Stomach Content Analysis Research Articles

Diet of crescentchests (Melanopareiidae) based on stomach content analysis

Diet of crescentchests (Melanopareiidae) based on stomach content analysis

Stomach content analysis in ariids: Insights of three catfish species from a marine protected area

Stomach content analysis in fish provides information about the diet, different trophic groups in the ichthyofauna and concerning the transfer and energy obtaining. The aquatic environment become receptacle for emerging pollutant such as plastic, that become available to the biota. The goal of this study was to describe the feeding of the three catfish species A. luniscutis, C. spixii and G. genidens, in a sexual and spatial approach, considering that are important catfish from a Marine Protected Area in Brazil (Cananeia-Iguape Estuarine-Lagoon Complex – CIELC), subjected to differential anthropogenic disturbances. The analyzed species had a diverse diet, with the occurrence of Crustacea fragments of several groups (e.i.: amphipoda, decapods, mysidae, palinura, caridea, penaeidae, stomatopoda and brachyura), Algae, Polychaeta, Ophiuroidea, Mollusca, vegetable matter, and fish fragments (e.i. otoliths, eggs, scale, fins, and fish debris). The food items of Cathorops spixii were composed mainly of Polychaeta, vegetable matter, and Crustacea. On the other hand, the main food items of Aspistor luniscutis were fish fragments, algae, and vegetable matter and in Genidens genidens predominated Crustacea and vegetable matter. Possible plastic fragments were found and had filamentous format with blue, red, and black color variations. The data of this research contribute to the promotion of knowledge about feeding in three species of catfish. Furthermore, it highlights the pollution of an environmental marine protection area.

Assessing Diet & Trophic Position of Fish in Chenderoh Reservoir, Malaysia: SCA & SIA Approach

The present study assessed and compared the diet and trophic positions (TP) of two carnivorous fish H. macrolepidota and C. ocellaris from Chenderoh Reservoir, Malaysia. The focal goal of the study was to understand the effects of invasive non-indigenous species (NIS), C. ocellaris, on the native indigenous (IS) fish species, H. macrolepidota. Data were acquired from September 2014 to February 2015 within the study area. The assessment was grounded in stomach content analysis (SCA) and stable isotope analysis (SIA), which collectively clarified the feeding habits and trophic positions (TP) of these selected fish. In total, 184 fish samples (comprising 64 individuals of H. macrolepidota and 120 individuals of C. ocellaris) underwent stomach content analysis (SCA). Additionally, 24 individuals (12 of H. macrolepidota and 12 of C. ocellaris), sampled from December 2014 to February 2015, were selected for stable isotope analysis (SIA). The mean RGL values for H. macrolepidota and C ocellaris were 0.98 ± 0.18 and 1.10 ± 0.15 (Mean ± SD), respectively, aligning with known ranges for carnivorous fish. These values also clarified that both species occupy higher TP in the food web as tertiary or quaternary consumers. SCA findings also revealed that fish and crustaceans were the predominant food categories for H. macrolepidota, while C. ocellaris predominantly fed on fish. The mean stomach fullness index (MSF) and the gastrosomatic index (GSI) corroborated the differences in the foraging performance of the fishes, with C. ocellaris having a higher MSF (2.03) compared to H. macrolepidota (0.65). These implied that C. ocellaris had plentiful of food and encountered fewer diet-related challenges in the ecosystem. From SIA, δ13C values indicated that the primary carbon sources for both species are C3 plants, particularly aquatic vegetation. Further, δ15N values further ensured that both H. macrolepidota and C. ocellaris are carnivorous in nature and occupy higher TP in the ecosystem.

Increasing marine trophic web knowledge through DNA analyses of fish stomach content: a step towards an ecosystem-based approach to fisheries research.

