determining reproductive success. In most studies of climate effects, the focus has been on large-scale environmental indices or temperature averaged over large geographical areas, neglecting that animals are affected by the local conditions in their home ranges. In riverine ecosystems, climate change is altering the flow regime, in addition to changes resulting from the increasing demand for renewable and clean hydropower. Together with increasing temperatures, this can lead to shifts in the time window available for successful breeding of birds associated with the riverine habitat. Here, we investigated specifically how the environmental conditions at the territory level influence timing of breeding in a passerine bird with an aquatic lifestyle, the white-throated dipper Cinclus cinclus. We relate daily river discharge and other important hydrological parameters, to a long-term dataset of breeding phenology (1978–2015) in a natural river system. Results Dippers bred earlier when winter river discharge and groundwater levels in the weeks prior to breeding were high, and when there was little snow in the catchment area. Breeding was also earlier at lower altitudes, although the effect dramatically declined over the period. This suggests that territories at higher altitudes had more open water in winter later in the study period, which permitted early breeding also here. Unexpectedly, the largest effect inducing earlier breeding time was territory river discharge during the winter months and not immediately prior to breeding. The territory river discharge also increased during the study period. Conclusions The observed earlier breeding can thus be interpreted as a response to climate change. Measuring environmental variation at the scale of the territory thus provides detailed information about the interactions between organisms and the abiotic environment.

scholarly journals Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

2018 ◽  
Vol 4 (4) ◽  
pp. 557-583 ◽  
Author(s):  
Jolie A.L. Gareis ◽  
Lance F.W. Lesack
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Bacterial Production ◽  
River Discharge ◽  
Bacterial Community Composition ◽  
Open Water ◽  
Growth Efficiency ◽  
Mackenzie Delta ◽  
River Deltas ◽  
Solar Exposure

Lake-rich Arctic river deltas are recharged with terrigenous dissolved organic matter (DOM) during the yearly peak water period corresponding with the solstice (24 h day−1 solar irradiance). Bacteria-free DOM collected during peak Mackenzie River discharge was exposed to sunlight for up to 14 days in June 2010. As solar exposure increased, carbon and lignin concentrations declined (10% and 42%, respectively, after 14 days), as did DOM absorptivity (62% after 14 days), aromaticity, and molecular weight. Photochemical changes were on par with those normally observed in Mackenzie Delta lakes over the entire open-water season. When irradiated freshet DOM was provided as a substrate, no significant differences were observed in community-level metabolism among five bacterial communities from representative delta habitats. However, bacterial abundance was significantly greater when nonirradiated (0 day) rather than irradiated DOM (7 or 14 days) was provided, while cell-specific metabolic measures revealed that per-cell bacterial production and growth efficiency were significantly greater when communities were provided irradiated substrate. This complex response to rapid DOM photodegradation may result from the production of inhibitory reactive oxygen species (ROS), along with shifts in bacterial community composition to species that are better able to tolerate ROS, or metabolize the labile photodegraded DOM.

scholarly journals Synergy of stereo cloud top height and ORAC optimal estimation cloud retrieval: evaluation and application to AATSR

2016 ◽  
Vol 9 (3) ◽  
pp. 909-928 ◽  
Author(s):  
Daniel Fisher ◽  
Caroline A. Poulsen ◽  
Gareth E. Thomas ◽  
Jan-Peter Muller
Keyword(s):  
A Priori ◽  
Single Layer ◽  
Optimal Estimation ◽  
Open Water ◽  
A Priori Information ◽  
Cloud Parameters ◽  
Cloud Properties ◽  
Priori Information ◽  
Cloud Parameter ◽  
The Impact

Abstract. In this paper we evaluate the impact on the cloud parameter retrievals of the ORAC (Optimal Retrieval of Aerosol and Cloud) algorithm following the inclusion of stereo-derived cloud top heights as a priori information. This is performed in a mathematically rigorous way using the ORAC optimal estimation retrieval framework, which includes the facility to use such independent a priori information. Key to the use of a priori information is a characterisation of their associated uncertainty. This paper demonstrates the improvements that are possible using this approach and also considers their impact on the microphysical cloud parameters retrieved. The Along-Track Scanning Radiometer (AATSR) instrument has two views and three thermal channels, so it is well placed to demonstrate the synergy of the two techniques. The stereo retrieval is able to improve the accuracy of the retrieved cloud top height when compared to collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), particularly in the presence of boundary layer inversions and high clouds. The impact of the stereo a priori information on the microphysical cloud properties of cloud optical thickness (COT) and effective radius (RE) was evaluated and generally found to be very small for single-layer clouds conditions over open water (mean RE differences of 2.2 (±5.9) microns and mean COD differences of 0.5 (±1.8) for single-layer ice clouds over open water at elevations of above 9 km, which are most strongly affected by the inclusion of the a priori).

