scholarly journals Seasonal habitat and length influence on the trophic niche of co-occurring tropical tunas in the eastern Atlantic Ocean

2019 ◽  
Vol 76 (1) ◽  
pp. 69-80 ◽  
Author(s):  
Fany Sardenne ◽  
N’Guessan Constance Diaha ◽  
Monin Justin Amandé ◽  
Iker Zudaire ◽  
Lydie I.E. Couturier ◽  
...  
Keyword(s):  
Trophic Position ◽  
Niche Partitioning ◽  
Niche Overlap ◽  
Monounsaturated Fatty Acids ◽  
Dry Mass ◽  
Trophic Niche ◽  
Top Predators ◽  
Thunnus Obesus ◽  
Eastern Atlantic Ocean ◽  
Tropical Tuna

In the Gulf of Guinea, bigeye tuna (Thunnus obesus; BET) and yellowfin tuna (Thunnus albacares; YFT) are an important part of commercial fisheries and play a prominent ecological role as top predators. Using fatty acid profiles and carbon and nitrogen stable isotopes, we examined their trophic niche partitioning in this understudied region. Trophic niche overlap was high (>70%), similar to percentages in other ocean basins. BET occupied a higher trophic position than YFT and fed on deeper prey (high δ15N values and high proportions of monounsaturated fatty acids). The trophic position of YFT decreased slightly in the last 15 years (δ15N values decreased by ∼0.5‰), suggesting a change in epipelagic communities, as observed in the eastern Pacific Ocean. Ontogenic changes were limited to BET. For both species, the dietary proportion of the diatom marker 20:5(n-3) increased in the seasonal upwelling area, highlighting the influence of seasonal habitat on the diet of tuna. The relatively lipid-rich muscle (∼6% dry mass) of Atlantic tropical tuna suggests a richer diet in this region than that of Indian Ocean tropical tuna and (or) differences in energy allocation strategies.

Body size as an important factor determining trophic niche partitioning in three syntopic rhinolophid bat species

Biologia ◽  
2013 ◽  
Vol 68 (1) ◽  
Author(s):  
Michal Andreas ◽  
Antonín Reiter ◽  
Eva Cepáková ◽  
Marcel Uhrin
Keyword(s):  
Species Coexistence ◽  
Niche Partitioning ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Prey Category ◽  
Faecal Pellets ◽  
Preferred Habitat ◽  
Stable Species ◽  
Percentage Volume ◽  
Body Sizes

AbstractWe investigated a community of syntopically occurring horseshoe bats (Rhinolophus hipposideros, R. euryale, R. ferrumequinum) in southern Slovakia. The faecal pellets of these bat species were collected in the field and later analysed under a dissecting microscope. The three species studied are known to be very similar as far as their ecology, echolocation and preferred habitats are concerned, but they diverge significantly in their body sizes. In this study, all three species fed predominantly on moths [59–80 percentage frequency (%f); 87–95 percentage volume (%vol)], but their diet compositions differed in the size of individuals consumed. The smallest bat species (R. hipposideros) fed only on the smallest moths (%f = 59; %vol = 87), the medium-sized species (R. euryale) mainly on medium-sized moths (%f = 60; %vol = 74) and the largest one (R. ferrumequinum) especially on the largest moths (%f = 54; %vol = 89). Despite similar preferred habitat and the main prey category, the rates of trophic niche overlap were surprisingly low. The trophic niche percentage overlap was 7–31% (computed from %f data) and 1–20% (computed from %vol data), respectively and suggests an extraordinary importance of mere divergences of bats in their body sizes for trophic niche partitioning and stable species coexistence.

scholarly journals Sympatry with the devil? Niche-based approach explains the mechanisms allowing coexistence of native and non-native salmonids

2016 ◽  
Author(s):  
Camille Musseau ◽  
Simone Vincenzi ◽  
Dušan Jesenšek ◽  
Stéphanie Boulêtreau ◽  
Frédéric Santoul ◽  
...  
Keyword(s):  
Rainbow Trout ◽  
Native Species ◽  
Niche Breadth ◽  
Trophic Position ◽  
Isotope Analysis ◽  
Growth Period ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Niche Shift ◽  
Marble Trout

