scholarly journals Trophic and individual efficiencies of size-structured communities

2008 ◽  
Vol 276 (1654) ◽  
pp. 109-114 ◽  
Author(s):  
K.H Andersen ◽  
J.E Beyer ◽  
P Lundberg
Keyword(s):  
Somatic Growth ◽  
Growth Efficiency ◽  
Trophic Levels ◽  
Individual Growth ◽  
Size Spectrum ◽  
Strongly Correlated ◽  
Predator Prey ◽  
Individual Level ◽  
The Individual ◽  
Individual Size

Individual and trophic efficiencies of size-structured communities are derived from mechanistically based principles at the individual level. The derivations are relevant for communities with a size-based trophic structure, i.e. where trophic level is strongly correlated with individual size as in many aquatic systems. The derivations are used to link Lindeman's trophic theory and trophic theory based on average individuals with explicit individual-level size spectrum theory. The trophic efficiency based on the transfer of mass between trophic levels through predator–prey interactions is demonstrated to be valid only when somatic growth can be ignored. Taking somatic growth into account yields an average individual growth efficiency that is smaller than the trophic efficiency.

scholarly journals Growth and behaviour of post-weaned Mérinos d'Arles ewe lambs, as measured by a Walk-over-Weighing system under Mediterranean grazing conditions.

2021 ◽  
Author(s):  
E. Leroux ◽  
I. Llach ◽  
G. Besche ◽  
J. D. Guyonneau ◽  
D. Montier ◽  
...  
Keyword(s):  
Warning System ◽  
High Volume ◽  
Individual Growth ◽  
Close Monitoring ◽  
Adaptation Period ◽  
Individual Level ◽  
Ewe Lambs ◽  
Frequent Monitoring ◽  
Farmer Decision Making ◽  
The Individual

Abstract Liveweight (LW) is a key and conventional indicator for monitoring and assessing overall animal performance and welfare, representing the progress along different physiological stages, while providing close indication of individual physical and health status. Measuring LW in practice is still, however, quite rare and infrequent under commercial sheep farming conditions, mainly because sessions are time-consuming, stressful either for the operator and the animals. A Walk-over-Weighing (WoW) system, already evaluated with other breeds under different conditions, was tested in this experiment lasting 14 weeks (i.e. 3 for acclimation and adaptation and 11 for data collection). We validated its use for routine and frequent monitoring the growth rate in post-weaned Merinos d'Arles ewe lambs, reared under Mediterranean grazing conditions. Similarly to previous work, the necessity for an initial adaptation period of the animals as well as for an essential data cleaning procedure of the raw database automatically collected by the WoW, were corroborated. Adaptation of naive ewe lambs enabled the required voluntary passages across the weigh platform and a high volume of individual and daily data after 2-3 weeks. Close monitoring of individual growth was then possible after performing sound data cleanings. A strong concordance of WoW LW data with the gold standard (a standard static scale) LW reference data was demonstrated. At the individual level, even with the lowest number of LW values collected with WoW, it was possible to monitor variations in LW at daily intervals. The establishment of an early warning system to help farmer decision making could therefore be possible. Our results show interesting perspectives for more precise and frequent monitoring of LW in grazing sheep without human intervention, compared to what is currently carried out on commercial farms.

scholarly journals Fish life history dynamics: shifts in prey size structure evoke shifts in predator maturation traits

2016 ◽  
Vol 73 (4) ◽  
pp. 693-708 ◽  
Author(s):  
Brian J. Shuter ◽  
Henrique C. Giacomini ◽  
Derrick de Kerckhove ◽  
Kris Vascotto
Keyword(s):  
Life History ◽  
Lake Trout ◽  
Size Structure ◽  
Prey Size ◽  
Empirical Support ◽  
Growth Efficiency ◽  
Size Ratio ◽  
Size Spectrum ◽  
Lower Growth ◽  
Predator Prey

