Can growth be used as a surrogate measure of walleye (Sander vitreus) abundance change?

2005 ◽  
Vol 62 (9) ◽  
pp. 2159-2168 ◽  
Author(s):  
Greg G Sass ◽  
James F Kitchell
Keyword(s):  
Positive Influence ◽  
Growth Patterns ◽  
Sander Vitreus ◽  
Adult Density ◽  
Lake Productivity ◽  
Regional Patterns ◽  
Density Dependent ◽  
Morphoedaphic Index ◽  
Improved Model ◽  
Surrogate Measures

We examined several models to determine the relative contributions of density-dependent and density-independent factors on walleye (Sander vitreus) growth in the ceded territory of Wisconsin from 1990 to 1999. We then used independent data from 2000 to determine how well each model predicted walleye growth and examined several models to determine if growth could be used to predict density. Adult density best predicted the mean size of age-3 males ( [Formula: see text]3m) and age-5 females ( [Formula: see text]5f). Density-independent measures of pH, the morphoedaphic index, maximum depth, and conductance had a positive influence on growth, while adult density negatively affected growth. The solely density-dependent models predicted [Formula: see text]3m and [Formula: see text]5f poorly in 2000. The addition of density-independent factors improved model predictions of [Formula: see text]3m and [Formula: see text]5f. Walleye growth did not predict adult walleye densities. Regional patterns in walleye growth were correlated with surrogate measures of lake productivity and to a lesser extent adult density. Density dependence had a relatively weak affect on growth patterns, suggesting that growth cannot be used as a surrogate method for monitoring abundance change.

Yield Properties and Structure of Boreal Percid Communities in Ontario

1977 ◽  
Vol 34 (10) ◽  
pp. 1613-1625 ◽  
Author(s):  
G. F. Adams ◽  
C. H. Olver
Keyword(s):  
Total Yield ◽  
Fishing Effort ◽  
Productive Capacity ◽  
Lake Productivity ◽  
Net Community Production ◽  
Yield Data ◽  
Northern Ontario ◽  
Fish Yield ◽  
Theoretical Yield ◽  
Morphoedaphic Index

A synoptic review of yield data for 70 northern Ontario lakes from 1917 to 1973 showed that percids mainly walleye (Stizostedion vitreum vitreum) constituted about one-third, by weight, of the total fish yield. This relationship, which was independent of fishing effort, lake size, and lake productivity, is considered to be an emergent property of this type of fish community and represents a degree of homeostasis within the community under exploitation. The relation of percid yield to theoretical yield (based on the morphoedaphic index — MEI) reflected organizational structure and suggested the existence of a community (percid) component within the MEI, and from this we recommend upper limits of percid harvest for boreal percid lakes.Most (83%) of the 70 lakes had an average total yield of less than 2.5 kg∙ha−1∙yr−1, 53% (37 lakes) yielding less than one-half of the theoretical yield (average 3.4 kg∙ha−1∙yr−1). Long-term average yields exceeded the theoretical maximums in only 11 lakes. Mesotrophic to slightly eutrophic waters appeared as optimum for percid yields.Inferences from the data suggest an unexploited boreal percid community is characterized by high community stability and low net community production with resiliency low because of the low productive capacity of the waters. A yield index (RYI), which was assumed to reflect both effort and vulnerability to exploitation, showed that fishing intensity tended to be higher on the smaller, less productive lakes in this study. Key words: Percidae, Stizostedion, community ecology, yield properties, management implications

Comparing growth patterns among field populations of cereal aphids reveals factors limiting their maximum abundance

2006 ◽  
Vol 96 (3) ◽  
pp. 269-277 ◽  
Author(s):  
A. Honek ◽  
V. Jarosik ◽  
A.F.G. Dixon
Keyword(s):  
Exponential Growth ◽  
Rhopalosiphum Padi ◽  
Growth Patterns ◽  
Aphid Population ◽  
Cereal Aphids ◽  
Cereal Aphid ◽  
Metopolophium Dirhodum ◽  
Density Dependent ◽  
Maximum Abundance ◽  
Aphid Density

AbstractCereal stands in central Europe are commonly infested with three species of aphids that may become serious pests. With increasing abundance, the proportion of a particular species in the total aphid population may remain constant, suggesting a density-independent exponential growth, or the proportion can change, suggesting density-dependent constraints on growth. The constraints that affect particular species, and thus their relative abundance, were studied. The proportionality between maximum abundances of the cereal aphids was studied using a 10-year census of the numbers of aphids infesting 268 winter wheat plots. For two species their abundance on leaves and ears was compared. With increasing aphid density the maximum abundance of Rhopalosiphum padi (Linnaeus) remained proportional, but not that of Sitobion avenae (Fabricius), which was constrained by the smaller surface area of ears compared to leaves. There was no evidence of inter-specific competition. Maximum abundance of R. padi and Metopolophium dirhodum (Walker) on leaves did not change proportionally as the proportion of M. dirhodum decreased with increasing overall aphid density. This decrease was probably caused by the restricted distribution of M. dirhodum, which is confined to leaves, where space is limiting. No change in proportion between populations was detected when the average densities were below 0.54 aphids per leaf or ear. Non-proportional relationships between aphid populations appeared to be due to spatial constraints, acting upon the more abundant population. Detecting the limitation of population growth can help with the assessment of when density-independent exponential growth is limited by density-dependent factors. This information may help in the development of models of cereal aphid population dynamics.

