Variation In Diet Composition Research Articles

Variation in the diets of Japanese martens Martes melampus

Abstract We reviewed dietary data in the literature for Japanese martens Martes melampus from 21 study sites covering the entire geographic range of the species, tested for differences in the diets of martens in evergreen and deciduous forests, and described variation in main diets and dietary diversity in relation to geographical and environmental variables. Fruits, mammals, and insects occurred at the highest frequencies in faeces throughout the species’ range. Mammal prey items and non‐fruits were detected less frequently in scats collected in evergreen forests than in deciduous forests, while non‐fruits were detected more frequently in evergreen forests. Three environmental variables (mean temperature, variation in the normalised difference vegetation index [NDVI], and snow depth) had significant effects on variation in dietary composition, but the relative contribution of each variable varied among food items. Geographical variables, on the other hand, had no significant effects on variation in dietary composition. Mean temperature explained the variation in insect feeding, which increased in forests with moderate temperature. Snow depth explained the variation in feeding on non‐insects and other vertebrates; the former increased in forests with lower snow depth, while the latter increased in forests with higher snow depth. Variation in NDVI, on the other hand, had no effect on variation in feeding on a specific dietary category. The snow depth had a significant effect on the variation in dietary diversity, which became lower in forests with moderate snow depth. The high plasticity in the dietary composition and dietary diversity might represent a behavioural trait acquired by Japanese martens to allow them to expand their range into various forests with different food availabilities. When studying the variation in feeding behaviour of omnivorous carnivores, multiple environmental variables need to be considered equally.

Diet Composition and Breeding Success of the Black-Winged Kite on the Lleida Plains in Relation to Population Size

We monitored the number of pairs and the diet of Black-winged Kite Elanus caeruleus on the Lleida Plains (Catalonia, NE Spain) from 1998 to 2012. We examined the diet by means of pellet analysis. Nesting was irregular with peak numbers in some years (2009-2010). We found a positive relationship between the percentage of rodents in the diet and breeding success, an inverse relationship between dietary breadth and breeding success, a negative relationship between dietary breadth and the percentage of rodents in the diet and no significant variation in diet composition or breeding success between low kite population and high kite population years. All of this was consistent with the response of a specialist predator taking advantage of rodent outbreaks. We conclude that the breeding of the Black-winged Kite on the Lleida Plains is more consistent with the existence of irruptive events than with a real colonization of the area.—Llorente-Llurba, E., Bota, G., Pujol-Buxo, E., Bonfil, J., Galvez, M., Montes, G., Bas, J., Moncasi, F., Pont, F. & Manosa, S. (2019). Diet composition and breeding success of the Black-winged Kite on the Lleida Plains in relation to population size. Ardeola, 66: 33-50.

Diet of benthivorous fish and prey availability in streams of the Pirapó River basin-PR

Abstract Aim This study aimed to investigate the diet of seven species of fish that consume predominantly benthic macroinvertebrates, and the availability of these organisms in the environment. We analyzed the occurrence of trophic segregation between species and the correlation between the abundance of macroinvertebrates in the diet and in the environment. Methods Fish and macroinvertebrates were sampled in three streams of the Pirapó River basin (Upper Paraná River - Brazil). Differences in diet composition between species were tested using a multivariate permutation analysis of variance (PERMANOVA). A Spearman Correlation was performed to test the relation between the abundance the macroinvertebrates consumed and those available in the environment. Results All species mainly consumed aquatic insect, and significant interspecific variations in diet composition were found for most of them. For five out of the seven species of fish analyzed no significant correlation was detected between the abundance of macroinvertebrates in the environment and in the diet. Conclusions The results showed that most of the species segregate and their diets are not positively correlated with the abundance of preys in the environment, indicating that the most consumed macroinvertebrates were not the most abundant in the environment. These results suggest that the fish species select the macroinvertebrates, and that the morphological and behavioral characteristics of both predators and prey are important in feeding fish from streams.

