A macroecological perspective on the fluctuations of exploited fish populations

2021 ◽  
Vol 665 ◽  
pp. 177-183
Author(s):  
AM Segura ◽  
R Wiff ◽  
AJ Jaureguizar ◽  
AC Milessi ◽  
G Perera
Keyword(s):  
Size Dependence ◽  
Trophic Position ◽  
The Body ◽  
Fish Populations ◽  
Population Fluctuations ◽  
Interacting Species ◽  
Temporal Variance ◽  
Density Relationship ◽  
Taylor’S Law ◽  
Macroscopic Approach

The natural variability of fish populations is increased by exploitation, but the specific mechanisms driving this variability are still debated. We propose a macroscopic approach combining the size-density relationship and Taylor’s law to predict the temporal variance of exploited and unexploited fish populations. Using information from 11 years of fishery-independent abundance surveys, we showed that the body-size dependence of the variance of exploited (targeted) and unexploited (non-targeted or bycatch) fish populations can be accurately predicted. Targeted fish populations showed a variability that was 2 orders of magnitude greater than that of non-targeted fish populations. Such variability was explained solely by the higher relative abundance of the former, regardless of their specific trophic position, while aggregated community fluctuation was lower in a high trophic position group. This study showed the usefulness of the macroscopic approach to predict fish variability and fishing effect in the whole community. This approach is complementary to other modeling strategies and seems to be useful in tackling the problem of variability in population fluctuations of exploited fish, particularly in cases where specific details of the interacting species are lacking.

scholarly journals The body-size dependence of mutual interference

2014 ◽  
Vol 10 (6) ◽  
pp. 20140261 ◽  
Author(s):  
John P. DeLong
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Size Dependence ◽  
Empirical Support ◽  
Mutual Interference ◽  
The Body ◽  
Wide Range ◽  
Stabilizing Effect ◽  
Body Sizes ◽  
Size Scales

The parameters that drive population dynamics typically show a relationship with body size. By contrast, there is no theoretical or empirical support for a body-size dependence of mutual interference, which links foraging rates to consumer density. Here, I develop a model to predict that interference may be positively or negatively related to body size depending on how resource body size scales with consumer body size. Over a wide range of body sizes, however, the model predicts that interference will be body-size independent. This prediction was supported by a new dataset on interference and consumer body size. The stabilizing effect of intermediate interference therefore appears to be roughly constant across size, while the effect of body size on population dynamics is mediated through other parameters.

Ecophysiological determinants of the variation in 137Cs concentrations between and within lacustrine fish populations

2005 ◽  
Vol 62 (12) ◽  
pp. 2727-2739 ◽  
Author(s):  
Marcus Sundbom ◽  
Markus Meili
Keyword(s):  
Body Size ◽  
Trophic Position ◽  
Fish Populations ◽  
Chernobyl Fallout ◽  
Population Means ◽  
Activity Concentrations ◽  
Resource Specialization ◽  
Total Variability ◽  
Biomagnification Factors ◽  
Fish Trophic Position

One decade after the Chernobyl fallout, the variability of 137Cs activity concentrations among fish within a Swedish lake was >20-fold based on 1361 individuals from seven species collected continually during 1996–1999. Of the total variability, 64% was due to differences between species but only 7% due to temporal variation, which was 1.3-fold for the whole community and 1.3- to 2-fold for population means. Contamination increased with body size (0.6- to 6-fold) and decreased with body condition in most species (1.3-fold). Body size and time together accounted for about half of the total variation within populations. Fish 137Cs was related to differences in feeding ecology, both between and within populations. Biomagnification factors ranged from 2.4 to 5.8. Contamination was highest in piscivorous populations and individuals, intermediate in herbivores and zooplanktivores, and lowest in fish specialized in benthic invertebrates despite their association with contaminated sediments. The 137Cs variance within populations was not correlated with their niche width but moderately positively correlated with fish trophic position and strongly positively correlated with functional omnivory (diversity in prey 137Cs). We conclude that individual resource specialization is an important source of variation in 137Cs concentrations within fish populations.

