scholarly journals Separating wild versus stocking components in fish recruitment without identification data: a hierarchical modelling approach

2017 ◽  
Vol 74 (7) ◽  
pp. 1111-1124
Author(s):  
Guillaume J.R. Dauphin ◽  
Catherine Brugel ◽  
Marion Legrand ◽  
Etienne Prévost
Keyword(s):  
Simulated Data ◽  
Wild Fish ◽  
Spatiotemporal Variations ◽  
Data Set ◽  
Management Advice ◽  
The Impact ◽  
Term Monitoring ◽  
Modelling Approach

Salmonid juvenile stocking programs are often poorly monitored due to the lack of identification between stocked and wild fish. In this study, a hierarchical Bayesian model is developed to take advantage of spatiotemporal variations of stocking and wild recruitment for estimating these two components despite the absence of identification data. It is first tested by means of simulated data and then applied to the 37 year abundance data set of the Atlantic salmon (Salmo salar) population of the Allier catchment (France). Despite the absence of identification data, juvenile densities could be estimated and split into wild and stocked components. We found that the stocked juveniles contributed significantly to the total juvenile production, while the wild reproduction continued to provide an important contribution. This approach is encouraging and promising from a management advice perspective. It is flexible enough to accommodate for case study specificities and shows that long-term monitoring abundances can be useful to assess the impact of stocking programs even in the absence of direct means of identifying stocked versus wild fish.

Investigation of a New Approach to Predict Water Quality Extremes with a Case Study of Chemical Determinands in Stream Water

1991 ◽  
Vol 24 (6) ◽  
pp. 25-33
Author(s):  
A. J. Jakeman ◽  
P. G. Whitehead ◽  
A. Robson ◽  
J. A. Taylor ◽  
J. Bai
Keyword(s):  
Water Quality ◽  
Stream Water ◽  
Probability Distributions ◽  
Management Strategies ◽  
Hybrid Modelling ◽  
Trend Model ◽  
Environmental Extremes ◽  
Modelling Approach

The paper illustrates analysis of the assumptions of the statistical component of a hybrid modelling approach for predicting environmental extremes. This shows how to assess the applicability of the approach to water quality problems. The analysis involves data on stream acidity from the Birkenes catchment in Norway. The modelling approach is hybrid in that it uses: (1) a deterministic or process-based description to simulate (non-stationary) long term trend values of environmental variables, and (2) probability distributions which are superimposed on the trend values to characterise the frequency of shorter term concentrations. This permits assessment of management strategies and of sensitivity to climate variables by adjusting the values of major forcing variables in the trend model. Knowledge of the variability about the trend is provided by: (a) identification of an appropriate parametric form of the probability density function (pdf) of the environmental attribute (e.g. stream acidity variables) whose extremes are of interest, and (b) estimation of pdf parameters using the output of the trend model.

scholarly journals Nutrient retention behind a tropical mega-dam: a case study of the Sardar Sarovar Dam, India

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Harish Gupta ◽  
S. Kiran Kumar Reddy ◽  
Mounika Chiluka ◽  
Vamshikrishna Gandla
Keyword(s):  
Arabian Sea ◽  
Inorganic Nitrogen ◽  
Nutrient Retention ◽  
Significant Loss ◽  
N Removal ◽  
Narmada River ◽  
Sardar Sarovar ◽  
The Impact

AbstractIn this study, we demonstrate the impact of the construction of a mega-dam on the nutrient export regime of a large tropical river into the Arabian Sea. Long-term (11 years) fortnight nutrient parameters, upstream and downstream to Sardar Sarovar (SS) Dam, were examined to determine the periodical change in nutrient fluxes from the Narmada River, India. During this 11-year period, the average discharge of the Narmada River upstream to Rajghat (35.3 km3 year−1) was higher than that of downstream at Garudeshwar (33.9 km3 year−1). However, during the same period, the suspended sediment load was reduced by 21 million tons (MT) from 37.9 MT at Rajghat to 16.7 MT at Garudeshwar. Similarly, mean concentrations of dissolved silica (DSi) reduced from 470 (upstream) to 214 µM (downstream), dissolved inorganic phosphate (DIP) from 0.84 to 0.38 µM, and dissolved inorganic nitrogen (DIN) from 43 to 1.5 µM. It means that about 54%, 55%, and 96% flux of DSi, DIP, and DIN retained behind the dam, respectively. The estimated denitrification rate (80,000 kg N km−2 year−1) for the reservoir is significantly higher than N removal by lentic systems, globally. We hypothesize that processes such as biological uptake and denitrification under anoxic conditions could be a key reason for the significant loss of nutrients, particularly of DIN. Finally, we anticipated that a decline in DIN fluxes (by 1.13 × 109 mol year−1) from the Narmada River to the Arabian Sea might reduce the atmospheric CO2 fixation by 7.46 × 109 mol year−1.

scholarly journals A Traveler’s Guide to the Multiverse: Promises, Pitfalls, and a Framework for the Evaluation of Analytic Decisions

2021 ◽  
Vol 4 (1) ◽  
pp. 251524592095492
Author(s):  
Marco Del Giudice ◽  
Steven W. Gangestad
Keyword(s):  
Degrees Of Freedom ◽  
A Priori ◽  
Simulated Data ◽  
Style Analysis ◽  
Data Set ◽  
Scant Attention ◽  
Equivalence Type ◽  
The Impact ◽  
Biased Estimates

