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ABSTRACT Fishery discards worldwide increase the availability of organic materials on the benthos, altering trophic relationships and potentially increasing the abundance of benthic consumers. Expert knowledge from fishers is a valuable yet often underutilized source of information to understand these dynamics. We interviewed Dungeness crab fishers (n = 24) to determine the most‐used bait types and to characterize regional and seasonal bait use strategies that drive inputs of organic matter into Oregon coastal waters during the commercial Dungeness crab fishery each year. Based on bomb calorimetry measurements of caloric densities of 12 commonly reported bait species, total energetic input was 12.99 × 109 kJ (3.10 B kcal) from bait in the 2019–2020 commercial ocean Dungeness season in Oregon, USA. Fishing effort and bait inputs were strongly seasonal, with 88% of effort concentrated in the first 60 days of the 9‐month‐long season but did not vary regionally. This large, temporally concentrated caloric input suggested that bait could contribute substantially to Dungeness crab productivity. Fisher respondents indicated that bait effectiveness was the most important motivating factor in choosing a bait type, more than availability or cost. [ABSTRACT FROM AUTHOR]

ABSTRACT Fishes use a variety of physical and biological resources that shift ontogenetically, seasonally and spatially. Quantifying what resources such as prey are required for persistence can improve understanding of ecological needs of fishes and riverine macrosystem functioning. Bowfin (Amia ocellicauda) and largemouth bass (Micropterus nigricans) cohabitate in their native range and potentially compete with one another. Yet, there have been no direct comparisons of their diets across spatial gradients to assess whether they partition resources or shift in prey use. We used multiple univariate and multivariate analyses to compare diet composition, diet overlap, feeding strategy, prey importance and diet partitioning between largemouth bass and bowfin across three reaches of the Upper Mississippi River. Largemouth bass ontogenetically shifted their diet from aquatic invertebrates to fishes and a more diverse assemblage of aquatic invertebrates. Bowfin and adult largemouth bass were top predators which consumed mostly crayfish and fish and overlapped in their diets. Despite overlapping diets, predators partitioned resources by consuming different lengths and abundances of prey, and largemouth bass had greater trophic plasticity. Within a predator group, few differences in diets existed spatially, underscoring the relative homogeneity in resource use potentially from similarities in the river's physical structure. Combined, prey use likely differed sufficiently to reduce potential competition between largemouth bass and bowfin, allowing long‐term coexistence in this system. Our results also highlighted the importance of crayfishes to riverine food webs and underscored the use of multiple prey and habitat types that sustain these predators. [ABSTRACT FROM AUTHOR]

In warm oligotrophic waters, photosymbiotic coral can flourish across a wide depth range (0–170+ m), extending to depths where light attenuates to ~0.1% of surface values. Conventional wisdom has long assumed that mixotrophic corals must increasingly rely on heterotrophy as the ambient light available to drive photosynthesis decreases with depth. However, evidence challenging this traditional dogma has been accumulating in recent years. Although some evidence suggests that some depth-generalist coral species likely increase their reliance on heterotrophy with increasing depth, there is growing evidence that other species do not. Analysis of bulk stable isotopes (δ13C and δ15N) applied to photosymbiotic corals has been used in several ways to infer their trophic ecology and their relative dependence on symbiont photosynthesis versus heterotrophic feeding. However, metrics based on bulk tissue δ13C and δ15N values are subject to considerable uncertainty due to the multiple factors that can affect their values independent of trophic ecology. These competing factors can be quite challenging to disentangle and have led to inconsistent results and conclusions regarding trends in coral heterotrophy with depth. The evidence to date suggests no uniform trophic pattern with increasing depth or decreasing light. Different corals appear to function differently, which is not surprising given their phylogenetic diversity. [ABSTRACT FROM AUTHOR]

Understanding how human activities affect wildlife is fundamental for global biodiversity conservation. Ongoing land use change and human‐induced climate change, compel species to adapt their behaviour in response to shifts in their natural environments. Such responses include changes to a species' diet or trophic ecology, with implications for the wider ecosystem. This is particularly the case for predatory species or those that occupy high positions within trophic webs, such as raptors. Between 2002 and 2019, we observed 1578 feeding events of the globally near threatened and understudied, Red‐necked Falcon (Falco chicquera) in Bangladesh. We explored the effects of mean monthly temperature, precipitation, temperature differences, and urban land cover on (a) mean prey weights and (b) dietary composition of 15 falcon pairs. Falcons hunted smaller prey items during months with increased temperatures and precipitation, and in more urban areas. However, during months with increased temperature differences, falcons tended to prey on larger prey items. Being specialist aerial hunters, these dietary patterns were largely driven by the probabilities of bats and birds in the diet. Falcons were more likely to prey on bats during warmer and wetter months. Furthermore, urban pairs tended to prey on bats, whereas more rural pairs tended to prey on birds. Mean monthly temperature difference, i.e., a proxy for climate change, was better at explaining the probability of bats in the falcon diet than mean monthly temperature alone. Anthropogenic dietary shifts can have deleterious effects on species with declining populations or those of conservation concern. The effects of urbanisation and human‐induced climate change are expected to continue into the foreseeable future. Therefore, our findings represent a cornerstone in our understanding of how falcons respond to an increasingly human‐dominated world. [ABSTRACT FROM AUTHOR]

Competition among pollinators for floral resources is a phenomenon of both basic and applied importance. While competition is difficult to measure directly under field conditions, it can be inferred indirectly through the measurement of floral resource depletion. In this study, we conducted a pollinator exclusion experiment to calculate nectar depletion rates in summer across 16 grassland sites in the German regions of Franconia and Saxony‐Anhalt. Overall depletion rates were estimated at 95% in Franconia and 79% in Saxony‐Anhalt, indicating strong nectar limitation and likely competition among pollinators for nectar. Despite being ubiquitous in our study regions, honey bees were scarce at our sites at the time of nectar sampling. This demonstrates that wild pollinators alone are capable of massive nectar depletion, and the addition of managed honey bees to wild pollinator communities may intensify already competitive conditions. Nevertheless, the manifest diversity of the pollinator communities at our sites indicates that other factors, such as non‐trophic constraints or temporal variation in nectar limitation, can mitigate competitive exclusion despite immediate conditions of acute nectar scarcity. [ABSTRACT FROM AUTHOR]

This study examines the importance of both macroalgal heterogeneity and specific macroalgal species or morphotypes to nursery provision for juvenile sparids (Diplodus capensis and Sarpa salpa) in a shallow (< 2 m), sheltered rocky cove in warm-temperate Algoa Bay, South Africa. The rocky cove is comprised of a mosaic of two main benthic habitats; canopy-forming Plocamium corallorhiza beds on rocky outcrops and flat reef dominated by low growing red algae morphotypes. We assessed macroalgal communities and the trophic ecology (stomach contents and isotopes), abundance and size structure of D. capensis and S. salpa in the two different benthic habitats and the resources/food associated with the dominant macroalgae species/morphotypes. We found high densities of S. salpa and D. capensis, in both high profile reef (rocky outcrops) and low profile (flat) reef. Within this habitat mosaic resources (epiphytes and macroinvertebrates) were more abundant in the non-canopy forming low growing macroalgae (Laurencia spp. and coralline turf algae) and these algae were also assimilated in the diets of both sparids. The high abundance of both juvenile S. salpa and D. capensis in high profile and low profile reef, suggests that within this mosaic of habitats these species may be using canopy-forming algae in the high profile reef for shelter and non-canopy forming algae in both the high and low profile reef for food. This shows that macroalgal habitats comprising several morphotypes have the potential to support higher juvenile diversity and abundance through both food provision and shelter. [ABSTRACT FROM AUTHOR]