Multispecies and ecosystem models, which are key for the implementation of ecosystem-based approaches to fisheries management, require extensive data on the trophic interactions between marine organisms, including changes over time. DNA metabarcoding, by allowing the simultaneous taxonomic identification of the community present in hundreds of samples, could be used for speeding up large-scale stomach content data collection. Yet, for DNA metabarcoding to be routinely implemented, technical challenges should be addressed, such as the potentially complicated sampling logistics, the detection of a high proportion of predator DNA, and the inability to provide reliable abundance estimations. Here, we present a DNA metabarcoding assay developed to examine the diet of five commercially important fish, which can be feasibly incorporated into routinary samplings. The method is devised to speed up the analysis process by avoiding the stomach dissection and content extraction steps, while preventing the amplification of predator DNA by using blocking primers. Tested in mock samples and in real stomach samples, the method has proven effective and shows great effectiveness discerning diet variations due to predator ecology or prey availability. Additionally, by applying our protocol to mackerel stomachs previously analyzed by visual inspection, we showcase how DNA metabarcoding could complement visually based data by detecting overlooked prey by the visual approach. We finally discuss how DNA metabarcoding-based data can contribute to trophic data collection. Our work reinforces the potential of DNA metabarcoding for the study and monitoring of fish trophic interactions and provides a basis for its incorporation into routine monitoring programs, which will be critical for the implementation of ecosystem-based approaches to fisheries management.

Food composition of diamondback puffer Lagocephalus guentheri Miranda Ribeiro, 1915 from the northeastern Mediterranean Sea

Stomach content analysis of fish not only helps document their food spectrum but also provides an overview of the food network they are involved in. In this study, we aimed to investigate the food composition of L. guentheri from the Iskenderun Bay, northeastern Mediterranean Sea. Specimens were collected from between January 2022 and August 2022. A total of 215 L. guentheri specimens stomachs were examined during the study for stomach content analysis. About 215 stomachs analysed, 60 (27.9%) stomachs were empty and 155 (72.1%) stomachs contained food items. Analysis of the diet composition showed that the fish are carnivorous and prey on pisces, crustacea, bivalves and cephalopoda. Based on the index of relative importance, pisces were identified as the most important prey (68%), followed by crustaceans (14%), bivalves (5%), cephalopoda (0.5%) and digested materials (12.5%). The results show that L. guentheri has a high feeding tendency to fish. This study increases the knowledge of the feeding preferences of L. guentheri. The present paper is also the first document on the diamondback puffer Lagocephalus guentheri food composition in the Mediterranean Sea.

Linking anatomical and histological traits of the digestive tract to resource consumption and assimilation of omnivorous tetra fishes.

This study explores the interplay between digestive tract traits, food intake, and assimilation in omnivorous tetra fishes (Psalidodon bifasciatus, P. aff. gymnodontus, and Bryconamericus ikaa) from the Iguaçu River basin, an ecologically significant region known for high endemism. We hypothesize that variations in digestive tracts across species would be associated with differences in diet, isotopic composition in fish tissues, and overall diet assimilation. To test this, we employed stereoscopic and light microscopy to characterize the gross anatomy, histomorphology, and histochemistry of fish digestive tracts. Additionally, we used stomach content and stable isotope analyses to trace fish diets. While these tetra fishes shared histological structures, disparities were noted in anatomical digestive traits and diet preferences. The smallest species, B. ikaa, with a shorter intestine, had fewer pyloric caeca and primarily consumed animal-based diets. Conversely, P. bifasciatus and P. aff. gymnodontus, with longer intestines, displayed numerous pyloric caeca and consumed a balanced mix of animal and plant items. Despite anatomical and dietary differences, all three species predominantly assimilated animal-origin food. The tetra fishes had histological variations among digestive tract segments, with the esophagus having the thickest muscular layer, gradually thinning towards the posterior intestine. The final portion of the intestine exhibited a significant expansion in the lumen perimeter, while the esophagus had the smallest lumen area. Goblet cells were most concentrated in the posterior intestine for all species. The gross anatomy of these tetra fishes aligns with their omnivorous habit, while diet assimilation was dominated by animal-origin food. These findings provide crucial insights into the structural and tissue characteristics of their digestive systems, laying the groundwork for deeper exploration into the physiological aspects of their digestive tracts and enhancing our understanding of their feeding strategies.

Trophic ecology of the greater amberjack in relation to marine environmental characteristics in Taiwanese waters illustrated by stable isotope and stomach content approach

