The interplay between fishery yield and top predator culling in a multispecies fishery context

2020 ◽  
Vol 37 (3) ◽  
pp. 351-363
Author(s):  
Michel Iskin da S Costa ◽  
Lucas Dos Anjos
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Fisheries Management ◽  
Fishery Management ◽  
Target Species ◽  
Top Predator ◽  
Predator Removal ◽  
Top Predators ◽  
Theoretical Population

Abstract In food webs, fishery can play the role of top predator, competing thus with other top predators for valuable food resources. In this view, it has been claimed in fisheries management that culling of top predators can be a means to improve fishery yield. To investigate this hypothesis, we use theoretical population models to assess in a multispecies context how fishery yield from target species harvest responds to top predator cull. Defying crisp summary, the four analysed food web models show that this response may be either positive or negative or both, indicating that in terms of multispecies fishery management the harvest yield may not accrue as a consequence of predator removal. In addition, this multitude of behaviours points also to the fact that the response of fishery yield to top predator cull may be difficult to assess.

scholarly journals Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes

2013 ◽  
Vol 71 (2) ◽  
pp. 406-416 ◽  
Author(s):  
T. O. M. Reilly ◽  
H. M. Fraser ◽  
R. J. Fryer ◽  
J. Clarke ◽  
S. P. R. Greenstreet
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Levels ◽  
Top Down ◽  
Bottom Up ◽  
Control Processes ◽  
Top Predators ◽  
Environmental Status ◽  
Fish Predators ◽  
Firth Of Forth

Abstract Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416. Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.

scholarly journals Eurasian milfoil in Gulf of Mexico estuaries: does invasion of complex submerged vegetation lead to a “trophic dead end” in estuarine food webs?

2018 ◽  
Author(s):  
Charles W Martin ◽  
John F Valentine
Keyword(s):  
Gulf Of Mexico ◽  
Food Web ◽  
Food Webs ◽  
Aquatic Vegetation ◽  
Myriophyllum Spicatum ◽  
Mobile Bay ◽  
Dead End ◽  
Faunal Communities ◽  
Eurasian Milfoil

Estuaries of the northern Gulf of Mexico contain an abundance of habitat-forming submerged aquatic vegetation (SAV) that provide refuge and protection for a variety of freshwater, estuarine, and marine organisms. However, many of these estuaries now contain numerous exotic species, the ultimate impacts of which are unclear. In the Mobile-Tensaw Delta, located in the upper portion of Mobile Bay, Alabama (USA), Eurasian milfoil (Myriophyllum spicatum, hereafter referred to as Myriophyllum) is now the most dominant submerged macrophyte. Myriophyllum is a structurally-complex macrophyte with the potential to dramatically alter estuarine food webs through reduced encounter rates between predators and their prey and other mechanisms. Previously, we surveyed faunal communities using throw traps, trawls, cores, and suction sampling to compare milfoil assemblages with other native macrophytes to explore the interactive role of hydrology, diel periodicity, and macrophyte presence in influencing community structure. Here, we use this previously collected data to generate a preliminary food web analyses to determine if milfoil, due to its high complexity, creates a "trophic dead end" and limits higher trophic level production. We found the number of nodes, links, linkage density, and connectance to all be greater in milfoil than Vallisneria americana (hereafter referred to as Vallisneria), indicating that a diverse, productive, and highly connected food web exists in this invasive habitat.

Coupling Modules in Space: A Landscape Theory

2011 ◽  
Author(s):  
Kevin S. McCann
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Large Scale ◽  
Landscape Scale ◽  
Food Web Structure ◽  
Web Structure ◽  
Web Architecture ◽  
Individual Traits ◽  
Bird Feeder

This chapter examines food webs at the landscape scale by focusing on the large-scale food web architecture that is deeply constrained by space. It begins with a discussion of how variability in space, time, and food web structure, coupled with the ability of organisms to rapidly respond to variation, affect the maintenance of the food web and its functions. It then explains how individual traits such as body size and foraging behavior relate to food web structure in space and time. It also considers the role of spatial constraints on food webs and how the existence of fast–slow pathways coupled by mobile adaptive predators gives rise to spatial asynchrony in the resources. The chapter concludes with a review of some empirical examples to show that some food webs display the bird feeder effect and that resource coupling of distinct habitats appears to stabilize food webs.

scholarly journals Strong nutrient-plant interactions enhance the stability of ecosystems

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Zachariah G. Schonberger ◽  
Kevin McCann ◽  
Gabriel Gellner
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Plant Interactions ◽  
Ecosystem Models ◽  
Resource Interactions ◽  
Ecosystem Theory ◽  
The Stability ◽  
Ecosystem Interactions ◽  
Food Web Theory

