Decline in Natural Fisheries — A Genetic Analysis and Suggestion for Recovery

1986 ◽  
Vol 43 (6) ◽  
pp. 1298-1306 ◽  
Author(s):  
Giora W. Wohlfarth
Keyword(s):  
Negative Selection ◽  
Natural Waters ◽  
Environmental Changes ◽  
Monitoring Program ◽  
Fish Populations ◽  
Natural Environments ◽  
Direct Effects ◽  
Resident Population ◽  
Selection For ◽  
Bodies Of Water

Overfishing and pollution of the aquatic environment, in addition to their direct effects on natural fisheries, may have also influenced natural fish populations genetically. Overfishing drastically reduces population size and, since the larger individuals are selectively removed, is equivalent to selection for smaller sized fish. Adaptation of natural fish populations to their environment must have been reduced by rapid environmental changes resulting from pollution and infestation. Inbreeding, negative selection, and lack of adaption are here considered as the genetic causes for the decline of natural fisheries and lack of recovery. Restocking programs involving hatchery stocks are unlikely to solve this problem, since these stocks were selected for adaptation to hatchery environments and not to natural environments. A series of studies have demonstrated heterosis of interstrain crossbreds, mainly between hatchery and wild stocks of salmonids, for performance in natural waters. Two strategies could be implemented in restocking programs: stocking spawners of a domestic strain (preferably of one sex) for interbreeding with the resident population or direct stocking of crossbred fry. This should be tested in small isolated bodies of water and needs to be accompanied by a monitoring program in order to evaluate the results and minimize hazards.

scholarly journals Synchronization-induced persistence versus selection for habitats in spatially coupled ecosystems

2013 ◽  
Vol 10 (87) ◽  
pp. 20130559 ◽  
Author(s):  
Adam Lampert ◽  
Alan Hastings
Keyword(s):  
Phase Transitions ◽  
Stochastic Systems ◽  
Environmental Changes ◽  
Heterogeneous Environments ◽  
Migration Rates ◽  
Stochastic Fluctuations ◽  
Key Factor ◽  
Spatially Extended ◽  
Unique Method ◽  
Selection For

Critical population phase transitions, in which a persistent population becomes extinction-prone owing to environmental changes, are fundamentally important in ecology, and their determination is a key factor in successful ecosystem management. To persist, a species requires a suitable environment in a sufficiently large spatial region. However, even if this condition is met, the species does not necessarily persist, owing to stochastic fluctuations. Here, we develop a model that allows simultaneous investigation of extinction due to either stochastic or deterministic reasons. We find that even classic birth–death processes in spatially extended ecosystems exhibit phase transitions between extinction-prone and persistent populations. Sometimes these are first-order transitions, which means that environmental changes may result in irreversible population collapse. Moreover, we find that higher migration rates not only lead to higher robustness to stochastic fluctuations, but also result in lower sustainability in heterogeneous environments by preventing efficient selection for suitable habitats. This demonstrates that intermediate migration rates are optimal for survival. At low migration rates, the dynamics are reduced to metapopulation dynamics, whereas at high migration rates, the dynamics are reduced to a multi-type branching process. We focus on species persistence, but our results suggest a unique method for finding phase transitions in spatially extended stochastic systems in general.

Genetic Diversity of Cronobacter sakazakii Isolates Collected from a Swiss Infant Formula Production Facility

2013 ◽  
Vol 76 (5) ◽  
pp. 883-887 ◽  
Author(s):  
ANDREA MÜLLER ◽  
ROGER STEPHAN ◽  
CLAUDIA FRICKER-FEER ◽  
ANGELIKA LEHNER
Keyword(s):  
Infant Formula ◽  
Monitoring Program ◽  
Sequence Type ◽  
Powdered Infant Formula ◽  
Cronobacter Sakazakii ◽  
Production Facility ◽  
Pfge Analysis ◽  
O Antigen ◽  
Selection For ◽  
Prevalent Species