The greater amberjack (Seriola dumerili) holds significant commercially and ecologically important large pelagic marine species in Taiwanese waters. The aim of this study was investigates its stomach contents and stable isotope signatures (δ13C and δ15N) were used to explore the trophic ecology and to detect the dietary variations by length, sex, and season and their associations with marine environmental characteristics. Utilizing a generalized additive model, we elucidate how marine environmental variables influence greater amberjack feeding habitats. Our findings revealed that the mixed layer depth and sea surface temperature explained the highest influence in the greater amberjack feeding ground. To reveal the trophic ecology of the greater amberjack and their ecosystem trophic dynamics, we used an innovative approach combining stomach content analysis (SCA) and stable isotope analysis (SIA) of carbon and nitrogen (δ13C and δ15N) coupled with Bayesian mixing model analysis. By contrast, some of the results in SIA were different from the most important food items identified in SCA; in general, they prefer to consume pelagic prey species. The Bayesian mixing models indicated that the target predator species diet structure was dominated by Trichiuridae and Leiognathidae prey species, as indicated by the highest δ15N values. The relationships of the greater amberjack weight and length were not significant with δ13C values (p > 0.05) but were significant (p < 0.001) with δ15N values. The relationships between trophic positions (TPs) in terms of length, sex, and season suggested an ontogenetic shift, with varied TP values between 4.01 and 5.18, indicating that the greater amberjack is the top-level predator species in the pelagic marine ecosystem. These findings can guide ecosystem-based adaptive fishery management and conservation because the local prey species depletion and variations in marine environmental conditions may affect greater amberjack fisheries in Taiwanese waters.

Fecal DNA metabarcoding helps characterize the Canada jay's diet and confirms its reliance on stored food for winter survival and breeding.

Accurately determining the diet of wild animals can be challenging if food items are small, visible only briefly, or rendered visually unidentifiable in the digestive system. In some food caching species, an additional challenge is determining whether consumed diet items have been previously stored or are fresh. The Canada jay (Perisoreus canadensis) is a generalist resident of North American boreal and subalpine forests with anatomical and behavioural adaptations allowing it to make thousands of arboreal food caches in summer and fall that are presumably responsible for its high winter survival and late winter/early spring breeding. We used DNA fecal metabarcoding to obtain novel information on nestling diets and compiled a dataset of 662 published and unpublished direct observations or stomach contents identifications of natural foods consumed by Canada jays throughout the year. We then used detailed natural history information to make informed decisions on whether each item identified to species in the diets of winter adults and nestlings was best characterized as 'likely cached', 'likely fresh' (i.e., was available as a non-cached item when it appeared in a jay's feces or stomach), or 'either possible'. Of the 87 food items consumed by adults in the winter, 39% were classified as 'likely cached' and 6% were deemed to be 'likely fresh'. For nestlings, 29% of 125 food items identified to species were 'likely cached' and 38% were 'likely fresh'. Our results support both the indispensability of cached food for Canada jay winter survival and previous suggestions that cached food is important for late winter/early spring breeding. Our work highlights the value of combining metabarcoding, stomach contents analysis, and direct observations to determine the cached vs. non-cached origins of consumed food items and the identity of food caches, some of which could be especially vulnerable to degradation through climate change.

Trophic Ecology of Post-Metamorphic &lt;i&gt;Dendropsophus minutus&lt;/i&gt; (Peters, 1872) in Coastal Wetlands of Southern Brazil (Hylidae: Dendropsophini)

Dendropsophus minutus is a hylid widely distributed in the Neotropics. Although this species is classified as «least concern», some populations are being affected by the advance of various anthropic activities. Despite previous studies on the biology of the species, some aspects of its trophic ecology are still unknown. We used stomach content analysis (SCA) and stable isotope analysis (SIA) to identify diet, trophic position and the primary food sources and preys that support a post-metamorphic population of D. minutus in the coastal plain of extreme southern Brazil. SCA revealed that Diptera (%PSIRI = 10.16), Hemiptera (%PSIRI = 5.83), and Araneae (%PSIRI = = 1.46) were present in the diet. The primary-producers-based mixing model indicated POM (particulate organic matter) as the main basal carbon source sustaining the analyzed specimens; whereas the prey-based mixing model showed that Hemiptera is the main resource assimilated by the species. Mean trophic position was 2.71, ranging between 2.52 and 2.91.