scholarly journals Vegetative and Fruit Resources as Determinants of Habitat use by Mature-Forest Birds During the Postbreeding Period

The Auk ◽  
2007 ◽  
Vol 124 (2) ◽  
pp. 494-507 ◽  
Author(s):  
Andrew C. Vitz ◽  
Amanda D. Rodewald
Keyword(s):  
Vegetation Structure ◽  
A Priori ◽  
Forest Birds ◽  
Canopy Height ◽  
Theoretic Approach ◽  
Mature Forest ◽  
Risk Of Predation ◽  
Structure Density ◽  
Information Theoretic Approach ◽  
Capture Rates

AbstractRecent studies have demonstrated that many birds of mature forests heavily use early-successional habitat during the postbreeding period. Two frequently invoked hypotheses to explain these shifts are that postbreeding birds select (1) dense cover to reduce risk of predation and (2) abundant fruit resources to facilitate foraging. Using mist nets between 15 June and 16 August in 2002 and 2003, we captured mature-forest birds during the postbreeding period in 12 regenerating hardwood clearcuts (three to seven years old) in southeast Ohio. Vegetation structure and fruit resources were measured at nine net locations within each clearcut. We applied an information-theoretic approach, where we used vegetative and fruit variables as predictors in seven a priori models to evaluate how habitat factors might explain capture rates. In two seasons, we captured 1,089 hatch-year (HY) and 445 after-hatch-year (AHY) postbreeding birds of 32 mature-forest species. In general, models reflecting habitat structure (density of low vegetation, canopy height) best explained variation in capture rates, which were negatively related to the density of low vegetation (<1.5 m) and positively related to canopy height. Extremely dense low vegetation may be disadvantageous if it inhibits movements and provides cryptic locations for ground predators. Instead, habitats with greater vertical structure (e.g., taller vegetation) and relatively less dense low vegetation below may provide better protection from aerial and ground predators. Overall, results suggest that vegetation structure may explain high use of early-successional forests by many birds during the postbreeding period, though fruit may be the most important factor for seasonal frugivores.Recursos Vegetativos y de Frutos como Determinantes del Uso de Hábitat por Aves de Bosque Maduro Durante el Período Posterior a la Reproducción

scholarly journals Seed Availability Does Not Ensure Regeneration in Northern Ecosystems of the Endangered Limber Pine

Forests ◽  
2019 ◽  
Vol 10 (2) ◽  
pp. 146 ◽  
Author(s):  
Vernon S. Peters ◽  
Darcy R. Visscher
Keyword(s):  
Seed Production ◽  
Abiotic Factors ◽  
A Priori ◽  
Production Capacity ◽  
Basal Area ◽  
Forest Composition ◽  
Theoretic Approach ◽  
Limber Pine ◽  
Seed Availability ◽  
Pine Regeneration

Research Highlights: When biotic interactions such as disease alter both the seed production capacity of stands, and seedling survivorship, the relative importance of seed availability versus substrate specificity may alter future regeneration opportunities for plant populations. Background and Objectives: We investigated the importance of disease severity, seed availability, and substrate limitation to the regeneration dynamics of the endangered limber pine, Pinus flexilis, in two ecosystems with varying forest composition, and different histories of white pine blister rust infection (WPBR; Cronartium ribicola). Materials and Methods: A total of 17 stands from the montane ecoregion (Alberta, Canada) were sampled for seed production between 2007–2010, seedling density, and age structure. Model selection using an information theoretic approach compared a series of a priori models and their combinations, based on our hypotheses on the role biotic variables play in the regeneration process. Results: Despite higher rates of WPBR infection, 2.3 times more seed was available for avian dispersers in the southern ecosystem. Recent seedling regeneration did not correspond to seed production (83 versus 251 seedlings/ha, in southern versus northern ecosystems, respectively), resulting in a seven-fold difference in seed to seedling ratios between ecosystems. Models suggest that disease and vegetation cover were important factors explaining the absence of regeneration in 79.4% of the plots sampled, while basal area (BA) of live limber pine, rocky substrates, ecosystem, South aspects, and slope enhanced limber pine regeneration. Seedling age structures suggest that recent regeneration is less likely in more diseased landscapes, than it was historically (40% versus 72.8% of seedlings < 20 years old, respectively, in southern versus northern ecosystems). Conclusions: At the northern limits of limber pine’s range, seed availability does not ensure regeneration, suggesting that other environmental or biotic factors hinder regeneration. Regeneration was consistently predicted to be lower in the southern ecosystem than in the northern ecosystem, suggesting that natural regeneration and the potential for population recovery are ecosystem dependent. We recommend that monitoring recent seedlings will aid the identification of biotic and abiotic factors affecting regeneration.

