scholarly journals Density-dependent changes in effective area occupied for sea-bottom-associated marine fishes

2016 ◽  
Vol 283 (1840) ◽  
pp. 20161853 ◽  
Author(s):  
James T. Thorson ◽  
Anna Rindorf ◽  
Jin Gao ◽  
Dana H. Hanselman ◽  
Henning Winker
Keyword(s):  
Ideal Free Distribution ◽  
Spatial Dynamics ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Effective Area ◽  
Marine Fishes ◽  
Population Declines ◽  
Density Dependent ◽  
Sea Bottom ◽  
Mixed Support

The spatial distribution of marine fishes can change for many reasons, including density-dependent distributional shifts. Previous studies show mixed support for either the proportional-density model (PDM; no relationship between abundance and area occupied, supported by ideal-free distribution theory) or the basin model (BM; positive abundance–area relationship, supported by density-dependent habitat selection theory). The BM implies that fishes move towards preferred habitat as the population declines. We estimate the average relationship using bottom trawl data for 92 fish species from six marine regions, to determine whether the BM or PDM provides a better description for sea-bottom-associated fishes. We fit a spatio-temporal model and estimate changes in effective area occupied and abundance, and combine results to estimate the average abundance–area relationship as well as variability among taxa and regions. The average relationship is weak but significant (0.6% increase in area for a 10% increase in abundance), whereas only a small proportion of species–region combinations show a negative relationship (i.e. shrinking area when abundance increases). Approximately one-third of combinations (34.6%) are predicted to increase in area more than 1% for every 10% increase in abundance. We therefore infer that population density generally changes faster than effective area occupied during abundance changes. Gadiformes have the strongest estimated relationship (average 1.0% area increase for every 10% abundance increase) followed by Pleuronectiformes and Scorpaeniformes, and the Eastern Bering Sea shows a strong relationship between abundance and area occupied relative to other regions. We conclude that the BM explains a small but important portion of spatial dynamics for sea-bottom-associated fishes, and that many individual populations merit cautious management during population declines, because a compressed range may increase the efficiency of harvest.

scholarly journals THE IDEAL DISTRIBUTION OF FARMERS: EXPLAINING THE EURO-AMERICAN SETTLEMENT OF UTAH

2017 ◽  
Vol 83 (1) ◽  
pp. 75-90 ◽  
Author(s):  
Peter M. Yaworsky ◽  
Brian F. Codding
Keyword(s):  
Population Density ◽  
Ideal Free Distribution ◽  
Negative Relationship ◽  
Coarse Grained ◽  
Distribution Model ◽  
Test Model ◽  
Fine Grained ◽  
Fine Grain ◽  
Model Predictions ◽  
The Ideal

Explaining how and why populations settle a new landscape is central to many questions in American archaeology. Recent advances in settlement research have adopted predictions from the Ideal Free Distribution model (IFD). While tests of IFD predictions to date rely either on archaeologically derived coarse-grained diachronic data or ethnographically derived fine-grained synchronic data, here we provide the first test using historically derived data that is both fine-grained and diachronic. Fine-grain diachronic data allow us to test model predictions at a temporal scale in line with human settlement decisions and to validate proxies for application in archaeological contexts. To test model predictions pertaining to the relationship between population density and habitat quality, we use data from the historical settlement of Utah. The results demonstrate a negative relationship between population density and the quality of habitats occupied. These results are consistent with IFD predictions, suggesting that Euro-American settlement of Utah resulted from individuals attempting to maximize individual returns via agricultural productivity. Our results provide a quantitative and testable explanation for population dispersion over time and explain the spatial distribution of population density today. The results support predictions derived from a general theory of behavior, providing an explanatory framework for colonization events worldwide.

scholarly journals Jack-of-all-trades paradigm meets long-term data: generalist herbivores are more widespread and locally less abundant

2020 ◽  
Author(s):  
C. Sudta ◽  
D.M. Salcido ◽  
M.L. Forister ◽  
T. Walla ◽  
S. Villamarín-Cortez ◽  
...  
Keyword(s):  
Spatial Scales ◽  
Negative Relationship ◽  
Positive Association ◽  
Interspecific Variation ◽  
Diet Breadth ◽  
Ecological Specialization ◽  
Dietary Specialization ◽  
Mixed Support ◽  
Term Data