AbstractModular food web theory shows how weak energetic fluxes resulting from consumptive interactions plays a major role in stabilizing food webs in space and time. Despite the reliance on energetic fluxes, food web theory surprisingly remains poorly understood within an ecosystem context that naturally focuses on material fluxes. At the same time, while ecosystem theory has employed modular nutrient-limited ecosystem models to understand how limiting nutrients alter the structure and dynamics of food webs, ecosystem theory has overlooked the role of key ecosystem interactions and their strengths (e.g., plant-nutrient; R-N) in mediating the stability of nutrient-limited ecosystems. Here, towards integrating food web theory and ecosystem theory, we first briefly review consumer-resource interactions (C-R) highlighting the relationship between the structure of C-R interactions and the stability of food web modules. We then translate this framework to nutrient-based systems, showing that the nutrient-plant interaction behaves as a coherent extension of current modular food web theory; however, in contrast to the rule that weak C-R interactions tend to be stabilizing we show that strong nutrient-plant interactions are potent stabilizers in nutrient-limited ecosystem models.

scholarly journals Aggregating a Plankton Food Web: Mathematical versus Biological Approaches

Mathematics ◽  
2018 ◽  
Vol 6 (12) ◽  
pp. 336 ◽  
Author(s):  
Ferenc Jordán ◽  
Anett Endrédi ◽  
Wei-chung Liu ◽  
Domenico D’Alelio
Keyword(s):  
Network Analysis ◽  
Food Web ◽  
Food Webs ◽  
Functional Role ◽  
Alternative Perspective ◽  
Connection Pattern ◽  
Unique Species ◽  
Topological Position ◽  
Biological Nature

Species are embedded in a web of intricate trophic interactions. Understanding the functional role of species in food webs is of fundamental interests. This is related to food web position, so positional similarity may provide information about functional overlap. Defining and quantifying similar trophic functioning can be addressed in different ways. We consider two approaches. One is of mathematical nature involving network analysis where unique species can be defined as those whose topological position is very different to others in the same food web. A species is unique if it has very different connection pattern compared to others. The second approach is of biological nature, based on trait-based aggregations. Unique species are not easy to aggregate with others because their traits are not in common with the ones of most others. Our goal here is to illustrate how mathematics can provide an alternative perspective on species aggregation, and how this is related to its biological counterpart. We illustrate these approaches using a toy food web and a real food web and demonstrate the sensitive relationships between those approaches. The trait-based aggregation focusing on the trait values of size (sv) can be best predicted by the mathematical aggregation algorithms.

Nutrient inputs versus piscivore biomass as the primary driver of reservoir food webs

2013 ◽  
Vol 70 (3) ◽  
pp. 367-380 ◽  
Author(s):  
Bryan T. Kinter ◽  
Stuart A. Ludsin
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Striped Bass ◽  
Gizzard Shad ◽  
Hybrid Striped Bass ◽  
Top Predator ◽  
Nutrient Inputs ◽  
Food Web Structure ◽  
Introduced Predators ◽  
The Impact

We used an ecosystem-based modeling approach, Ecopath with Ecosim, to explore the relative importance of a top-down biotic management lever (top predator introduction) versus a bottom-up abiotic management lever (alteration of nutrient inputs) in regulating biomass in reservoir food webs. To do so, we modeled three Ohio reservoirs that varied in ecosystem productivity. For each, we simulated five hybrid striped bass (Morone chrysops × Morone saxatilis) (introduced top predator) biomass levels at three nutrient input levels (n = 15 simulations per reservoir). Nutrient inputs influenced the food web more than introduced predators within each reservoir. Further, across all three reservoirs, the impact of stocked hybrid striped bass on the equilibrium biomass of phytoplankton, prey fish (gizzard shad, Dorosoma cepedianum), and native top predators (e.g., largemouth bass, Micropterus salmoides) was <3%, <14%, and <20%, respectively, of the maximum impact of changes in nutrient inputs on these components. Thus, in mesotrophic to hypereutrophic reservoirs that are dominated by omnivorous gizzard shad, manipulating allochthonous inputs of nutrients offers agencies a more powerful means to regulate food web structure than manipulation of top predator biomass.

scholarly journals Eurasian milfoil in Gulf of Mexico estuaries: does invasion of complex submerged vegetation lead to a “trophic dead end” in estuarine food webs?

