Interspecific Competition and Population Control in Freshwater Fish

1956 ◽  
Vol 13 (3) ◽  
pp. 327-342 ◽  
Author(s):  
P. A. Larkin
Keyword(s):  
Interspecific Competition ◽  
Freshwater Fish ◽  
Quantitative Data ◽  
Population Control ◽  
Feeding Habits ◽  
Reproductive Potential ◽  
Habitat Type ◽  
Fish Populations ◽  
Population Interaction

Interspecific competition is defined as the demand of more than one organism for the same resource of the environment in excess of immediate supply. When two species are "competing for a niche" the term competition has been used to include phenomena such as predation of the two species on each other, competition to avoid a parasite, etc. Making this distinction in natural situations is unrealistic. In the limited sense in which interspecific competition is defined above, it is a discrete phenomenon, which with other phenomena such as predation, can be measured as a factor involved in interaction between species.Freshwater environments offer comparatively few opportunities for specialization in fishes. In consequence many species have a relatively wide tolerance of habitat type, a flexibility of feeding habits and in general share many resources of their environment with several other species of fish. Cannibalism and mutual predation are common complications of competitive relationships between species. The organization of freshwater fish communities is thus characterized by breadth at each level of the food chain rather than by a height of a pyramid of numbers. Flexible growth rate and high reproductive potential permit fish populations to tide over unfavorable periods of competition. In these circumstances it is difficult to separate the role of interspecific competition from other phenomena as a factor of population control. As a subordinate factor, predisposing fish to loss from other causes, interspecific competition may act to influence population levels. There is need for quantitative data and mathematical models for study of the types of population interaction typical in freshwater fish associations.

Population Control (Review Article)

1961 ◽  
Vol 1 (3) ◽  
pp. 89-98
Author(s):  
Karol J. Krotki
Keyword(s):  
Population Control ◽  
Review Article ◽  
Small Enterprise ◽  
Opportunity Costs ◽  
Relative Importance ◽  
Factual Information ◽  
Undue Influence ◽  
Clear Cut ◽  
Economic Considerations

Discussions about the role of small enterprise in economic development tend to remain inconclusive partly because of the difficulty of assessing the relative importance of economic and non-economic objectives and partly because of the dearth of factual information on which to base an economic calculus. It is probably true, moreover, that, because of a lack of general agreement as to the economic case for or against small enterprise, non-economic considerations, including some merely romantic attitudes toward smallness and bigness, tend to exert an undue influence on public policies. There may, of course, be no clear-cut economic case. And noneconomic considerations should and will inevitably weigh significantly in policy decisions. If, however, some of the economic questions could be settled by more and better knowledge, these decisions could more accurately reflect the opportunity costs of pursuing non-economic objectives.

scholarly journals Wood Pastures: A Transitional Habitat between Forests and Pastures for Dung Beetle Assemblages

Forests ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
László Somay ◽  
Viktor Szigeti ◽  
Gergely Boros ◽  
Réka Ádám ◽  
András Báldi
Keyword(s):  
Functional Group ◽  
Animal Health ◽  
Habitat Type ◽  
Dung Beetle ◽  
Dung Beetles ◽  
Livestock Grazing ◽  
Pitfall Traps ◽  
Assemblage Composition ◽  
Beetle Assemblages

Wood pastures are home to a variety of species, including the dung beetle. Dung beetles are an important functional group in decomposition. Specifically, in terms of livestock manure, they not only contribute to nutrient cycling but are key players in supporting human and animal health. Dung beetles, however, are declining in population, and urgent recommendations are needed to reverse this trend. Recommendations need to be based on solid evidence and specific habitats. Herein, we aimed to investigate the role of an intermediate habitat type between forests and pastures. Wood pastures are key areas for dung beetle conservation. For this reason, we compared dung beetle assemblages among forests, wood pastures, and grasslands. We complemented this with studies on the effects of dung type and season at three Hungarian locations. Pitfall traps baited with cattle, sheep, or horse dung were used in forests, wood pastures, and pasture habitats in spring, summer, and autumn. Dung beetle assemblages of wood pastures showed transient characteristics between forests and pastures regarding their abundance, species richness, Shannon diversity, assemblage composition, and indicator species. We identified a strong effect of season and a weak of dung type. Assemblage composition proved to be the most sensitive measure of differences among habitats. The conservation of dung beetles, and the decomposition services they provide, need continuous livestock grazing to provide fresh dung, as well as the maintenance of wood pastures where dung beetle assemblages typical of forests and pastures can both survive.