Diet Variability of Steelhead/Rainbow Trout in a Coastal Basin in Central California: Relative Importance of Seasonal, Spatial, and Ontogenetic Variation

AbstractDiets of stream‐dwelling salmonids vary at multiple spatial and temporal scales, but the relative importance of different sources of variation has rarely been evaluated for a population. In a small coastal basin in central California, we sampled diets of steelhead/Rainbow Trout Oncorhynchus mykiss monthly for a year from two reaches that differed in the presence of streambed travertine (calcium carbonate) to determine the relative magnitude of spatial, seasonal, and ontogenetic variation in consumption and diet composition. Seasonal parameters (cosine function terms for months in periodic regression and multivariate models) and fish size (FL) were greater sources of variation than differences between the two study reaches, and seasonal and ontogenetic patterns were evident despite high interindividual variability. Seasonal parameters explained the most variation in diet composition, which varied in an orderly pattern over the year. Consumption was highest in spring and summer for both aquatic and terrestrial prey, and seasonal parameters accounted for more variation than fish size for consumption of aquatic prey but this was reversed for terrestrial prey and total consumption. The main ontogenetic trend was increased consumption of terrestrial invertebrates: from 15‐20% of the energy consumed by 60–100‐mm fish to 60% of the energy consumed by fish larger than 160 mm. In addition, diet breadth (taxonomic richness and prey size) and the degree of variation among individuals also increased with fish size. Diet differences between sites were relatively small and included higher consumption of aquatic invertebrates at the site without travertine in 4 months and modest differences in the relative abundances of common prey taxa. Although seasonal and ontogenetic patterns were evident, interindividual variation was the dominant scale of diet variation, and diets of individual fish ranged from specialized to generalized relative to the population. Based on these findings, O. mykiss appeared to be opportunistic feeders that took advantage of diverse aquatic and terrestrial prey available in these study reaches.

Spatial-temporal analysis of the diet of a non-native fish in the Santa Cruz Reservoir, Brazilian semi-arid

Abstract Aim The diet of Plagioscion squamosissimus present in the Santa Cruz Reservoir, Rio Grande do Norte, Brazil, was investigated, evaluating the influences of spatial and temporal variations and abiotic factors in the utilization of food resources. Methods The samplings were performed quarterly between February 2011 and November 2014. Of the 525 specimens captured, 375 presented food items in the stomachs. The diet was determined using: (i) Feeding Index (IAi); (ii) and the graphical interpretation of the food strategy through non-metric multidimensional scaling (NMDS) analyzes, the differences in diet being tested from Permutational Multivariate Analyzes of Variance (PERMANOVA). To verify if environmental variables influence the Canonical Correspondence Analyzes (CCA) were used, using the data from the IAi the environmental data, being the significance of the axes tested through Monte Carlo simulations. Results The species feed mainly on items of animal origin, vegetable being a resource ingested accidentally. The diet was composed of shrimp, fish, insect, mollusk and vegetable, the latter rarely found. The shrimp was the main item (92.57%) and the insects (7.24%) accessory items. Spatial and temporal ordering demonstrated that the species didn’t present variation in diet composition, as well as a low association between diet and environmental variables. Conclusion P. squamosissimus is characterized as carcinophagous, due to the predominance of shrimp in its diet, evidencing that the species is adapted to the conditions offered by the Brazilian semi-arid environment.

DNA metabarcoding unveils multiscale trophic variation in a widespread coastal opportunist.

