Sex-specific spatial use of the winter foraging areas by Magellanic penguins and assessment of potential conflicts with fisheries during winter dispersal

Magellanic penguins (Spheniscus magellanicus) disperse widely during winter and are a major consumer of marine resources over the Patagonian Shelf. Magellanic penguins were equipped with geolocators at Martillo Island in late February- early March 2017 and recaptured at the beginning of the next breeding season to recover the devices and to collect blood samples for stable carbon (δ13C) and nitrogen (δ15N) isotope analysis. We evaluated their whole winter dispersal and their trophic niche by sex during the last month of the winter dispersal. Also, we evaluated their spatial overlap with bottom trawl and shrimp fisheries using data from satellite fisheries monitoring. Penguins dispersed northwards up to 42°S and showed latitudinal spatial segregation between sexes during May to August (females were located further north than males). In contrast, during the last month of the winter dispersal females were located more southerly and showed lower trophic position than males. Also, females did not dive as deep as males during winter. We found high overlap between both fisheries and penguin’s spatial use in regions with documented interaction. However, no sex-specific statistical differences with fisheries overlap were found. Our results highlight the importance of understanding the spatial domains of each sex and assessment of their potential conflicts with bottom trawl fishery and shrimp fishery during the winter period.

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Inter-annual variation in the trophic niche of Magellanic penguins Spheniscus magellanicus during the pre-molt period in the Beagle Channel

Marine Ecology Progress Series ◽

10.3354/meps13518 ◽

2020 ◽

Vol 655 ◽

pp. 215-225

Author(s):

S Dodino ◽

L Riccialdelli ◽

MJ Polito ◽

K Pütz ◽

A Raya Rey

Keyword(s):

Diet Composition ◽

Annual Variation ◽

Isotope Analysis ◽

Trophic Niche ◽

Carbon And Nitrogen ◽

Spheniscus Magellanicus ◽

Beagle Channel ◽

Annual Variations ◽

Magellanic Penguins ◽

Key Species

Inter-annual variations in the diets of seabirds are often a reflection of resource availability, with population dynamics and community structure implications. We investigated the trophic niche of Magellanic penguins Spheniscus magellanicus during the pre-molt stage in 6 years (2009 and 2013-2017) at Martillo Island, Beagle Channel, Argentina, using carbon and nitrogen stable isotope analysis of feathers. We found higher values in 2009 compared to the other years for both isotopes and estimated different proportions of prey in the diet of Magellanic penguins throughout the years. In 2009, penguins consumed mainly a mixture of benthic and benthopelagic fish, whereas from 2013 to 2017, the proportion of the pelagic form of squat lobster Munida gregaria, considered a key species in the Beagle Channel, increased over time and nearly dominated diets in 2017. Our results confirm that Magellanic penguins act as sentinels, reflecting shifts in the marine community of the Beagle Channel via inter-annual variation in their trophic niche and diet composition.

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Evidence for inter- and intraspecific trophic niche separation among deepwater elasmobranchs on the southern Great Barrier Reef, Australia

Marine Ecology Progress Series ◽

10.3354/meps13221 ◽

2020 ◽

Vol 636 ◽

pp. 107-121

Author(s):

SEM Munroe ◽

CL Rigby ◽

NE Hussey

Keyword(s):

Great Barrier Reef ◽

Trophic Ecology ◽

Isotope Analysis ◽

Niche Overlap ◽

Trophic Niche ◽

Feeding Strategies ◽

Niche Separation ◽

Isotopic Niche ◽

Barrier Reef ◽

Trawl Fishery

Quantifying the trophic structure and interactions of deepwater (>200 m depth) elasmobranch assemblages is required to improve our understanding of deepwater ecosystems and the impacts of increased deepwater exploitation. To this end, we investigated the trophic ecology of deepwater elasmobranchs on the Great Barrier Reef (GBR) using a stable isotope (δ13C and δ15N) approach. Our study included 4 species captured in the southern GBR deepwater eastern king prawn trawl fishery: the eastern spotted gummy shark Mustelus walkeri, the piked spurdog Squalus megalops, the pale spotted catshark Asymbolus pallidus, and the Argus skate Dentiraja polyommata. The δ13C and δ15N values of all 4 species ranged from -18.6 to -16.2‰ and 8.3 to 13.8‰, respectively. The small δ13C range was likely due to the limited number of unique carbon baseline sources typically found in deepwater environments. Despite this, 3 of the 4 species exhibited relatively low core (40% SEAb) isotopic niche overlap (<1 to 44%). Isotopic niche separation may be driven by multiple interacting factors including morphology, feeding strategies, or resource partitioning to reduce competition. Isotope analysis also provided evidence for intraspecific variation; S. megalops, D. polyommata and M. walkeri exhibited significant increases in δ15N (~3‰) and δ13C (~2‰) with size. Latitude, longitude, and depth had statistically significant but comparatively minor effects on isotope values (≤1‰) of the 4 species. Cumulatively, our results indicate that isotopic variation among deepwater elasmobranchs on the GBR is principally driven by size and species-level differences in resource use.

