Major Prey Research Articles

Abundance of snow leopard (Panthera uncia) and its wild prey in Chhekampar VDC, Manaslu Conservation Area, Nepal

Snow leopard (Panthera uncia) is the striking symbol as well as an indicator of intact eco-regions of high mountains it inhabits. Despite the advancement in new methods, scholars argue that signs are still a reliable indicator for the purpose of habitat use study of snow leopards. The relative abundance of snow leopard and its major prey species such as blue sheep (Pseudois nayar) and Himalayan tahr (Hemitragus jemlahicus) in the Chhekampar Village Development Committee within the Tsum Valley of the Manaslu Conservation Area was determined by sign survey using Snow Leopard Information Management System (SLIMS) and block survey using Vantage Point Method, respectively. We also assessed human snow leopard conflict through household and key informant survey. The encounter rate of snow leopard signs were 3.57/km on an average, indicating low abundance, whereas prey species such as blue sheep and Himalayan tahr had 3.8 and 1.8 animals/km2, respectively. The livestock depredation rate was 1.29% with snow leopard accounting to only 0.32% of the total. Due to the low abundance of snow leopard but sufficient number of large-sized wild prey species, livestock predation by snow leopard was minimum, and therefore, the local people had positive perception towards snow leopard conservation. Though the present situation including the local religious tradition and social norms is supportive in conservation of snow leopard, it may not sustain unless incentive programs are encouraged timely.Banko Janakari, Vol. 27, No. 1, Page : 11-20

Metabarcoding analysis of the stomach contents of the Antarctic Toothfish (Dissostichus mawsoni) collected in the Antarctic Ocean.

Stomach contents of the Antarctic toothfish, Dissostichus mawsoni, collected from subareas 58.4 and 88.3, were analyzed using next generation sequencing (NGS) technology. After processing the raw reads generated by the MiSeq platform, a total of 131,233 contigs (130 operational taxonomic units [OTUs]) were obtained from 163 individuals in subarea 58.4, and 75,961 contigs (105 OTUs) from 164 fish in subarea 88.3. At 98% sequence identity, species names were assigned to most OTUs in this study, indicating the quality of the DNA barcode database for the Antarctic Ocean was sufficient for molecular analysis, especially for fish species. A total of 19 species was identified from the stomach of D. mawsoni in this study, which included 14 fish species and five mollusks. More than 90% of contigs belonged to fish species, supporting the postulate that the major prey of D. mawsoni are fish. Two fish species, Macrourus whitsoni and Chionobathyscus dewitti, were the most important prey items (a finding similar to that of previous studies). We also obtained genotypes of prey items by NGS analysis, identifying an additional 17 representative haplotypes in this study. Comparison with three previous morphological studies and the NGS-based molecular identification in this study extended our knowledge regarding the prey of D. mawsoni, which previously was not possible. These results suggested that NGS-based diet studies are possible, if several current technical limitations, including the quality of the barcode database or the development of precise molecular quantification techniques to link them with morphological values, are overcome. To achieve this, additional studies should be conducted on various marine organisms.

Diet of Bengal Tigers (Panthera tigris tigris) in Chitwan National Park, Nepal

AbstractWe studied the diet of the Bengal tigers (Panthera tigris tigris) in Chitwan National Park, Nepal, by identifying 109 prey items from 85 tiger scats. Tigers in this region fed upon eight different mammal species. Chital (Axis axis) was the major prey with a frequency of 45% of the Tigers’ diet. The occurrence of other prey species included sambar (Cervus unicolor, 23%), wild pig (Sus scrofa, 15%), hog deer (Axis porcinus, 9%), barking deer (Muntiacus muntjak, 4%), and gaur (Bos gaurus, 2%). Tigers also hunted livestock, but this prey comprised a small component of the relative biomass (buffalo 5% and cow 2%). Our study suggests that the tiger depends mostly upon wild prey for its subsistence in the Chitwan National Park, but will also sporadically hunt livestock.