A thorough understanding of ecological networks relies on comprehensive information on trophic relationships among species. Since unpicking the diet of many organisms is unattainable using traditional morphology‐based approaches, the application of high‐throughput sequencing methods represents a rapid and powerful way forward. Here, we assessed the application of DNA metabarcoding with nearly universal primers for the mitochondrial marker cytochrome c oxidase I in defining the trophic ecology of adult brown shrimp, Crangon crangon, in six European estuaries. The exact trophic role of this abundant and widespread coastal benthic species is somewhat controversial, while information on geographical variation remains scant. Results revealed a highly opportunistic behaviour. Shrimp stomach contents contained hundreds of taxa (>1,000 molecular operational taxonomic units), of which 291 were identified as distinct species, belonging to 35 phyla. Only twenty ascertained species had a mean relative abundance of more than 0.5%. Predominant species included other abundant coastal and estuarine taxa, including the shore crab Carcinus maenas and the amphipod Corophium volutator. Jacobs’ selectivity index estimates based on DNA extracted from both shrimp stomachs and sediment samples were used to assess the shrimp's trophic niche indicating a generalist diet, dominated by crustaceans, polychaetes and fish. Spatial variation in diet composition, at regional and local scales, confirmed the highly flexible nature of this trophic opportunist. Furthermore, the detection of a prevalent, possibly endoparasitic fungus (Purpureocillium lilacinum) in the shrimp's stomach demonstrates the wide range of questions that can be addressed using metabarcoding, towards a more robust reconstruction of ecological networks.

How much is enough? Effects of technical and biological replication on metabarcoding dietary analysis.

DNA metabarcoding is increasingly used in dietary studies to estimate diversity, composition and frequency of occurrence of prey items. However, few studies have assessed how technical and biological replication affect the accuracy of diet estimates. This study addresses these issues using the European free‐tailed bat Tadarida teniotis, involving high‐throughput sequencing of a small fragment of the COI gene in 15 separate faecal pellets and a 15‐pellet pool per each of 20 bats. We investigated how diet descriptors were affected by variability among (a) individuals, (b) pellets of each individual and (c) PCRs of each pellet. In addition, we investigated the impact of (d) analysing separate pellets vs. pellet pools. We found that diet diversity estimates increased steadily with the number of pellets analysed per individual, with seven pellets required to detect ~80% of prey species. Most variation in diet composition was associated with differences among individual bats, followed by pellets per individual and PCRs per pellet. The accuracy of frequency of occurrence estimates increased with the number of pellets analysed per bat, with the highest error rates recorded for prey consumed infrequently by many individuals. Pools provided poor estimates of diet diversity and frequency of occurrence, which were comparable to analysing a single pellet per individual, and consistently missed the less common prey items. Overall, our results stress that maximizing biological replication is critical in dietary metabarcoding studies and emphasize that analysing several samples per individual rather than pooled samples produce more accurate results.

Diet of Neotropical parrots is independent of phylogeny but correlates with body size and geographical range

Body mass and geographical range are two main drivers of diet in animals, yet how these factors influence diet in the morphologically and ecologically diverse avian group of Psittaciformes is little known. We reviewed current knowledge of the diet of Neotropical parrots and assessed the relation between diet (breadth and composition), phylogeny, body mass and geographical range. Diet has been documented for 98 of 165 species, but information is available only for 34 of 59 threatened species, and countries with high species diversity (> 20 species) had few studies (one to seven). Neotropical parrot species consumed 1293 plant species of 125 families. When assessing the relative frequency of different food items in the diet (seed, fruits, flowers, leaves, nectar, bark and stems), we found that parrots mostly exploited seeds (41.9%) and fruits (38.3%) of native species. Diet overlap was very low among genera (0.006–0.321). At the species level, geographical range and body size explained the variation in diet composition. In particular, small parrots of restricted distribution had a distinct diet composition relative to either large or widely distributed species. Although body size and geographical range showed phylogenetic inertia, diet was independent of phylogenetic history. Our review not only reveals ecological factors explaining diet in a generalist group but also exposes information gaps across the Neotropical region.

Differences in trophic resources and niches of two juvenile predatory species in three Pangani estuarine zones, Tanzania: stomach contents and stable isotope approaches