A bioenergetic framework is developed to predict optimal life history responses to environmentally driven changes in the rate of energy production by a predator. This framework is used to predict the responses of age at maturation, size at maturation, and asymptotic size to changes in the predator–prey size ratio. Predators feeding on relatively smaller prey (i.e., having larger predator–prey size ratios) have lower growth efficiency and are predicted as a consequence to mature earlier, at smaller sizes, and reach smaller asymptotic sizes. This prediction was tested using a 78-year time series (1936–2013) of data from a natural population of lake trout (Salvelinus namaycush) in Lake Opeongo, Algonquin Park, Ontario, Canada. A large decrease in the predator–prey size ratio for this population occurred over the period 1950–1965 when a preferred prey (cisco, Coregonus artedii) was introduced to the lake. This decrease was followed by ∼20 years of constancy in the size ratio and then 25 years of progressive increase. Lake trout life history responded plastically during both periods and consistently with our predictions. Extensive analysis of available data provided little empirical support for alternative explanations for the observed changes in lake trout size and maturity (e.g., changes in cisco and (or) lake trout density and harvest rates). The framework developed here derives plastic life history changes from fixed developmental thresholds that are based on the scaling of net production with body size and can be used to predict the shape of maturation reaction norms for the major shifts in community structure that are compactly summarized by changes in size spectrum parameters.

Predator-Prey Interactions

Ecology ◽  
2013 ◽  
Author(s):  
Timothy C. Roth II ◽  
Maria Thaker
Keyword(s):  
Population Dynamics ◽  
Natural World ◽  
Ecological Interactions ◽  
Community Interactions ◽  
Predator Prey ◽  
Individual Level ◽  
Prey Interaction ◽  
Definition Of ◽  
The Individual ◽  
Phenotypic Responses

All animals are either predators or prey and, in most cases, they are both. The interactions involved in attempting to eat and avoid being eaten have strong and wide-reaching influences across all facets of ecology, from individual phenotypic responses and population dynamics, to community interactions, and even to how we attempt to manage and conserve the natural world. As in many subfields of ecology, the science behind predator-prey investigations has been driven by theory, including important advances in generating and testing predictions. This article highlights the breadth of influence that predator-prey interactions have on ecology. The sections that follow address the effects of predator-prey interactions, such as those at the individual level, expressed through behavior, morphology, physiology, and life history, as well as their effects on population dynamics and community composition. At the individual level, the predator-prey interaction will be arranged in two perspectives: those of the predator and those of the prey. The article also considers the less typical and more integrative aspects of predator-prey interactions, such as their physiological and neurological mechanisms and their relevance for questions associated with conservation. In addition, this article will consider the validity of including parasitism and herbivory within the broad definition of predation. A great deal of debate is ongoing as to whether these two ecological interactions possess similar enough qualities with predation to be characterized as one phenomenon. Those sections of this article will cover this debate and provide the reader with resources with which to consider this question.

Surrogate endpoints for overall survival (OS) in head and neck squamous cell carcinoma (HNSCC): Evaluation using individual data of 23,737 patients

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 6035-6035
Author(s):  
S. Michiels ◽  
A. Le Maître ◽  
M. Buyse ◽  
T. Burzykowski ◽  
J. Bogaerts ◽  
...  
Keyword(s):  
Correlation Coefficient ◽  
Treatment Effects ◽  
Randomized Trials ◽  
Correlation Coefficients ◽  
Surrogate Endpoint ◽  
Bivariate Distribution ◽  
Surrogate Endpoints ◽  
Strongly Correlated ◽  
Individual Level ◽  
The Individual

6035 Background: The gold standard endpoint in randomized trials of HNSCC is OS. Our objective was to study if event-free survival (EFS) or loco-regional control (LRC) could be good surrogate endpoints to estimate the effect of radiotherapy (RT) and chemotherapy (CT) on OS. This would permit to decrease the duration and cost of the development of new treatments for HNSCC. Methods: EFS is the time from randomization to first event (loco-regional, distant recurrence or death), LRC the time from randomization to first loco-regional event. Individual patient data from two meta-analyses (MARCH; Bourhis, Lancet 2006, MACH-NC; Bourhis, ASCO 2004) were used. At the individual level, the rank correlation coefficient ρ between the surrogate endpoint (EFS or LRC) and OS was estimated from the bivariate distribution of these endpoints. At the trial level, the correlation coefficient R between treatment effects (estimated by log hazard ratios) on the surrogate endpoint and OS was estimated from a linear regression. EFS and LRC would be acceptable surrogates only if the correlation coefficients ρ and R were close to 1. Results: At the individual level, EFS was more strongly correlated with OS than LRC. For RT, treatment effects on both LRC and EFS were strongly correlated with those on OS. For CT, the correlation coefficients between treatment effects on EFS and OS were larger than those between LRC and OS. Conclusions: The preliminary analysis indicates that EFS can be used as a surrogate for OS to evaluate the treatment effect in randomized trials of patients with HNSCC. LRC is a possible alternative in RT alone trials. Unrestricted grants from ARC, LNCC, PHRC, Sanofi-Aventis. [Table: see text] [Table: see text]

