scholarly journals Elevated nonlinearity as indicator of transition to overexploitation in fish stocks

2016 ◽  
Author(s):  
Vasilis Dakos ◽  
Sarah M. Glaser ◽  
Chih-hao Hsieh ◽  
George Sugihara
Keyword(s):  
Trophic Structure ◽  
Type Model ◽  
Western Atlantic ◽  
Economic Implications ◽  
Fish Stocks ◽  
As Species ◽  
Abrupt Changes ◽  
Risk Of Extinction ◽  
Statistical Metrics

AbstractEcosystems may experience abrupt changes such as species extinctions, reorganisations of trophic structure, or transitions from stable population dynamics to strongly irregular fluctuations. Although most of these changes have important ecological and at times economic implications, they remain notoriously difficult to detect in advance. Here, we use a Ricker-type model to simulate the transition of a hypothetical stable fisheries population either to irregular boom-bust dynamics or to overexploitation. Our aim is to infer the risk of extinction in these two scenarios by comparing changes in variance, autocorrelation, and nonlinearity between unexploited and exploited populations. We find that changes in these statistical metrics reflect the risk of extinction but depend on the type of dynamical transition. Variance and nonlinearity increase similarly in magnitude along both transitions. In contrast, autocorrelation depends strongly on the presence of underlying oscillating dynamics. We also compare our theoretical expectations to indicators measured in long-term datasets of fish stocks from the California Cooperative Oceanic Fisheries Investigation in the Eastern Pacific and from the Northeast Shelf in the Western Atlantic. Our results suggest that elevated variance and nonlinearity could be potentially used to rank exploited fish populations according to their risk of extinction.

scholarly journals Elevated nonlinearity as an indicator of shifts in the dynamics of populations under stress

2017 ◽  
Vol 14 (128) ◽  
pp. 20160845 ◽  
Author(s):  
Vasilis Dakos ◽  
Sarah M. Glaser ◽  
Chih-hao Hsieh ◽  
George Sugihara
Keyword(s):  
Nonlinear Models ◽  
Type Model ◽  
Forecast Performance ◽  
Economic Implications ◽  
Equilibrium Dynamics ◽  
Abrupt Changes ◽  
Local Extinctions ◽  
Abrupt Shifts ◽  
The Stability ◽  
Dynamics Of Populations

Populations occasionally experience abrupt changes, such as local extinctions, strong declines in abundance or transitions from stable dynamics to strongly irregular fluctuations. Although most of these changes have important ecological and at times economic implications, they remain notoriously difficult to detect in advance. Here, we study changes in the stability of populations under stress across a variety of transitions. Using a Ricker-type model, we simulate shifts from stable point equilibrium dynamics to cyclic and irregular boom–bust oscillations as well as abrupt shifts between alternative attractors. Our aim is to infer the loss of population stability before such shifts based on changes in nonlinearity of population dynamics. We measure nonlinearity by comparing forecast performance between linear and nonlinear models fitted on reconstructed attractors directly from observed time series. We compare nonlinearity to other suggested leading indicators of instability (variance and autocorrelation). We find that nonlinearity and variance increase in a similar way prior to the shifts. By contrast, autocorrelation is strongly affected by oscillations. Finally, we test these theoretical patterns in datasets of fisheries populations. Our results suggest that elevated nonlinearity could be used as an additional indicator to infer changes in the dynamics of populations under stress.

Oil pollution and fisheries

1982 ◽  
Vol 297 (1087) ◽  
pp. 401-411 ◽  
Keyword(s):  
Water Quality ◽  
Adverse Effects ◽  
Oil Pollution ◽  
Coastal Areas ◽  
Short Term ◽  
Fish Stocks ◽  
Local Impacts ◽  
Reduced Water ◽  
Long Term Adverse Effects

The term ‘pollution’ is taken in its broadest sense and effects are recognized to be due to interference, tainting and toxicity. Each of these types of impact is discussed and assessed. It is concluded that no long-term adverse effects on fish stocks can be attributed to oil but that local impacts can be extremely damaging in the short term and that produce from specific localities can be tainted and unmarketable for long periods. In some coastal areas oil can be one among several contributors to reduced water quality, and the implications of this are discussed.