BackgroundEstuaries are primary habitats that serve as feeding and nursery grounds for most juvenile marine fish. However, estuaries have been used as fishing grounds by the artisanal fishers in Tanzania. The slow-growing predatory fish at juvenile and sub-adult stages are among the most frequently caught species that functionally enhance multiple linkages of energy pathways within the food web. Stomach contents and stable isotopes (δ13C and δ15N) were used to describe the nutritional sources and trophic niches between the co-existing benthic, predatory species, Carangoides chrysophrys and Epinephelus malabaricus in the Pangani estuary, Tanzania.ResultsThe findings indicated significant inter-specific variations in dietary composition (PERMANOVA, p = 0.001, pseudo-F = 15.81). The prey-specific index of relative importance (%PSIRI) indicated that juvenile shrimps (%PSIRI = 51.4) and Teleostei (%PSIRI = 26.5) were the main diets of C. chrysophrys while brachyura (%PSIRI = 38.8), juvenile shrimps (%PSIRI = 25.6) and Teleostei (%PSIRI = 23.3) were important diets of E. malabaricus. The isotope mixing models indicated that the predatory fish species accumulate nutrients derived from similar autotrophic sources, microphytobenthos, seagrass and macro-algae via consumption of small fish, including clupeids and mugilids. Yet, they significantly showed different isotopic niche width with varying degree of niche overlap across the longitudinal estuary gradient. This situation was justified by the presence of basal food sources among the estuarine zones that isotopically were different.ConclusionThe reliance of both predators on clupeids and mugilid preys that are trophically linked with estuarine and marine basal food sources, is an indication of low estuarine food webs’ connectivity to the fresh water related food web. This situation is most likely threatening the stability of the estuarine food web structure. Management strategies and plans in place should be cautiously implemented to ensure the balanced anthropogenic freshwater use in the catchment and fishing activities, for the maintenance of the Pangani estuarine ecosystem health.

Seasonal variations in diet composition, diet breadth and dietary overlap between three commercially important fish species within a flood-pulse system: The Tonle Sap Lake (Cambodia).

Tropical lakes and their associated floodplain habitats are dynamic habitat mosaics strongly influenced by seasonal variations in hydrologic conditions. In flood-pulse systems, water level oscillations directly influence the connectivity to floodplain habitats for fish. Here, we aimed to investigate whether seasonal changes in the water level of a flood-pulse system (the Tonle Sap Lake, Cambodia) differentially affect diet breadth and dietary overlap of three common and commercially important fish species (Anabas testudineus, Boesemania microplepis and Notopterus notopterus) presenting important differences in their life-cycle (e.g. seasonal migration). For this purpose, the three fish species were sampled at four locations spread over the lake and their stomach contents extracted for analyses. Dietary differences were investigated across seasons regarding the diet composition and diet breadth of each species as well as the amount of dietary overlap between species. We found that the proportion of empty stomachs changed similarly across seasons for the three species, thus suggesting that ecological differences between species are not sufficient to outweigh the effect of seasonal variations in resource abundance. In contrast, changes in diet composition were species-specific and can be explained by ecological and behavioral differences between species. Diet breadth differed between species in all seasons, except during the wet season, and tended to be higher during the dry season when dietary overlap was the lowest. These variations likely result from changes in the diversity and amount of resources and may lead to habitat use shifts with potential implications for competitive interactions. In particular, increasing connectivity to floodplain habitats may reduce the competitive pressure during the wet season, while resource scarcity during the dry season may constrain individuals to diversify their diet to avoid competition. Overall, our results suggest a considerable plasticity in the feeding behavior of the three species as demonstrated by seasonal variation in both diet breadth and dietary overlap. Such variations can be explained by a number of factors and processes, including changes in resource availability or competitive interactions between individuals for resources, whose relative influence might vary depending on the magnitude and the timing of the flood-pulse driving the connectivity to floodplain habitats. Gaining knowledge on the seasonal evolution of fish’s diet is relevant for fisheries management and conservation and our result could be used to guide aquaculture development in Cambodia.