Cold‐water lakes situated in high latitudes and altitudes have pivotal socio‐ecological importance both globally and locally. However, they are increasingly threatened by multiple anthropogenic stressors, such as climate change, hydropower and invasive species. The development of efficient management strategies is therefore urgently needed and requires a comprehensive understanding of the factors influencing the biodiversity and ecological processes of these ecosystems. We provide a holistic knowledge base for informed future research and management by addressing the interplay between local and global environmental drivers of food webs in Arctic charr (Salvelinus alpinus, Salmonidae) and brown trout (Salmo trutta, Salmonidae) dominated cold‐water lakes in Fennoscandia. The trophic niche and population dynamics of these generalist top consumers provide extensive insights into the effects of natural and anthropogenic drivers on food webs in intensively studied Fennoscandian cold‐water lakes, covering marked biogeographical gradients in abiotic and biotic conditions. Drawing on a synthesis of existing literature, our focus is on three pivotal drivers: (1) lake location and connectivity, (2) lake area and morphometry and (3) fish community composition. These drivers significantly influence the complexity and the origin and flow of energy in lake food webs, and ultimately the size structure of the charr and trout populations. Furthermore, we highlight ongoing environmental changes in Fennoscandian cold‐water lakes caused by hydropower and invasive species. Finally, we identify crucial knowledge gaps and propose management actions for improving the future state of Fennoscandian cold‐water lake ecosystems and their charr and trout populations. [ABSTRACT FROM AUTHOR]

The Atlantic bigeye Priacanthus arenatus is among the main target species by small-scale fisheries in the southwestern Atlantic. Due to its importance to small-scale fisheries, information regarding its trophic ecology is essential for the development of sustainable management plans. Using combined stomach content (SCA) and stable isotope analysis (SIA), the current study examined Atlantic bigeye feeding ecology, including evidence for ontogenetic and intra-annual (i.e. seasonal) diet variation. The diet of Atlantic bigeye was comprised of 16 prey species but was dominated by pelagic crustaceans (53.3% in number) and pelagic fish (19.7%), and benthic crustaceans (11.0%). SCA identified diet variation among seasons (higher dissimilarity in Spring vs. Autumn), which is most likely related to the occurrence of intense coastal upwellings. Significant positive relationships between fish size and δ15N and δ13C values indicated an ontogenetic diet and potential habitat shift; broad isotopic niche area in small individuals (size class I: 115–169 mm) narrowed with increasing body size with the highest niche overlap occurring between size class II (170 to 243 mm) and class III (244 to 308 mm). Overall, the combined SCA and SIA approach determined that the Atlantic bigeye's diet is closely connected to the pelagic food web. These data provide an improved understanding of ontogenetic and seasonal variation in Atlantic bigeye predator-prey interactions in the southwestern Atlantic. [ABSTRACT FROM AUTHOR]

This study used a novel approach combining stable isotope data and condensed multivariate fatty acid data to define comparative niche space and overlap of six sympatric sharks from the south‐west Indian Ocean: Galeocerdo cuvier, Sphyrna zygaena, Sphyrna lewini, Carcharias taurus, Carcharodon carcharias and Carcharhinus obscurus. G. cuvier had the smallest fatty acid niche space but exhibited the largest range in δ13C, suggestive of foraging across multiple environments (habitat generalist) but on nutritionally similar prey in a narrow trophic band (nutritional specialist). The remaining five species had comparatively higher δ15N, pelagic‐based fatty acids and larger fatty acid niche spaces, suggesting they are nutritional generalists with a preference for higher trophic level prey. Niche space was not associated with conservation status despite declining populations for half of the species studied. This suggests that resource availability is not a limiting factor for these species and that their mobile nature provides them access to diverse habitats and resources, while exposing them to a broad range of anthropogenic threats, muting the relationship between conservation status and resource use. The combined approach allowed for a comprehensive representation of niche space, distinguishing species based on trophic level, basal carbon sources and pelagic and coastal prey consumption. The presented integrated approach provides greater detail and resolution of elasmobranch trophic ecology that could not be achieved with either fatty acid or stable isotope analysis alone. [ABSTRACT FROM AUTHOR]

Diet has been identified as a major driver of reef fish lineage diversification, producing one of the most speciose vertebrate assemblages today. Yet, there is minimal understanding of how, when and why diet itself has evolved. To address this, we used a comprehensive gut content dataset, alongside a recently developed phylogenetic comparative method to assess multivariate prey use across a diverse animal assemblage, coral reef fishes. Specifically, we investigated the diversification, transitions and phylogenetic conservatism of fish diets through evolutionary time. We found two major pulses of diet diversification: one at the end-Cretaceous and one during the Eocene, suggesting that the Cretaceous–Palaeogene mass extinction probably provided the initial ecological landscape for fish diets to diversify. The birth of modern families during the Eocene then provided the foundation for a second wave of dietary expansion. Together, our findings showcase the role of extinction rebound events in shaping the dietary diversity of fishes on present-day coral reefs. [ABSTRACT FROM AUTHOR]

ABSTRACT Motivation Main Types of Variables Contained Spatial Location and Grain Time Period and Grain Major Taxa and Level of Measurement Software Format Terrestrial predators play key roles in cycling nutrients, as well as limiting prey populations, and shaping the behaviour of their prey. Prehistoric, historic and ongoing declines of the world's predators have reshaped terrestrial ecosystems and are a topic of conservation concern. However, the availability of ecologically relevant predator functional traits is limited, hampering efforts to understand macroecological changes in this ecologically important functional group. Here, we present CarniTraits, a comprehensive open‐access functional trait database of all late Quaternary (~130,000 ybp) terrestrial mammalian predators (149 species, ≥1 kg body mass, ≥50% vertebrate meat consumption).Mammalian terrestrial predator functional traits including body mass, diet, scavenging, locomotion, cooperative hunting, hunting habitat, hunting method, bone consumption, temporal activity patterns, brain mass and encephalisation quotient.Global.Late Quaternary (the last ~130,000 years).All late Quaternary terrestrial mammalian predators (149 species, ≥1 kg body mass, ≥50% vertebrate meat consumption).csv. [ABSTRACT FROM AUTHOR]

Weakfish (Cynoscion regalis) is not federally managed but feeds on species of management and ecological interest. We examined the trophic ecology of weakfish in Chesapeake Bay and the coastal and offshore waters of the eastern United States. For these areas, we determined the dominant prey of weakfish; identified how much diet variation was explained by the factors: season, size class, and year; and quantified prey biomass removed by weakfish from 2007 to 2019. In general, diet composition was mostly dominated by Engraulidae, Osteichthyes (bony fishes), and Mysidacea, and significantly varied by season and size class in Chesapeake Bay and coastal waters, although this was less dramatic in Chesapeake Bay. The total amount of variance explained by the three factors was 23.1% (Chesapeake Bay) and 14.7% (coastal waters), with year not being a significant factor in explaining weakfish diet variation for these areas. Weakfish total prey biomass removal occurred primarily in coastal waters in the fall and small size class (annual mean: approximately 41,038 t; maximum: approximately 63,793 t). Highly opportunistic feeders, weakfish cannibalism also played an essential part of their diet. These results have implications for fisheries and ecosystem management of weakfish when considering ecological interactions in regulatory approaches, such as recruitment and cannibalism, competition with federally managed fishes, and the natural mortality of their prey. [ABSTRACT FROM AUTHOR]