AbstractSome of the most common ecological interactions are between plants and herbivorous insects, and these relationships are central to the study of ecological specialization. We address established assumptions about the positive association between local abundance and dietary specialization using a 17-year dataset on the caterpillars of Ecuador. Our long-term data include standardized plot-based samples as well as general, regional collections, allowing for investigations across spatial scales and using different indices of abundance for 1917 morphospecies of Lepidoptera from 33 families. We find that specialists are locally more abundant than generalists, consistent with a key component of the “jack of all trades, master of none” hypothesis, which has otherwise received poor to mixed support from previous studies that have mostly involved fewer species and shorter time series. Generalists achieve greater prevalence across the landscape, and we find some evidence for geographic variation in the abundance-diet breadth relationship, in particular among elevational bands. Interspecific variation in abundance also had a negative relationship with diet breadth, with specialists having more variable abundances across species. The fact that more specialized species can be both rare and common highlights the ecological complexity of specialization.

scholarly journals An integrated population model for estimating the relative effects of natural and anthropogenic factors on a threatened population of Pacific trout

2019 ◽  
Author(s):  
Mark D. Scheuerell ◽  
Casey P. Ruff ◽  
Joseph H. Anderson ◽  
Eric M. Beamer
Keyword(s):  
At Risk ◽  
Population Model ◽  
Habitat Restoration ◽  
Negative Relationship ◽  
Anthropogenic Factors ◽  
List Type ◽  
Population Demographics ◽  
Density Dependent ◽  
Integrated Population Model ◽  
The North

SummaryAssessing the degree to which at-risk species are regulated by density dependent versus density independent factors is often complicated by incomplete or biased information. If not addressed in an appropriate manner, errors in the data can affect estimates of population demographics, which may obfuscate the anticipated response of the population to a specific action.We developed a Bayesian integrated population model that accounts explicitly for interannual variability in the number of reproducing adults and their age structure, harvest, and environmental conditions. We apply the model to 41 years of data for a population of threatened steelhead troutOncorhynchus mykissusing freshwater flows, ocean indices, and releases of hatchery-born conspecifics as covariates.We found compelling evidence that the population is under strong density dependence, despite being well below its historical population size. In the freshwater portion of the lifecycle, we found a negative relationship between productivity (offspring per parent) and peak winter flows, and a positive relationship with summer flows. We also found a negative relationship between productivity and releases of hatchery conspecifics. In the marine portion of the lifecycle, we found a positive correlation between productivity and the North Pacific Gyre Oscillation. Furthermore, harvest rates on wild fish have been sufficiently low to ensure very little risk of overfishing.Synthesis and applications.The evidence for density dependent population regulation, combined with the substantial loss of juvenile rearing habitat in this river basin, suggests that habitat restoration could benefit this population of at-risk steelhead. Our results also imply that hatchery programs for steelhead need to be considered carefully with respect to habitat availability and recovery goals for wild steelhead. If releases of hatchery steelhead have indeed limited the production potential of wild steelhead, there are likely significant tradeoffs between providing harvest opportunities via hatchery steelhead production, and achieving wild steelhead recovery goals.

scholarly journals Length of productive life the cows of Simmental breed

2021 ◽  
Vol 213 (10) ◽  
pp. 31-39
Author(s):  
L. Ignat'eva ◽  
A. Sermyagin
Keyword(s):  
Milk Yield ◽  
Russian Federation ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Cattle Breeding ◽  
Productive Life ◽  
The Russian Federation ◽  
The Republic ◽  
First Time ◽  
The Relationship

Abstract. The purpose of the research was to assess the duration of the length of productive life of Simmental cows. Methods. The research was carried out on Simmental cows bred in 14 regions of the Russian Federation, the total livestock was 8 832 heads. The calculation of the heritability coefficients and correlation (genetic and paratypic) was carried out by using the programs RENUMF90 and REMLF90. Results. A fairly strong relationship was established between the duration of a productive life (months) and the age of culling (lactations) r = +0.795, the length of productive life (months) and lifetime productivity within the range of +0.669…+0.714. However, the relationship between the age of culling (lactations) and lifetime productivity is moderate, from +0.261 to +0.316. A moderate negative relationship was obtained between the age of culling (lactations) and milk yield per first lactation from –0.472 to –0.486. The average relationship was found between milk yield per first lactation and lifetime productivity from +0.567 to +0.588. Cows of the Altai Territory (3.08 lactations or 61.6 months), the Republic of Mordovia (3.38 lactations or 62.4 months) and the Lipetsk region (3.40 lactations or 65.7 months) were distinguished by low age of culling. While the greatest length of productive life was noted in animals and Bryansk (5.48 lactations or 86.9 months) and Irkutsk regions (4.57 lactations or 77.1 months). Bryansk (23 630 kg of milk), Tyumen (18 156 kg) and Irkutsk (17 751 kg) regions occupied the leading positions in lifetime productivity of cows in the sample, while the outsiders were the regions of traditional cattle breeding - Altai Territory (12658 kg of milk), the Republic of Bashkiria (12 482 kg). Scientific novelty. For the population Simmental cattle of the Russian Federation, for the first time, an assessment of selection and genetic parameters of lifelong productivity and length of productive life of Simmental cows was carried out, depending on the breeding region.