Hyperplastic Forming: Process Potential and Factors Affecting Formability

1999 ◽  
Vol 601 ◽  
Author(s):  
Glenn S. Daehn ◽  
Vincent J. Vohnout ◽  
Subrangshu Datta
Keyword(s):  
Boundary Conditions ◽  
Sample Size ◽  
Active Control ◽  
High Velocity ◽  
Size Dependence ◽  
Recent Model ◽  
The Body ◽  
Electromagnetic Forming ◽  
Forming Process ◽  
Factors Affecting

AbstractThis paper has two distinct goals. First, we argue in an extended introduction that high velocity forming, as can be implemented through electromagnetic forming, is a technology that should be developed. As a process used in conjunction with traditional stamping, it may offer dramatically improved formability, reduced wrinkling and active control of springback among other advantages. In the body of the paper we describe the important factors that lead to improved formability at high velocity. In particular, high sample velocity can inhibit neck growth. There is a sample size dependence where larger samples have better ductility than those of smaller dimensions. These aspects are at least partially described by the recent model of Freund and Shenoy. In addition to this, boundary conditions imposed by sample launch and die impact can have important effects on formability.

Food chain length in a large floodplain river: planktonic or benthic reliance as a limiting factor

2017 ◽  
Vol 68 (7) ◽  
pp. 1336 ◽  
Author(s):  
M. Saigo ◽  
L. Ruffener ◽  
P Scarabotti ◽  
M. Marchese
Keyword(s):  
Chain Length ◽  
Food Chain ◽  
Trophic Position ◽  
Paraná River ◽  
The Body ◽  
Parana River ◽  
Ecosystem Size ◽  
Food Chain Length ◽  
Top Predators ◽  
Middle Paraná

Food chain length (FCL) is a key integrative variable describing ecosystem functioning. The aim of the present study was to test the hypothesis that the relative importance of planktonic and benthic energy pathways is a major factor affecting FCL in the Middle Paraná River. Samples were obtained from in eight waterbodies, measuring chlorophyll-a concentrations and the abundance of benthic invertebrates and the trophic position of top predators by stable isotope analysis. There was no evidence that resource availability, disturbances or ecosystem size limited FCL. Similarly, the body size and trophic position of predators were not correlated. However, the relative abundance of planktonic and benthic resources was correlated with FCL. In addition, stable isotopes analysis showed that the benthic reliance of top predators is correlated with their trophic position. The results of the present study indicate that because the major benthic primary consumer is a large fish (Prochilodus lineatus), the size structure of individual food chains is an important factor determining FCL. Whereas in floodplain rivers large detritivorous fishes are targets of commercial fishing, overfishing in the Middle Paraná River could be expected to increase FCL, the opposite effect to that seen in marine environments.

scholarly journals Loss of functionally unique species may gradually undermine ecosystems

2010 ◽  
Vol 278 (1713) ◽  
pp. 1886-1893 ◽  
Author(s):  
Eoin J. O'Gorman ◽  
Jon M. Yearsley ◽  
Tasman P. Crowe ◽  
Mark C. Emmerson ◽  
Ute Jacob ◽  
...  
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Ecosystem Functioning ◽  
Trophic Position ◽  
Interaction Strength ◽  
Natural Systems ◽  
Interacting Species ◽  
Weakly Interacting ◽  
Taxonomic Groups ◽  
Unique Species

Functionally unique species contribute to the functional diversity of natural systems, often enhancing ecosystem functioning. An abundance of weakly interacting species increases stability in natural systems, suggesting that loss of weakly linked species may reduce stability. Any link between the functional uniqueness of a species and the strength of its interactions in a food web could therefore have simultaneous effects on ecosystem functioning and stability. Here, we analyse patterns in 213 real food webs and show that highly unique species consistently tend to have the weakest mean interaction strength per unit biomass in the system. This relationship is not a simple consequence of the interdependence of both measures on body size and appears to be driven by the empirical pattern of size structuring in aquatic systems and the trophic position of each species in the web. Food web resolution also has an important effect, with aggregation of species into higher taxonomic groups producing a much weaker relationship. Food webs with fewer unique and less weakly interacting species also show significantly greater variability in their levels of primary production. Thus, the loss of highly unique, weakly interacting species may eventually lead to dramatic state changes and unpredictable levels of ecosystem functioning.

scholarly journals Body size–trophic position relationships among fishes of the lower Mekong basin

2017 ◽  
Vol 4 (1) ◽  
pp. 160645 ◽  
Author(s):  
Chouly Ou ◽  
Carmen G. Montaña ◽  
Kirk O. Winemiller
Keyword(s):  
Body Size ◽  
Trophic Interactions ◽  
Fish Assemblages ◽  
Trophic Position ◽  
Isotope Analysis ◽  
The Body ◽  
Tropical Fish ◽  
Feeding Guilds ◽  
Mekong Basin ◽  
Lower Mekong Basin

