Fishing through (and up) Alaskan food webs

2009 ◽  
Vol 66 (2) ◽  
pp. 201-211 ◽  
Author(s):  
Michael A. Litzow ◽  
Daniel Urban
Keyword(s):  
Time Series ◽  
Trophic Level ◽  
High Trophic Level ◽  
Climate Index ◽  
Climate Regime ◽  
Fisheries Sustainability ◽  
Competing Hypotheses ◽  
Mean Trophic Level ◽  
Highly Correlated ◽  
Historical Periods

We used a 112-year time series of Alaskan fishery catches to test competing hypotheses concerning trends in mean catch trophic level, a widely used indicator of fisheries sustainability. We found that mean trophic level has generally remained steady or increased in recent decades on Alaska-wide and regional scales, indicating stable catches of high trophic level taxa. During historical periods of declining mean trophic level, catches of upper trophic level taxa either increased or remained steady, contrary to the predictions of the “fishing down the food web” hypothesis. Further, a climate index was highly correlated (r = 0.69–0.97) with mean trophic level and (or) the related fisheries in balance (FIB) index across climate regime shifts in the 1940s and 1970s, indicating that climate effects, particularly on high trophic level taxa, can act as the major driver of variability in these parameters. These results provide a contrast to the view of ubiquitous declines in mean trophic level of fishery catches, driven by overexploitation and serial stock replacement.

Historical changes in mean trophic level of southern Australian fisheries

2014 ◽  
Vol 65 (10) ◽  
pp. 884 ◽  
Author(s):  
Heidi K. Alleway ◽  
Sean D. Connell ◽  
Tim M. Ward ◽  
Bronwyn M. Gillanders
Keyword(s):  
Trophic Level ◽  
Spatial Data ◽  
South Australia ◽  
Trophic Levels ◽  
High Trophic Level ◽  
Fishing Pressure ◽  
Time Line ◽  
The Mean ◽  
Mean Trophic Level ◽  
Catch Statistics

Decreases in the mean trophic level (MTL) of fishery catches have been used to infer reductions in the abundance of high trophic level species caused by fishing pressure. Previous assessments of southern Australian fisheries have been inconclusive. The objectives of the present study were to provide more accurate estimates of MTL using disaggregated taxonomic and spatial data. We applied the model of MTL to fisheries catch statistics for the state of South Australia from 1951 to 2010 and a novel set of historical market data from 1936 to 1946. Results show that from 1951 to 2010, MTL declined by 0.16 of a trophic level per decade; a rate greater than the global average of 0.10 but equivalent to similar regional investigations in other areas. This change is mainly attributable to large increases in catches of sardine, rather than reductions in the catches of high trophic level species. The pattern is maintained when the historical data is included, providing a time line from 1936 to 2010. Our results show a broadening of the catch of lower trophic levels and suggest care in interpretation of MTL of catches because reductions do not necessarily reflect change in high trophic level species by fishing pressure.

scholarly journals Decadal‐Scale Variation in Mean Trophic Level in Beibu Gulf Based on Bottom‐Trawl Survey Data

2021 ◽  
Vol 13 (3) ◽  
pp. 174-182
Author(s):  
Li Su ◽  
Zuozhi Chen ◽  
Kui Zhang ◽  
Youwei Xu ◽  
Shannan Xu ◽  
...  
Keyword(s):  
Survey Data ◽  
Trophic Level ◽  
Bottom Trawl ◽  
Beibu Gulf ◽  
Trawl Survey ◽  
Bottom Trawl Survey ◽  
Decadal Scale ◽  
Mean Trophic Level ◽  
Scale Variation

USE OF DISSOLVED ORGANIC MATTER BY MICROORGANISMS: FORMATION OF WATER QUALITY IN A POND OF A HIGH TROPHIC LEVEL

Fisheries ◽  
2020 ◽  
Vol 2020 (5) ◽  
pp. 25-29
Author(s):  
Anatoliy Sadchikov ◽  
Sergey Ostroumov
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Organic Carbon ◽  
Dissolved Organic Matter ◽  
Trophic Level ◽  
Aquatic Ecosystem ◽  
High Trophic Level ◽  
Bacterioplankton Community ◽  
Algae And Bacteria

The role of algae and bacteria in the consumption and mineralization of dissolved organic matter (DOM) in a highly trophic aquatic ecosystem was studied. The phytoplankton and bacterioplankton community consumed 60% of added DOM in August and 56% of DOM in September. Of the uptaken DOM, a significant amount of organic carbon was mineralized. In August 42.7% and in September 29% of organic carbon (of the consumed organic matter) were used for respiration.

scholarly journals Estimating Conditional Transfer Entropy in Time Series Using Mutual Information and Nonlinear Prediction