Conservation biology of marine fishes: perceptions and caveats regarding assignment of extinction risk

2001 ◽  
Vol 58 (1) ◽  
pp. 108-121 ◽  
Author(s):  
Jeffrey A Hutchings
Keyword(s):  
Population Size ◽  
Extinction Risk ◽  
Population Decline ◽  
Empirical Support ◽  
Marine Fishes ◽  
Marine Biodiversity ◽  
Population Declines ◽  
High Fecundity ◽  
Reproductive Rates ◽  
Biological Extinction

Quantitative criteria used to assign species to categories of extinction risk may seriously overestimate these risks for marine fishes. Contemporary perception is that marine fishes may be less vulnerable to extinction than other taxa, because of great natural variability in abundance, high fecundity, rapid population growth, and an intrinsically high capability of recovering from low population size. Contrary to perception, however, there appears to be generally little theoretical or empirical support for the hypotheses that marine fish are more likely to experience large reductions in population size, to produce unusually high levels of recruitment, to have higher reproductive rates, or to recover more rapidly from prolonged population declines than nonmarine fishes. Although existing population-decline criteria may not accurately reflect probabilities of biological extinction, they do appear to reflect the converse-population recovery. Insufficient support for contemporary perceptions of their susceptibility to extinction, coupled with caveats associated with the assignment of extinction risk, suggest that significant increases in the population-decline thresholds used to assign marine fishes to at-risk categories would be inconsistent with a precautionary approach to fisheries management and the conservation of marine biodiversity.

scholarly journals VALUASI EKONOMI OBJEK WISATA HUTAN MANGROVE MUNJANG DI DESA KURAU BARAT KABUPATEN BANGKA TENGAH

2020 ◽  
Vol 14 (1) ◽  
pp. 101
Author(s):  
Soleha Soleha ◽  
Yudi Sapta Pranoto ◽  
Evahelda Evahelda
Keyword(s):  
Pearson Correlation ◽  
Economic Value ◽  
Negative Relationship ◽  
Strong Relationship ◽  
Survey Method ◽  
Carbon Dioxide Absorption ◽  
Tourist Attractions ◽  
Travel Costs ◽  
The Cost

This study aims to calculate economic value based on travel costs and environmental services of Mangrove Munjang Forest attractions. This research was conducted in the supporting Mangrove Munjang Forest in Kurau Barat Village, Koba Subdistrict, Central Bangka Regency starting in November 2018 until June 2019. The research method used was the survey method. The sampling method using simple accidental sampling for the determination of 100 respondents obtained using the Rao Purba formula, and the method of analysing travel costs using Pearson Correlation analysis. The results of the study showed that the overall economic value of Mangrove Munjang Forests was Rp28.292.560.968 per year that is the flora value of Rp15.037.827.000, fauna value Rp7.286.730.000, carbon dioxide absorption value is Rp4.261.243.068 and the value of travel cost is Rp1.706.760.900. The correlation between the cost of travel and the number of visits showed a strong relationship namely -,540 with the direction of a negative relationship namely the higher the cost of travel incurred by visitors, the lower the visitor’s desire to travel o tourist attractions and vice versa.