Goat and Sheep Grazing in Shrub-Infested Semi-arid Woodlands of New South Wales.

1986 ◽  
Vol 8 (2) ◽  
pp. 140 ◽  
Author(s):  
BH Downing
Keyword(s):  
Animal Species ◽  
New South ◽  
Economic Implications ◽  
Dietary Preferences ◽  
South Wales ◽  
Continuous Grazing ◽  
Local Observation ◽  
Grazing Systems ◽  
Western Division

Examination of data on dietary preferences of sheep, goats and cattle suggests that different grazing systems are desirable for each of the three major woodland types (belah-rosewood, mulga, poplar box) examined. Competition for herbs, frequently palatable to all animal species, indicates that goats and sheep are unsuitable for joint use either in heavily wooded country or where annual herbaceous production is less than 200 kg-ha. Supplementary feeding, fire and judicious stocking are proposed as a strategy for inducing goats to eat a proportion of unpalatable shrubs. The literature provides little helpful information on how rangelands in the Western Division should be managed. No reports are given on comparisons of grazing systems, such as rotational grazing, rotational resting, and continuous grazing. No guidance is given on grazing after burning of the rangeland. Recommendations are generally against the use of goats for control of woody plants, whereas local observation shows this to be an apparently effective practice. The recommendations are mostly based on experimental procedures which, although suitable for detecting animal dietary preferences in the short term, are less appropriate for investigation of the effects of grazing on range condition in the long term. Some suggestions are made towards a different approach for: investigating the effects of grazing by sheep and goats on rangeland condition, and the economic implications of this in terms of animal production.

scholarly journals The Period Changes of YY Eridani

1998 ◽  
Vol 11 (1) ◽  
pp. 370-370
Author(s):  
C.-H. Kim ◽  
J.H. Jeong ◽  
O. Demircan ◽  
Z. Muyesseroulu ◽  
E. Budding
Keyword(s):  
Activity Cycle ◽  
Light Level ◽  
Magnetic Activity ◽  
Third Body ◽  
Period Increase ◽  
Activity Effect ◽  
Abrupt Changes ◽  
Massive Component ◽  
Photoelectric Observations

A total of eighteen times of minimum lights for YY Eri were determined from relatively new or unpublished photoelectric observations collected from Korea and Turkey. All minima available to us were intensively analyzed to deduce the character of period variation of YY Eri. It is either formed by a sinusoidal variation superimposed on an upward parabola, or a set of abrupt changes. The abrupt changes appeared to have alternatively occured in the pattern of two increases following one decrease, which may be an indication of sinusoidal variations rather than real sudden changes of period. Upward parabolic variation can be due to a secular period increase caused by mass transfer from less massive to more massive component. The sinusoidal character can arise from a third body or from a strong magnetic activity cycle. Long term sinusoidal light level variation in the light curves supports the cyclic magnetic activity effect on the orbital period. However, the third body hypothesis can not be ruled out by the present data.

scholarly journals Indicators of AEI Applied to the Delaware Estuary

2002 ◽  
Vol 2 ◽  
pp. 169-189 ◽  
Author(s):  
Lawrence W. Barnthouse ◽  
Douglas G. Heimbuch ◽  
Vaughn C. Anthony ◽  
Ray W. Hilborn ◽  
Ransom A. Myers
Keyword(s):  
Meta Analysis ◽  
Juvenile Fish ◽  
Fish Populations ◽  
Weight Of Evidence ◽  
Data Sets ◽  
Delaware Estuary ◽  
Fish Stocks ◽  
Trends Analysis ◽  
Definition Of