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1124
Author(s):  
Payam Shahsavari Baboukani ◽  
Carina Graversen ◽  
Emina Alickovic ◽  
Jan Østergaard
Keyword(s):  
Time Series ◽  
State Of The Art ◽  
Difficult Case ◽  
Nonlinear Prediction ◽  
False Detection ◽  
Uniform Embedding ◽  
Embedding Technique ◽  
New Information ◽  
Highly Correlated ◽  
Intracranial Electroencephalography

We propose a new estimator to measure directed dependencies in time series. The dimensionality of data is first reduced using a new non-uniform embedding technique, where the variables are ranked according to a weighted sum of the amount of new information and improvement of the prediction accuracy provided by the variables. Then, using a greedy approach, the most informative subsets are selected in an iterative way. The algorithm terminates, when the highest ranked variable is not able to significantly improve the accuracy of the prediction as compared to that obtained using the existing selected subsets. In a simulation study, we compare our estimator to existing state-of-the-art methods at different data lengths and directed dependencies strengths. It is demonstrated that the proposed estimator has a significantly higher accuracy than that of existing methods, especially for the difficult case, where the data are highly correlated and coupled. Moreover, we show its false detection of directed dependencies due to instantaneous couplings effect is lower than that of existing measures. We also show applicability of the proposed estimator on real intracranial electroencephalography data.

Co-movement of precious metals and forecasting using scale by scale wavelet transform

2017 ◽  
Vol 04 (01) ◽  
pp. 1750007 ◽  
Author(s):  
Emrah Oral ◽  
Gazanfer Unal
Keyword(s):  
Time Series ◽  
Wavelet Transform ◽  
Moving Average ◽  
Precious Metals ◽  
Wavelet Coherence ◽  
Frequency Scale ◽  
Time Space ◽  
Daily Data ◽  
Gold Silver ◽  
Highly Correlated

In this paper, a new approach is proposed to improve forecasting performances. We analyze the co-movement of precious metals (daily data of gold, silver and platinum starting from July, 2011) using multiple wavelet coherence and determine the movement dependencies on frequency–time space. The data is split into frequencies using scale by scale continuous wavelet transform. All three time series retaining the same frequency scale are (i) selected, (ii) inversed and (ii) forecasted using multivariate model, Vector Auto Regressive Moving Average (VARMA). We conclude that the efficiency of VARMA forecasting is substantially increased because of same frequency highly correlated time series obtained by using scale by scale wavelet transform. Moreover, the direction of price shift (increasing/decreasing trend) is prospected to an adequately distinguishable degree.

scholarly journals Variability and trends in dynamical forcing of tropical lower stratospheric temperatures

2014 ◽  
Vol 14 (24) ◽  
pp. 13439-13453 ◽  
Author(s):  
S. Fueglistaler ◽  
M. Abalos ◽  
T. J. Flannaghan ◽  
P. Lin ◽  
W. J. Randel
Keyword(s):  
Heat Flux ◽  
Time Series ◽  
Reanalysis Data ◽  
Heat Fluxes ◽  
Momentum Balance ◽  
Latitude Belt ◽  
Eddy Heat Flux ◽  
Temperature Trends ◽  
Highly Correlated ◽  
Additional Support

Abstract. The contribution of dynamical forcing to variations and trends in tropical lower stratospheric 70 hPa temperature for the period 1980–2011 is estimated based on ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The dynamical forcing is estimated from the tropical mean residual upwelling calculated with the momentum balance equation, and with a simple proxy based on eddy heat fluxes averaged between 25° and 75° in both hemispheres. The thermodynamic energy equation with Newtonian cooling is used to relate the dynamical forcing to temperature. The deseasonalised, monthly mean time series of all four calculations are highly correlated (~ 0.85) with temperature for the period 1995–2011 when variations in radiatively active tracers are small. All four calculations provide additional support to previously noted prominent aspects of the temperature evolution 1980–2011: an anomalously strong dynamical cooling (~ −1 to −2 K) following the Pinatubo eruption that partially offsets the warming from enhanced aerosol, and a few years of enhanced dynamical cooling (~ −0.4 K) after October 2000 that contributes to the prominent drop in water entering the stratosphere at that time. The time series of dynamically forced temperature calculated with the same method are more highly correlated and have more similar trends than those from the same reanalysis but with different methods. For 1980–2011 (without volcanic periods), the eddy heat flux calculations give a dynamical cooling of ~ −0.1 to ~ −0.25 K decade−1 (magnitude sensitive to latitude belt considered and reanalysis), largely due to increasing high latitude eddy heat flux trends in September and December–January. The eddy heat flux trends also explain the seasonality of temperature trends very well, with maximum cooling in January–February. Trends derived from momentum balance calculations show near-zero annual mean dynamical cooling, with weaker seasonal trends especially in December–January. These contradictory results arising from uncertainties in data and methods are discussed and put in context to previous analyses.