Unique diet and Philonema sp. infections in reservoir‐rearing juvenile Chinook Salmon

AbstractObjectiveDams and reservoirs can alter juvenile growth and survival of migratory salmonids through several physical and biological mechanisms. Juvenile Chinook Salmon Oncorhynchus tshawytscha that are produced upstream of large hydropower dams may have associated passage mortality, but the reservoirs created by these dams can support rapid growth. Characterizing the biotic drivers of growth and mortality in reservoirs may aid in understanding the cumulative effects of river impoundments on migratory salmonid populations. The purpose of this study was to understand how reservoirs facilitate rapid growth in juvenile Chinook Salmon.MethodsWe analyzed stomach contents to determine diet composition throughout the summer and fall. We also recorded prevalence of the parasitic nematode Philonema sp. in the coeloms of fish.ResultWe found that juvenile Chinook Salmon frequently consumed young‐of‐year centrarchids, which likely contributed to rapid growth. Piscivory was highest from July through October and decreased with surface temperature from November through December. Correspondingly, zooplankton and arthropod consumption increased in November and December. Prevalence of visible Philonema sp. infections in the coelom was high (34.6%), negatively associated with time, and nonlinearly associated with fork length.ConclusionThese findings reveal unique diet patterns and suggest potential parasite‐associated mortality in reservoir‐rearing Chinook Salmon, but more detailed studies across a longer time scale are needed to robustly assess the population‐level effects of this parasite.

Feeding strategies of the ocean white fish (Caulolatilus princeps) and white spotted sand bass (Paralabrax albomaculatus) inside the Galapagos Marine Reserve

Understanding the diet of two demersal species, the ocean white fish (Caulolatilus princeps) and white spotted sand bass (Paralabrax albomaculatus) provides insights into the trophic strategies they have evolved to co-exist in rocky reefs and soft bottom habitats in the Galapagos Marine Reserve (GMR). We applied two complementary techniques (stomach content and stable isotopes analysis) to determine the trophic habits between species, and categories (sex, life stages and seasons). Sampling was carried out in several sites of fishing importance within the GMR between 2017 and 2018, obtaining 254 stomachs and 58 muscle samples for C. princeps, and 14 stomachs and 34 muscle samples for P. albomaculatus. Trophic spectrum (diet composition), of both predators contained pelagic and benthic prey. The slender anchovy (Anchoa ischana) was the most important prey for C. princeps with no significant differences in the diet between sex, life stages or seasons (p > 0.05); while the most important prey for P. albomaculatus was the threadfin bass (Pronotogrammus multifasciatus). The δ13C and δ15N signatures were significantly different among species (tvalue = 11.81, p < 0.05 and tvalue = 4.67, p <0.05, respectively) suggesting differences in the carbon source (i.e., feeding areas) as well as the preference for different trophic levels (i.e., different prey). Intraspecific analysis in C. princeps showed no differences within sex, life stage and seasons (p > 0.05). Feeding strategies were similar for both predators, with a reduced trophic niche and high variability between preys consumed. This work provides baseline information on two species of ecological and commercial importance within the GMR and highlights the value of trophic studies to generate useful information for an ecosystem-based fisheries management.

Feeding ecology of Chaeturichthys stigmatias during autumn in Haizhou Bay

Research about feeding ecology of fish is important to understand individual behavior and population development, which is also the basic to analyze trophic structure and function of aquatic ecosystems. Chaetrichthys stigmatias is one of the key species in the Haizhou Bay fisheries ecosystem, which has critical ecological niche within the food web. In this study, we collected samples through bottom trawl surveys during the fall of 2018 in the Haizhou Bay, and analyzed the feeding ecology of C. stigmatias based on both stomach content analysis and stable isotope technology. The results showed that the primary diet groups for C. stigmatias were Ophiuroidea and Shrimp, including Ophiothrix marenzelleri, Ophiopholis mirabilis, Ophiura sarsii, Penaeidae, and Alpheus japonicus. The range of δ13C values of C. stigmatias was from -19.39‰ to -15.74‰, with an average value of (-18.07±0.87)‰, which had no significant correlation with body length. The range of δ15N values was from 8.16‰ to 12.86‰, with an average value of (10.14±1.51)‰, which was positively correlated with body length. The trophic level of C. stigmatias showed a positive relationship with body length, with an average value of (3.74±0.34) and a range value of 3.32 to 4.20 among different size groups. The contribution rates of different prey groups varied significantly. Based on the structural equation modeling, we found that the feeding intensity of C. stigmatias was primally influenced by body length, sea bottom salinity, sea bottom temperature, and water depth, with a particularly signi-ficant positive correlation with body length. The combination of stable isotope technology and stomach content analysis methods could contribute to comprehensive understanding on the feeding ecology of C. stigmatias, providing essential data and foundation for research on trophic structures and resource conservation in the Haizhou Bay ecosystem.

Coexistence, resource partitioning, and fisheries management: A tale of two mesopredators in equatorial waters.