AbstractNiche-based hypotheses have been proposed to explain processes and mechanisms of success in the establishment of non-native species into native communities. Competition due to niche overlap may lead to native species niche shift and to native species replacement. To understand the ecological consequences of trophic interactions between non-native rainbow trout and native and endangered marble trout, we used as model system the Idrijca river (Western Slovenia) in which marble trout occurs either in allopatry (MTa) or in sympatry (MTs) with rainbow trout (RTs). We focused on different metrics of niche change such as centroid shift, niche overlap and trophic niche breadth using stable isotope analysis (δ15N and δ13C). Our results showed plasticity in niche overlap between MTs and RTs and niche shift of marble trout when occurring in sympatry with RTs, but not due to a niche replacement of MTs by RTs. Niche breadth of marble trout increases in sympatry and the trophic position during the growth period was higher for MTs than MTa.

Spatial trophic variability of a coastal apex predator, the giant trevally Caranx ignobilis, in the western Indian Ocean

2020 ◽  
Vol 641 ◽  
pp. 195-208
Author(s):  
JR Glass ◽  
R Daly ◽  
PD Cowley ◽  
DM Post
Keyword(s):  
Indian Ocean ◽  
Trophic Ecology ◽  
Niche Breadth ◽  
Trophic Position ◽  
Western Indian Ocean ◽  
Trophic Niche ◽  
Niche Width ◽  
Apex Predator ◽  
Ontogenetic Changes ◽  
Top Predators

Top predators have substantial downstream effects on the structure, function, and resilience of ecosystems. The influence of top predators on an ecosystem can vary if they occur within multiple habitat types and have a wide niche breadth due to spatiotemporal changes in diet. We examined spatial patterns in trophic position and niche width for an economically important reef-associated fishery species, the giant trevally Caranx ignobilis. We sampled 4 localities in the western Indian Ocean representing different habitats: coral atolls, coastal reefs, and granitic islands. We analyzed isotopic ratios of carbon (13C/12C) and nitrogen (15N/14N), and performed compound-specific amino acid stable isotope analysis (AA-CSIA) to control for baseline nitrogen variation. Our analysis of 12 juveniles and 43 adults revealed wide variation in trophic niche breadth between sampling sites and an offshore to coastal gradient in carbon that drove niche distinctiveness between localities. We observed niche width patterns suggestive of ontogenetic changes in diet and habitat utilization and larger niche sizes at the oceanic island sites than the coastal site. Trophic position estimates ranged from 3.5-5, expanding the trophic range of C. ignobilis relative to previous studies using AA-CSIA and placing it at the equivalent trophic level as many predatory sharks. Our study corroborates prior evidence that C. ignobilis is an important apex predator in reef and island ecosystems. Additionally, we show how evaluating spatiotemporal components of trophic ecology of marine predators is critical for characterizing their functional role and ecosystem influence, allowing for targeted conservation efforts.

scholarly journals ISÓTOPOS ESTÁVEIS E OUTRAS FERRAMENTAS EM ESTUDOS TRÓFICOS DE PEIXES EM RIACHOS TROPICAIS

2021 ◽  
Vol 25 (02) ◽  
pp. 283-300
Author(s):  
Míriam Pilz Albrecht ◽  
◽  
Andressa da Silva Reis ◽  
Vinicius Neres-Lima ◽  
Eugenia Zandonà ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Environmental Changes ◽  
Trophic Position ◽  
Isotope Analysis ◽  
Aquatic Organisms ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Tropical Streams ◽  
Stream Fish ◽  
The Impact

Stable isotope analysis (SIA) has become an essential tool in Ecology, being increasingly used in studies of fish in tropical streams. The SIA allows to reconstruct the animals' diet and its intraspecific variation, to trace the contributions of the main basal resources throughout the food web, to calculate trophic position and trophic niche, including niche overlap and its alterations, and to build food webs. The SIA is also used to understand the impact of environmental changes on fish communities and other aquatic organisms. The number of such studies is increasing in Brazil, but there are still several gaps. In this study, we present the basic concepts on stable isotopes analysis in trophic studies of stream fish - especially those of carbon, nitrogen and hydrogen - their premises, uses and limitations, presenting examples from tropical streams. We also explore new conceptual tools in this area, still not used for stream fish in Brazil, such as fatty acids, stable isotopes in specific compounds, nutritional geometry and ecological stoichiometry concepts such as the Threshold Elemental Ratio.

