scholarly journals The effects of seasonal processes on size spectrum dynamics

2016 ◽  
Vol 73 (4) ◽  
pp. 598-610 ◽  
Author(s):  
Samik Datta ◽  
Julia L. Blanchard
Keyword(s):  
Environmental Variability ◽  
Management Strategies ◽  
Growth Curves ◽  
Fishing Effort ◽  
Size Spectrum ◽  
Interspecies Interactions ◽  
Community Size ◽  
Modelling Framework ◽  
Batch Spawning ◽  
Similar Growth

The recent advent of dynamic size spectrum models has allowed the analysis of life processes in marine ecosystems to be carried out without the high complexity arising from interspecies interactions within dense food webs. In this paper, we use “mizer”, a size spectrum modelling framework, to investigate the consequences of including the seasonal processes of plankton blooms and batch spawning in the model dynamics. A multispecies size spectrum model is constructed using 12 common North Sea fish species, with growth, predation, and mortality explicitly modelled, before simulating both seasonal plankton blooms and batch spawning of fish (using empirical data on the spawning patterns of each species). The effect of seasonality on the community size spectrum is investigated; it is found that with seasonal processes included, the species spectra are more varied over time, while the aggregated community spectrum remains fairly similar. Growth of seasonally spawning mature individuals drops significantly during peak reproduction, although lifetime growth curves follow nonseasonal ones closely. On analysing properties of the community spectrum under different fishing scenarios, seasonality generally causes more varied spectrum slopes and lower yields. Under seasonal conditions, increasing fishing effort also results in greater temporal variability of fisheries yields due to truncation of the community spectrum towards smaller sizes. Further work is needed to evaluate robustness of management strategies in the context of a wider range of seasonal processes and behavioural strategies, as well as longer term environmental variability and change.

A STUDY OF RATES OF GROWTH OF YORKSHIRE, LACOMBE, LANDRACE, AND CROSSBRED PIGS FROM BIRTH TO 200 LB

1964 ◽  
Vol 44 (3) ◽  
pp. 315-319
Author(s):  
J. M. Bell
Keyword(s):  
Growth Rates ◽  
Early Life ◽  
Growth Curves ◽  
Rates Of Growth ◽  
Similar Growth ◽  
Crossbred Pigs

Growth records were obtained from 12 research establishments across Canada for pigs fed according to current (1960–63) recommendations of nutrition and management. Growth curves showing age in days and weight in pounds are presented for the various breeds and crossbreds, for between-station comparisons, for comparison of upper and lower quartiles in purebred pigs, and for comparison of growth rates of purebreds with that of Yorkshires of 20 to 25 years ago.Age at 200 lb averaged from 152 to 187 days, among 10 stations for the Yorkshire breed. Pigs of each of the pure breeds reached 200 lb about 3 weeks earlier than that indicated in previous studies. Crossbred pigs of each of four different crosses grew more rapidly than average Yorkshires, some reaching 200 lb in 140 days and having gains in excess of 2.3 lb/day during the finishing period. Yorkshire, Lacombe, and Landrace pigs had similar growth curves. The upper quartile averaged 1.8 and the lower 1.4 lb/day gain between 100 and 200 lb weights. Slow-maturing pigs tended to be below average throughout life but differences in maturity between stations seemed to reflect differing rates of gain in early life, since finishing period gains were similar in 8 of 10 stations.

scholarly journals Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework

2013 ◽  
Vol 70 (4) ◽  
pp. 768-781 ◽  
Author(s):  
Paul Marchal ◽  
Youen Vermard
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Spatially Explicit ◽  
Catch Per Unit Effort ◽  
Modelling Framework ◽  
Control Rules ◽  
Bioeconomic Modelling ◽  
Stock Assessments ◽  
Fleet Dynamics

Abstract Marchal, P., and Vermard, Y. 2013. Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework. – ICES Journal of Marine Science, 70: 768–781. We have used in this study a spatially explicit bioeconomic modelling framework to evaluate management strategies, building in both data-rich and data-limited harvest control rules (HCRs), for a mix of deepwater fleets and species, on which information is variable. The main focus was on blue ling (Molva dypterygia). For that species, both data-rich and data-limited HCRs were tested, while catch per unit effort (CPUE) was used either to tune stock assessments, or to directly trigger management action. There were only limited differences between the performances of both HCRs when blue ling biomass was initialized at the current level, but blue ling recovered more quickly with the data-rich HCR when its initial biomass was severely depleted. Both types of HCR lead, on average, to a long-term recovery of both blue ling and saithe (Pollachius virens) stocks, and some increase in overall profit. However, that improvement is not sufficient to guarantee sustainable exploitation with a high probability. Blue ling CPUE did not always adequately reflect trends in biomass, which mainly resulted from fleet dynamics, possibly in combination with density-dependence. The stock dynamics of roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo) and deepwater sharks (Centrophorus squamosus and Centroscymnus coelolepis) were little affected by the type of HCR chosen to manage blue ling.

