Size Spectrum Theory

2019 ◽  
pp. 15-37
Author(s):  
Ken H. Andersen
Keyword(s):  
Body Size ◽  
Power Law ◽  
Clearance Rate ◽  
Size Structure ◽  
Prey Size ◽  
Marine Ecosystem ◽  
Size Spectrum ◽  
Predator Prey ◽  
Predation Mortality ◽  
Size Preference

This chapter follows the size-structure of the entire marine ecosystem. It shows how the Sheldon spectrum emerges from predator–prey interactions and the limitations that physics and physiology place on individual organisms. How predator–prey interactions and physiological limitations scale with body size are the central assumptions in size spectrum theory. To that end, this chapter first defines body size and size spectrum. Next, it shows how central aspects of individual physiology scale with size: metabolism, clearance rate, and prey size preference. On that basis, it is possible to derive a power-law representation of the size spectrum by considering a balance between the needs of an organism (its metabolism) and the encountered prey, which is determined by the spectrum, the clearance rate, and the size preference. Lastly, the chapter uses the solution of the size spectrum to derive the expected size scaling of predation mortality.

scholarly journals Fish life history dynamics: shifts in prey size structure evoke shifts in predator maturation traits

2016 ◽  
Vol 73 (4) ◽  
pp. 693-708 ◽  
Author(s):  
Brian J. Shuter ◽  
Henrique C. Giacomini ◽  
Derrick de Kerckhove ◽  
Kris Vascotto
Keyword(s):  
Life History ◽  
Lake Trout ◽  
Size Structure ◽  
Prey Size ◽  
Empirical Support ◽  
Growth Efficiency ◽  
Size Ratio ◽  
Size Spectrum ◽  
Lower Growth ◽  
Predator Prey

A bioenergetic framework is developed to predict optimal life history responses to environmentally driven changes in the rate of energy production by a predator. This framework is used to predict the responses of age at maturation, size at maturation, and asymptotic size to changes in the predator–prey size ratio. Predators feeding on relatively smaller prey (i.e., having larger predator–prey size ratios) have lower growth efficiency and are predicted as a consequence to mature earlier, at smaller sizes, and reach smaller asymptotic sizes. This prediction was tested using a 78-year time series (1936–2013) of data from a natural population of lake trout (Salvelinus namaycush) in Lake Opeongo, Algonquin Park, Ontario, Canada. A large decrease in the predator–prey size ratio for this population occurred over the period 1950–1965 when a preferred prey (cisco, Coregonus artedii) was introduced to the lake. This decrease was followed by ∼20 years of constancy in the size ratio and then 25 years of progressive increase. Lake trout life history responded plastically during both periods and consistently with our predictions. Extensive analysis of available data provided little empirical support for alternative explanations for the observed changes in lake trout size and maturity (e.g., changes in cisco and (or) lake trout density and harvest rates). The framework developed here derives plastic life history changes from fixed developmental thresholds that are based on the scaling of net production with body size and can be used to predict the shape of maturation reaction norms for the major shifts in community structure that are compactly summarized by changes in size spectrum parameters.

Measures of fish community size structure as indicators for stream monitoring programs

2020 ◽  
Vol 77 (5) ◽  
pp. 824-835
Author(s):  
Isaac A. Sutton ◽  
Nicholas E. Jones
Keyword(s):  
Land Use ◽  
Body Size ◽  
Power Law ◽  
Size Range ◽  
Size Structure ◽  
Size Spectrum ◽  
Community Size ◽  
Stream Monitoring ◽  
Lotic Ecosystem ◽  
Size Diversity

Characterization of community size structure presents an alternative to taxa-based approaches commonly applied to assess lotic ecosystem health. However, few studies have explored the relationship between community size structure and land use stresses in lotic systems. In the present study, we investigated use of metrics including mean body size, body size range, size diversity, size evenness, and the size spectrum slope as indicators of land use disturbance in streams. We also explored the effects of sampling intensity (one- versus three-pass electrofishing) on these size-based variables. We found significant decreases in size range and diversity with increased urban cover. In contrast, mean body size, size evenness, and size spectrum slopes were unrelated to variation in land use. Fewer than 25% of samples collected conformed to the power law model predicted for size distributions in aquatic ecosystems. However, increased departure from the power law form was related to agricultural cover and the use of three-pass electrofishing.