Rock hind (Epinephelus adscensionis) and spotted moray (Gymnothorax moringa) are ubiquitous mesopredators that co-occur in the nearshore waters of Ascension Island in the South Atlantic Ocean, where they have significant cultural and subsistence value, but management of their non-commercial take is limited. This isolated volcanic system is home to high biomass and low species diversity, which poses two key questions: How can two mesopredators that perform similar ecological roles coexist? And if these two species are so ecologically similar, can they be managed using the same approach? Here, we combined acoustic telemetry, stomach content analysis, and stable isotope analysis to (i) explore space use and diet choices within and between these two species and (ii) to assess appropriate species-specific management options. Although rock hind had high residency and small calculated home ranges (0.0001-0.3114 km2), spotted moray exhibited shorter periods of residency (<3 months) before exiting the array. Vertical space use differed significantly across the 20-month tracking period, with individual differences in vertical space observed for both species. A hierarchical generalized additive model using 12-h averaged depth data identified that rock hind occurred lower in the water column than spotted moray, with both species occupying moderately deeper depths at night versus day (+1.6% relative depth). Spotted moray depth was also significantly predicted by lunar illumination. Aggregating samples by species and tissue type, Bayesian ecological niche modeling identified a 53.14%-54.15% and 78.02%-97.08% probability of niche overlap from fin clip and white muscle, respectively, whereas limited stomach content data indicated a preference for piscivorous prey. Variability in niche breadth between years suggests these species may exploit a range of prey items over time. These findings indicate that although these two species perform a similar ecological role by feeding on prey occupying the same trophic levels, subtle differences in movement behaviors between them suggest a one-rule-fits-all management approach is not likely the most effective option.

Natural Food Intake and Its Contribution to Tambaqui Growth in Fertilized and Unfertilized Ponds

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.

Diet of the Invasive Atlantic Blue Crab Callinectes sapidus Rathbun, 1896 (Decapoda, Portunidae) in the Guadalquivir Estuary (Spain)

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.

Quantification of finfish assemblages associated with mussel and seaweed farms in southwest UK provides evidence of potential benefits to fisheries

Low trophic aquaculture, including shellfish and seaweed farming, offers a potentially sustainable food source and may provide additional environmental benefits, including the creation of new feeding, breeding and nursery areas for fish of commercial and ecological importance. However, quantitative assessments of fish assemblages associated with aquaculture sites are lacking. We used pelagic baited remote underwater videos (BRUVs) and hook and line catches to survey summer fish assemblages at 2 integrated blue mussel Mytilus edulis and kelp (predominantly Saccharina latissima) farms in southwest UK. We recorded at least 11 finfish species across the surveys, including several of commercial importance, with farmed mussels and/or kelps supporting significantly higher levels of abundance and richness than reference areas outside farm infrastructure. Farmed kelp provided temporary habitat due to seasonal harvesting schedules, whereas farmed mussels provided greater habitat stability due to overlapping interannual growth cycles. Stomach content analysis of fish caught at the farms revealed that some low trophic level species had high proportions of amphipods in their stomachs, which also dominated epibiont assemblages at the farms. Higher trophic level fish stomachs contained several lower trophic level fish species, suggesting that farms provide new foraging grounds and support secondary and tertiary production. Although not identified to species level, juvenile fish were abundant at both farms, suggesting potential provisioning of nursery or breeding grounds; however, this needs further verification. Overall, this study provides evidence that shellfish and seaweed aquaculture can support and enhance populations of commercially and ecologically important fish species through habitat provisioning.

Combined stomach contents and stable isotope analysis reveal feeding habits of Japanese jack mackerel (Trachurus japonicus) in the East China Sea

Japanese jack mackerel (Trachurus japonicus) is an economically important pelagic fish in the East China Sea. Knowledge is still limited regarding the feeding habits of this species in this area. Based on bottom trawl surveys conducted in the southern coastal area of Zhejiang during August in 2019 and 2020, we analyzed the feeding ecology of T. japonicus using stomach contents analysis and the stable isotope approach. The results indicated that the δ13C value for T. japonicus ranged from − 17.72 % to ;−14.30 %, and the δ15N value ranged from 10.89 % to 13.03 %. Two-way analysis of variance indicated significant annual and ontogenetic variations in the δ13C value, thereby suggesting changes in the final nutrient sources for T. japonicus in different growth stages and years. The trophic level of T. japonicus was estimated as from 3.35 to 4.46. In general, the trophic level of T. japonicus increased with growth, although the ontogenetic variation was not significant. The main food groups identified for T. japonicus based on stomach contents analysis were fish, shrimp, crabs, cephalopods, and small crustaceans. The results obtained by stable isotope analysis showed that the nutrient contribution rate of small crustaceans to the diet of T. japonicus was highest in both years, followed by shrimp. The feeding habits of T. japonicus had obvious ontogenetic variations, and the average contribution of fish species increased as the size of the predator increased. The results obtained in this study provide detailed feeding information about T. japonicus in the East China Sea.