Ecological correlates of pneumonia epizootics in bighorn sheep herds

2001 ◽  
Vol 79 (8) ◽  
pp. 1423-1432 ◽  
Author(s):  
Ryan J Monello ◽  
Dennis L Murray ◽  
E Frances Cassirer
Keyword(s):  
Horizontal Transmission ◽  
Bighorn Sheep ◽  
Ovis Canadensis ◽  
Domestic Sheep ◽  
Population Declines ◽  
Density Dependent ◽  
Temperature Regimes ◽  
Reservoir Hosts ◽  
The Relationship ◽  
Population Numbers

Bighorn sheep (Ovis canadensis) populations commonly experience pneumonia outbreaks caused by Pasteurella spp. that result in a partial or complete dieoff. Although several factors can contribute to Pasteurella spp. transmission or infectivity in bighorn sheep, to date the importance of such factors in population declines has not been rigorously examined. We evaluated the relationship between pneumonia-induced dieoffs in bighorn sheep and environmental and biological factors by analyzing demographic information for 99 herds across the species' geographic range. Our analysis revealed that 88% of pneumonia-induced dieoffs occurred at or within 3 years of peak population numbers, which implies that density-dependent forces such as food shortage or stress contribute to bighorns' susceptibility to pneumonia. There were few differences in the growth rates of dieoff and non-dieoff populations, suggesting that pneumonia did not manifest itself demographically prior to an outbreak. On average, abundance of lambs was most dramatically reduced post outbreak (–66%) relative to that of either rams (–35%) or ewes (–42%). Deviations in normal precipitation and temperature regimes were not associated with the onset of pneumonia outbreaks, but herds found in proximity to domestic sheep tended to be more susceptible to dieoff. Our results suggest that bighorn sheep herds are rendered vulnerable to pneumonia principally through density-dependent factors, as well as through horizontal transmission of Pasteurella spp. from domestic sheep serving as reservoir hosts.

scholarly journals Salinity stress increases the severity of ranavirus epidemics in amphibian populations

2020 ◽  
Vol 287 (1926) ◽  
pp. 20200062 ◽  
Author(s):  
Emily M. Hall ◽  
Jesse L. Brunner ◽  
Brandon Hutzenbiler ◽  
Erica J. Crespi
Keyword(s):  
Salinity Stress ◽  
Negative Relationship ◽  
Environmental Dna ◽  
Transmission Efficiency ◽  
Decay Rates ◽  
Mass Mortality ◽  
Population Declines ◽  
Elevated Salinity ◽  
Chronic Stressor ◽  
Small Change

The stress-induced susceptibility hypothesis, which predicts chronic stress weakens immune defences, was proposed to explain increasing infectious disease-related mass mortality and population declines. Previous work characterized wetland salinization as a chronic stressor to larval amphibian populations. Thus, we combined field observations with experimental exposures quantifying epidemiological parameters to test the role of salinity stress in the occurrence of ranavirus-associated mass mortality events. Despite ubiquitous pathogen presence (94%), populations exposed to salt runoff had slightly more frequent ranavirus related mass mortality events, more lethal infections, and 117-times greater pathogen environmental DNA. Experimental exposure to chronic elevated salinity (0.8–1.6 g l −1 Cl − ) reduced tolerance to infection, causing greater mortality at lower doses. We found a strong negative relationship between splenocyte proliferation and corticosterone in ranavirus-infected larvae at a moderate elevation of salinity, supporting glucocorticoid-medicated immunosuppression, but not at high salinity. Salinity alone reduced proliferation further at similar corticosterone levels and infection intensities. Finally, larvae raised in elevated salinity had 10 times more intense infections and shed five times as much virus with similar viral decay rates, suggesting increased transmission. Our findings illustrate how a small change in habitat quality leads to more lethal infections and potentially greater transmission efficiency, increasing the severity of ranavirus epidemics.

Examining the age‐performance relationship for entrepreneurs: Does the innovativeness of a venture make a difference?

2015 ◽  
Vol 18 (1) ◽  
pp. 41-57 ◽  
Author(s):  
Kanti V. Prasad ◽  
Kyle Ehrhardt ◽  
Yiyuan Liu ◽  
Kamlesh Tiwari
Keyword(s):  
Representative Sample ◽  
Negative Relationship ◽  
Performance Outcomes ◽  
Nascent Entrepreneurs ◽  
Venture Performance ◽  
Contingency Perspective ◽  
Mixed Support ◽  
And Performance ◽  
The Relationship ◽  
Moderating Role

Whether older or younger entrepreneurs may be better positioned to achieve performance outcomes for their ventures is a much debated question. Here, we draw on Galenson℉s theory of creativity to propose a contingency perspective for understanding the relationship between entrepreneur age and venture performance, suggesting that a venture℉s level of innovativeness plays a moderating role. Results from a representative sample of 1,182 nascent entrepreneurs revealed mixed support for our hypotheses. While a negative relationship was found between entrepreneur age and performance for those developing “innovative” ventures, no relationship was found between entrepreneur age and performance for those developing “imitative” ventures.

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