Using an individual-based model of fish assemblages to study the response of size spectra to changes in fishing

2004 ◽  
Vol 61 (3) ◽  
pp. 414-431 ◽  
Author(s):  
Yunne-Jai Shin ◽  
Philippe Cury
Keyword(s):  
Fish Assemblages ◽  
Prey Availability ◽  
Empirical Studies ◽  
Marine Ecosystem ◽  
Predatory Fish ◽  
Size Spectrum ◽  
Individual Based Model ◽  
Size Spectra ◽  
Predation Mortality ◽  
Body Shapes

For most fish species, strong environmental constraints imposed by living in an aquatic medium have produced converging streamlined body forms without prehensile appendices. This similarity in body shapes highlights a common predation constraint: a predatory fish must have a jaw large enough to swallow its prey. Fish diets may then reflect local prey availability and predator–prey size ratios. Based on this size-based opportunistic predation process, the multispecies individual-based model OSMOSE (Object-oriented Simulator of Marine ecOSystem Exploitation) is used to investigate to what extent the size distribution of fish communities can contribute to better our understanding of the functioning of marine food webs and the ecosystem effects of fishing. Strong similarity in shape is found between simulated size spectra and those described in empirical studies. The existence of a curvature towards small size classes is discussed in the light of the size-based predation hypothesis, which implies that smaller fish may undergo higher predation mortality. Applying linear and quadratic regressions to the simulated size spectra allows the detection of variations in fishing pressure and the proposal of different ways to quantify them. In particular, it is shown that the slope of the size spectrum decreases quasilinearly with fishing mortality and that the curvature could help to detect ecosystem overexploitation.

scholarly journals Running the gauntlet: the predation environment of small fish in the northern Gulf of St Lawrence, Canada

2005 ◽  
Vol 62 (3) ◽  
pp. 412-416 ◽  
Author(s):  
Daniel E. Duplisea
Keyword(s):  
Body Size ◽  
North Sea ◽  
Prey Size ◽  
Small Fish ◽  
Size Spectra ◽  
Predator Prey ◽  
The North ◽  
Prefer Prey ◽  
Seal Population ◽  
The North Sea

Abstract Predation size spectra were constructed for the northern Gulf of St Lawrence, covering prey size ranges that include pre-recruit cod. Predation by fish and harp seals was modelled with a log-normally distributed predator–prey size ratio along with a relationship between predator body size and the energy required. Fish concentrate predation on prey of weight 0.5–2 g, whereas harp seals prefer prey of 60–125 g. It is speculated that predation caused by harp seals on pre-recruits could be a major factor limiting cod recruitment in the system. The northern Gulf of St Lawrence is a cold boreal system with a large predatory seal population, and cod recruit older than elsewhere. Therefore, cod recruitment may be more strongly affected by predation in the northern Gulf of St Lawrence than in warmer systems such as the North Sea, where recruitment is strongly influenced by temperature.

scholarly journals Climate-induced changes in bottom-up and top-down processes independently alter a marine ecosystem

2012 ◽  
Vol 367 (1605) ◽  
pp. 2962-2970 ◽  
Author(s):  
Malte Jochum ◽  
Florian D. Schneider ◽  
Tasman P. Crowe ◽  
Ulrich Brose ◽  
Eoin J. O'Gorman
Keyword(s):  
Body Size ◽  
Body Mass ◽  
Nutrient Enrichment ◽  
Size Structure ◽  
Marine Ecosystem ◽  
Shore Crab ◽  
Top Predator ◽  
Top Down ◽  
Microalgal Biomass ◽  
Bottom Up

Climate change has complex structural impacts on coastal ecosystems. Global warming is linked to a widespread decline in body size, whereas increased flood frequency can amplify nutrient enrichment through enhanced run-off. Altered population body-size structure represents a disruption in top-down control, whereas eutrophication embodies a change in bottom-up forcing. These processes are typically studied in isolation and little is known about their potential interactive effects. Here, we present the results of an in situ experiment examining the combined effects of top-down and bottom-up forces on the structure of a coastal marine community. Reduced average body mass of the top predator (the shore crab, Carcinus maenas ) and nutrient enrichment combined additively to alter mean community body mass. Nutrient enrichment increased species richness and overall density of organisms. Reduced top-predator body mass increased community biomass. Additionally, we found evidence for an allometrically induced trophic cascade. Here, the reduction in top-predator body mass enabled greater biomass of intermediate fish predators within the mesocosms. This, in turn, suppressed key micrograzers, which led to an overall increase in microalgal biomass. This response highlights the possibility for climate-induced trophic cascades, driven by altered size structure of populations, rather than species extinction.

scholarly journals Joint evolution of predator body size and prey-size preference

2007 ◽  
Vol 22 (6) ◽  
pp. 771-799 ◽  
Author(s):  
Tineke A. Troost ◽  
Bob W. Kooi ◽  
Ulf Dieckmann
Keyword(s):  
Body Size ◽  
Prey Size ◽  
Size Preference ◽  
Joint Evolution

scholarly journals Macroscale patterns of oceanic zooplankton composition and size structure