scholarly journals Human disturbance increases trophic niche overlap in terrestrial carnivore communities

2020 ◽  
Vol 117 (43) ◽  
pp. 26842-26848 ◽  
Author(s):  
Philip J. Manlick ◽  
Jonathan N. Pauli
Keyword(s):  
Interspecific Competition ◽  
Human Disturbance ◽  
Niche Partitioning ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Resource Consumption ◽  
Apex Predators ◽  
Biological Organization ◽  
Food Subsidies ◽  
The Impact

Animal foraging and competition are defined by the partitioning of three primary niche axes: space, time, and resources. Human disturbance is rapidly altering the spatial and temporal niches of animals, but the impact of humans on resource consumption and partitioning—arguably the most important niche axis—is poorly understood. We assessed resource consumption and trophic niche partitioning as a function of human disturbance at the individual, population, and community levels using stable isotope analysis of 684 carnivores from seven communities in North America. We detected significant responses to human disturbance at all three levels of biological organization: individual carnivores consumed more human food subsidies in disturbed landscapes, leading to significant increases in trophic niche width and trophic niche overlap among species ranging from mesocarnivores to apex predators. Trophic niche partitioning is the primary mechanism regulating coexistence in many communities, and our results indicate that humans fundamentally alter resource niches and competitive interactions among terrestrial consumers. Among carnivores, niche overlap can trigger interspecific competition and intraguild predation, while the consumption of human foods significantly increases human–carnivore conflict. Our results suggest that human disturbances, especially in the form of food subsidies, may threaten carnivores by increasing the probability of both interspecific competition and human–carnivore conflict. Ultimately, these findings illustrate a potential decoupling of predator–prey dynamics, with impacts likely cascading to populations, communities, and ecosystems.

Trophic niche overlap in two syntopic colubrid snakes (Hierophis viridiflavus and Zamenis longissimus) with contrasted lifestyles

2012 ◽  
Vol 33 (1) ◽  
pp. 37-44 ◽  
Author(s):  
Hervé Lelièvre ◽  
Pierre Legagneux ◽  
Gabriel Blouin-Demers ◽  
Xavier Bonnet ◽  
Olivier Lourdais
Keyword(s):  
Diet Composition ◽  
Feeding Rate ◽  
Species Coexistence ◽  
Niche Partitioning ◽  
Stomach Contents ◽  
Niche Overlap ◽  
Trophic Niche ◽  
Temperate Climate ◽  
Feeding Strategies ◽  
Mean Body Temperature

In many organisms, including snakes, trophic niche partitioning is an important mechanism promoting species coexistence. In ectotherms, feeding strategies are also influenced by lifestyle and thermoregulatory requirements: active foragers tend to maintain high body temperatures, expend more energy, and thus necessitate higher energy income. We studied diet composition and trophic niche overlap in two south European snakes (Hierophis viridiflavus and Zamenis longissimus) in the northern part of their range. The two species exhibit contrasted thermal adaptations, one being highly mobile and thermophilic (H. viridiflavus) and the other being elusive with low thermal needs (Z. longissimus). We analyzed feeding rate (proportion of snakes with indication of a recent meal) and examined more than 300 food items (fecal pellets and stomach contents) in 147 Z. longissimus and 167 H. viridiflavus. There was noticeable overlap in diet (overlap of Z. longissimus on H. viridiflavus = 0.62; overlap of H. viridiflavus on Z. longissimus = 0.80), but the similarity analyses showed some divergence in diet composition. Dietary spectrum was wider in H. viridiflavus, which fed on various mammals, birds, reptiles, and arthropods whereas Z. longissimus was more specialized on mammals and birds. The more generalist nature of H. viridiflavus was consistent with its higher energy requirements. In contrast to our expectation, feeding rate was apparently higher in Z. longissimus than in H. viridiflavus, but this could be an artifact of a longer transit time in Z. longissimus, given its lower mean body temperature. These results allow a better understanding of the ability to coexist in snakes belonging to temperate climate colubrid communities.

scholarly journals Quantifying the increase in fishing efficiency due to the use of drifting FADs equipped with echosounders in tropical tuna purse seine fisheries