In this study, 141 Cronobacter isolates that were collected based on a hygienic monitoring program performed in a powdered infant formula production facility in Switzerland between September 2011 and October 2012 were further characterized. Isolates were identified to the species level by molecular methods, and strains of Cronobacter sakazakii were further subtyped by applying PCR-based O-antigen serotyping, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). C. sakazakii was the most prevalent species identified (93.6%). Among this collection of isolates, representatives of all but one O-antigen serotype (serotype O5) were recognized. MLST analysis of 19 selected isolates revealed that most of the typeable isolates belonged to sequence type (ST) 4. Correlations between ST4 and serotype O2 and between ST83 and serotype O7 were observed. PFGE analysis revealed clusters with multiple isolates, including strains from samples collected at different time points and sampling sources. Generally, the observed heterogeneity among strains collected over the 13 months of the monitoring program was high, suggesting a constant flux among strains rather than a selection for persisting organisms.

scholarly journals Pampean lizard assemblage from subtropical Brazil: a temporal analysis

2011 ◽  
Vol 83 (4) ◽  
pp. 1345-1358 ◽  
Author(s):  
Gisele R. Winck ◽  
Tiago G. Dos Santos ◽  
Sonia Z. Cechin
Keyword(s):  
Environmental Changes ◽  
Seasonal Pattern ◽  
Natural Populations ◽  
Temporal Analysis ◽  
Natural Environments ◽  
Human Occupation ◽  
Environmental Disturbances ◽  
Pampa Biome ◽  
History Of ◽  
Recruitment Period

The increasing human occupation of natural environments is one of the greatest threats to biodiversity. To mitigate the negative anthropogenic effects, it is necessary to understand the characteristics of natural populations and the natural history of species. A study was conducted with an assemblage of lizards from a disturbed area of the Pampa biome, from February 2001 to January 2004. The assemblage showed a unimodal seasonal pattern, with the recruitment period occurring during the warmer months. The captures were seasonal for two of the three monitored years, and concentrated within warmer months. The minimum temperature explained the number of catches for the assemblage as a whole. However, when the species were analyzed individually, the temperature only explained the seasonal occurrence of Teius oculatus. The abundance of species was significantly different in the third year of study for Cercosaura schreibersii and Ophiodes striatus. This latter species was no longer registered in the study area from May 2003 until the end of the study. Therefore, O. striatus may be more sensitive to environmental changes, considering the events of change in vegetation during the study. With frequent and increasing environmental disturbances, it is necessary to take conservation measures and encourage the increase of knowledge on Pampean lizards.

scholarly journals Negative frequency-dependent selection maintains coexisting genotypes during fluctuating selection

2019 ◽  
Author(s):  
Caroline B. Turner ◽  
Sean W. Buskirk ◽  
Katrina B. Harris ◽  
Vaughn S. Cooper
Keyword(s):  
Evolutionary Dynamics ◽  
Burkholderia Cenocepacia ◽  
Natural Environments ◽  
Fluctuating Selection ◽  
Frequency Dependent ◽  
Frequency Dependent Selection ◽  
Fluctuating Environment ◽  
Fluctuating Environments ◽  
Negative Frequency Dependent Selection ◽  
Selection For

AbstractNatural environments are rarely static; rather selection can fluctuate on time scales ranging from hours to centuries. However, it is unclear how adaptation to fluctuating environments differs from adaptation to constant environments at the genetic level. For bacteria, one key axis of environmental variation is selection for planktonic or biofilm modes of growth. We conducted an evolution experiment with Burkholderia cenocepacia, comparing the evolutionary dynamics of populations evolving under constant selection for either biofilm formation or planktonic growth with populations in which selection fluctuated between the two environments on a weekly basis. Populations evolved in the fluctuating environment shared many of the same genetic targets of selection as those evolved in constant biofilm selection, but were genetically distinct from the constant planktonic populations. In the fluctuating environment, mutations in the biofilm-regulating genes wspA and rpfR rose to high frequency in all replicate populations. A mutation in wspA first rose rapidly and nearly fixed during the initial biofilm phase but was subsequently displaced by a collection of rpfR mutants upon the shift to the planktonic phase. The wspA and rpfR genotypes coexisted via negative frequency-dependent selection around an equilibrium frequency that shifted between the environments. The maintenance of coexisting genotypes in the fluctuating environment was unexpected. Under temporally fluctuating environments coexistence of two genotypes is only predicted under a narrow range of conditions, but the frequency-dependent interactions we observed provide a mechanism that can increase the likelihood of coexistence in fluctuating environments.