Decisions made by researchers while analyzing data (e.g., how to measure variables, how to handle outliers) are sometimes arbitrary, without an objective justification for choosing one alternative over another. Multiverse-style methods (e.g., specification curve, vibration of effects) estimate an effect across an entire set of possible specifications to expose the impact of hidden degrees of freedom and/or obtain robust, less biased estimates of the effect of interest. However, if specifications are not truly arbitrary, multiverse-style analyses can produce misleading results, potentially hiding meaningful effects within a mass of poorly justified alternatives. So far, a key question has received scant attention: How does one decide whether alternatives are arbitrary? We offer a framework and conceptual tools for doing so. We discuss three kinds of a priori nonequivalence among alternatives—measurement nonequivalence, effect nonequivalence, and power/precision nonequivalence. The criteria we review lead to three decision scenarios: Type E decisions (principled equivalence), Type N decisions (principled nonequivalence), and Type U decisions (uncertainty). In uncertain scenarios, multiverse-style analysis should be conducted in a deliberately exploratory fashion. The framework is discussed with reference to published examples and illustrated with the help of a simulated data set. Our framework will help researchers reap the benefits of multiverse-style methods while avoiding their pitfalls.

scholarly journals Evaluation of the Impact of Timber Truck Configuration and Tare Weight on Payload Efficiency: An Australian Case Study

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 855
Author(s):  
Mark W. Brown
Keyword(s):  
Load Management ◽  
Vehicle Design ◽  
Forest Industry ◽  
Post Operation ◽  
Gross Vehicle Weight ◽  
Australian Case ◽  
Trends Over Time ◽  
The Impact

The forest industry tends to plan, and model transportation costs based on the potential payload benefits of increased legal gross vehicle weight (GVW) by deploying different configurations, while payload benefits of a configuration can be significantly influenced by the vehicle design tare weight. Through this research the relative benefit of increased legal GVW of different configurations is compared across Australia over a 13-year period from 2006 to 2019, by examining data collected post operation across multiple operations. This approach is intended to offer realistic insight to real operations not influenced by observation and thus reflect long-term operating behaviour. The inclusion of the three most common configuration classes in Australian forestry over a 13-year period has also allowed the exploration of load management between configurations and potential trends over time. When considering the legal GVW and the tare weight impacts across the fleets, the semi-trailer has an 8 t payload disadvantage compared to B-Doubles and 19.6 t disadvantage compared to road trains.

scholarly journals A routing-benefited deployment approach combining static and dynamic layouts for underwater optical wireless networks

2021 ◽  
Vol 17 (2) ◽  
pp. 155014772199961
Author(s):  
Zhongwei Shen ◽  
Hongxi Yin ◽  
Yanjun Liang ◽  
Rigele Maao ◽  
Lianyou Jing
Keyword(s):  
Optical Communication ◽  
Loss Rate ◽  
Communication Model ◽  
Optical Wireless ◽  
Wireless Optical Communication ◽  
Area Of Interest ◽  
Virtual Force ◽  
The Impact ◽  
Term Monitoring

A routing-benefited deployment algorithm combining static and dynamic layouts is proposed, and its comprehensive performance evaluation is given in this article. The proposed routing-benefited deployment algorithm is intended to provide a suitable network deployment and subsequent data transmission approach for underwater optical networking and communication. Static nodes are anchored for long-term monitoring, and movable nodes can adjust their depths based on the virtual force and move with the variation of area-of-interest changing. Then, nodes begin to collect data that they can monitor and transmit to sink nodes. Here, the underwater wireless optical communication model is described to actualize the real environment, and the vector-based forwarding protocol is particularly considered to compare the impact of different deployment algorithms on routing. It is shown by simulation experiment results that routing-benefited deployment algorithm outperforms several existing traditional virtual force deployment algorithms in terms of coverage, lifetime, energy consumption balance, packet-loss rate, and time-delay.

scholarly journals Storm Driven Migration of the Napatree Barrier, Rhode Island, USA

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 330
Author(s):  
Bryan A. Oakley
Keyword(s):  
Rhode Island ◽  
Shoreline Change ◽  
Aerial Photographs ◽  
Tropical Storms ◽  
Lower Intensity ◽  
Storm Activity ◽  
The Impact ◽  
Washover Fan

Napatree Point, an isolated barrier in southern Rhode Island, provides a case study of barrier spit migration via storm driven overwash and washover fan migration. Documented shoreline changes using historical surveys and vertical aerial photographs show that the barrier had little in the way of net change in position between 1883 and 1939, including the impact of the 1938 hurricane. The barrier retreated rapidly between 1945 and 1975, driven by both tropical and extra-tropical storms. The shoreline position has been largely static since 1975. The removal of the foredune during the 1938 hurricane facilitated landward shoreline migration in subsequent lower intensity storms. Dune recovery following the 1962 Ash Wednesday storm has been allowed due to limited overwash and barrier migration over the last several decades. Shoreline change rates during the period from 1945–1975 were more than double the rate of shoreline change between 1939 and 2014 and triple the rate between 1883 and 2014, exceeding the positional uncertainty of these shoreline pairs. The long-term shoreline change rates used to calculate coastal setbacks in Rhode Island likely underestimate the potential for rapid shoreline retreat over shorter time periods, particularly in a cluster of storm activity. While sea-level rise has increased since 1975, the barrier has not migrated, highlighting the importance of storms in barrier migration.

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