Graphical Estimation of Rates of Mortality and Growth

1970 ◽  
Vol 27 (1) ◽  
pp. 204-208 ◽  
Author(s):  
Roger H. Green
Keyword(s):  
Growth Rate ◽  
Mortality Rate ◽  
Individual Growth ◽  
Individual Growth Rate ◽  
Population Mortality ◽  
The Individual ◽  
Average Size ◽  
Individual Size

A method is presented by which the individual growth rate and the population mortality rate can be estimated graphically in certain populations, given only knowledge of maximum individual size and of average size at two times of the year. The four graphs that are given may be used in several different ways, depending on the information available.

scholarly journals Astrogliosis mapping in individual brains using multidimensional MRI

2022 ◽  
Author(s):  
Dan Benjamini ◽  
David S Priemer ◽  
Daniel P Perl ◽  
David L brody ◽  
Peter J Basser
Keyword(s):  
Ex Vivo ◽  
Correlation Study ◽  
Strongly Correlated ◽  
Cortical Tissue ◽  
Individual Level ◽  
Spatial Sensitivity ◽  
Protein Deposition ◽  
The Central Nervous System ◽  
Histological Images ◽  
The Individual

There are currently no noninvasive imaging methods available for astrogliosis mapping in the central nervous system despite its essential role in the response to injury, disease, and infection. We have developed a machine learning-based multidimensional MRI framework that provides a signature of astrogliosis, distinguishing it from normative brain at the individual level. We investigated ex vivo cortical tissue specimen derived from subjects who sustained blast induced injuries, which resulted in scar-border forming astrogliosis without being accompanied by other types of neuropathology. By performing a combined postmortem radiology and histopathology correlation study we found that astrogliosis induces microstructural changes that are robustly detected using our framework, resulting in MRI neuropathology maps that are significantly and strongly correlated with co-registered histological images of increased glial fibrillary acidic protein deposition. The demonstrated high spatial sensitivity in detecting reactive astrocytes at the individual level has great potential to significantly impact neuroimaging studies in diseases, injury, repair, and aging.

scholarly journals Do genomics and sex predict migration in a partially migratory salmonid fish, Oncorhynchus mykiss?

2019 ◽  
Vol 76 (11) ◽  
pp. 2080-2088 ◽  
Author(s):  
Suzanne J. Kelson ◽  
Michael R. Miller ◽  
Tasha Q. Thompson ◽  
Sean M. O’Rourke ◽  
Stephanie M. Carlson
Keyword(s):  
Life History ◽  
Oncorhynchus Mykiss ◽  
Genomic Region ◽  
Strongly Correlated ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
Individual Level ◽  
Highly Correlated ◽  
The Individual ◽  
Specific Genomic Region

Partial migration is a common phenomenon wherein populations include migratory and resident individuals. Whether an individual migrates or not has important ecological and management implications, particularly within protected populations. Within partially migratory populations of Oncorhynchus mykiss, migration is highly correlated with a specific genomic region, but it is unclear how well this region predicts migration at the individual level. Here, we relate sex and life history genotype, determined using >400 single nucleotide polymorphisms (SNPs) on the migratory-linked genomic region, to life history expression of marked juvenile O. mykiss from two tributaries to the South Fork Eel River, northern California. Most resident fish were resident genotypes (57% resident, 37% heterozygous, 6% migratory genotype) and male (78%). Most migratory fish were female (62%), but were a mixture of genotypes (30% resident, 45% heterozygous, 25% migratory genotype). Sex was more strongly correlated with life history expression than genotype, but the best-supported model included both. Resident genotypes regularly migrated, highlighting the importance of conserving the full suite of life history and genetic diversity in partially migratory populations.