Body size is frequently claimed to be a major determinant of animal trophic interactions, yet few studies have explored relationships between body size and trophic interactions in rivers, especially within the tropics. We examined relationships between body size and trophic position (TP) within fish assemblages in four lowland rivers of the Lower Mekong Basin in Cambodia. Stable isotope analysis (based on δ 15 N) was used to estimate TP of common fish species in each river, and species were classified according to occupation of benthic versus pelagic habitats and major feeding guilds. Regression analysis yielded strong correlations between body size and TP among fishes from the Sesan and Sreprok rivers, but not those from the Mekong and Sekong rivers. The Mekong fish assemblage had higher average TP compared with those of other rivers. The relationship between body size and TP was positive and significantly correlated for piscivores and omnivores, but not for detritivores and insectivores. The body size–TP relationship did not differ between pelagic and benthic fishes. Body size significantly predicted TP within the orders Siluriformes and Perciformes, but not for Cypriniformes, the most species-rich and ecologically diverse order in the Lower Mekong River. We conclude that for species-rich, tropical fish assemblages with many detritivores and invertivores, body size would not be an appropriate surrogate for TP in food web models and other ecological applications.

scholarly journals Interannual temperature variability is a principal driver of low-frequency fluctuations in marine fish populations

2022 ◽  
Vol 5 (1) ◽  
Author(s):  
Peter van der Sleen ◽  
Pieter A. Zuidema ◽  
John Morrongiello ◽  
Jia Lin J. Ong ◽  
Ryan R. Rykaczewski ◽  
...  
Keyword(s):  
Marine Fish ◽  
Population Change ◽  
Environmental Variability ◽  
Trophic Position ◽  
Low Frequency ◽  
Economic Security ◽  
Fish Populations ◽  
Growth Variability ◽  
Sst Variability ◽  
Frequency Fluctuations

AbstractMarine fish populations commonly exhibit low-frequency fluctuations in biomass that can cause catch volatility and thus endanger the food and economic security of dependent coastal societies. Such variability has been linked to fishing intensity, demographic processes and environmental variability, but our understanding of the underlying drivers remains poor for most fish stocks. Our study departs from previous findings showing that sea surface temperature (SST) is a significant driver of fish somatic growth variability and that life-history characteristics mediate population-level responses to environmental variability. We use autoregressive models to simulate how fish populations integrate SST variability over multiple years depending on fish life span and trophic position. We find that simulated SST-driven population dynamics can explain a significant portion of observed low-frequency variability in independent observations of fisheries landings around the globe. Predictive skill, however, decreases with increasing fishing pressure, likely due to demographic truncation. Using our modelling approach, we also show that increases in the mean and variance of SST could amplify biomass volatility and lessen its predictability in the future. Overall, biological integration of high-frequency SST variability represents a null hypothesis with which to explore the drivers of low-frequency population change across upper-trophic marine species.

scholarly journals Size dependence of offspring production in isopods: a synthesis

ZooKeys ◽  
2018 ◽  
Vol 801 ◽  
pp. 337-357 ◽  
Author(s):  
Andrzej Antoł ◽  
Marcin Czarnoleski
Keyword(s):  
Parental Care ◽  
Clutch Size ◽  
Life Histories ◽  
Size Dependence ◽  
The Body ◽  
Offspring Size ◽  
Female Size ◽  
Indeterminate Growth ◽  
Offspring Number ◽  
Offspring Production

In isopods, parental care takes the form of offspring brooding in marsupial pouches. Marsupial brooding was an important step towards the origin of terrestrial lifestyles among isopods, but its potential role in shaping isopod life histories remains unknown. It is here considered that marsupial brooding imposes costs and creates a temporary association between the survival of mothers and that of their offspring. Integrating findings from different life history models, we predicted that the effects of marsupial brooding set selective conditions for the continuation of growth after maturation, which leads to indeterminate growth, and the production of larger offspring by larger females. Based on this perspective, a study on the size dependence of offspring production in the woodlouse Porcellioscaber was performed and the generality of the results was tested by reviewing the literature on offspring production in other isopods. In P.scaber and almost all the other studied isopods, clutch size is positively related to female size. Such dependence is a necessary pre-condition for the evolution of indeterminate growth. The body mass of P.scaber differed six-fold between the largest and smallest brooding females, indicating a high potential for post-maturation growth. Our review showed that offspring size is a rarely studied trait in isopods and that it correlates negatively with offspring number but positively with female size in nearly half of the studied species. Our study of P.scaber revealed similar patterns, but the positive effect of female size on offspring size occurred only in smaller broods, and the negative relation between clutch size and offspring size occurred only in larger females. We conclude that the intraspecific patterns of offspring production in isopods agree with theoretical predictions regarding the role of offspring brooding in shaping the adaptive patterns of female investment in growth, reproduction, and the parental care provided to individual offspring.

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