scholarly journals Awakening the oocyte: controlling primordial follicle development

Reproduction ◽  
2009 ◽  
Vol 137 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Eileen A McLaughlin ◽  
Skye C McIver
Keyword(s):  
Population Control ◽  
Reproductive Potential ◽  
Animal Husbandry ◽  
Primordial Follicle ◽  
Domestic Animal ◽  
Follicle Growth ◽  
Cellular Mechanisms ◽  
Primordial Follicles ◽  
Control Oocyte ◽  
Signalling Systems

Oocytes are sequestered in primordial follicles before birth and remain quiescent in the ovary, often for decades, until recruited into the growing pool throughout the reproductive years. Therefore, activation of follicle growth is a major biological checkpoint that controls female reproductive potential. However, we are only just beginning to elucidate the cellular mechanisms required for either maintenance of the quiescent primordial follicle pool or initiation of follicle growth. Understanding the intracellular signalling systems that control oocyte maintenance and activation has significant implications for improving female reproductive productivity and longevity in mammals, and has application in domestic animal husbandry, feral animal population control and infertility in women.

An inter-dependence of flood and drought: disentangling amphibian beta diversity in seasonal floodplains

2017 ◽  
Vol 68 (11) ◽  
pp. 2115 ◽  
Author(s):  
Leonardo F. B. Moreira ◽  
Tainá F. Dorado-Rodrigues ◽  
Vanda L. Ferreira ◽  
Christine Strüssmann
Keyword(s):  
Community Structure ◽  
Environmental Factors ◽  
Quantitative Data ◽  
Explanatory Variable ◽  
Biotic Interactions ◽  
Ecological Role ◽  
Β Diversity ◽  
Amphibian Community ◽  
Dry Seasons

Species composition in floodplains is often affected by different structuring factors. Although floods play a key ecological role, habitat selection in the dry periods may blur patterns of biodiversity distribution. Here, we employed a partitioning framework to investigate the contribution of turnover and nestedness to β-diversity patterns in non-arboreal amphibians from southern Pantanal ecoregion. We investigated whether components of β-diversity change by spatial and environmental factors. We sampled grasslands and dense arboreal savannas distributed in 12 sampling sites across rainy and dry seasons, and analysed species dissimilarities using quantitative data. In the savannas, both turnover and nestedness contributed similarly to β diversity. However, we found that β diversity is driven essentially by turnover, in the grasslands. In the rainy season, balanced variation in abundance was more related to altitude and factors that induce spatial patterns, whereas dissimilarities were not related to any explanatory variable during dry season. In the Pantanal ecoregion, amphibian assemblages are influenced by a variety of seasonal constraints on terrestrial movements and biotic interactions. Our findings highlighted the role of guild-specific patterns and indicated that mass effects are important mechanisms creating amphibian community structure in the Pantanal.

scholarly journals Exploring the Role of the Speech-language Therapist in City Centre Preschools

2012 ◽  
Vol 2 (2) ◽  
Author(s):  
Sandra Du Plessis
Keyword(s):  
Quantitative Data ◽  
Preschool Teachers ◽  
City Centre ◽  
Medium Of Instruction ◽  
Language Therapist ◽  
Service Delivery Models ◽  
Descriptive Survey ◽  
Delivery Models ◽  
Innovative Techniques

This study investigates the perception of the strengths and challenges that face city centre preschool teachers and preschool learners in the acquisition of English as medium of instruction and to use the results to explore the role of speech-language therapists in this context. A descriptive survey, incorporating a quantitative data collection method, was selected as the research design and a questionnaire was developed as a survey instrument. The findings identified the strengths as including the creative communication strategies employed by the pre-schoolers and the innovative techniques of the teachers. Perceived challenges include a cultural and linguistic mismatch between teachers and learners and communication barriers that cause emotional and behavioural problems in classrooms. The study suggests that speech-language therapists need to consider and employ service delivery models instead of traditional models with the preschool teachers.

scholarly journals Determinants of Postpartum Visits in Breastfeeding Mother

2016 ◽  
Vol 5 (1) ◽  
pp. 106
Author(s):  
Eny Retna Ambarwati ◽  
Endang Khoirunnisa ◽  
Triantoro Safaria
Keyword(s):  
Quantitative Data ◽  
Health Workers ◽  
Post Partum ◽  
Public Awareness ◽  
Intervention Group ◽  
Community Empowerment ◽  
Control Group ◽  
Maternal Deaths ◽  
The Village