Continental shelves experience many human pressures with demersal fisheries central to disturbing the ocean floor. However, ecological processes such as predation rates of benthos and their relationship with bottom fishing are often unknown for large marine ecosystems. We examined the amount of benthos consumed by 14 benthivorous fishes, the overlap between benthos predation and bottom fishing (dredge and trawl gear), and temporal trends in benthivorous fish abundance and the number of fishing trips on the northeast US continental shelf. Mean annual predation (biomass of prey removed) and 95% confidence intervals ranged from .0002 (.0001–.0003) to 3967 (1761–7112) t per 10‐min area squared grid cell and prey taxa for these benthivorous fishes. Predation and bottom fishing had overlapping footprints of activity, which were slightly stronger for dredge gear. Trophic success (ratio of prey biomass eaten to the biomass of the benthivore community per grid cell) revealed more Bivalvia, Gammaridea, and Polychaeta eaten in areas targeted by trawling with more fish biomass. In contrast, dredging did not target fish biomass, but these areas had increased (Echinoidea, Gammaridea, and other benthos) or decreased (Ophiuroidea) trophic success relative to dredging footprint, suggesting habitat preferences for benthic prey and demersal fisheries have converged rather than diverged. Despite declines in bottom fishing, recent increases in benthivorous fish abundance and growing interest in ocean floor use suggest that fisheries managers should ensure benthivores have sufficient prey resources relative to their community size and human pressures to promote long‐term sustainability of demersal fisheries and healthy ecosystems. [ABSTRACT FROM AUTHOR]

Arthropod–bat interactions are often considered as a base model for studying factors underlying predator–prey coevolutionary processes. Bats developed ultrasonic echolocation to hunt, and in response some arthropods developed defense mechanisms such as ultrasonic hearing, allowing them to elude bat predators. The present study analyzes the feeding patterns of bats, focusing on sonic-auditory sensory mechanisms in predator–prey interactions. Next-generation DNA sequence data from fecal samples were used to analyze the diet of 17 bat species from Mexico. Arthropod prey taxa were classified according to their auditory traits, and echolocation data were recompiled from literature review. We: (i) classified arthropod families according to their hearing ability; (ii) estimated arthropod taxon richness and proportion in the diet of each bat species; and (iii) used multidimensional scaling, principal component analysis, and regression to analyze prey consumption patterns in relation to their auditory traits and in relation to echolocation characteristics of bats. Finally, we analyzed the relationship between foraging time and auditory characteristics of prey. Families with hearing organs correspond to the orders Lepidoptera and Orthoptera. We registered 20 families of Lepidoptera and 5 of Orthoptera—7 and 3 with hearing organs, respectively. Of these orders, families lacking ears were recorded in the diet of a few bat species. Our results support the allotonic frequency hypothesis predicting a difference in emission frequency intervals between predator and prey. However, we found that the consumption of earless moths is less frequent and is related to diurnal and twilight activity—hence, their consumption is limited to bat species foraging early. Results indicate bats feed on arthropod prey successfully despite the ultrasonic hearing ability of the prey. These results may be due to counteradaptations that allow maintenance of an asymmetric "arms race" between bats and eared insects that favors the predator. [ABSTRACT FROM AUTHOR]

Here we describe the dietary patterns of the culpeo or Andean fox (Lycalopex culpaeus) on a biogeographical scale. We also analyse the influence of exotic lagomorphs on its diet and explore differences between culpeo subspecies. We selected 17 mutually comparable diet studies, which include 19 independent diet assessments. Then, we extracted and standardized the values of the different diet components from these studies and calculated the relative frequency of occurrence of the 10 main trophic groups that we found. Further, we calculated the Shannon‐Wiener H′ trophic diversity index. The results showed that small mammals (41%), lagomorphs (21%), invertebrates (12.4%) and large herbivores (7.3%) were the most consumed groups. A factorial analysis of all trophic groups rendered four orthogonal factors that were used as response variables in relation to a set of environmental predictors. Altitude correlated with most factors (i.e. trophic groups). Exotic lagomorphs were consumed in lowlands, in higher latitudes and in regions showing high values of the human footprint index, enriching in those areas the culpeo's trophic spectrum. There were no differences in diet between the two main culpeo subspecies analysed, L.c. culpaeus and L.c. andinus. Finally, the best explanatory models (general linear model) of trophic diversity selected, using Akaike's information criterion, showed that the most diverse diets were those composed of large herbivores, edentates, carnivorous species, birds and herptiles (i.e. reptiles and frogs). Trophic diversity was low in rainy areas where big rodents dominated the diet. Neither latitude nor altitude seemed to have an effect on the trophic diversity of the culpeos, as they were not retained by the final models. [ABSTRACT FROM AUTHOR]

Multiple species of the elephant fishes (Mormyridae) commonly coexist in sympatry in most African tropical rivers and lakes. In this study, we investigated the trophic ecology and potential trophic niche partitioning of eleven mormyrid fish species from the Sanaga River system in Cameroon using the stable isotope composition of carbon and nitrogen in the muscle samples. Albeit most mormyrids mainly feed on invertebrates, we found differences in isotope ratios, and we report signs of the trophic niche partitioning among species. We further found significant differences in isotopic signatures within the Mormyrus genus, suggesting ecological niche diversification among three closely related species. We have also evaluated differences in the isotopic signals between seasons in four species, which could be possibly caused by species migration and/or anthropogenic agricultural activities. To evaluate body shape, we applied geometric morphometric analyses, and we show that most of the species are clearly morphologically separated. We focused on the mormyrid ecomorphology to identify a possible interaction between shape and ecology, and we found a relationship between the δ13C (but not δ15N) isotopic signal and morphology, suggesting their interplay during mormyrid evolution. Overall, we present robust evidence of the trophic niche partitioning within the mormyrid species community, and we integrate trophic ecology with morphometrics, shedding light on the enigmatic evolutionary history of these fascinating African fishes. [ABSTRACT FROM AUTHOR]

Animal food is one of the most important ecological aspects of one species. Studying this factor is fundamental to understanding their life history, microhabitat use, and interactions with other species. Amphibians are an interesting group to understand the food chains because they interact with aquatic and terrestrial environments. Among them, Trachycephalus typhonius is a widespread treefrog in South America but there is still a lack of knowledge about its natural history. Therefore, we described the feeding habits of T. typhonius from a relictual humid forest mountain in Brazilian semiarid. The present study was conducted in the Maranguape mountain, Ceará state, Brazil during the rainy season from April to May 2019. We collected the individuals using visual and auditory searches. Overall, we found 24 specimens of T. typhonius, in which all of them had stomach contents. We identified 11 prey categories, in which coleopterans and orthopterans were the most important prey item for this species' diet. It is also important to point out that plant pieces were found in the stomach of eight individuals, which might suggest a purposeful consumption. Additionally, we found no significant differences regarding the abundance, richness, and composition of prey items consumed by males and females. In contrast, we observed individuals with largest mouth breadth tend to select prey items more volumetric. Overall, our study is the pioneer to investigate the feeding habits of T. typhonius from a montane ecosystem in Brazilian semiarid region and contributes to increasing the knowledge about its natural history. [ABSTRACT FROM AUTHOR]

Simple Summary: This research investigated microplastic ingestion in two marine crustacean species of high commercial importance, namely the Giant Red Shrimp Aristaeomorpha foliacea and the Deep-Water Rose Shrimp Parapenaeus longirostris. The primary purpose of this study was to better understand how these species are affected by microplastic pollution, a growing concern in the marine environment worldwide. Based on stable isotope analysis of muscle tissue and on the examination of their gastrointestinal tracts, it was found that the trophic niche of the two species is similar, but the type of particles ingested differed significantly in terms of shape, colour, size class, and polymer. These outcomes shed light on the pervasive impact of microplastic contamination on marine wildlife, emphasising potential threats to consumers at higher levels of the food web. A better knowledge of pathways that microplastics follow through marine food webs is crucial for understanding the ecological implications posed by this emerging contaminant. Increasing plastic contamination poses a serious threat to marine organisms. Microplastics (MPs) ingestion can represent a risk for the organism itself and for the ultimate consumer. Through the analysis of the gastrointestinal tract, coupled with stable isotope analysis on the muscle tissue, this study provides insights into the relationship between MPs pollution and ecology in two commercial marine species caught in the Central Tyrrhenian Sea: Aristaeomorpha foliacea and Parapenaeus longirostris. Stable isotope analysis was conducted to determine the trophic position and the trophic niche width. The gastrointestinal tracts were processed, and the resultant MPs were analysed under FT-IR spectroscopy to estimate the occurrence, abundance, and typology of the ingested MPs. The trophic level of the species was similar (P. longirostris TP = 3 ± 0.10 and A. foliacea TP = 3.1 ± 0.08), with an important trophic niche overlap, where 38% and 52% of P. longirostris and A. foliacea has ingested MPs, respectively. Though species-level differences may not be evident regarding MP's abundance per individual, a high degree of dissimilarity was noted in the typologies of ingested particles. This research provides valuable insights into how MPs enter marine trophic webs, stressing that isotopic niche analysis should be combined with other methods to explain in detail the differences in MPs ingestion. [ABSTRACT FROM AUTHOR]