Thermal forest zone explains regional variations in the diet composition of the Japanese marten (Martes melampus)

Examining biogeographical variations in species’ diet is important for linking key ecological traits between consumers and their environment. While the trophic ecology of the Holarctic martens has been globally synthesised, systematic information on the feeding ecology of martens (Martes spp.) in Asia is still deficient compared to species in Europe and North America. Here we conduct a meta-analysis based on literature describing regional and seasonal variation in diet composition of the Japanese marten (Martes melampus). Across nine study areas in the Japanese archipelago, annual marten diet mainly comprised fruits, invertebrates, and mammals. Cluster analysis divided these into three groups according to the similarity in composition. Dietary niche breadth and the relative frequency of occurrence of the mammalian prey was significantly higher in sub-alpine/cool-temperate than warm-temperate thermal forest zones, whereas the occurrence of fruits was significantly higher in warm-temperate than sub-alpine/cool-temperate zones. Seasonal analysis showed significant effects across all four seasons on the frequency of occurrence of mammals, invertebrates, and fruits. The Japanese marten is a flexible and opportunistic feeder with the potential to maintain its key macronutrient requirements by adapting its feeding strategy to changes in resource variability and environmental conditions. This trophic plasticity may advantage the Japanese marten in coping with human-induced rapid environmental change, as global analysis has projected for martens across other regions.

Seasonal food habits and prey selection of Amur tigers and Amur leopards in Northeast China

We analyzed the scats of Amur tigers and Amur leopards, and examined their annual and seasonal food habits in Northeast China to comprehend their coexistence. Wild boar had the highest annual and seasonal consumption frequencies by the tigers, while both roe deer and sika deer were mostly preyed by the leopards annually. The three species appeared to be the key preys in terms of high proportion of consumed biomass by the two felids. Our data also revealed numerous mid-sized carnivores and small mammals included in the two felids’ food list. We used the relative abundance and biomass density estimation in prey density estimation to calculate the prey preferences of tigers and leopards, and both methods confirmed that Amur tigers strongly preferred wild boar. However, preference estimations of Amur leopards were not consistant, or even opposite to one another from the two methods. The results of the study suggested that prey preference of predators is largely determined by body size of the prey species. Variation in diet composition of the two felids suggests that resource partitioning may contribute to their coexistence.

Diet and trophic level of the longnose spurdog, Squalus blainville (Risso, 1826) in the 25-nautical mile Fisheries Management Zone around the Maltese Islands

The longnose spurdog, Squalus blainville (Risso, 1826), is reported to feed on bony fishes, cephalopods and crustaceans but misidentifications have resulted in ambiguities. This study describes and quantitatively analyses the diet of S. blainville in waters surrounding the Maltese Islands and compares the results with other Mediterranean populations to identify any regional or temporal variation. Additionally, variations in dietary composition with season, maturity, size and sex are investigated for the Maltese population.The diet of 255 individuals, collected from the 25-nautical mile Fisheries Management Zone around the Maltese Islands, was characterised using frequency of occurrence, wet weight and numerical occurrence of food items for sex, maturity, size and seasonal categories. Mediterranean International Trawl Survey (MEDITS) data for the period 2007–2015,which was derived from samples collected within the Food and Agriculture Organisation of the United Nations’s (FAO) General Fisheries Commission for the Mediterranean (GFCM) Geographical Sub-Area 15 (GSA 15), were analysed to identify any relationship between sex, maturity and depth. S. blainville fed on prey items belonging to four main groups: Crustacea, Mollusca, Teleostei and Sipuncula.Mollusca had the highest % IRI (Index of Relative Importance) for the total sample (52.5% of the IRI) and second were teleosts (% IRI=41.4). In terms of habitat, 63.51% of the identified prey categories were demersal, followed by benthic (28.65%) and then pelagic prey categories (7.84%). The highest dietary overlap was observed between seasons, and between immature and mature females; least overlap was between mature and immature males. An increase in size results in more predation especially on cephalopods. Mature and immature individuals were recorded at all depths. Our results indicate that there is some variation in diet between sexes and between maturity stages both in prey items and in the relative contribution of benthic, demersal, and pelagic prey.