An Evaluation of RNA–DNA Ratio as a Measure of Long-Term Growth in Fish Populations

1973 ◽  
Vol 30 (2) ◽  
pp. 195-199 ◽  
Author(s):  
Terry A. Haines
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Growth Rates ◽  
Population Growth Rate ◽  
Environmental Changes ◽  
Age Distribution ◽  
Smallmouth Bass ◽  
Fish Populations ◽  
Population Growth Rates

The value of RNA–DNA ratio as a measure of long-term growth of fish populations under semi-natural conditions and when subjected to environmental manipulations was determined. Populations of carp and smallmouth bass of known age distribution were established in artificial ponds maintained at two fertility levels. After 15 months, population growth rates (as percent increase in weight) and RNA–DNA ratios of muscle tissue from selected fish were measured. Each species exhibited a range of population growth rates. The relation between population growth rate and individual fish RNA–DNA ratio for each species was significant. When reproduction occurred, the relation was not significant unless young-of-the-year fish were excluded from population growth rate calculations. Age of fish was also found to have an important effect on RNA–DNA ratio, with the ratio being higher in younger fish.RNA–DNA ratio can be a reliable indicator of long-term population growth in fish when population age structure is known and recruitment is controlled. The method has potential for use in detecting response to environmental changes before growth rate changes become severe.

Setting the scene and how to read the book

2018 ◽  
pp. 3-10
Keyword(s):  
Public Health ◽  
Human Health ◽  
Urban Areas ◽  
Environmental Changes ◽  
Natural Environments

Human health depends on nature. This is a basic statement on which the fundaments of this book rest. Functional and diverse ecosystems, from which we derive fresh air and water, soil to grow food, timber to build houses, settings for play and recreation, are a prerequisite for human health and survival. The latest centuries’ unprecedented speed in societal and environmental changes has come to threaten the health of natural environments and by this threatening our own health. While we cannot, and should not, reverse the trend of sound development, we need to find better and healthier ways to interact with nature—in urban as well as in non-urban areas. This chapter will give a background to this book’s development and put the topic of nature and public health into a broad, outreaching context. It also presents an overview of the book’s full content, giving a brief description of each chapter.

Food Availability and Consumption by Young Connecticut River Shad Alosa sapidissima

1972 ◽  
Vol 29 (10) ◽  
pp. 1495-1499 ◽  
Author(s):  
Raymond C. Levesque ◽  
Roger J. Reed
Keyword(s):  
Stomach Content ◽  
Food Habits ◽  
Negative Selection ◽  
Content Volume ◽  
American Shad ◽  
Initial Time ◽  
Connecticut River ◽  
Alosa Sapidissima ◽  
Selection For ◽  
Selection Of

Food habits of young American shad (Alosa sapidissima) were studied in the Connecticut River above Holyoke, Massachusetts, 1969. Diurnal feeding data revealed a peak in stomach content volume at 8:00 PM during midsummer. Larval shad fed mainly on aquatic crustaceans and tendipedid larvae and pupae. Juveniles ingested the most abundant organisms: crustaceans, tendipedid larvae and pupae, hydropsychid larvae and adult insects. Electivity data indicated positive selection for tendipedid pupae and crustaceans and negative selection for hydropsychid larvae and tendipedid larvae. Selection of Trichoptera larvae by young shad in significant amounts was documented for the initial time.