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

10.1101/068171 ◽

2016 ◽

Cited By ~ 1

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.

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Trophic plasticity of the highly invasive topmouth gudgeon (Pseudorasbora parva) inferred from stable isotope analysis

10.1101/617688 ◽

2019 ◽

Cited By ~ 2

Author(s):

Matteo Rolla ◽

Sofia Consuegra ◽

Carlos Garcia de Leaniz

Keyword(s):

Stable Isotope ◽

Stable Isotope Analysis ◽

Condition Factor ◽

Trophic Position ◽

Isotope Analysis ◽

Trophic Niche ◽

Pseudorasbora Parva ◽

Trophic Plasticity ◽

Topmouth Gudgeon ◽

South Wales

AbstractA wide trophic niche and high trophic plasticity are often invoked to explain the successful establishment of many aquatic invaders, but there is little information regarding the diet of most invasive fish in European waters. We combined stomach content and stable isotope analysis (SIA) of13C and15N to examine the trophic niche of the highly invasive topmouth gudgeon (Pseudorasbora parva) in four contrasting ponds and reservoirs in South Wales. Marked differences in diet and trophic position were found among neighbouring systems only a few kilometres apart. The most diverse diet was found in ponds with the fewest number of inter-specific competitors, and resulted in topmouth gudgeon having the highest condition factor, the widest variation in δ13C and δ15N values, and the highest carbon content, typical of generalist feeders. In contrast, topmouth gudgeon that coexisted with other cyprinids, were much more likely to have empty stomachs and relied almost exclusively on plant seeds, resulting in fish having a poor condition factor and low trophic position. Comparisons with other trophic studies indicate that variation in isotope values among neighbouring sites can exceed variation across continents, making it difficult to predict the diet or trophic impacts of the invasive topmouth gudgeon. Given the importance of obtaining reliable data on trophic position for risk assessment, our study shows that the use of SIA could be used to prioritize control and eradication measures that take into account trophic plasticity.

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

Oecologia Australis ◽

10.4257/oeco.2021.2502.05 ◽

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.

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Improvements of Population Fitness and Trophic Status of a Benthic Predatory Fish Following a Trawling Ban

Frontiers in Marine Science ◽

10.3389/fmars.2021.614219 ◽

2021 ◽

Vol 8 ◽

Author(s):

Lily S. R. Tao ◽

Yanny K. Y. Mak ◽

Valerie C. M. Ho ◽

Ronia C.-t. Sham ◽

Tommy T. Y. Hui ◽

...

Keyword(s):

Hong Kong ◽

Body Size ◽

Size Structure ◽

Trophic Position ◽

Isotope Analysis ◽

Trophic Niche ◽

Trophic Dynamics ◽

Predatory Fish ◽

Benthic Habitats ◽

Fish Samples

Trawl fisheries have been shown to cause overfishing and destruction of benthic habitats in the seabed. To mitigate these impacts, a trawling ban has been enforced in Hong Kong waters since December 31, 2012 to rehabilitate the ecosystem and enhance fisheries resources. Previous studies demonstrated that reduced trawling activities would increase the heterogeneity of benthic habitats, thereby enhancing species richness and abundance of benthic fauna and providing more prey resources for predatory fishes. This study aimed to test a hypothesis that the population and trophic dynamics of the Bartail flathead Platycephalus indicus, a heavily fished benthic predatory fish, at inner and outer Tolo Channel of Hong Kong (i.e., EI and EO) improved with increases in their body size, abundance, biomass, trophic niche, and trophic position after the trawl ban. Samples were collected from trawl surveys before and after the trawl ban to compare the pre-ban and post-ban populations of P. indicus from EI and EO. Body size, abundance, and biomass were assessed in 2004, 2013–2014, and 2015–2016, whereas trophic niche and trophic position were analyzed based on stable isotopes of fish samples collected in dry season of 2012, 2015, and 2018. Following the trawl ban, the abundance and biomass of P. indicus increased in EO, with body size increased in EI. Furthermore, as indicated by the results of stable isotope analysis (SIA) on their tissues and prey items, trophic niche, and trophic position of P. indicus increased in EI and EO, respectively. Our study demonstrated that the trawl ban had promoted the recovery of a predatory fish population through restoring size structure and trophic dynamics.

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Gut microbiome is affected by inter-sexual and inter-seasonal variation in diet for thick-billed murres (Uria lomvia)

Scientific Reports ◽

10.1038/s41598-020-80557-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Esteban Góngora ◽

Kyle H. Elliott ◽

Lyle Whyte

Keyword(s):