2020 ◽  
Author(s):  
Gwenaëlle Wain ◽  
Loreleï Guéry ◽  
David Michael Kaplan ◽  
Daniel Gaertner
Keyword(s):  
New Technology ◽  
Recent Change ◽  
Purse Seine ◽  
Catch Per Unit Effort ◽  
Katsuwonus Pelamis ◽  
Thunnus Obesus ◽  
Efficiency Increase ◽  
Tropical Tuna ◽  
Floating Objects ◽  
The Impact

Abstract Numerous pelagic species are known to associate with floating objects (FOBs), including tropical tunas. Purse seiners use this behaviour to facilitate the capture of tropical tunas by deploying artificial drifting fish aggregating devices (dFADs). One major recent change has been the integration of echosounders in satellite-tracked GPS buoys attached to FOBs, allowing fishers to remotely estimate fishable biomass. Understanding the effects of this new technology on catch of the three main tuna species (yellowfin tuna, Thunnus albacares; bigeye tuna, Thunnus obesus; and skipjack tuna, Katsuwonus pelamis) is important to accurately correct for this change in catch-per-unit-effort (CPUE) indices used for stock assessments. We analysed catch data from the French purse seine fleet for the period 2010–2017 in the Indian Ocean to assess the impact of this fleet’s switch to echosounder buoys around 2012. Results indicate that echosounders do not increase the probability a set will be succesful, but they have a positive effect on catch per set, with catches on average increasing by ≈2−2.5 tonnes per set (≈10%) when made on the vessel's own dFADs equipped with an echosounder buoy. Increases were due to a decrease in sets below ≈25 tonnes and an increase in those greater than ≈25 tonnes, with a non-linear transition around this threshold. This increase explains the considerable investment of purse seiners in echosounder buoys, but also raises concerns about bias in stock size estimates based on CPUE if we do not correct for this fishing efficiency increase.

scholarly journals The food web in a subterranean ecosystem is driven by intraguild predation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Andrea Parimuchová ◽  
Lenka Petráková Dušátková ◽  
Ľubomír Kováč ◽  
Táňa Macháčková ◽  
Ondřej Slabý ◽  
...  
Keyword(s):  
Food Web ◽  
Trophic Interactions ◽  
Intraguild Predation ◽  
Linear Models ◽  
Niche Overlap ◽  
Trophic Niche ◽  
High Availability ◽  
Large Prey ◽  
Arthropod Predators ◽  
Body Sizes

AbstractTrophic interactions of cave arthropods have been understudied. We used molecular methods (NGS) to decipher the food web in the subterranean ecosystem of the Ardovská Cave (Western Carpathians, Slovakia). We collected five arthropod predators of the species Parasitus loricatus (gamasid mites), Eukoenenia spelaea (palpigrades), Quedius mesomelinus (beetles), and Porrhomma profundum and Centromerus cavernarum (both spiders) and prey belonging to several orders. Various arthropod orders were exploited as prey, and trophic interactions differed among the predators. Linear models were used to compare absolute and relative prey body sizes among the predators. Quedius exploited relatively small prey, while Eukoenenia and Parasitus fed on relatively large prey. Exploitation of eggs or cadavers is discussed. In contrast to previous studies, Eukoenenia was found to be carnivorous. A high proportion of intraguild predation was found in all predators. Intraspecific consumption (most likely cannibalism) was detected only in mites and beetles. Using Pianka’s index, the highest trophic niche overlaps were found between Porrhomma and Parasitus and between Centromerus and Eukoenenia, while the lowest niche overlap was found between Parasitus and Quedius. Contrary to what we expected, the high availability of Diptera and Isopoda as a potential prey in the studied system was not corroborated. Our work demonstrates that intraguild diet plays an important role in predators occupying subterranean ecosystems.

scholarly journals Indian Grey Wolf and Striped Hyaena sharing from the same bowl: High niche overlap between top predators in a human-dominated landscape

2021 ◽  
pp. e01682
Author(s):  
Tanoy Mukherjee ◽  
Ishita Chongder ◽  
Shankhamala Ghosh ◽  
Akash dutta ◽  
Abhishek Singh ◽  
...  
Keyword(s):  
Niche Overlap ◽  
Grey Wolf ◽  
Top Predators
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