Differentiated macrophyte types as a habitat for rotifers in small mid-forest water bodies

Biologia ◽  
2009 ◽  
Vol 64 (6) ◽  
Author(s):  
Anna Basińska ◽  
Natalia Kuczyńska-Kippen
Keyword(s):  
Water Body ◽  
Catchment Area ◽  
Trophic State ◽  
Positive Relationship ◽  
Open Water ◽  
Physical Chemical ◽  
Rotifer Community ◽  
Chemical Factors ◽  
Rotifer Communities ◽  
Eutrophic Species

AbstractThe rotifer community structure may be shaped by a variety of environmental factors, including biological parameters, such as predation or competition, as well as by physical-chemical factors, among which the kind of macrophyte substratum and parameters relating to the trophic state and to the catchment area conditions are of great importance. Another impact on rotifer composition, abundance and frequency may be expected when considering differentiated macrophyte types (including helophytes, nymphaeids and elodeids) within a group of eight ponds located within a mid-forest catchment area, which was the main aim of the present study. Detailed analysis on the participation of indicator eutrophic rotifer species provided an additional goal of this investigation in order to qualify the trophic state of this kind of water body located within the Wielkopolska region, in the central western part of Poland.The presence of 117 taxa, including 7 species that are rare or infrequently distributed in the Polish fauna was recorded. The number of taxa and rotifer abundance differed greatly in respect to the specific water body and to the type of substratum. The vegetated zones dominated by elodeids were characterised by the most various and most abundant rotifer communities as well as by the highest values of the Shannon-Weaver index. This reflects a positive relationship between the heterogeneity of habitat and the structure of rotifer communities. It was also found that helophytes and the open water zone possessed the highest, while elodeids the lowest percentage of eutrophic species.

scholarly journals Iterative Forecasting Improves Near-Term Predictions of Methane Ebullition Rates

2021 ◽  
Vol 9 ◽  
Author(s):  
Ryan P. McClure ◽  
R. Quinn Thomas ◽  
Mary E. Lofton ◽  
Whitney M. Woelmer ◽  
Cayelan C. Carey
Keyword(s):  
Null Model ◽  
Open Water ◽  
Forecast Model ◽  
Great Promise ◽  
Ecological Processes ◽  
Total Uncertainty ◽  
Predictive Skill ◽  
Iterative Model ◽  
The Future ◽  
Near Term

Near-term, ecological forecasting with iterative model refitting and uncertainty partitioning has great promise for improving our understanding of ecological processes and the predictive skill of ecological models, but to date has been infrequently applied to predict biogeochemical fluxes. Bubble fluxes of methane (CH4) from aquatic sediments to the atmosphere (ebullition) dominate freshwater greenhouse gas emissions, but it remains unknown how best to make robust near-term CH4 ebullition predictions using models. Near-term forecasting workflows have the potential to address several current challenges in predicting CH4 ebullition rates, including: development of models that can be applied across time horizons and ecosystems, identification of the timescales for which predictions can provide useful information, and quantification of uncertainty in predictions. To assess the capacity of near-term, iterative forecasting workflows to improve ebullition rate predictions, we developed and tested a near-term, iterative forecasting workflow of CH4 ebullition rates in a small eutrophic reservoir throughout one open-water period. The workflow included the repeated updating of a CH4 ebullition forecast model over time with newly-collected data via iterative model refitting. We compared the CH4 forecasts from our workflow to both alternative forecasts generated without iterative model refitting and a persistence null model. Our forecasts with iterative model refitting estimated CH4 ebullition rates up to 2 weeks into the future [RMSE at 1-week ahead = 0.53 and 0.48 loge(mg CH4 m−2 d−1) at 2-week ahead horizons]. Forecasts with iterative model refitting outperformed forecasts without refitting and the persistence null model at both 1- and 2-week forecast horizons. Driver uncertainty and model process uncertainty contributed the most to total forecast uncertainty, suggesting that future workflow improvements should focus on improved mechanistic understanding of CH4 models and drivers. Altogether, our study suggests that iterative forecasting improves week-to-week CH4 ebullition predictions, provides insight into predictability of ebullition rates into the future, and identifies which sources of uncertainty are the most important contributors to the total uncertainty in CH4 ebullition predictions.