Valuing feedback mechanisms between water and energy systems in hydropower networks

2021 ◽  
Author(s):  
Rachel Koh ◽  
Jordan Kern ◽  
AFM Kamal Chowdhury ◽  
Stefano Galelli
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
Renewable Energy Sources ◽  
Management Strategies ◽  
Energy System ◽  
Water Systems ◽  
Feedback Mechanism ◽  
Production Costs ◽  
Feedback Mechanisms ◽  
Modelling Framework

<p>Multi-sector modelling frameworks are fundamental platforms for exploring the complex interactions between the water and energy sectors. While acknowledging the pivotal role of hydropower within the energy system, it is essential to understand the feedback mechanisms between power and water systems to guide the design of hydropower operations and enhance water-energy management strategies. With this in mind, we developed a modelling framework hinged on a bidirectional coupling between water and power system models. We simulate the constraints imposed by water availability on grid operations as well as the feedback between the state of the energy and water systems. For example, the framework explicitly accounts for conditions of hydropower oversupply, during which part of the water could be stored in reservoirs or allocated to other sectors. The flexibility added to the system gives operators control over desired reservoirs, and allows the system to exploit the benefits warranted by a more efficient use of renewable energy. We evaluate the framework on a real-world case study based on the Cambodian grid, which relies on hydro, solar, and thermoelectric resources. In our analysis, we demonstrate that managing hydropower reservoirs with the feedback mechanism in mind allows us to improve system’s performance—evaluated in terms of power production costs and CO<sub>2</sub> emissions. Overall, our work contributes a novel modelling tool for climate-water-energy nexus studies, working towards an optimal integration of hydropower and other renewable energy sources into power systems.</p>

Calibration of the zooplankton community size spectrum as an indicator of change in Canadian Shield lakes

2019 ◽  
Vol 76 (12) ◽  
pp. 2268-2287
Author(s):  
Lauren Emily Barth ◽  
Brian John Shuter ◽  
William Gary Sprules ◽  
Charles Kenneth Minns ◽  
James Anthony Rusak
Keyword(s):  
Zooplankton Community ◽  
Canadian Shield ◽  
Rate Of Change ◽  
Crustacean Zooplankton ◽  
Size Spectrum ◽  
Community Size ◽  
Mean Values ◽  
Sampling Protocols ◽  
Stable Characteristic ◽  
Shield Lakes

Developing the crustacean zooplankton community size spectrum into an indicator of change in lakes requires quantification of the natural variability in the size spectrum related to broad-scale seasonal, annual, and spatial factors. Characterizing seasonal patterns of variation in the size spectrum is necessary so that monitoring programs can be designed to minimize the masking effects that seasonal processes can have on detecting longer-term temporal change. We used a random effects model to measure monthly, annual, and interlake variability in the slope (i.e., relative abundance of small and large organisms) and centered height (i.e., total abundance) of the crustacean zooplankton normalized abundance size spectrum from 1981 to 2011 among eight Canadian Shield lakes. Consistent with theoretical predictions, the slope was a relatively stable characteristic of the zooplankton community compared with the height, which varied significantly among lakes. We identified a seasonal signal in height and slope and used a mixed effects model to characterize the linear rate of change from May to October; there was an overall decline in height and an overall increase in slope. Seasonal variance was greater than annual variance for both the height and the slope, suggesting that long-term monitoring of lakes and interlake comparisons using zooplankton size spectra should be based on temporally standardized sampling protocols that minimize the effects of seasonal processes. We recommend sampling the zooplankton community in midsummer because this results in size spectrum estimates close to seasonal mean values.

scholarly journals The MINOUWApp: a web-based tool in support of by-catch and discards management