Puerperal is likely in the occurrence of maternal deaths, and should receive health care during childbirth to be visited by a health worker at least 3 times since birth. This type of research was descriptive quantitative. The quantitative data obtained from questionnaires, using T-test. The research sample was breastfeeding mothers in the village of Balecatur as the intervention group and breastfeeding mothers in the village of Ambarketawang as the control group. There are significant differences of knowledge, behavior in the treatment of post-partum mothers between the intervention group and the control group with significant value in total of <0.05, influenced by the role of cadres, social suport, the role of health workers. Post partum visits conducted by community empowerment strategies, women as the main actors. The role of leaders, social support affect the success of efforts to increase postnatal visits among others disseminating information, provide examples, sensitize, motivate, guide, moving targets and the community and facilitating thus the knowledge, skills and increased public awareness can foster public participation in the postnatal visit.

scholarly journals Effects of multigenerational exposure and phenotypic variation on a freshwater fish species exposed to elevated carbon dioxide (CO2)

2021 ◽  
Author(s):  
◽  
Jenna Laurel Fleet
Keyword(s):  
Carbon Dioxide ◽  
Freshwater Fish ◽  
Elevated Co2 ◽  
Phenotypic Variation ◽  
Mrna Abundance ◽  
Fish Populations ◽  
High Co2 ◽  
Filial Generation ◽  
Behavioural Phenotypes ◽  
Carbon Dioxide Co2

The amount of dissolved carbon dioxide (CO2) and the acidity of aquatic ecosystems is increasing as atmospheric CO2 concentrations increase due to human activities. Changes in pH and dissolved CO2 can have considerable aversive effects on fish physiology and behaviour, which can result in negative effects on fish populations. Multigenerational studies have found that the conditions experienced by parents can have significant effects on the performance of their offspring and understanding these effects can help to predict how fish populations will cope in future conditions. Additionally, repeatable behavioural phenotypes are good predictors of trends in behaviour, can be useful predictors of other physiological and life history traits, and can be subject to selection pressures. Unfortunately, the effects of elevated CO2 on freshwater fishes over multiple generations, and the effects of behavioural phenotypes, are poorly understood. In my thesis, freshwater Japanese Medaka (Oryzias latipes) were used to investigate the influence of phenotypic variation and differences in time of exposure (generational) on biological responses to elevated CO2. Lab-reared medaka were divided into ‘responsive’ and ‘non-responsive’ groups based on behavioural differences from the population mean during acute exposure to high CO2 in a common shuttling and novel tank behavioural assay. Responsive and non-responsive fish in parental generation (P) were subdivided and exposed to either control (~480 ppm) or high CO2 (~1250 ppm) conditions over a 6-week period. Following this time, eggs from this generation were collected and randomly selected into either high or control conditions, where they were hatched and reared until maturation (filial generation one (F1), 18 weeks). Eggs from F1 were collected and hatched and reared in the same conditions as their parents until adulthood (filial generation two (F2), 24 weeks). Body condition (size, weight and length), behaviour (total distance moved, time spent in the outer zone of the behavioural arena, and swimming direction), reproductive (number of eggs, size of eggs, and survival to hatch) performance, and the relative abundance of various mRNA transcripts in whole brain tissue of fish was measured across these three generations. Behavioural phenotypes influenced reproduction for P and F2 generation fish, and growth for F1 and F2 fish; suggesting that intraspecific variation in behavioural phenotypes may influence how medaka respond to elevated CO2. However, behavioural phenotypes did not have a significant effect on mRNA abundance on genes targeted in my study. Multigenerational exposure to elevated CO2 were shown to improve the performance of offspring in some measures and resulted in changes of mRNA abundance of several genes. Transgenerational exposure, where a parent or grandparent was exposed to elevated CO2 but the offspring were not exposed to elevated CO2, resulted in some deleterious effects suggesting that, generally, exposure to environmental conditions that differ from that of their parents may put fish especially at risk. In my thesis, current CO2 exposure appeared to be the best predictor of overall condition, where fish exposed to elevated CO2 were worse off than fish exposed to control CO2 conditions. The results of this research contribute to filling a current gap of knowledge in understanding how freshwater fish will respond to future conditions over an ecologically-relevant time scale. Importantly, this information will contribute to generating more informed decisions on freshwater ecosystem management and future research directions. Marine and freshwater environments offer food and water security and are of high importance to the economy and the health of our planet, making my research relevant to our broader society.

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