Venomous marine gastropods of the superfamily Conoidea possess a rich arsenal of toxins, including neuroactive toxins. Venom adaptations might have played a fundamental role in the radiation of conoideans; nevertheless, there is still no knowledge about the venom of the most diversified family of the group: Raphitomidae Bellardi, 1875. In this study, transcriptomes were produced from the carcase, salivary glands, and proximal and distal venom ducts of the northeastern Atlantic species Raphitoma purpurea (Montagu, 1803). Using a gut barcoding approach, we were also able to report, for the first time, molecular evidence of a vermivorous diet for the genus. Transcriptomic analyses revealed over a hundred putative venom components (PVC), including 69 neurotoxins. Twenty novel toxin families, including some with high levels of expansion, were discovered. No significant difference was observed between the distal and proximal venom duct secretions. Peptides related to cone snail toxins (Cerm06, Pgam02, and turritoxin) and other venom-related proteins (disulfide isomerase and elevenin) were retrieved from the salivary glands. These salivary venom components may constitute ancestral adaptations for venom production in conoideans. Although often neglected, salivary gland secretions are of extreme importance for understanding the evolutionary history of conoidean venom. [ABSTRACT FROM AUTHOR]

We aimed to characterize the trophic ecology and test the hypothesis of niche overlap between four sympatric batoid species of the subtropical South Atlantic. Data were collected between 2017 and 2022 from two artisanal fishery communities in southern Brazil. Batoid's stomach contents were identified, separated into categories, and weighed. We calculated the Levins, Pianka's, and Prey-specific index of relative dietary importance (PSIRI) and performed a similarity test using PERMANOVA and the similarity percentage (SIMPER) for niche analysis. We analyzed 229 stomachs of four batoid species, 187 containing foods. All species showed a narrow food niche. The most important diet items for each species were Leptochaela serratorbita and Onuphidae for Dasyatis hypostigma; Nematoda for Pseudobatos horkelii; L. serratorbita, Sicyonia dorsalis and Portunidae for Rioraja agassizii and Achelous spinicarpus and fish for Sympterygia bonapartii. The analyses showed dissimilarity among the species' diets without significant niche overlap. Our results detected the absence of significant niche overlap among batoid species, suggesting other types of niche partitioning and spatiotemporal habitat variation. This information could be considered for local management plans. [ABSTRACT FROM AUTHOR]

What are the roles of determinism and contingency in evolution? The paleontologist and evolutionary biologist Stephen J. Gould raised this question in his famous thought experiment of replaying lifes tape. Settings where independent lineages have repeatedly adapted to similar ecological niches (i.e., parallel evolution) are well suited to address this question. Here, we quantified whether repeated ecological shifts across 53 mammalian and 50 avian host species are associated with parallel gut microbiota changes. Our results indicate that parallel shifts in host diet are associated with greater gut microbiota parallelism (i.e., more deterministic). While further research will be necessary to obtain a comprehensive picture of the circumstances under which deterministic gut microbiota changes might be expected, our study can be instrumental in motivating the use of more quantitative methods in microbiota research. This, in turn, can help us better understand microbiota dynamics during adaptive evolution of their hosts.

In warm oligotrophic waters, photosymbiotic coral can flourish across a wide depth range (0–170+ m), extending to depths where light attenuates to ~0.1% of surface values. Conventional wisdom has long assumed that mixotrophic corals must increasingly rely on heterotrophy as the ambient light available to drive photosynthesis decreases with depth. However, evidence challenging this traditional dogma has been accumulating in recent years. Although some evidence suggests that some depth-generalist coral species likely increase their reliance on heterotrophy with increasing depth, there is growing evidence that other species do not. Analysis of bulk stable isotopes (δ13C and δ15N) applied to photosymbiotic corals has been used in several ways to infer their trophic ecology and their relative dependence on symbiont photosynthesis versus heterotrophic feeding. However, metrics based on bulk tissue δ13C and δ15N values are subject to considerable uncertainty due to the multiple factors that can affect their values independent of trophic ecology. These competing factors can be quite challenging to disentangle and have led to inconsistent results and conclusions regarding trends in coral heterotrophy with depth. The evidence to date suggests no uniform trophic pattern with increasing depth or decreasing light. Different corals appear to function differently, which is not surprising given their phylogenetic diversity.

White sharks (Carcharodon carcharias) play a crucial ecological role, shaping ecosystems through direct predation and risk effects. On the east coast of Australia, immature white sharks are broadly distributed, inhabiting a wide range of habitats and ecosystems from temperate Tasmania to tropical North Queensland. Using stable isotopes and fatty acids of muscle and plasma, we examined the diet and habitat use of 136 immature white sharks (152-388 cm total length) captured on SMART drumlines on the East Australian coast. This facilitated the temporal assessment of white shark trophic ecology from a few weeks to approximately a year. Biochemistry of muscle samples showed that white sharks predominantly feed on low trophic level prey from coastal environments. A seasonal shift in diet was evident, with the increasing proportions of essential fatty acids in muscle tissues during spring and summer suggesting a greater consumption of high-nutrition preys during those months compared to autumn and winter. By combining stable isotope and fatty acid analysis, we gain a comprehensive understanding of immature white shark diet in eastern Australia. Our results confirm that white sharks are generalist predators that exhibit seasonal shifts in their diet. Their high use of coastal habitats reinforces the importance of these areas for foraging, which is crucial for growth and development during this critical life stage. [ABSTRACT FROM AUTHOR]

The California sea lion (Zalophus californianus) population in the Gulf of California has shown a significant abundance decline. However, its 13 breeding colonies have distinct individual dynamics modulated by regional environmental conditions. Thus, the relationship between environmental variability and population growth is complex and must be analyzed regionally. Los Islotes is the only colony that has steadily increased since the 1980s. The goal of this study was to determine the interannual changes in abundance and foraging habits (trophic breadth/habitat use) of adult females, and the interannual abundance and body mass of pups of the California sea lion colony from Los Islotes (Southwest Gulf of California) and its relationship with anomalous warming events. For this purpose, monthly population counts were carried out during the breeding seasons (2013–2018) and their interannual variability was analyzed. In addition, 152 pups were captured and weighted, and a small portion of hair was sampled to analyse the stable isotopes of nitrogen (δ15N) and carbon (δ13C) to obtain annual isotopic areas with the program R (SIBER routine). A 50–60% decrease in pups abundance was documented in warm years, such as 2014 and 2015, compared to 2013. Furthermore, pup body mass was negatively affected (by around 3 kg) during anomalous warming events in 2014 and 2018. The largest isotopic areas (3.18‰2 and 2.88‰2) were observed in 2016 and 2018, as a probable result of greater dispersion of adult females during their foraging trips. These results suggest adult females show adaptive responses to environmental variability. It is relevant to continue monitoring and understanding the dynamics of this colony, especially under current environmental change scenarios. [ABSTRACT FROM AUTHOR]