The Impact of Conventional War on Natural Areas of the USSR

1989 ◽  
Vol 16 (4) ◽  
pp. 317-321 ◽  
Author(s):  
Nicolai N. Smirnov
Keyword(s):  
Freshwater Ecosystems ◽  
Fish Populations ◽  
Inland Waters ◽  
Natural Areas ◽  
Wide Range ◽  
Bodies Of Water ◽  
The Impact

Military destruction by conventional arms of both terrestrial and freshwater ecosystems is described, with emphasis placed on the effects of World Wars I and II on the territory of the USSR (especially of Russia, Byelorussia, and Ukraine). It is shown that a wide range of serious damage is done in terrestrial natural areas: to forests which may be decimated, to mammals which are commonly killed, and to the land which is extensively disturbed and rendered infertile or even uncultivable. Inland waters, too, are widely disturbed, though numerous new bodies of water may be formed in various ways, while fisheries are commonly disturbed, though ‘Wartime military activities can greatly reduce fish catches, to the benefit of fish populations.’

scholarly journals A Two-Step Immunomagnetic Microbead-Based Method for the Isolation of Human Primary Skin Telocytes/CD34+ Stromal Cells

2020 ◽  
Vol 21 (16) ◽  
pp. 5877 ◽  
Author(s):  
Eloisa Romano ◽  
Irene Rosa ◽  
Bianca Saveria Fioretto ◽  
Elena Lucattelli ◽  
Marco Innocenti ◽  
...  
Keyword(s):  
Stromal Cells ◽  
Functional Data ◽  
Cell Separation ◽  
Negative Selection ◽  
Immune Surveillance ◽  
In Vitro Study ◽  
Homeostasis Regulation ◽  
Selection For ◽  
Insight Into

Telocytes (TCs), commonly referred to as TCs/CD34+ stromal cells, are a peculiar type of interstitial cells with distinctive morphologic traits that are supposed to exert several biological functions, including tissue homeostasis regulation, cell-to-cell signaling, immune surveillance, and reparative/regenerative effects. At present, the majority of studies investigating these cells are mainly descriptive and focus only on their morphology, with a consequent paucity of functional data. To gain relevant insight into the possible functions of TCs, in vitro analyses are clearly required, but currently, the protocols for TC isolation are only at the early stages and not fully standardized. In the present in vitro study, we describe a novel methodology for the purification of human primary skin TCs through a two-step immunomagnetic microbead-based cell separation (i.e., negative selection for CD31 followed by positive selection for CD34) capable of discriminating these cells from other connective tissue-resident cells on the basis of their different immunophenotypic features. Our experiments clearly demonstrated that the proposed method allows a selective purification of cells exhibiting the peculiar TC morphology. Isolated TCs displayed very long cytoplasmic extensions with a moniliform silhouette (telopodes) and presented an immunophenotypic profile (CD31−/CD34+/PDGFRα+/vimentin+) that unequivocally differentiates them from endothelial cells (CD31+/CD34+/PDGFRα−/vimentin+) and fibroblasts (CD31−/CD34−/PDGFRα+/vimentin+). This novel methodology for the isolation of TCs lays the groundwork for further research aimed at elucidating their functional properties and possible translational applications, especially in the field of regenerative medicine.

scholarly journals Tuning environmental timescales to evolve and maintain generalists

2020 ◽  
Vol 117 (23) ◽  
pp. 12693-12699 ◽  
Author(s):  
Vedant Sachdeva ◽  
Kabir Husain ◽  
Jiming Sheng ◽  
Shenshen Wang ◽  
Arvind Murugan
Keyword(s):  
Neutralizing Antibodies ◽  
Environmental Changes ◽  
Dynamic Environments ◽  
Affinity Maturation ◽  
Natural Environments ◽  
Broadly Neutralizing Antibodies ◽  
Complex Dynamic ◽  
Changing Environments ◽  
Cell Affinity ◽  
Do So

Natural environments can present diverse challenges, but some genotypes remain fit across many environments. Such “generalists” can be hard to evolve, outcompeted by specialists fitter in any particular environment. Here, inspired by the search for broadly neutralizing antibodies during B cell affinity maturation, we demonstrate that environmental changes on an intermediate timescale can reliably evolve generalists, even when faster or slower environmental changes are unable to do so. We find that changing environments on timescales comparable with evolutionary transients in a population enhance the rate of evolving generalists from specialists, without enhancing the reverse process. The yield of generalists is further increased in more complex dynamic environments, such as a “chirp” of increasing frequency. Our work offers design principles for how nonequilibrium fitness “seascapes” can dynamically funnel populations to genotypes unobtainable in static environments.

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