We evaluated the impacts of entrainment and impingement at the Salem Generating Station on fish populations and communities in the Delaware Estuary. In the absence of an agreed-upon regulatory definition of “adverse environmental impact” (AEI), we developed three independent benchmarks of AEI based on observed or predicted changes that could threaten the sustainability of a population or the integrity of a community.Our benchmarks of AEI included: (1) disruption of the balanced indigenous community of fish in the vicinity of Salem (the “BIC” analysis); (2) a continued downward trend in the abundance of one or more susceptible fish species (the “Trends” analysis); and (3) occurrence of entrainment/impingement mortality sufficient, in combination with fishing mortality, to jeopardize the future sustainability of one or more populations (the “Stock Jeopardy” analysis).The BIC analysis utilized nearly 30 years of species presence/absence data collected in the immediate vicinity of Salem. The Trends analysis examined three independent data sets that document trends in the abundance of juvenile fish throughout the estuary over the past 20 years. The Stock Jeopardy analysis used two different assessment models to quantify potential long-term impacts of entrainment and impingement on susceptible fish populations. For one of these models, the compensatory capacities of the modeled species were quantified through meta-analysis of spawner-recruit data available for several hundred fish stocks.All three analyses indicated that the fish populations and communities of the Delaware Estuary are healthy and show no evidence of an adverse impact due to Salem. Although the specific models and analyses used at Salem are not applicable to every facility, we believe that a weight of evidence approach that evaluates multiple benchmarks of AEI using both retrospective and predictive methods is the best approach for assessing entrainment and impingement impacts at existing facilities.

Clinical and economic implications of upper gastrointestinal adverse events in Asian rheumatological patients on long-term non-steroidal anti-inflammatory drugs

2018 ◽  
Vol 21 (5) ◽  
pp. 943-951 ◽  
Author(s):  
Lydia Say Lee Pok ◽  
Fatiha Hana Shabaruddin ◽  
Maznah Dahlui ◽  
Sargunan Sockalingam ◽  
Mohd Shahrir Mohamed Said ◽  
...  
Keyword(s):  
Adverse Events ◽  
Economic Implications ◽  
Inflammatory Drugs ◽  
Anti Inflammatory ◽  
Gastrointestinal Adverse Events ◽  
Upper Gastrointestinal

The Global Fish Market: Internationalization and Globalization, 1880-1997

1998 ◽  
Author(s):  
Poul Holm
Keyword(s):  
Global Market ◽  
Fishing Industry ◽  
Fish Stocks ◽  
Fish Market ◽  
Exclusive Economic Zones ◽  
Long Term Trends ◽  
Western Nations ◽  
Economic Zones ◽  
The Way

This chapter attempts to determine how globalisation and internationalisation affected the fishing industry, and which members of the global market profited and which suffered due to these developments. The author considers the long-term trends in production and markets; trawling and transport revolutions; worldwide exploitation of fish stocks; territorialisation; and Exclusive Economic Zones (EEZ), and the way these factors affected Eastern and Western nations differently.

scholarly journals Long-term trends in wild-capture and population dynamics point to an uncertain future for captive elephants

2019 ◽  
Vol 286 (1899) ◽  
pp. 20182810 ◽  
Author(s):  
John Jackson ◽  
Dylan Z. Childs ◽  
Khyne U. Mar ◽  
Win Htut ◽  
Virpi Lummaa
Keyword(s):  
Population Dynamics ◽  
Wild Populations ◽  
Birth Rates ◽  
As Species ◽  
In Captivity ◽  
Elephant Population ◽  
Long Term Trends ◽  
Uncertain Future ◽  
Primary Focus

Maintaining sustainable populations in captivity without supplementation through wild-capture is a major challenge in conservation that zoos and aquaria are working towards. However, the capture of wild animals continues for many purposes where conservation is not the primary focus. Wild-capture hinders long-term conservation goals by reducing remaining wild populations, but the direct and long-term indirect consequences of wild-capture for captive population viability are rarely addressed using longitudinal data. We explored the implications of changes in wild-capture on population dynamics in captivity over 54 years using a multi-generational studbook of working Asian elephants ( Elephas maximus ) from Myanmar, the largest remaining captive elephant population. Here we show that population growth and birth rates declined between 1960 and 2014 with declines in wild-capture. Importantly, wild-caught females had reduced birth rates and a higher mortality risk. However, despite the disadvantages of wild-capture, the population may not be sustainable without it, with immediate declines owing to an unstable age-structure that may last for 50 years. Our results highlight the need to assess the long-term demographic consequences of wild-capture to ensure the sustainability of captive and wild populations as species are increasingly managed and conserved in altered or novel environments.

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