We used an extensive multispecies dataset to examine how C and N stable isotope ratios (δ13C and δ15N) of aquatic consumers varied with body size in populations of northern lakes. Ontogenetic variation in tissue δ13C and δ15N was evident in a diversity of aquatic consumers. Relationships with body size tended to be stronger and more consistently positive for δ15N, and more variable in nature for δ13C. Among-population variation in ontogenetic slopes was greater for δ13C than for δ15N for most biota examined. Relationships between δ13C and δ15N and body size were still significant even after accounting for variation owing to tissue C:N and body condition. Ontogenetic variation was more strongly linked to age than body size in some fishes, particularly for δ15N, but age effects, inferred from growth rate, also accounted for variation in δ13C and δ15N beyond body size effects; δ13C tended to be positively related and δ15N tended to be negatively related to growth rate. There was only limited evidence of concordance in ontogenetic slopes between co-habiting pairs of species, suggesting that the factors driving ontogenetic variation in stable isotope ratios may be largely species- or population-specific. However, ontogenetic slopes of individual taxa were related to various lake habitat features representing climate, ecosystem size, and water clarity. The proportion of isotopic niche space attributable to ontogenetic variation can be substantial and this has implications for applying and interpreting isotopic niche metrics. Our study provides the broadest and most comprehensive analysis of ontogenetic variation in isotopic compositions of freshwater consumers to date and our results underscore the need to account for this variation in the analysis of freshwater food webs. [ABSTRACT FROM AUTHOR]

Trophic ecology has major implications for understanding species' natural history and functional role in ecosystems. This type of information is key to define resource requirements and constraints for conservation planning, especially for threatened specialist species. Here we describe the items that compose the diet of giant armadillos (Priodontes maximus) in the Brazilian wetlands, characterizing their functional role and evaluating if they are true myrmecophages. We sorted 113 fecal samples collected throughout 10 years of monitoring of 29 individuals to identify prey items to the finest possible taxonomic level. Then we estimated the Relative Frequency of Occurrence of each item. The sampling effort was shown to closely represent the expected local prey diversity. Giant armadillos preyed on a diverse array of invertebrates and plants: 23 morphotypes of Isoptera, 50 morphotypes of Hymenoptera, 14 types of seeds, one vertebrate (bone), unidentifiable fragments of Arthropoda, Scarabaeidae fragments, invertebrate eggs, and Acari. All individuals consumed termites (Cornitermes sp. and Nasutermitinae) and plant fragments. There was a high variation on the occurrence of ant morphotypes among samples, most being consumed by few individuals. The most consumed ants were Carebara coeca and Atta vollenweideri, considered crop pests, highlighting armadillo's importance to society through pest control. Fruits were consumed opportunistically by multiple individuals, likely not incidentally as previously hypothesized, and the role of this large mammal as a seed disperser should be further explored. Although giant armadillo's diet is more diverse than expected, the high prevalence of termites and ants confirms its myrmecophagous specialization, making them the largest Neotropical specialist insectivore. [ABSTRACT FROM AUTHOR]

Ecosystem function is maintained in part by direct species interactions, but indirect interactions and non‐consumptive effects may be of equal ecological importance. Along the west coast of North America, the recent population collapse of the predatory sunflower sea star Pycnopodia helianthoides has been implicated in the proliferation of the purple sea urchin Strongylocentrotus purpuratus, and a concurrent decline in kelp canopy cover in several locales. Recent work began to quantify the predation rates effects (i.e., direct consumptive effects) of Pycnopodia on sea urchins that may lead to density‐mediated indirect effects on kelp. However, the importance of non‐consumptive effects on urchin behavior and the possible trait‐mediated indirect effects of Pycnopodia on kelp are not well understood. This leaves a critical gap in our knowledge about how these predators may be controlling grazer populations and, indirectly, primary production by macroalgae in nearshore habitats. We measured the non‐consumptive behavioral effects of Pycnopodia on S. purpuratus in the laboratory including grazing rates, feeding behavior, and movement of starved versus fed urchins, the latter simulating urchin metabolic conditions within urchin barrens. We found that the presence of a waterborne Pycnopodia cue reduced the grazing rate of fed urchins by 50% over short (~24 h) time scales. In contrast, starved urchins consumed kelp and did not exhibit an escape response in the presence of a Pycnopodia cue. This study highlights a trait‐mediated indirect interaction between Pycnopodia, S. purpuratus, and kelp, showing how the urchin response to a predator cue may differ based on urchin metabolic conditions or ecosystem state, and helps clarify the positive role of Pycnopodia on kelp forest health. [ABSTRACT FROM AUTHOR]

Crinoids of the Order Comatulida are renowned for harboring a remarkable diversity of symbiotic organisms within echinoderms, including polychaetes, myzostomids, gastropods, crustaceans, brittle stars, or fish. Crinoids provide essential services to their symbionts, such as shelter, access to food resources, mating areas, nesting grounds, and nurseries. Symbionts within crinoids developed a variety of strategies, including foraging in the arm ambulacral grooves, preying upon other symbionts, living within galls, or accessing suspended food particles from the water column. In this work, we focused on the Great Reef of Toliara, where we collected specimens from seven crinoid species. Among the 84 crinoids examined, a total of 285 symbiotic organisms were retrieved. These symbionts were either moving freely on their host or found within cysts. Stable isotope analyses of carbon and nitrogen for both hosts and symbionts have shown that (a) all crinoids shared a common trophic niche; (b) a community-based approach indicated that crinoids initiated trophic networks primarily based on suspended particulate organic matter; (c) non-specific symbionts exhibited consistent dietary preferences regardless of their host; (d) myzostomids inhabiting cysts were found to feed on their host tissues; and (e) free-moving symbionts displayed divergent trophic niches linked to their predatory, kleptoparasitic, or filter-feeding behaviors. This research underscores the role of crinoids, particularly comatulid species, as key components of tropical ecosystems in the Western Indian Ocean, inhabited by a hidden biodiversity with complex trophic networks. Their intricate morphology accommodates a range of feeding strategies, supporting a diverse associated fauna. [ABSTRACT FROM AUTHOR]

We modeled feeding of the Atlantic salmon (Salmo salar) parr to understand the role of global (cross‐continental) and regional (river) spatial scales for delineating feeding patterns. The diet composition differed between Eurasia and North America populations. Geographic location (latitude and elevation) had an influence for the most common prey (Ephemeroptera, Diptera and Plecoptera). The random factors (sampling location and river) had a strong explanatory power in our models, suggesting that local drivers may override the effects of large‐scale drivers. [ABSTRACT FROM AUTHOR]

The development of diverse capture mechanisms during foraging allows predators to select their preys and succeed in their capture, with the least energy expenditure possible. In this context, we seek to understand how prey selection mechanisms exhibited by freshwater fish piscivores relate to their foraging mode. The study was carried out in the floodplain of the Upper Paraná River, where fish were captured from March 2006 to June 2013. The fish were identified and measured, their stomachs were removed, and the stomach contents were analysed. Quantile regressions were used to evaluate possible effects and relationships between the sizes of piscivores and their prey. A significant positive effect on the predator–prey size relationship was observed, indicating an increased size of consumed prey with increased size of piscivore, mainly for Acestrorhynchus lacustris, Hoplerythrinus unitaeniatus, Hoplias intermedius, Hoplias mbigua, Hoplias sp. 2, Pseudoplatystoma corruscans, Rhaphiodon vulpinus and Salminus brasiliensis. Ambush predators were more likely to consume slow‐moderate and fast prey, while pursue predators only consume fast prey. Several mechanisms can influence a piscivore's foraging behaviour, and body size is an important factor for both the piscivore and its prey. From the prey's point of view, the way they swim and the complexity of the habitat are important characteristics to ensure their survival. For piscivores, the foraging mode will influence the type of prey consumed, depending on the prey's swimming mode. [ABSTRACT FROM AUTHOR]