Feeding Relationships among Six Seagrass-associated Fishes in the Northeastern Gwangyang Bay, Southern Korea

We conducted dietary analyses of six seagrass-associated fish species inhabiting northeastern Gwangyang Bay, Korea. These six species consumed a variety of benthic invertebrates and teleosts, but their preferences for different food resources varied. Although all species consumed crustaceans, the contributions of different crustacean taxa differed among the species’ diets. Caridean shrimps and crabs were a significant part of the Hexagrammos agrammus and H. otakii diets, respectively, while amphipods were consumed mainly by Sebastes inermis. Caridean shrimps and prawns were abundant within the Lateolabrax japonicas diet, but were not common prey resources for Pseudopleuronectes yokohamae or S. schlegelii. Polychaetes and ophiurids were ingested by P. yokohamae, and the former prey taxon also made moderate contributions to the diets of H. agrammus and L. japonicus. With the exception of P. yokohamae, the diets of all species included teleosts. Teleosts contributed the largest proportion of the S. schlegelii diet, followed by the S. inermis and L. japonicas diets; however, H. agrammus and H. otakii rarely consumed teleosts. Non-metric multidimensional scaling (nMDS) ordination plots and permutational analysis of variance (PERMANOVA) revealed the variation in dietary composition among species and the contributions of each prey taxon. These interspecific differences in diet increase the range of food resources available to these fishes, thereby reducing competition for resources within the fish community in this region.

Effect of Season on Diet Composition, Dry Matter Intake and Digestibility in Adult Sheep Grazed on Sub-Alpine Pastures of Kashmir Valley

The present study was designed to analyzes the seasonal variations in diet composition, nutrient intake and digestibility of sub-alpine pastures of Kashmir valley in mature sheep. The experiment was conducted in two seasons of summer (June) and autumn (October) at two locations (MRCSG, Shuhama, Location-I and SBF, Dachigam, Location-II) having different vegetative covers. The apparent digestibility of most of the nutrients was higher (P<0.05) in summer than in autumn season. The ME, TDN and DCP contents of the summer pastures were higher (P<0.05) than the autumn pastures at both locations. Dry matter intake from the summer pastures was higher than the winter pastures at both locations and their corresponding digestibilities also followed the same trend. Calcium intake was higher (P<0.05) in summer at location-I compared to location-II. However, P intake (g/d) from both pastures was higher (P<0.05) in summer than autumn season. The TDN intake (g/d) was deficient by 7% and ME intake (Mcal/d) by 5% in comparison to ICAR feeding standard (2013) in summer season at location-I while in autumn season the deficiency increased to 44 and 43%, respectively. Location-II offered adequate nutrients to animals in summer season while in autumn season the deficiency of 24% in TDN intake (g/d) and 22% in ME intake (Mcal/d) was observed. The DCP intake (g/d) was deficit by 12% at location-I in the autumn season while in summer season it was adequate at both the locations. Hence, the pastures at both the locations were deficient in energy especially in autumn season.