Prey preference follows phylogeny: evolutionary dietary patterns within the marine gastropod group Cladobranchia (Gastropoda: Heterobranchia: Nudibranchia)

BackgroundThe impact of predator-prey interactions on the evolution of many marine invertebrates is poorly understood. Since barriers to genetic exchange are less obvious in the marine realm than in terrestrial or freshwater systems, non-allopatric divergence may play a fundamental role in the generation of biodiversity. In this context, shifts between major prey types could constitute important factors explaining the biodiversity of marine taxa, particularly in groups with highly specialized diets. However, the scarcity of marine specialized consumers for which reliable phylogenies exist hampers attempts to test the role of trophic specialization in evolution. In this study, RNA-Seq data is used to produce a phylogeny of Cladobranchia, a group of marine invertebrates that feed on a diverse array of prey taxa but mostly specialize on cnidarians. The broad range of prey type preferences allegedly present in two major groups within Cladobranchia suggest that prey type shifts are relatively common over evolutionary timescales.ResultsIn the present study, we generated a well-supported phylogeny of the major lineages within Cladobranchia using RNA-Seq data, and used ancestral state reconstruction analyses to better understand the evolution of prey preference. These analyses answered several fundamental questions regarding the evolutionary relationships within Cladobranchia, including support for a clade of species from Arminidae as sister to Tritoniidae (which both preferentially prey on Octocorallia). Ancestral state reconstruction analyses supported a cladobranchian ancestor with a preference for Hydrozoa and show that the few transitions identified only occur from lineages that prey on Hydrozoa to those that feed on other types of prey.ConclusionsThere is strong phylogenetic correlation with prey preference within Cladobranchia, suggesting that prey type specialization within this group has inertia. Shifts between different types of prey have occurred rarely throughout the evolution of Cladobranchia, indicating that this may not have been an important driver of the diversity within this group.

Comparative diets and foraging strategies of subyearling Atlantic salmon, brown trout, and rainbow trout during winter

Over-winter survival of salmonids in streams is thought to be an important population regulation mechanism. Yet because of the difficulty of conducting field studies due to adverse weather or ice conditions, compared to other seasons, salmonid ecology during winter is least understood. Consequently, we sought to examine interspecific feeding associations of an important salmonid stream assemblage in the Lake Ontario watershed during winter. The diets of Atlantic salmon (Salmo salar) parr, brown trout (S. trutta) parr, and rainbow trout (Oncorhynchus mykiss) parr were significantly different in February but not in March. Salmonid diets differed from the benthos and the drift during both months. Dipterans (chironomids, simuliids, and tipulids) and ephemerellids were the major prey taxa consumed. All three species fed more heavily on prey items from the benthos than from the drift. The diet of Atlantic salmon had the highest similarity to the benthos whereas the diet of brown trout had the lowest similarity to the drift. All three salmonid species generally selected ephemerellids, limnephilids, and chironomids and avoided elmids. These winter feeding observations are the first reported for this specific salmonid assemblage and will help managers better understand interspecific associations during this critical period.

Energetic requirements of green sturgeon (Acipenser medirostris) feeding on burrowing shrimp (Neotrypaea californiensis) in estuaries: importance of temperature, reproductive investment, and residence time

Habitat use can be complex, as tradeoffs among physiology, resource abundance, and predator avoidance affect the suitability of different environments for different species. Green sturgeon (Acipenser medirostris), an imperiled species along the west coast of North America, undertake extensive coastal migrations and occupy estuaries during the summer and early fall. Warm water and abundant prey in estuaries may afford a growth opportunity. We applied a bioenergetics model to investigate how variation in estuarine temperature, spawning frequency, and duration of estuarine residence affect consumption and growth potential for individual green sturgeon. We assumed that green sturgeon achieve observed annual growth by feeding solely in conditions represented by Willapa Bay, Washington, an estuary annually frequented by green sturgeon and containing extensive tidal flats that harbor a major prey source (burrowing shrimp, Neotrypaea californiensis). Modeled consumption rates increased little with reproductive investment (<0.4%), but responded strongly (10–50%) to water temperature and duration of residence, as higher temperatures and longer residence required greater consumption to achieve equivalent growth. Accordingly, although green sturgeon occupy Willapa Bay from May through September, acoustically-tagged individuals are observed over much shorter durations (34 d + 41 d SD, N = 89). Simulations of <34 d estuarine residence required unrealistically high consumption rates to achieve observed growth, whereas longer durations required sustained feeding, and therefore higher total intake, to compensate for prolonged exposure to warm temperatures. Model results provide a range of per capita consumption rates by green sturgeon feeding in estuaries to inform management decisions regarding resource and habitat protection for this protected species.