Concerns about competition between pollinators are predicated on the assumption of floral resource limitation. Floral resource limitation, however, is a complex phenomenon involving the interplay of resource production by plants, resource demand by pollinators, and exogenous factors—like weather conditions—that constrain both plants and pollinators. In this study, we examined nectar limitation during the mass flowering of rosaceous fruit trees in early spring. Our study was set in the same region as a previous study that found severe nectar limitation in summer grasslands. We used this seasonal contrast to evaluate two alternative hypotheses concerning the seasonal dynamics of floral resource limitation: either (H1) rates of resource production and consumption are matched through seasonal time to maintain a consistent degree of resource limitation, or (H2) a mismatch of high floral resource production and low pollinator activity in early spring creates a period of relaxed resource limitation that intensifies later in the year. We found generally much lower depletion in our spring study compared to the near 100% depletion found in the summer study, but depletion rates varied markedly through diel time and across sampling days, with afternoon depletion rates sometimes exceeding 80%. In some cases, there were also pronounced differences in depletion rates across simultaneously sampled floral species, indicating different degrees of nectar exploitation. These findings generally support the seasonal mismatch hypothesis (H2) but underscore the complex contingency of nectar depletion. The challenge of future work is to discern how the fluctuation of resource limitation across diel, inter‐diel, and seasonal time scales translates into population‐level outcomes for pollinators. [ABSTRACT FROM AUTHOR]

Spatial and temporal zooplankton feeding dynamics across the water column of lakes are key for understanding site-specific acquisition of diet sources. During this 6-week lake study, we examined stable carbon (δ13C) and nitrogen (δ15N) isotopes and conducted compound-specific fatty acid (FA) stable isotope analysis (CSIA) of edible seston in the epi-, meta-, and hypolimnion, and zooplankton of Lake Lunz, Austria. We predicted that CSIA of essential FA can discern the foraging grounds of zooplankton more accurately than the commonly used bulk stable isotopes. The δ13C and δ15N values of seston from different lake strata were similar, whereas a dual CSIA approach using stable carbon and hydrogen isotopes of FA (δ13CFA and δ2HFA) provided sufficient isotopic difference in essential FA to discern different lake strata-specific diet sources throughout the study period. We present a CSIA model that suggests strata-specific foraging grounds for different zooplankton groups, indicating higher preference of cladocerans for feeding on epilimnetic diet sources, while calanoid copepods retained more hypolimnetic resources. The CSIA approach thus yields strata-specific information on foraging strategies of different zooplankton taxa and provides more details on the spatial and temporal trophodynamics of planktonic food webs than commonly used bulk stable isotopes. [ABSTRACT FROM AUTHOR]

Understanding the trophic structure of species assemblages is crucial in order to comprehend how syntropic species coexist in space and time. Bats are the second most taxonomically diverse group of mammals and display a wide range of dietary strategies. Due to their ability to disperse over water, ca. 60% of all extant bat species occur on islands and for the most part their interspecific ecological interactions are poorly known. Using DNA metabarcoding, this study offers the first insights into the diet of Macaronesian bats by providing a holistic overview of prey consumed by all 3 bat species found on Madeira Island (Pipistrellus maderensis , Nyctalus leisleri verrucosus , and Plecotus austriacus) and investigating both interspecific (between P. maderensis and N. l. verrucosus) and intraspecific (between female and male N. l. verrucosus) dietary differences. We identified a total of 110 species of arthropod prey in the diet of the 3 bat species, including multiple agriculture and forestry pest species, a human disease-relevant species, and numerous taxa not previously recorded on the island. Lepidoptera was the primary prey order for all 3 bat species. The diet composition of P. maderensis and N. l. verrucosus differed significantly, with P. maderensis consuming more Diptera and multiple prey taxa not found in the diet of N. l. verucosus. Moreover, male N. l. verrucosus exhibited a broader niche breadth than females. This study is among the first to use DNA metabarcoding to evaluate the diet of insular bats and thus greatly advances knowledge regarding the trophic ecology and pest suppression services of these poorly-known mammals. [ABSTRACT FROM AUTHOR]

Shallow coral reefs are being increasingly degraded as a result of natural and anthropogenic threats. Mesophotic coral ecosystems (MCEs) are an extension of shallow reefs at depths of ∼30–150 m that harbor depth generalists and specialists, acclimatized to changes in physical factors. A faunal break in MCEs occurs between upper (∼30–60 m) and lower (∼60–150 m) depths, representing transitional and endemic communities, respectively. The trophic ecology of MCEs shifts from autotrophic to heterotrophic processes with increasing depth, and trade-offs in the utilization of dissolved organic matter and particulate organic matter. While dispersal of MCE larvae could reseed degraded shallow reefs, genetic evidence is equivocal, suggesting site-specific connectivity patterns; anthropogenic disturbances at mesophotic depths indicate that MCEs may be as susceptible to stressors as shallow reefs are. The function and stability of mesophotic coral ecosystems (MCEs) have been extensively studied in recent years. These deep reefs are characterized by local physical processes, particularly the steep gradient in irradiance with increasing depth, and their impact on trophic resources. Mesophotic reefs exhibit distinct zonation patterns that segregate shallow reef biodiversity from ecologically unique deeper communities of endemic species. While mesophotic reefs are hypothesized as relatively stable refuges from anthropogenic stressors and a potential seed bank for degraded shallow reefs, these are site-specific features, if they occur at all. Mesophotic reefs are now known to be susceptible to many of the same stressors that are degrading shallow reefs, suggesting that they require their own specific conservation and management strategies. [ABSTRACT FROM AUTHOR]

Co-occurring predators often exhibit ecological niche partitioning, resulting from competition over evolutionary time. However, in productive estuarine ecosystems with high resource availability, predators may occupy similar niches without conflict. Determining the degree of niche partitioning and overlap among co-occurring predators can provide insights into a food web's function and its potential resiliency to perturbations. This study used stable isotope analysis to assess the trophic ecology of four predators in Galveston Bay, Texas, USA: spotted seatrout, black drum, bull shark, and alligator gar. Spatially distinct primary producer isotopic ratios emerged for both δ13C and δ15N following salinity regimes, which translated to similar patterns in predator tissue. The volume and overlap among species' trophic niches also varied spatially, with species-specific expansion and contraction of niches across the freshwater-marine continuum. The observed niche patterns were likely related to movements, with implications for trophic coupling across the estuarine landscape. Using regional delineations for baseline values yielded trophic position estimates that were validated by compound-specific stable isotopes and were similar (3.77 to 3.96) for all species but black drum (3.25). Trophic position increased with body length for all species but black drum, and these relationships differed when using estuary-wide versus regionally distinct baselines. Alligator gar gut contents were examined, which primarily aligned with piscivory but also included previously unreported taxa (insect, mammal). Collectively, these results provide evidence for spatial and ontogenetic shifts in trophic ecology within this predator assemblage and highlight the importance of spatial scale when using stable isotopes to examine estuarine food webs. [ABSTRACT FROM AUTHOR]

The Atlantic blue crab Callinectes sapidus (Decapoda, Portunidae) Rathbun, 1896 is native to the east coasts of North and South America and has recently expanded its distribution in the non-native range into the Gulf of Cadiz (SW Iberian Peninsula, Europe). Considering the impacts caused by this invasive species in numerous estuarine ecosystems and its generalist feeding behavior, this study aims to provide the first account of the Atlantic blue crab diet on the East Atlantic coast. We studied the species' feeding habits using stomach content analyses to predict food web interactions and putative impacts. Samples were obtained in the Guadalquivir estuary (SW Spain, Europe), which was colonized in 2017. The main food items identified on their stomach were, fish (49.9%), mollusks (44.4%) and crabs (32.3%). They also consumed plant material (27.2%), and the sediment (32.3%) in their digestive tract was likely the result of secondary ingestion. The Atlantic blue crab exhibited the same omnivorous behavior as in the native area. There was no sexual variation in diet composition or feeding activity in general, but there was a seasonal variation in the diet composition of females. The decrease of the caramote prawn Penaeus kerathurus (Forskål 1775) observed in the Guadalquivir estuary since 2021 is likely not due to the Atlantic blue crab because they seldomly eat this prey. Overall, our study provides clear baseline information to expand the knowledge about the ecological roles of the Atlantic blue crab in non-native ecosystems. [ABSTRACT FROM AUTHOR]