2018 ◽  
Author(s):  
Charles W Martin ◽  
John F Valentine
Keyword(s):  
Gulf Of Mexico ◽  
Food Web ◽  
Food Webs ◽  
Aquatic Vegetation ◽  
Myriophyllum Spicatum ◽  
Mobile Bay ◽  
Dead End ◽  
Faunal Communities ◽  
Eurasian Milfoil

Estuaries of the northern Gulf of Mexico contain an abundance of habitat-forming submerged aquatic vegetation (SAV) that provide refuge and protection for a variety of freshwater, estuarine, and marine organisms. However, many of these estuaries now contain numerous exotic species, the ultimate impacts of which are unclear. In the Mobile-Tensaw Delta, located in the upper portion of Mobile Bay, Alabama (USA), Eurasian milfoil (Myriophyllum spicatum, hereafter referred to as Myriophyllum) is now the most dominant submerged macrophyte. Myriophyllum is a structurally-complex macrophyte with the potential to dramatically alter estuarine food webs through reduced encounter rates between predators and their prey and other mechanisms. Previously, we surveyed faunal communities using throw traps, trawls, cores, and suction sampling to compare milfoil assemblages with other native macrophytes to explore the interactive role of hydrology, diel periodicity, and macrophyte presence in influencing community structure. Here, we use this previously collected data to generate a preliminary food web analyses to determine if milfoil, due to its high complexity, creates a "trophic dead end" and limits higher trophic level production. We found the number of nodes, links, linkage density, and connectance to all be greater in milfoil than Vallisneria americana (hereafter referred to as Vallisneria), indicating that a diverse, productive, and highly connected food web exists in this invasive habitat.

scholarly journals The interplay among prey preference, nutrient enrichment and stability in an omnivory system

2009 ◽  
Vol 69 (4) ◽  
pp. 1027-1035 ◽  
Author(s):  
LDB. Faria ◽  
MIS. Costa
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Interactions ◽  
Nutrient Enrichment ◽  
Strong Influence ◽  
Prey Preference ◽  
Top Predator ◽  
The Subject ◽  
The Stability

Food webs usually display an intricate mix of trophic interactions where multiple prey are common. In this context omnivory has been the subject of intensive analysis regarding food web stability and structure. In a three species omnivory setting it is shown that the modeling of prey preference by the top predator may exert a strong influence on the short as well as on the long term dynamics of the respective food web. Clearly, this has implications concerning the stability and the structure of omnivory systems under disturbances such as nutrient enrichment.

The Role of Stochastic Simulations to Extend Food Web Analyses

2011 ◽  
pp. 163-196 ◽  
Author(s):  
Marco Scotti
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Position ◽  
Interaction Strength ◽  
Skewed Distribution ◽  
Stochastic Simulations ◽  
Trophic Chain ◽  
Dominance Relations ◽  
Top Predators ◽  
Secondary Extinction

Food webs are schematic representations of who eats whom in ecosystems. They are widely used in linking process to pattern (e.g., degree distribution and vulnerability) and investigating the roles played by particular species within the interaction web (e.g., centrality indices and trophic position). First, I present the dominator tree, a topological structure reducing food web complexity into linear pathways that are essential for energy delivery. Then, I describe how the dominance relations based on dominator trees extracted from binary food webs may be modified by including interaction strength. Consequences related to the skewed distribution of weak links towards the trophic chain are discussed to explain higher risks of secondary extinction that characterize top predators dominated by basal species. Finally, stochastic simulations are introduced to suggest an alternative approach to static analyses based on food web topology. Ranking species importance using stochastic-based simulations partially contradicts the predictions based on network analyses.

When sharks are away, rays will play: effects of top predator removal in coral reef ecosystems

2020 ◽  
Vol 641 ◽  
pp. 145-157 ◽  
Author(s):  
CS Sherman ◽  
MR Heupel ◽  
SK Moore ◽  
A Chin ◽  
CA Simpfendorfer
Keyword(s):  
Coral Reef ◽  
Video Frame ◽  
Top Predator ◽  
Mesopredator Release ◽  
Predator Removal ◽  
Ecosystem Effects ◽  
Top Predators ◽  
Coral Reef Ecosystems ◽  
Video Systems ◽  
Predator Abundance

Shark abundances are decreasing on many coral reefs, but the ecosystem effects of this loss are poorly understood. Rays are a prevalent mesopredator in tropical coral reef ecosystems that are preyed upon by top predators like sharks. Studies have suggested reduced predator abundances lead to increases in mesopredator abundance (mesopredator release). We examined the relationship between top predator abundances and the abundance and behaviour of 2 small benthic ray genera using baited remote underwater video systems (BRUVS) across 6 countries. Where predators were more abundant, 2 genera of small benthic rays were sighted less often, possibly because of lower abundances. Small ray behaviour was also significantly affected by predator abundance. Individuals of focal ray species visited BRUVS significantly fewer times at sites with higher predator abundances. Where predators were less abundant, rays spent significantly more time in the video frame, and were more likely to feed from bait bags. In addition to predator abundance, small ray presence was significantly influenced by reef relief and depth. Neotrygon spp. were more abundant on deeper, lower relief habitats, while Taeniura spp. were more prevalent in reef-associated shallow, high relief habitats. Overall, this study found that predator abundance had a significant effect on small benthic ray abundance and behaviour in the presence of BRUVS. Results demonstrate that changes in both abundance and behaviour associated with predator loss may make the interpretation of phenomenon like mesopredator release more difficult to identify unless behavioural effects are considered.

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