A Preliminary Study on the Distribution Pattern, Feeding Behavior and Invasiveness of the Exotic Fish, Chitala ornata (Clown Knife Fish) in the Sub Water Ways of Attanagalu Oya

Increasing threat from the introduced invasive species has been identified as one of the major risk factors for the extinction of freshwater fishes. There are number of identified freshwater alien species which have become invasive within Sri Lankan natural waters. However, there is a dearth of information regarding many of these alien invasive species. Therefore, this research project focused on elucidation of distribution pattern, food and feeding habitats and invasiveness of Chitala ornata, an alien invasive freshwater fish species in potentially new site of infestation in the Attanagalu oya and its tributaries over a period of three months as a preliminary study. Key objectives of the study were, to find out the present distribution of C. ornata in Attanagalu Oya and its tributaries, to evaluate the food and feeding habits of C. ornata through gut analysis and to find out the presence of other invasive/introduced species in the area. Over the study peroid, 50 individuals of C. ornata ranging from 21cm to >80cm were collected using hook and line fishing gear and captured fish were deep-frozen immediately after capturing to avoid the deterioration of the food items within the fish gut. Fish gut analyses have been carried out under laboratory conditions. Morphological measures, frequency of occurrence and Index of fullness were calculated. The results indicated that C. ornata has established in the Attanagalu oya basin in areas such as Ekala and Kotugoda. Gut content analysis indicated that C. ornata feeds on significant number of native fish species. Five major prey fish species, consisting 58 Hirikanaya (Labeo dussumeri), 35 Rathu waral katu kuriya (Puntius kelumi), 23 Iri ankutta (Mystuss vittatus), 13 Walapoththa (Ompok bimaculatus) and 16 Illeya (Megalops cyprinoides) were found to make up the diet of 28 adults and 05 juveniles of C. ornata. The average Index of fullness was 378.19. Frequencies of occurrence are 0.606, 0.485, 0.424, 0.121 and 0.242 respectively for L.dussumeri, P. kelumi, M. vittatus, O. bimaculatus and M. cyprinoides. Out of these five species P. kelumi is listed as an endangered endemic species. Other than fishes, one shrimp species, molluscs and fish eggs were also recorded as their food items. Further, other exotic species such as Tank cleaner (Pterygoplichthys spp.) and giant gourami (Osphronemus goramy) were also recorded in the Attanagalu oya. It was concluded that immediate steps should be taken to manage this potentially harmful Alien invasive species in the Attanagalu Oya basin. Keywords: Invasive, Exotic, Fresh water, Chitala, Attanagalu oya

Feeding by Calanus glacialis in a high arctic fjord: potential seasonal importance of alternative prey

AbstractThe copepod species Calanus glacialis is an important component of arctic marine food webs, where it is the numerically dominant zooplankton grazer and serves as a major prey item for fish, seabirds, and other predators. These copepods are typically considered to be phytoplanktivorous, although they are also known to feed on microzooplankton, and little is known about their diet in fall and winter. To investigate their feeding, C. glacialis gut contents were analyzed over an annual cycle in a seasonally ice covered arctic fjord using next generation sequencing of 18S rDNA. During the spring bloom, diatoms, particularly Thalassiosira spp., were important contributors to the dietary sequence reads. In addition to diatoms, Chytridiomycetes, fungal parasites of diatoms, also made up a large proportion of dietary sequence reads during this productive season. This provides one of the first indications of the potential importance of the mycoloop in marine environments. Just prior to the spring bloom, chaetognath sequences dominated the prey sequence reads from C. glacialis, suggesting potential predation on eggs or other early life stages of chaetognaths by C. glacialis. Other indications of omnivorous feeding outside of the spring bloom period included sequence reads from polychaetes in summer, at the time of peak polychaete larval abundance, and from Metridia spp. (Copepoda) in winter in prey sequences from C. glacialis. Incorporating such predation into our knowledge of Calanus spp. behaviour may help refine our understanding of Calanus spp. ecology, and potential responses of C. glacialis to ongoing climate change.