Feeding ecology of Hexagrammos otakii in Haizhou Bay

PDF HTML阅读 XML下载 导出引用 引用提醒 海州湾大泷六线鱼摄食生态研究 DOI: 作者: 作者单位: 1. 中国海洋大学 水产学院, 山东 青岛 266003;2. 青岛海洋科学与技术国家实验室, 海洋渔业科学与食物产出过程功能实验室, 山东 青岛 266237;3. 中国科学院 海洋研究所, 中国科学院海洋生态与环境科学重点实验室, 山东 青岛 266071 作者简介: 许莉莉(1988-),女,硕士研究生,主要从事渔业资源生态学研究.E-mail:xvlili1990@163.com 通讯作者: 中图分类号: S931 基金项目: 国家自然科学基金项目（31772852）；中央高校基本科研业务费专项（201562030，201612004）；青岛海洋科学与技术国家实验室鳌山科技创新计划项目（2015ASKJ02）. Feeding ecology of Hexagrammos otakii in Haizhou Bay Author: Affiliation: 1. College of Fisheries, Ocean University of China, Qingdao 266003, China;2. Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China;3. Key Laboratory of Marine Ecology & Environmental Sciences of Chinese Academy of Sciences, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据2011年3—12月在海州湾及其邻近海域进行的5个航次底拖网调查，通过分析531尾大泷六线鱼（）的胃含物样品，对其摄食生态进行了初步研究。结果表明，大泷六线鱼摄食的饵料种类有60余种，虾类、蟹类、双壳类是其最主要的3种饵料类群，优势饵料生物有东方缝栖蛤（ sp.）等；其食物组成存在明显的季节变化和体长变化，全年均大量摄食虾类，夏季还摄食一定量的蟹类，秋季摄食多毛类和头足类的比例较高。随着体长的增长，大泷六线鱼摄食的饵料生物由小型甲壳类逐渐转变为体型较大的虾类和鱼类。大泷六线鱼的空胃率和平均胃饱满指数存在明显的季节变化，春季空胃率最高，冬季空胃率最低；平均胃饱满指数春季最高，秋季最低。典范对应分析表明，体长是影响大泷六线鱼摄食的主要因子，其次是底层水温、叶绿素a和pH。 Abstract:The present study investigated the feeding habits of in Haizhou Bay and adjacent waters by analyzing the stomach contents of 531 individuals collected from March to December 2011. More than 60 prey species were investigated, with the dominant species being sp. and the main prey groups being shrimp, crabs, and bivalves. The feeding habits of exhibited significant seasonal variation. Shrimp were a major prey group during all four seasons, but a large number of crabs were consumed during summer, whereas the greatest proportions of Polychaeta and Cephalopoda prey were observed during autumn. Ontogenetic variation in diet composition was also observed. For example, small mainly consumed small crustaceans, whereas larger individuals mainly consumed fish and shrimp. Feeding intensity (i.e., percentage of empty stomachs and mean stomach fullness index) also exhibited seasonal variation. The greatest empty stomach percentages and mean stomach fullness indices were both observed during spring, whereas the lowest empty stomach percentages and mean stomach fullness indices were observed during winter and autumn, respectively. Canonical correspondence analysis (CCA) indicated that body length was the most important factor affecting the diet composition of , followed by sea bottom temperature, local chlorophyll a, and seawater pH. 参考文献 相似文献 引证文献

Mechanisms of climate-change-induced species decline: spatial, temporal and long-term variation in the diet of an endangered marsupial carnivore, the eastern quoll

Context Climate change is having significant impacts on species worldwide. The endangered eastern quoll (Dasyurus viverrinus) has recently undergone rapid and severe population decline, with no sign of recovery. Spatially and temporally-explicit weather modelling suggests a prolonged period of unfavourable weather conditions during 2001–03 as the proximate cause of decline. However, the mechanisms of this weather-induced decline are not currently understood. Aims The aim of this study was to investigate the hypothesis that changing weather conditions have altered the availability of key prey species, potentially contributing to the species’ decline. Methods We analysed 229 scats collected from 125 individual wild quolls across four sites between July 2011 and May 2012. Variation in dietary composition and niche breadth was compared across sites and seasons. We also compared contemporary dietary composition and niche breadth to historic dietary studies performed before the species’ decline, to identify any key changes in dietary composition over time. Key results Dietary composition and niche breadth were similar across sites but differed between seasons. Dietary niche contracted during winter (July) and early spring (September) when insect larvae formed the bulk of quoll diet, rendering the species vulnerable to weather-related fluctuations in food availability at that time. Large differences were also evident between current and historic dietary composition, with a marked shift from insect larvae to mammals, predominantly due to a reduction in corbie (Oncopera intricata) and southern armyworm (Persectania ewingii) moth larvae. Quoll abundance appears positively related to corbie larva abundance during winter, and both quoll and corbie larva abundance appear negatively related to winter rainfall. Conclusions The lower contribution of insects at sites with low quoll densities suggests that insects represent an important food item for eastern quolls during winter, when dietary niche is narrowest and energy demands are highest. Our findings suggest that weather-induced fluctuations in quoll abundance, including the significant statewide decline during 2001–03, are potentially driven by weather-induced fluctuations in corbie larva abundance. Implications Continued deterioration in climatic suitability with recent and predicted climate change could further threaten eastern quolls through reductions in the availability and stability of reliable food sources at critical life-history stages when dietary options are already limited.