scholarly journals Age-based and reproductive biology of the Pacific Longnose Parrotfish Hipposcarus longiceps from Guam

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4079 ◽  
Author(s):  
Brett M. Taylor ◽  
Eric Cruz
Keyword(s):  
Life History ◽  
Fishery Management ◽  
Stock Assessment ◽  
Fork Length ◽  
Growth Patterns ◽  
Life History Trait ◽  
Fishery Resource ◽  
Species Vulnerability ◽  
The Pacific ◽  
Improved Model

The Pacific longnose parrotfish Hipposcarus longiceps (Valenciennes 1840) represents a prime fishery resource throughout much of the tropical Pacific. In this study, we sampled the species from the Guam commercial fishery market across five consecutive years to characterize reproductive and age-based demographic information imperative for informed fishery management. Compared with other parrotfishes, this species was found to be large-bodied, but has only a moderate life span of 10 + years. Hipposcarus longiceps was confirmed as a diandric protogynous hermaphrodite with highly sex-specific growth patterns and an overall mean asymptotic length of 434 mm fork length (FL). Females were estimated to reach median maturity at 329 mm FL (2.4 years) and have a median length at female-to-male sex change of 401 mm FL. Life-history trait values derived here were used to update previous models relating life history and vulnerability to overexploitation. We found that enhancement of just one species’ trait values improved model fits considerably, which strengthens the conclusion that life-history traits are a strong determinant of species’ vulnerability in the parrotfishes. This information is an imperative complement to other data sources facilitating formal stock assessment of a key fishery target.

scholarly journals Increasing adult density compromises anti-bacterial defense in Drosophila melanogaster

2022 ◽  
Author(s):  
Paresh Nath Das ◽  
Aabeer Kumar Basu ◽  
Nagaraj Guru Prasad
Keyword(s):  
Immune Response ◽  
Drosophila Melanogaster ◽  
Immune System ◽  
Population Density ◽  
Post Infection ◽  
Physiological Stress ◽  
Pathogen Transmission ◽  
Adult Density ◽  
Density Dependent ◽  
Adult Drosophila

The density-dependent prophylaxis hypothesis predicts that risk of pathogen transmission increases with increase in population density, and in response to this, organisms mount a prophylactic immune response when exposed to high density. This prophylactic response is expected to help organisms improve their chances of survival when exposed to pathogens. Alternatively, organisms living at high densities can exhibit compromised defense against pathogens due to lack of resources and density associated physiological stress; the density stress hypothesis. We housed adult Drosophila melanogaster flies at different densities and measured the effect this has on their post-infection survival and resistance to starvation. We find that flies housed at higher densities show greater mortality after being infected with bacterial pathogens, while also exhibiting increased resistance to starvation. Our results are more in line with the density-stress hypothesis that postulates a compromised immune system when hosts are subjected to high densities.

scholarly journals Thinning Effect of C Sequestration along an Elevation Gradient of Mediterranean Pinus spp. Plantations

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1583
Author(s):  
Antonio M. Cachinero-Vivar ◽  
Guillermo Palacios-Rodríguez ◽  
Miguel A. Lara-Gómez ◽  
Rafael M. Navarro-Cerrillo
Keyword(s):  
Carbon Sequestration ◽  
Elevation Gradient ◽  
Fold Increase ◽  
C Sequestration ◽  
Positive Influence ◽  
Growth Patterns ◽  
Fixation Capacity ◽  
Mediterranean Pine ◽  
Pinus Spp ◽  
Thinning Effect

Forests are key elements in mitigating the effects of climate change due to the fact of their carbon sequestration capacity. Forest management can be oriented to optimise the carbon sequestration capacity of forest stands, in line with other productive objectives and the generation of ecosystem services. This research aimed to determine whether thinning treatments have a positive influence on the growth patterns of some of the main Mediterranean pine species and, therefore, on their Carbon (C) fixation capacity, both in terms of living biomass and soil organic carbon. The results obtained show that C sequestration capacity (biomass and SOC) increased at higher thinning intensities due to the induced alterations in tree growth patterns. We observed almost a 1.5-fold increase in P. nigra and P. sylvestris, respectively, and over a two-fold increase in P. pinaster under heavy thinning treatments; SOC stocks were affected by the intensity of the thinning treatments. These results can contribute to improving silvicultural practices aimed at C sequestration in forest plantations located in dry areas of the Mediterranean.