Analysis of historic jack pine budworm outbreaks in the Prairie provinces of Canada

1988 ◽  
Vol 18 (9) ◽  
pp. 1152-1158 ◽  
Author(s):  
W. Jan A. Volney
Keyword(s):  
Time Series ◽  
Severity Index ◽  
Jack Pine ◽  
Stationary Time Series ◽  
Sufficient Information ◽  
Outbreak Area ◽  
Jack Pine Budworm ◽  
Annual Time Series ◽  
Time Series Analyses ◽  
Highly Correlated

The annual Forest Insect and Disease Survey reports of the Canadian Forestry Service were used to develop a jack pine budworm (Choristoneurapinus Freeman) defoliation severity index for a 50-year span. The region covered was the western half of the host's (Pinusbanksiana Lamb.) range. An interpretation of this record permitted the construction of an annual time series of the total area moderately to severely or severely defoliated. The area of outbreaks has increased over the period. This trend was removed from the data to obtain a stationary time series. Analyses of the time series showed that there was a statistically significant periodicity to the size of outbreaks. An examination of the sample autocorrelation function revealed that only the past year's outbreak area was significantly correlated with that of the current year's outbreak. The model identified by applying the Box–Jenkins methodology to these results was inadequate, indicating that the series itself does not contain sufficient information for predictions. Outbreak area and the total area burned in Manitoba and Saskatchewan 4–7 years previously were highly correlated. Despite the crudity of the data, these relations could be exploited to develop predictors of outbreak size and occurrence. The significance of these results for forest management in the region is discussed.

Dynamic correlation of Eastern and Western markets and forecasting: Scale-by-scale wavelet-based approach

2017 ◽  
Vol 04 (04) ◽  
pp. 1750040 ◽  
Author(s):  
Emrah Oral ◽  
Gazanfer Unal
Keyword(s):  
Time Series ◽  
Wavelet Transform ◽  
Moving Average ◽  
Wavelet Coherence ◽  
Vector Autoregressive ◽  
Frequency Space ◽  
Time Frequency ◽  
Dynamic Correlation ◽  
Frequency Scale ◽  
Highly Correlated

In this paper, dynamic four-dimensional (4D) correlation of eastern and western markets is analyzed. A wavelet-based scale-by-scale analysis method has been introduced to model and forecast stock market data for strongly correlated time intervals. The daily data of stock markets of SP500, FTSE and DAX (western markets) and NIKKEI, TAIEX and KOSPI (eastern markets) are obtained from 2009 to the end of 2016 and their co-movement dependencies on time–frequency space using 4D multiple wavelet coherence (MWC) are determined. Once the data is detached into levels of different frequencies using scale-by-scale continuous wavelet transform, all of the time series possessing the same frequency scale are selected, inversed and forecasted using multivariate model, vector autoregressive moving average (VARMA). It is concluded that the efficiency of forecasting is increased substantially using the same-frequency highly correlated time series obtained by scale-by-scale wavelet transform. Moreover, the increasing or decreasing trend of prospected price shift is foreseen fairly well.

Fireproof killer whales (Orcinus orca): flame-retardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada

2006 ◽  
Vol 63 (1) ◽  
pp. 224-234 ◽  
Author(s):  
Peter S Ross
Keyword(s):  
British Columbia ◽  
Trophic Level ◽  
Polybrominated Diphenyl Ethers ◽  
Marine Mammals ◽  
Polychlorinated Biphenyl ◽  
High Trophic Level ◽  
Orcinus Orca ◽  
Weight Of Evidence ◽  
Older Individuals ◽  
Killer Whales

Long-lived and high trophic level marine mammals are vulnerable to accumulating often very high concentrations of persistent chemicals, including pesticides, industrial by-products, and flame retardants. In the case of killer whales (Orcinus orca), some of the older individuals currently frequenting the coastal waters of British Columbia (BC) were born during the First World War, well before the advent of widespread chemical manufacture and use. BC's killer whales are now among the most polychlorinated biphenyl (PCB) contaminated marine mammals in the world. While the "legacy" PCBs have largely been banned, polybrominated diphenyl ethers (PBDEs) have recently emerged as a major concern. The endocrine-disrupting nature of these two persistent fire retardants in biota spells trouble at the top of the food chain, with increasing evidence of effects on reproductive health, the immune system, and development in exposed mammals. The heavy contamination of BC's killer whales, coupled with their long life span and high trophic level, highlights the need for a "weight of evidence" approach in research, conservation planning, and regulatory decisions. Given the global nature of contaminant dispersion, such approaches can only be effective when carried out on both national and international scales.

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