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Manoela C. Brandão ◽  
Fabio Benedetti ◽  
Séverine Martini ◽  
Yawouvi Dodji Soviadan ◽  
Jean-Olivier Irisson ◽  
...  
Keyword(s):  
Body Size ◽  
Community Composition ◽  
Climate Models ◽  
Size Structure ◽  
Fish Larvae ◽  
The Body ◽  
Community Level ◽  
Feeding Strategies ◽  
Size Spectrum ◽  
Zooplankton Abundance

AbstractOcean plankton comprise organisms from viruses to fish larvae that are fundamental to ecosystem functioning and the provision of marine services such as fisheries and CO2 sequestration. The latter services are partly governed by variations in plankton community composition and the expression of traits such as body size at community-level. While community assembly has been thoroughly studied for the smaller end of the plankton size spectrum, the larger end comprises ectotherms that are often studied at the species, or group-level, rather than as communities. The body size of marine ectotherms decreases with temperature, but controls on community-level traits remain elusive, hindering the predictability of marine services provision. Here, we leverage Tara Oceans datasets to determine how zooplankton community composition and size structure varies with latitude, temperature and productivity-related covariates in the global surface ocean. Zooplankton abundance and median size decreased towards warmer and less productive environments, as a result of changes in copepod composition. However, some clades displayed the opposite relationships, which may be ascribed to alternative feeding strategies. Given that climate models predict increasingly warmed and stratified oceans, our findings suggest that zooplankton communities will shift towards smaller organisms which might weaken their contribution to the biological carbon pump.

Size-based approaches to aquatic ecosystems and fisheries science: a symposium in honour of Rob Peters

2016 ◽  
Vol 73 (4) ◽  
pp. 471-476 ◽  
Author(s):  
Henrique C. Giacomini ◽  
Brian J. Shuter ◽  
Julia K. Baum
Keyword(s):  
Community Structure ◽  
Body Size ◽  
Empirical Studies ◽  
Ecosystem Dynamics ◽  
Future Research ◽  
Size Spectrum ◽  
Ecological Change ◽  
Size Spectra ◽  
Predator Prey ◽  
Fisheries Science

This special issue honours Rob Peters’ outstanding contributions to the field of aquatic ecology. It focuses on the size spectrum approach — in which individual organisms, rather than species, are the most basic biological unit — and highlights applications of this approach to fisheries management. The 21 papers in this issue cover three subject areas: (i) the use of size spectra to characterize variation in community structure, (ii) the development of size-based models of ecosystem dynamics to address fisheries questions, and (iii) applications of size-based theory to examine the consequences of variation in predator–prey size relationships, body size – trophic level relationships, and body size – life history relationships. The empirical studies herein demonstrate the utility of size spectra as indicators of population or community structure and for detecting impacts associated with environmental change. Future research focused on refining size-based sampling methods, standardizing metrics and analytical methods, understanding model sensitivity to the underlying assumptions, and comparative studies across ecosystems will enhance our ability to reliably interpret changes in size spectrum characteristics, thus facilitating their use as indicators of ecological change.

scholarly journals Ecological consequences of body size decline in harvested fish species: positive feedback loops in trophic interactions amplify human impact

2013 ◽  
Vol 9 (2) ◽  
pp. 20121103 ◽  
Author(s):  
Asta Audzijonyte ◽  
Anna Kuparinen ◽  
Rebecca Gorton ◽  
Elizabeth A. Fulton
Keyword(s):  
Body Size ◽  
Positive Feedback ◽  
Species Interactions ◽  
Management Practices ◽  
Marine Ecosystem ◽  
Ecosystem Model ◽  
Feedback Loops ◽  
Predation Mortality ◽  
Marine Ecosystem Model ◽  
Body Sizes

Humans are changing marine ecosystems worldwide, both directly through fishing and indirectly through climate change. One of the little explored outcomes of human-induced change involves the decreasing body sizes of fishes. We use a marine ecosystem model to explore how a slow (less than 0.1% per year) decrease in the length of five harvested species could affect species interactions, biomasses and yields. We find that even small decreases in fish sizes are amplified by positive feedback loops in the ecosystem and can lead to major changes in natural mortality. For some species, a total of 4 per cent decrease in length-at-age over 50 years resulted in 50 per cent increase in predation mortality. However, the magnitude and direction in predation mortality changes differed among species and one shrinking species even experienced reduced predation pressure. Nevertheless, 50 years of gradual decrease in body size resulted in 1–35% decrease in biomasses and catches of all shrinking species. Therefore, fisheries management practices that ignore contemporary life-history changes are likely to overestimate long-term yields and can lead to overfishing.

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