Female northern elephant seals (Mirounga angustirostris) are migratory animals that form colonies along the coasts of California and the Baja California Peninsula, Mexico. A recent decline in abundance has been recorded in this species Mexican distribution, which is an important reason to investigate the different ecological processes operating in these colonies. The aim of this study was to determine values of stable isotope ratios (ô13C and ô15N) in pup fur as foraging maternal indicators. During the same breeding season (2015), pup fur samples were collected to investigate these foraging variations between the two major Mexican colonies--Guadalupe Island (GI) and the San Benito Archipelago (SBA). Isotopic areas were built using the 'SIBER' package in R, and a custom hierarchical Bayesian model was used to compare the values from both localities. Mean (± standard deviation [SD]) ô13C values for individuals from GI and the SBA were -16.9 ± 0.8%o and -17.3 ± 0.4%o, respectively, while ô15N values were 17.4 ± 1.1%o and 16.7 ± 1.1%o, respectively. The difference between the posterior means indicated a high probability (P > 99%) of GI having higher stable isotope ratio values than the SBA. For the posterior SDs, there were highly probable differences (P = 100%) only for ô13C, where GI had a higher dispersion. Such differences explained why GI presented a wider isotopic niche area than the SBA, indicating more diverse foraging habits along GI's offshore-inshore gradient. Additionally, GI showed higher ô15N values than the SBA. Although this could be related to a slightly higher trophic position for GI individuals, the latitudinal effects of foraging grounds with distinct isotopic baselines remain a plausible explanation for the variations in both isotope ratios, suggesting that individuals from the SBA foraged in a more northerly location than those from GI. This study provides valuable knowledge about how females from both colonies partition resources, especially regarding habitat use. [ABSTRACT FROM AUTHOR]

Animal transport of energy and nutrients through food webs and across ecosystem boundaries is highly dynamic in time and space, challenging our ability to quantify ecological processes. Energy and nutrient flux in individual animals can be measured with data on growth, biochemistry, and trophic ecology, but scaling individual processes up to entire animal communities is inherently difficult. On coral reefs, new frameworks have been developed to predict growth rates, nutrient cycling, micronutrient concentrations, and energy sources in fishes, helping to uncover ecosystem functions and services. Filling data gaps and comparing flux frameworks with existing ecosystem tools will improve quantitative predictions and help ecologists trace energy and nutrient flux in other aquatic systems. The movement of energy and nutrients through ecological communities represents the biological 'pulse' underpinning ecosystem functioning and services. However, energy and nutrient fluxes are inherently difficult to observe, particularly in high-diversity systems such as coral reefs. We review advances in the quantification of fluxes in coral reef fishes, focusing on four key frameworks: demographic modelling, bioenergetics, micronutrients, and compound-specific stable isotope analysis (CSIA). Each framework can be integrated with underwater surveys, enabling researchers to scale organismal processes to ecosystem properties. This has revealed how small fish support biomass turnover, pelagic subsidies sustain fisheries, and fisheries benefit human health. Combining frameworks, closing data gaps, and expansion to other aquatic ecosystems can advance understanding of how fishes contribute to ecosystem functions and services. [ABSTRACT FROM AUTHOR]

Simple Summary: Environmental factors, maternal inheritance, and feeding success are influential factors in fish growth, especially during the larval stage, encompassing their early days of life. Growth rates play a crucial role in larval survival, particularly in species with high energy requirements such as the Atlantic bluefin tuna (ABFT). Our analyses of two patches of ABFT larvae collected in the Gulf of Mexico's spawning region during different years reveal variable larval growth, depending on prey availability. Larval growth also shows a direct relationship to maternal feeding. Estimates of larval trophic positions are primarily influenced by food web length and energy transmission efficiency, leading to differences in larval growth and underscoring the importance of considering trophic dynamics in interpreting results. These findings offer novel insights into how these factors affect ABFT larval growth, potentially informing conservation efforts and fisheries management strategies by governmental institutions. Two cohorts of Atlantic bluefin tuna (Thunnus thynnus) larvae were sampled in 2017 and 2018 during the peak of spawning in the Gulf of Mexico (GOM). We examined environmental variables, daily growth, otolith biometry and stable isotopes and found that the GOM18 cohort grew at faster rates, with larger and wider otoliths. Inter and intra-population analyses (deficient vs. optimal growth groups) were carried out for pre- and post-flexion developmental stages to determine maternal and trophodynamic influences on larval growth variability based on larval isotopic signatures, trophic niche sizes and their overlaps. For the pre-flexion stages in both years, the optimal growth groups had significantly lower δ15N, implying a direct relationship between growth potential and maternal inheritance. Optimal growth groups and stages for both years showed lower C:N ratios, reflecting a greater energy investment in growth. The results of this study illustrate the interannual transgenerational trophic plasticity of a spawning stock and its linkages to growth potential of their offsprings in the GOM. [ABSTRACT FROM AUTHOR]

Mysids, besides krill, play a significant role in energy transfer and carbon sequestration. The ecology of coastal species is better understood than that of deep dwelling species such as Boreomysis arctica. The objectives of this study were to quantify spatiotemporal variations in body condition and the trophic level of B. arctica in autumn and winter, under sea-ice conditions in the St. Lawrence system, using a multimarker approach. We sampled along a 1000 km transect. Mean abundances in winter were higher in the estuary compared to the Gulf of St. Lawrence. Body condition, measured as total lipid content, was higher in winter than in autumn. Lipids of B. arctica were mainly composed of wax esters, thereby B. arctica is richer in energetic lipids compared to the three dominant krill species. We also observed seasonal differences in the trophic level of B. arctica, revealing carnivorous behavior in autumn compared to omnivory in winter. High intra-specific variability in both energetic strategy and feeding behavior was found that is potentially due to opportunistic feeding. Energy rich reserves suggest that B. arctica could act as a valuable prey for both benthic and pelagic consumers and thus playing a key role in bentho-pelagic energy transfer. [ABSTRACT FROM AUTHOR]

Quantifying the tropic position (TP) of an animal species is key to understanding its ecosystem function. While both bulk and compound-specific analyses of stable isotopes are widely used for this purpose, few studies have assessed the consistency between and within such approaches. Champsocephalus gunnari is a specialist teleost that predates almost exclusively on Antarctic krill Euphausia superba. This well-known and nearly constant trophic relationship makes C. gunnari particularly suitable for assessing consistency between TP methods under field conditions. In the present work, we produced and compared TP estimates for C. gunnari and its main prey using a standard bulk and two amino acid-specific stable isotope approaches (CSI-AA). One based on the difference between glutamate and phenylalanine (TPGlx-Phe), and the other on the proline-phenylalanine difference (TPPro-Phe). To do that, samples from C. gunnari, E. superba and four other pelagic invertebrate and fish species, all potential prey for C.gunnari, were collected off the South Orkney Islands between January and March 2019, analyzed using standard isotopic ratio mass spectrometry methods and interpreted following a Bayesian approach. Median estimates (CI95%) for C. gunnari were similar between TPbulk (3.6; CI95%: 3.0-4.8) and TPGlx-Phe(3.4; CI95%:3.2-3.6), and lower for TPPro-Phe (3.1; CI95%:3.0-3.3). TP differences between C. gunnari and E. superba were 1.4, 1.1 and 1.2, all compatible with expectations from the monospecific diet of this predator (ΔTP=1). While these results suggest greater accuracy for Glx-Phe and Pro-Phe, differences observed between both CSI-AA approaches suggests these methods may require further validation before becoming a standard tool for trophic ecology. [ABSTRACT FROM AUTHOR]