Growth Patterns in a Newfoundland Atlantic Herring (Clupea harengus harengus) Stock

1982 ◽  
Vol 39 (3) ◽  
pp. 454-461 ◽  
Author(s):  
J. A. Moores ◽  
G. H. Winters
Keyword(s):  
Growth Patterns ◽  
Clupea Harengus ◽  
Atlantic Herring ◽  
Compensation Mechanism ◽  
Biotic Factors ◽  
Density Dependent ◽  
Growth Compensation ◽  
Abiotic And Biotic Factors ◽  
Clupea Harengus Harengus ◽  
Independent Effects

Growth patterns in a discrete Atlantic herring (Clupea harengus harengus) stock were examined using back-calculated lengths derived from otolith measurements and empirical data. The influence of abiotic and biotic factors on growth was examined and evaluated for possible density-dependent or density-independent effects. The results give little evidence to support density-dependent herring growth in the 1st year, but suggest density-independent growth regulated by temperature. A growth compensation mechanism appears to occur in subsequent years resulting in a stable maturation pattern within the stock.Key words: herring, growth, density-dependent, density-independent, growth compensation, maturation

An Improved Dynamic Load-Balancing Model

2017 ◽  
Vol 5 (3) ◽  
pp. 33-48 ◽  
Author(s):  
Wenqian Shang ◽  
Di Liu ◽  
Ligu Zhu ◽  
Dongyu Feng
Keyword(s):  
Big Data ◽  
Load Balancing ◽  
Dynamic Load ◽  
Rapid Development ◽  
Prediction Method ◽  
Positive Influence ◽  
Dynamic Load Balancing ◽  
Web Server Cluster ◽  
Load Balancing Algorithm ◽  
Improved Model

With the rapid development of big data and the national big data strategy is put forward, the Web server cluster facing more complex and severe challenges. The traditional load balancing algorithm has obvious limitations. This paper proposes a dynamic load-balancing model based on the SSAWF (Strong Suspend And Weak Forecast) mechanism. This model uses strong suspend mechanism and cubic exponential smoothing prediction method based on AHP algorithm for dynamic load balancing scheduling. Results of the experiments show that the improved model has more positive influence on read/ write performance of the cluster under abnormal system transient performance, high concurrency and high system load interaction, that's to say the load balancing effect is better than the traditional load balancing.

scholarly journals Density-dependent effects as key drivers of intraspecific size structure of six abundant fish species in lakes across Europe

2016 ◽  
Vol 73 (4) ◽  
pp. 519-534 ◽  
Author(s):  
Ignasi Arranz ◽  
Thomas Mehner ◽  
Lluís Benejam ◽  
Christine Argillier ◽  
Kerstin Holmgren ◽  
...  
Keyword(s):  
Body Size ◽  
Density Dependence ◽  
Fish Species ◽  
Size Structure ◽  
Catch Per Unit Effort ◽  
Lake Productivity ◽  
Size Spectra ◽  
Fish Size ◽  
Density Dependent ◽  
Size Diversity

We studied fish size structure by using mean size, size diversity, and the slope of linear size spectra of six common European fish species along large-scale environmental gradients. We further analyzed the response of these three size metrics to environmental variables and to density-dependent effects, i.e., relative estimates of abundance (catch per unit effort, CPUE). We found differences in the strength of main predictors of size structure between the six species, but the direction of the response was relatively similar and consistent for most of the size metrics. Mean body size was negatively related to temperature for perch (Perca fluviatilis), roach (Rutilus rutilus), and ruffe (Gymnocephalus cernuus). Lake productivity (expressed as total phosphorus concentration) and lake depth were also predictors of size structure for four of six species. Moreover, we found a strong density dependence of size structure for all species, resulting in lower mean body size and size diversity and steeper size spectra slopes when density dependence increases. This suggests that density dependence is a key driver of fish size structure.

Reproductive strategies and growth patterns in four legumes

1978 ◽  
Vol 56 (4) ◽  
pp. 413-416 ◽  
Author(s):  
R. A. Turkington ◽  
P. B. Cavers
Keyword(s):  
Reproductive Strategies ◽  
Dry Matter ◽  
Trifolium Pratense ◽  
Growth Patterns ◽  
Density Dependent ◽  
Selection Theory ◽  
Plant Parts ◽  
Medicago Lupulina ◽  
Density Dependent Regulation

The partitioning of dry matter into component plant parts has been traced for four legumes. The four species were chosen to represent different positions along the r-K continuum. Three of the species, Medicago lupulina, M. sativa, and Trifolium pratense, behaved essentially as predicted by r- and K-selection theory. However, the stolons of T. repens are formed within 7 weeks of germination and thus permit this species to reproduce sooner than Medicago lupulina can reproduce by seed. In this way, T. repens can behave as an r strategist in an environment imposing density-dependent regulation (a ‘K' type environment).

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