scholarly journals The impact of fiscal and monetary policies on unemployment problem in Nigeria (managerial economic perspective)

2015 ◽  
Vol 5 (2) ◽  
pp. 101-109
Author(s):  
Nick Attamah ◽  
Anthony Igwe ◽  
Wilfred Isioma Ukpere
Keyword(s):  
Monetary Policy ◽  
Exchange Rates ◽  
Money Supply ◽  
Positive Relationship ◽  
A Priori ◽  
Government Expenditure ◽  
Unit Roots ◽  
Monetary Policies ◽  
The Impact ◽  
Unemployment Problem

This paper investigates the impact of fiscal and Monetary Policies on Unemployment Problem in Nigeria and covers the periods 1980 to 2013. To achieve this, fiscal policy was captured here by government expenditures and revenues respectively while monetary policy was proxied by broad Money Supply (M2), Interest and Exchange rates respectively. The methodology adopted was econometric analysis employing OLS techniques and unit roots of the series were examined using the Augmented Dickey-Fuller after which the co-integration tests was conducted using the Engle Granger approach. Error correction models were estimated to take care of the short run dynamics. It was found that while government expenditure had a positive relationship with unemployment problem in Nigeria, the result of government revenue was negative and insignificant on unemployment problem. For monetary policy, it was found that money supply and exchange rate had positive and significant impact while interest rate has only a positive relationship on unemployment problem in Nigeria. This meets the a priori expectation. The study also revealed that increases in interest and exchange rates escalate unemployment by increasing cost of production which discourages the private sector from employing large workforce. On the other hand, national productivity measured by real GDP had a negative and significant impact on unemployment rate in Nigeria. This paper recommends that for an effective combat to unemployment problem in Nigeria, there should be a systematic diversion of strategies, thus more emphasis should be laid on aggressively pursuing entrepreneurial development and increased productivity. Again government should aggressively focus on investment, employment generation and economic growth that has mechanism to trickle does to the masses.

scholarly journals Angler and environmental influences on walleye Sander vitreus and muskellunge Esox masquinongy angler catch in Escanaba Lake, Wisconsin 2003–2015

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0257882
Author(s):  
Stephanie L. Shaw ◽  
Kathryn M. Renik ◽  
Greg G. Sass
Keyword(s):  
Environmental Factors ◽  
Solar Radiation ◽  
Open Water ◽  
Weather Conditions ◽  
Catch Rate ◽  
Sander Vitreus ◽  
Memory Retention ◽  
Esox Masquinongy ◽  
Catch Rates ◽  
Diel Period

Angler trip success and catch rates are dependent upon a fishes’ vulnerability to angling. Angling vulnerability can be influenced by angler-specific attributes (i.e., bait choice, lure size, use of a guide), and individual fish traits (i.e., boldness, aggression, stress responsiveness, and memory retention). The mechanisms that function in a fishes’ angling vulnerability, and contribute to catch rate, are likely correlated with environmental factors however, the influence of environmental factors on angling vulnerability are not well understood. We used the long-term (1946 –present) compulsory creel dataset from Escanaba Lake, WI, USA to test for interactions between angling vulnerability (i.e., angler trip success and catch rates) and environmental factors to better understand these dynamics in recreational fisheries. Our objective was to test for the influence of angler associated variables and environmental factors on open water angler trip success (i.e., catch ≥ one fish) and catch rate of walleye Sander vitreus and muskellunge Esox masquinongy during 2003–2015 using a hurdle model approach. Fishing trip success and catch rates for both species were most strongly influenced by angler-related variables (i.e., guide status, bait type, the proportion of the fish population previously caught). Environmental factors associated with lower light intensity (i.e., diel period, mean daily solar radiation, solar-Julian day interaction) had a positive influence on walleye vulnerability. Lower air temperatures and lunar position (moon overhead or underfoot) and phase (gibbous’ and full moon) also had a positive effect on walleye angling. Muskellunge trip success and catch rate were positively influenced by light metrics (i.e., diel period and mean daily solar radiation) and increased with air temperature. Lunar variables (position and phase), as well as wind speed and direction also influenced muskellunge angling vulnerability. A better understanding of the influence of environmental factors on angling vulnerability is an important component of fisheries management as management goals focus on balancing fish populations and creating satisfactory catch rates to enhance the angling experience. Our results suggest that angler-specific variables, light, temperature, lunar, and weather conditions influenced species-specific angling vulnerability for walleye and muskellunge.

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