Gecko: A Continuous 2D World for Ecological Modeling

1997 ◽  
Vol 3 (3) ◽  
pp. 147-163 ◽  
Author(s):  
Ginger Booth
Keyword(s):  
Spatial Competition ◽  
Trophic Levels ◽  
Resource Acquisition ◽  
Individual Growth ◽  
Chain Model ◽  
Natural Ecosystem ◽  
Individual Level ◽  
Ecosystem Level ◽  
Individual Based Simulation ◽  
Multiple Species

An individual-based simulation system, named Gecko, is presented for modeling multiple species at multiple trophic levels, on a spatially explicit, continuous two-dimensional landscape. Biologically motivated rules are specified at an individual level, and resulting behaviors are observed at an ecosystem level. Individuals are represented by circles with free range on a resource-producing plane. These circles grow allometrically with biomass of fixed resources. Resource acquisition behaviors include competition by area overlap for producers, and movement based on perception and intent. Individual-level energetics are explicitly modeled with inefficient assimilation, resource transformation, and allometrically specified metabolic costs. Individual growth and reproduction requires a history of successful resource acquisition. Terrestrial producer, herbivore, and carnivore species classes are included, extensible to further classes. A grassland food chain model of “plants,” “grasshoppers,” and “spiders” is used to demonstrate ecosystem-level results of given individual-level behaviors. Ecosystem-level behaviors include a trophic cascade of indirect carnivore-producer interaction effects; stable persistence of all populations; a near-realistic biomass pyramid; and spatial competition and coexistence of multiple producer species. Initial Gecko results show promise for application in both theoretical and natural ecosystem modeling.

scholarly journals Century-long cod otolith biochronology reveals individual growth plasticity in response to temperature

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Szymon Smoliński ◽  
Julie Deplanque-Lasserre ◽  
Einar Hjörleifsson ◽  
Audrey J. Geffen ◽  
Jane A. Godiksen ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Population Level ◽  
Climatic Conditions ◽  
Individual Growth ◽  
Individual Level ◽  
Thermal Plasticity ◽  
Individual Effects ◽  
The Individual

Abstract Otolith biochronologies combine growth records from individual fish to produce long-term growth sequences, which can help to disentangle individual from population-level responses to environmental variability. This study assessed individual thermal plasticity of Atlantic cod (Gadus morhua) growth in Icelandic waters based on measurements of otolith increments. We applied linear mixed-effects models and developed a century-long growth biochronology (1908–2014). We demonstrated interannual and cohort-specific changes in the growth of Icelandic cod over the last century which were mainly driven by temperature variation. Temperature had contrasting relationships with growth—positive for the fish during the youngest ages and negative during the oldest ages. We decomposed the effects of temperature on growth observed at the population level into within-individual effects and among‐individual effects and detected significant individual variation in the thermal plasticity of growth. Variance in the individual plasticity differed across cohorts and may be related to the mean environmental conditions experienced by the group. Our results underscore the complexity of the relationships between climatic conditions and the growth of fish at both the population and individual level, and highlight the need to distinguish between average population responses and growth plasticity of the individuals for accurate growth predictions.

Production at the Individual Level

2020 ◽  
pp. 127-148
Author(s):  
Michael J. Fogarty ◽  
Jeremy S. Collie
Keyword(s):  
Body Weight ◽  
Temperature Effects ◽  
Aquatic Organisms ◽  
Individual Growth ◽  
Ecological Research ◽  
Response Variable ◽  
Individual Level ◽  
Natural Choice ◽  
Allometric Functions ◽  
The Individual

Models of individual growth commonly used in fisheries and ecological research can be built around simple allometric functions representing the build-up of body mass (anabolism) and metabolic loss terms incorporating the effects of respiration, egestion, and excretion. From a bioenergetic perspective, body weight is a natural choice for the response variable in these models because it can be readily recast in terms of energy. Temperature affects virtually every dimension of the biology and ecology of aquatic organisms. Modifications of traditional models of individual growth can be augmented to account for temperature effects. The development of ‘full’ bioenergetic models considering each of the individual elements of production is a natural culmination of the issues described above. By invoking mass-balance constraints the bioenergetic approach offers important avenues for estimating elements of production that can be difficult to otherwise obtain.

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