2020 ◽  
Vol 192 (12) ◽  
Author(s):  
Lorenzo D’Andrea ◽  
Aida Campos ◽  
Karim Erzini ◽  
Paulo Fonseca ◽  
Simone Franceschini ◽  
...  
Keyword(s):  
Management Strategies ◽  
Fishing Effort ◽  
Negative Effects ◽  
Web Based ◽  
Management Plans ◽  
By Catch ◽  
Selection Of Species ◽  
Areas Of Interest ◽  
Ecosystem Based Fisheries Management ◽  
Selection Of

AbstractCurrent fishing practices often do not allow adequate selection of species or sizes of fish, resulting in unwanted catches, subsequently discarded, with the consequent negative effects on both marine communities and fisheries profitability. The cross-analysis of density patches of potential unwanted catches and distribution of fishing effort can support the identification of spatial-temporal hot-spots in which the fishing pressure should be reduced to limit the amount of discards. The MinouwApp represents a technological and methodological framework to bring different, and structurally complex, sources of georeferenced data together into a simple visual interface aiming to interactively explore temporal ranges and areas of interest. The objective is to improve the understanding of fisheries dynamics, including discards, thus contributing to the implementation of discard management plans in a context of participative, ecosystem-based fisheries management strategies.

Carcase composition and the use of sample joints in the indigenous Malawi goat

1994 ◽  
Vol 1994 ◽  
pp. 210-210
Author(s):  
J A Kirk ◽  
R A Cooper ◽  
L Kamwanja
Keyword(s):  
Regression Analysis ◽  
Management Strategies ◽  
Growth Curves ◽  
Base Line ◽  
Maize Stover ◽  
Breeding Programmes ◽  
Few Data ◽  
Base Line Data ◽  
Adequate Data ◽  
Blue Gum

Few data are available on the growth and carcase characteristics of the indigenous Malawi goat, despite the fact that goats provide 20% of the meat consumed in Malawi. Better husbandry and breeding programmes can only be developed and implemented when adequate data on the performance and potential of populations have been collected. This trial was undertaken to provide base line data, in order to allow comparisons to be drawn when alternative management strategies are adopted.Does were housed in a blue-gum-pole khola, roofed with galvanised iron, in pens measuring 4m2. Each pen held 10-14 does. Feeding was based upon the grazing of indigenous pastures but the goats also had access to maize stover during the dry season. Kids were weighed at birth and fortnightly thereafter. Castrate kids, in groups of S, were slaughtered at birth and at intervals of 5kg between Skg and 25kg. Following slaughter, carcases were split down the backbone, weighed, packed into individual polythene bass and stored at -20°C to await dissection. In March 1990 right hand sides were thawed, weighed and cut into six primal joints. To reduce any errors caused by abattoir procedures the axis vertebra was removed from all carcases and discarded. Each joint was then subjected to a full dissection, using butchers’ knives, into lean, bone and fat components and the weight of each component recorded. The data generated from these dissections were used to develop aliometric growth curves for each joint and for each tissue, using multiple regression analysis.

scholarly journals Parameter uncertainty of a dynamic multispecies size spectrum model

2016 ◽  
Vol 73 (4) ◽  
pp. 589-597 ◽  
Author(s):  
Michael A. Spence ◽  
Paul G. Blackwell ◽  
Julia L. Blanchard
Keyword(s):  
Time Series ◽  
Time Series Data ◽  
Size Structure ◽  
Management Strategies ◽  
Optimization Methods ◽  
Series Data ◽  
Size Spectrum ◽  
Aquatic Communities ◽  
The North ◽  
Spectrum Model

Dynamic size spectrum models have been recognized as an effective way of describing how size-based interactions can give rise to the size structure of aquatic communities. They are intermediate-complexity ecological models that are solutions to partial differential equations driven by the size-dependent processes of predation, growth, mortality, and reproduction in a community of interacting species and sizes. To be useful for quantitative fisheries management these models need to be developed further in a formal statistical framework. Previous work has used time-averaged data to “calibrate” the model using optimization methods with the disadvantage of losing detailed time-series information. Using a published multispecies size spectrum model parameterized for the North Sea comprising 12 interacting fish species and a background resource, we fit the model to time-series data using a Bayesian framework for the first time. We capture the 1967–2010 period using annual estimates of fishing mortality rates as input to the model and time series of fisheries landings data to fit the model to output. We estimate 38 key parameters representing the carrying capacity of each species and background resource, as well as initial inputs of the dynamical system and errors on the model output. We then forecast the model forward to evaluate how uncertainty propagates through to population- and community-level indicators under alternative management strategies.