You are what, where, and when you eat: seasonal and ontogenetic changes in a tropical tadpole’s diet

Abstract Tadpole diet is likely to vary in response to environmental conditions and nutritional needs throughout growth and development. We investigated seasonal variation in diet composition of Bokermannohyla saxicola tadpoles and compared diets between two developmental stages with a significant difference in size. We found that the diet of B. saxicola tadpoles was dominated by periphytic algae, in accordance with their benthic habits. Considering number of cells ingested, tadpole trophic niches were broader in more advanced developmental stages. Tadpole trophic niches were narrower during the summer (wet season) than during the winter (dry season), which may reflect increased consumption of more energetic food items during the warm period when primary productivity is expected to be higher. Tadpole metabolism is likely to be higher in the summer and increased energetic needs might be supplied in this manner. However, results differed when biovolume was considered instead of number of cells ingested, with larger items assuming a greater importance and niches being usually larger in the summer. In these cases, the increased ingestion of diatoms (likely to be more nutritive) in the summer may decrease the relative importance of large algae (e.g., Mougeotia sp.) that form the bulk of the diet. Both food availability/accessibility and tadpole feeding behaviour driven by nutritional needs may influence patterns of food acquisition. Given the importance of biofilms to tadpole diet, studies on the mechanisms by which tadpole nutritional needs and environmental conditions interact are likely to provide important insights into the dynamics of aquatic food webs.

Feeding ecology and consumption rate of broadbill swordfish (Xiphias gladius) in Ecuadorian waters

The feeding ecology and consumption rate of the broadbill swordfish (SWO, Xiphias gladius) from Ecuadorian waters were assessed by stomach content analysis of 256 individuals ranging between 91 and 291 cm in straight fork length (FL). Based on the alimentary index (%AI), the jumbo squid (Dosidicus gigas) was the most important prey species (58.93%AI), followed by bullet and frigate tunas (Auxis spp.) (17.94%AI). Permutational multivariate analysis of variance (PERMANOVA) detected one size-related shift in feeding habits to occur at FL ~ 190 cm, whereas no spatial variations in diet composition were observed. Similarity percentages (SIMPER) analysis revealed that the diet of small SWO (≤ 140 cm FL) and medium SWO (140–190 cm FL) was mainly characterized by Dosidicus gigas (contributing to 50.77 and 66.82% of the similarities, respectively) and Auxis spp. (18.14 and 17.23%, respectively); Auxis spp. and Thysanoteuthis rhombus, however, were the greatest contributors to the similarity in large SWO (≥ 190 cm FL) (47.87 and 22.06%, respectively). The daily meal was estimated to be 468.03–676.78 g day−1, which corresponded to a daily ration of 1.63–8.24% body mass (BM, in g) day−1. The results of this study indicate that the SWO is a mesopelagic predator that plays an important role in structuring the pelagic ecosystem of the Ecuadorian Pacific Ocean.

Diet Composition, Feeding Periodicity, and Prey Selection of Slimy Sculpin During Winter

Abstract Slimy Sculpin Cottus cognatus is an important component of the benthic ichthyofauna of many lakes and streams in the northern latitudes of North America. Although considerable information exists on the feeding ecology of this species, there is essentially no information available on winter feeding. Consequently, we examined the winter feeding ecology of Slimy Sculpins in a central New York stream. Ephemeropterans (37.8%) and trichopterans (31.2%) were the primary prey taxa consumed in January. There was evidence of diel variation in diet composition, with ephemeropterans making up 24.1% of the diet at 0400 hours and 46.7% at 1600 hours and trichopterans contributing 22.7% at 1200 hours and 43.8% at 2000 hours. During winter, Slimy Sculpins selected chironomids (0.46) and trichopterans (0.43) and avoided coleopterans (−0.84) and nonchironomid dipterans (−0.67). Peak food consumption of Slimy Sculpins occurred at night. Winter feeding patterns of Slimy Sculpins in Grout Brook, a second-order tributary of Skaneateles Lake in central New York, contrasted sharply with observations from other studies carried out during other seasons. Our findings are a significant contribution on the winter feeding ecology of this important benthic species and illustrate the need for both diel and winter studies to fully understand life history characteristics.