Abstract Understanding how human activities affect wildlife is fundamental for global biodiversity conservation. Ongoing land use change and human‐induced climate change, compel species to adapt their behaviour in response to shifts in their natural environments. Such responses include changes to a species' diet or trophic ecology, with implications for the wider ecosystem. This is particularly the case for predatory species or those that occupy high positions within trophic webs, such as raptors. Between 2002 and 2019, we observed 1578 feeding events of the globally near threatened and understudied, Red‐necked Falcon (Falco chicquera) in Bangladesh. We explored the effects of mean monthly temperature, precipitation, temperature differences, and urban land cover on (a) mean prey weights and (b) dietary composition of 15 falcon pairs. Falcons hunted smaller prey items during months with increased temperatures and precipitation, and in more urban areas. However, during months with increased temperature differences, falcons tended to prey on larger prey items. Being specialist aerial hunters, these dietary patterns were largely driven by the probabilities of bats and birds in the diet. Falcons were more likely to prey on bats during warmer and wetter months. Furthermore, urban pairs tended to prey on bats, whereas more rural pairs tended to prey on birds. Mean monthly temperature difference, i.e., a proxy for climate change, was better at explaining the probability of bats in the falcon diet than mean monthly temperature alone. Anthropogenic dietary shifts can have deleterious effects on species with declining populations or those of conservation concern. The effects of urbanisation and human‐induced climate change are expected to continue into the foreseeable future. Therefore, our findings represent a cornerstone in our understanding of how falcons respond to an increasingly human‐dominated world.

Abstract Multiple species of the elephant fishes (Mormyridae) commonly coexist in sympatry in most African tropical rivers and lakes. In this study, we investigated the trophic ecology and potential trophic niche partitioning of eleven mormyrid fish species from the Sanaga River system in Cameroon using the stable isotope composition of carbon and nitrogen in the muscle samples. Albeit most mormyrids mainly feed on invertebrates, we found differences in isotope ratios, and we report signs of the trophic niche partitioning among species. We further found significant differences in isotopic signatures within the Mormyrus genus, suggesting ecological niche diversification among three closely related species. We have also evaluated differences in the isotopic signals between seasons in four species, which could be possibly caused by species migration and/or anthropogenic agricultural activities. To evaluate body shape, we applied geometric morphometric analyses, and we show that most of the species are clearly morphologically separated. We focused on the mormyrid ecomorphology to identify a possible interaction between shape and ecology, and we found a relationship between the δ13C (but not δ15N) isotopic signal and morphology, suggesting their interplay during mormyrid evolution. Overall, we present robust evidence of the trophic niche partitioning within the mormyrid species community, and we integrate trophic ecology with morphometrics, shedding light on the enigmatic evolutionary history of these fascinating African fishes.

Parallel evolution of phenotypic traits is regarded as strong evidence for natural selection and has been studied extensively in a variety of taxa. However, we have limited knowledge of whether parallel evolution of host organisms is accompanied by parallel changes of their associated microbial communities (i.e., microbiotas), which are crucial for their hosts' ecology and evolution. Determining the extent of microbiota parallelism in nature can improve our ability to identify the factors that are associated with (putatively adaptive) shifts in microbial communities. While it has been emphasized that (non)parallel evolution is better considered as a quantitative continuum rather than a binary phenomenon, quantitative approaches have rarely been used to study microbiota parallelism. We advocate using multivariate vector analysis (i.e., phenotypic change vector analysis) to quantify direction and magnitude of microbiota changes and discuss the applicability of this approach for studying parallelism, and we compiled an R package for multivariate vector analysis of microbial communities ('multivarvector'). We exemplify its use by reanalyzing gut microbiota data from multiple fish species that exhibit parallel shifts in trophic ecology. We found that multivariate vector analysis results were largely consistent with other statistical methods, parallelism estimates were not affected by the taxonomic level at which the microbiota is studied, and parallelism might be stronger for gut microbiota function compared to taxonomic composition. This approach provides an analytical framework for quantitative comparisons across host lineages, thereby providing the potential to advance our capacity to predict microbiota changes. Hence, we emphasize that the development and application of quantitative measures, such as multivariate vector analysis, should be further explored in microbiota research in order to better understand the role of microbiota dynamics during their hosts' adaptive evolution, particularly in settings of parallel evolution.

Bonnethead and Caribbean sharpnose sharks frequent coastal waters, rendering them vulnerable to overexploitation, with the bonnethead shark listed as endangered by the IUCN. Marine Protected Areas (MPAs) have been suggested as a management strategy to regulate shark-exploitation. Moreover, it's essential to identify key areas where nursery grounds (NG) and adult habitats overlap to prioritize conservation zones within MPAs. Along the Caribbean Sea, several NG have been identified for larger shark species, but little is known for smaller sharks. In Bocas del Toro (BDT-Panamanian Caribbean), both bonnethead and Caribbean sharpnose sharks are distributed, with the former appearing to be genetically isolated. The local MPA in BDT doesn't include a NG identified near Solarte Island. In this study, to provide ecological information on bonnethead and Caribbean sharpnose sharks within this potential NG, we evaluated stable isotopes (δ13C and δ15N) and total-mercury (THg) values in their fins. The results revealed a higher proportion of small-adult sharks in the NG, emphasizing the necessity of conducting a comprehensive study to further characterize this area. Moreover, there was no niche-partitioning between the two species and their diets primarily consisted of small prey-items, as evidenced by the significant and negative relationship between isotopic values. Both species exhibited low THg levels in their fins. Based on these initial results and previous genetic data, it appears that BDT plays a critical role as a habitat for sharks. Thus, extending the local MPA to cover the potential NG could effectively ensure conservation of bonnethead and Caribbean sharpnose sharks in BDT. [ABSTRACT FROM AUTHOR]

Natural food available in ponds can complement formulated feed in fed aquaculture. This study elucidated the natural food intake and its contribution to tambaqui (Colossoma macropomum) growth in fertilized and unfertilized ponds, using stable isotope and stomach contents analyses. Additionally, it described the impact of fertilization management on natural food availability, fish performance, and production costs. Tambaqui juveniles (93.8 ± 15.0 g) were stocked (0.55 fish/m2) in fertilized (Fert) and unfertilized (NoFert) ponds (600 m2) for a culture period of 10 months in quadruplicate. A lower food conversion ratio was observed in Fert ponds. The main natural food items ingested by tambaqui were insects, vegetables, and cladocerans. Plankton contributed 39.4% and 10.7% of muscle formation in Fert and NoFert ponds, respectively. Pond fertilization (2.45 g of nitrogen and 0.80 g of phosphorus per square meter every two weeks) did not significantly affect fish growth, survival, or productivity but had a slightly influence on water quality parameters. However, fertilization increased the zooplankton density (through phytoplankton) in the water, thereby increasing autochthonous food availability for tambaqui consumption. This species demonstrates the ability to alternate between natural food sources and commercial feed without compromising its development. Consequently, tambaqui exhibits suitability for farming within restorative and integrated aquaculture systems as well as intensive systems reliant on commercial feed. [ABSTRACT FROM AUTHOR]

Scarce information is available on the trophic ecology and feeding habitats of the Peruvian Tern Sternula lorata. We searched 15 Peruvian Tern colonies along the coast of northern Chile during the breeding seasons of 2008 to 2018 to evaluate the tern's main food source. We collected samples of prey remains found near nests as well as prey items regurgitated by chicks and adults during our visits. We found that the Peruvian Tern is mainly piscivorous, secondarily feeding on some cephalopods and euphausiids. Pacific Saury Scomberesox saurus and Paloma Pompano Trachinotus paitensis were the main prey found near nests, but regurgitated prey was dominated by the Peruvian Anchoveta Engraulis ringens. Fish prey sizes ranged from 36 to 192 mm. These findings expand existing knowledge of the feeding ecology of this endangered seabird during its breeding season. [ABSTRACT FROM AUTHOR]