Building a modelling framework to simulate ecosystem processes under changing climate: the long road from Biome-BGC to Biome-BGCMAg

2020 ◽  
Author(s):  
Dóra Hidy ◽  
Nándor Fodor ◽  
Roland Hollós ◽  
Zoltán Barcza
Keyword(s):  
Greenhouse Gas ◽  
Water Cycle ◽  
Net Primary Production ◽  
Management Strategies ◽  
Biogeochemical Model ◽  
Dynamic Allocation ◽  
Plant Mortality ◽  
Climate Conditions ◽  
University Of Montana ◽  
Modelling Framework

<p>During the past 15 years, our research group was developing the Biome-BGCMAg (formerly known as Biome-BGCMuSo) biogeochemical model to improve its ability to simulate carbon and water cycle in different ecosystems, with options for managed croplands, grasslands, and forests. We made various model improvements based on the results of model validation and benchmarking. Our goal is to have a model that is suitable for estimating and predicting greenhouse gas fluxes of different ecosystems at various scales under changing management and climate conditions.</p><p>The current, most recent model is called Biome-BGCMAg which is a process-based, biogeochemical model that simulates the storage and flux of water, carbon, and nitrogen in the soil-plant-atmosphere system. Biome-BGCMAg was derived from the widely known Biome-BGC v4.1.1 model developed by the Numerical Terradynamic Simulation Group (NTSG), University of Montana, USA. One of the most important model developments is the implementation of a multilayer soil module with water, carbon, nitrogen, and soil organic matter profiles. We implemented drought and anoxic soil state-related plant mortality. Alternative calculation methods for various processes were implemented to support possible algorithm ensemble modelling approach. Optional dynamic allocation algorithm was introduced using predefined phenophases based on growing degree day method. We implemented optional temperature dependence of allocation and possible assimilation downregulation as a function of temperature. Nitrogen budget simulation was improved. Furthermore, human intervention modules were developed to simulate cropland management (e.g. planting, harvest, ploughing, and application of fertilizers) and forest thinning. Dynamic whole plant mortality was implemented in the model to enable more realistic simulation of forest stand development. Last (but not least) conditional management (irrigation and mowing) was introduced to analyze the effect of different management strategies in the future. We started to build a sophisticated R based software to increase the visibility of the model and enable its use by the wider scientific community.</p><p>In our first attempt to simulate national scale greenhouse gas budget with Biome-BGCMAg 2.0, we executed the model at 10 x 10 km spatial resolution for Hungary, using eco-physiological parameterization and prescribed management for maize, winter wheat, forests and grassland. The first results revealed that the spatial pattern of net primary production and crop yield is not represented well by the model. Based on the first experiences we introduced new features within Biome-BGCMAg 2.1 that address soil water deficit related photosynthesis down-regulation. Missing stomatal conductance effect on C4 photosynthesis was also addressed by the new developments. </p>

scholarly journals Assessing uncertainty of a multispecies size-spectrum model resulting from process and observation errors

2015 ◽  
Vol 72 (8) ◽  
pp. 2223-2233 ◽  
Author(s):  
Chongliang Zhang ◽  
Yong Chen ◽  
Yiping Ren
Keyword(s):  
Life History ◽  
Community Structure ◽  
Fisheries Management ◽  
Dynamic Models ◽  
Environmental Variability ◽  
Size Spectrum ◽  
Sampling Errors ◽  
Fishing Activity ◽  
Scale Parameters ◽  
Spectrum Model

AbstractEcosystem models, specifically multispecies dynamic models, have been increasingly used to project impacts of fishing activity on the trophodynamics of ecosystems to support ecosystem-based fisheries management. Uncertainty is unavoidable in modelling processes and needs to be recognized and properly quantified before models are utilized. Uncertainty was assessed in this study for a multispecies size-spectrum model that quantifies community structure and ecological characteristics. The uncertainty was assumed to result from errors in fish life-history and metabolic scale parameters, environmental variability, fishing variability, and sampling errors. Given the same level of imprecision, metabolic scale parameters had the dominant influence on the uncertainty of the size spectrum modelling results, followed by life-history parameters. Both types of errors led to “scenario uncertainty”, suggesting the possible existence of alternative states of community structure. Environmental variability, fishing variability, and observation errors resulted in “statistical uncertainty”, implying that such uncertainty can be described adequately in statistical terms. The results derived from such a simulation study can provide guidance for identifying research priorities to help narrow the gap in scientific knowledge and reduce the uncertainty in fisheries management.

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