Gut Microbiome ◽

Sulfur Isotopes ◽

Trophic Position ◽

Isotope Analysis ◽

16S Rrna Gene Sequencing ◽

Rrna Gene ◽

Uria Lomvia ◽

Fecal Microbiome ◽

Prey Specialization ◽

Rrna Gene Sequencing

AbstractThe role of the gut microbiome is increasingly being recognized by health scientists and veterinarians, yet its role in wild animals remains understudied. Variations in the gut microbiome could be the result of differential diets among individuals, such as variation between sexes, across seasons, or across reproductive stages. We evaluated the hypothesis that diet alters the avian gut microbiome using stable isotope analysis (SIA) and 16S rRNA gene sequencing. We present the first description of the thick-billed murre (Uria lomvia) fecal microbiome. The murre microbiome was dominated by bacteria from the genus Catellicoccus, ubiquitous in the guts of many seabirds. Microbiome variation was explained by murre diet in terms of proportion of littoral carbon, trophic position, and sulfur isotopes, especially for the classes Actinobacteria, Bacilli, Bacteroidia, Clostridia, Alphaproteobacteria, and Gammaproteobacteria. We also observed differences in the abundance of bacterial genera such as Catellicoccus and Cetobacterium between sexes and reproductive stages. These results are in accordance with behavioural observations of changes in diet between sexes and across the reproductive season. We concluded that the observed variation in the gut microbiome may be caused by individual prey specialization and may also be reinforced by sexual and reproductive stage differences in diet.

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Trophic Trait Evolution Explains Variation in Nutrient Excretion Stoichiometry among Panamanian Armored Catfishes (Loricariidae)

Diversity ◽

10.3390/d11060088 ◽

2019 ◽

Vol 11 (6) ◽

pp. 88

Author(s):

Eric K. Moody ◽

Fernando Alda ◽

Krista A. Capps ◽

Oscar Puebla ◽

Benjamin L. Turner

Keyword(s):

Significant Variation ◽

Trophic Position ◽

Nutrient Recycling ◽

Trophic Niche ◽

Relative Importance ◽

Closely Related Species ◽

Trait Evolution ◽

Nutrient Excretion ◽

Nutrient Mineralization ◽

Excretion Rates

Variation in nutrient excretion rates and stoichiometric ratios (e.g., nitrogen to phosphorus) by consumers can have substantial effects on aquatic ecosystem function. While phylogenetic signals within an assemblage often explain variation in nutrient recycling rates and stoichiometry, the phylogenetically conserved traits that underlie this phenomenon remain unclear. In particular, variation in nutrient excretion stoichiometry across a phylogeny might be driven by phylogenetic patterns in either diet or body stoichiometry. We examined the relative importance of these traits in explaining variation in nutrient recycling rates and stoichiometry in a diverse family of Neotropical-armored catfishes, Loricariidae, in Panamanian streams. We found significant variation in nutrient mineralization traits among species and subfamilies, but variation in nutrient excretion stoichiometry among species was best explained by trophic position rather than body stoichiometry. The variation in trophic position among Panamanian species was consistent with variation in the trophic niche of their genera across South America, suggesting that phylogenetic patterns underpin the evolution of trophic and nutrient excretion traits among these species. Such geographical variation in nutrient mineralization patterns among closely related species may be common, given that trophic variation in fish lineages occurs widely. These results suggest that information on trophic trait evolution within lineages will advance our understanding of the functional contribution of animals to biogeochemical cycling.

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Trophic ecology of sea urchins in coral-rocky reef systems, Ecuador

PeerJ ◽

10.7717/peerj.1578 ◽

2016 ◽

Vol 4 ◽

pp. e1578 ◽

Cited By ~ 8

Author(s):

Nancy Cabanillas-Terán ◽

Peggy Loor-Andrade ◽

Ruber Rodríguez-Barreras ◽

Jorge Cortés

Keyword(s):

Stable Isotope ◽

Trophic Ecology ◽

Habitat Degradation ◽

Sea Urchins ◽

Relative Proportion ◽

Isotope Analysis ◽

Niche Overlap ◽

Trophic Niche ◽

Rocky Reef ◽

Trophic Overlap

Sea urchins are important grazers and influence reef development in the Eastern Tropical Pacific (ETP).Diadema mexicanumandEucidaris thouarsiiare the most important sea urchins on the Ecuadorian coastal reefs. This study provided a trophic scenario for these two species of echinoids in the coral-rocky reef bottoms of the Ecuadorian coast, using stable isotopes. We evaluated the relative proportion of algal resources assimilated, and trophic niche of the two sea urchins in the most southern coral-rocky reefs of the ETP in two sites with different disturbance level. Bayesian models were used to estimate the contribution of algal sources, niche breadth, and trophic overlap between the two species. The sea urchins behaved as opportunistic feeders, although they showed differential resource assimilation.Eucidaris thouarsiiis the dominant species in disturbed environments; likewise, their niche amplitude was broader than that ofD. mexicanumwhen conditions were not optimal. However, there was no niche overlap between the species. The Stable Isotope Analysis in R (SIAR) indicated that both sea urchins shared limiting resources in the disturbed area, mainlyDictyotaspp. (contributions of up to 85% forD. mexicanumand up to 75% forE. thouarsii). The Stable Isotope Bayesian Ellipses in R (SIBER) analysis results indicated less interspecific competition in the undisturbed site. Our results suggested a trophic niche partitioning between sympatric sea urchin species in coastal areas of the ETP, but the limitation of resources could lead to trophic overlap and stronger habitat degradation.

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