Temporal changes in the diet composition and trophic level of walleye pollock (Gadus chalcogrammus) inhabiting the middle-eastern coast of Korea

The influences of oceanographic changes on diet composition and trophic level for pollock (Gadus chalcogrammus) inhabiting the East Sea off the Korean coast were examined based on stomach content and stable isotope analyses during 2016 and 2017. The diets of pollock consisted mainly of benthic crustaceans (particularly carid shrimps and euphausiids) and cephalopods, with a predominance of teleosts in the diets of larger individuals in deeper habitats. In 2016, amphipods, carid shrimps and cephalopods featured strongly in pollock diets, and the contribution of amphipods decreased in the diets of larger individuals and deeper depths. In 2017, euphausiids dominated at shallower depths, whereas the contributions of carid shrimps and teleosts increased in deeper habitats. Body-size-related differences in carbon stable isotope (δ13C) values were present in both 2016 and 2017, but size-related differences in nitrogen stable isotope (δ15N) values were only observed in 2017. The increased contribution of euphausiids during 2017 resulted in a distinct decrease in the trophic level of pollock compared to co-occurring higher trophic level predators, which can be linked to changes in habitat water temperature. Combined stomach contents and isotopic analyses provide a more comprehensive understanding of how fish diets and trophic levels fluctuate with changes in the type and abundance of prey resources in response to environmental changes.

Пищевой рацион перепела в осенний период в Ставропольском крае

Quails (Coturnix coturnix (Linnaeus, 1758)) are the only migratory Galliformes species. Quails are nestling ground-dwelling birds, feeding on seeds and crawling insects. Wild quails inhabit many parts of Russia. Quail farming is quite popular because quail meat is low in calories and possesses a number of beneficial properties, e.g., it is rich in proteins, contains little fat and virtually no carbohydrates, etc. As a rule, quails winter in Transcaucasia and Southern Europe; however, they sometimes prefer to stay in southern regions for the winter. This article introduces the autumn food habits of quails in the Central Ciscaucasia.&#x0D; The research relied on the analysis of stomach contents of 156 birds killed by hunters or hit by vehicles in several districts of the Stavropol Region. The material was collected in the autumn in 2008–2021.&#x0D; In the Central Ciscaucasia, quails are mesophiles and inhabit abandoned wheat and pea fields. The population fluctuates from year to year, depending on spring weather conditions. Their optimal nestling grounds include irrigated fields and areas near canals and ponds. In the steppe regions, they prefer agricultural areas, e.g., orchards, vineyards, holiday villages, sheep sheds, green belts along fields, roads, and railways, etc. Being phytophages, they rely on plant and, to a lesser extent, animal forage. &#x0D; In the autumn, they feeding on green plants, wheat grain, seeds of cultivated and wild plants, and insect larvae.

The spread of the non-indigenous species Bregmaceros nectabanus Whitley, 1941 (Osteichthyes: Bregmacerotidae) in the eastern Mediterranean

This study reports the first record and some features of two individuals of the Lessepsian migrant species smallscale codlet, Bregmaceros nectabanus, found in the stomachs of two individuals of European hake, Merluccius merluccius, sampled in the northern Ionian Sea (eastern Mediterranean) during the MEDITS International Bottom Trawl Survey. The two European hake were collected on muddy bottoms in September 2021 at 63 m depth (39.34950 ºN; 16.52350 ºE) and at 240 m depth (39.07156 ºN; 17.12626 ºE). Their morphological traits together with otolith and scale characteristics allowed the identification of the two specimens found in the stomachs as B. nectabanus. The analysis of the stomach contents for the larger individual is also reported. This finding underlines the utility of stomach content analysis as an indirect method to study the biodiversity of deep-sea ecosystems, including the spread of non-indigenous species as indicators of global warming.