Contribution to the feeding habits and reproductive biology of narrow-barred Spanish mackerel, Scomberomorus commerson (Lacèpéde, 1801) (Teleostei: Scombridae), in the northern Persian Gulf

In this study, the feeding habits and reproductive behavior of narrow-barred Spanish mackerel, Scomberomorus commerson , in the northern Persian Gulf during five months from October 2011 to December 2012 have been investigated. Specimens were purchased from the fishermen at several landing sites. Feeding and nutrition results showed that sardines are the major prey items of S. commerson . Secondary prey species included ponyfish, halfbeak and Indian mackerel fishes. Mature females (Stages III, IV) were mostly observed between April to July. By July, most of the studied fishes were in recovery or spent stages (Stages IV, V) indicating the end of the spawning season. The result of gonado-somatic index (GSI) study in 184 male and female specimens indicated the highest reproductive activity from April to July with the peak in July. The total sex ratio of 69 males and 115 females was 0.6:1 and it was not significantly different during study periods except autumn season. The minimum and maximum cavity index (CV) for both sexes were from 22.5% in December to 68.0% in October, respectively. Sardines were the most prevalent components of the diet of S. commerson . Based on the obtained results, it can be suggested that that banning of the Spanish mackerel catch in the June-July, which is the peak of spawning period, may help brood stocks. Banning the sardine catch may also benefit management of S. commerson in the Persian Gulf.

Mortality processes of hatchery-reared Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel) larvae in relation to their piscivory

In mass culture of Pacific bluefin tuna Thunnus orientalis, yolk-sac larvae of other species are fed as a major prey item to tuna larvae from 7 to 8 mm in total length. Marked growth variations in tuna larvae are frequently observed after feeding of yolk-sac larvae, and this variation in the growth of tuna larvae is subsequently a factor leading to the prevalence of cannibalistic attacks. To elucidate details of the mortality process of hatchery-reared tuna larvae after the initiation of yolk-sac larvae feeding, we compared the nutritional and growth histories of the surviving (live) tuna larvae to those of the dead fish, found dead on the bottom of the tank, as direct evidence of their mortality processes. Cause of mortality of tuna larvae 3 and 5 days after the initiation of feeding of yolk-sac larvae was assessed from nitrogen stable isotope and otolith microstructure analyses. Stable isotope analysis revealed that the live fish rapidly utilized prey fish larvae, but the dead fish had depended more on rotifers relative to the live fish 3 and 5 days after the initiation of feeding of yolk-sac larvae. The growth histories based on otolith increments were compared between the live and dead tuna larvae and indicated that the live fish showed significantly faster growth histories than dead fish. Our results suggest that fast-growing larvae at the onset of piscivory could survive in the mass culture tank of Pacific bluefin tuna and were characterized by growth-selective mortality.

Early feeding of round goby (Neogobius melanostomus) fry

Abstract Larval and early juvenile stages have been shown to strongly influence recruitment variability for fishes, with successful foraging during these stages improving growth and survival. This study provides the first targeted study of the early juvenile (“fry”) diet of the round goby ( Neogobius melanostomus ), a prominent Great Lakes invasive fish. We sampled diurnally in diverse benthic environments of nearshore western Lake Michigan and two coastal tributaries. Three major prey types numerically dominated the diurnal benthic diet: harpacticoid copepods, chydorid cladocerans and chironomid larvae. Pelagic prey, of the types observed in nocturnal, pelagic studies, were rare. It was typical for the local diet of round goby fry to feature a primary prey type which contributed > 50% numerically to the total diet, which may be associated with patchy distributions of benthic prey. An ontogenetic diet shift from harpacticoids to chydorids was suggested between 6–26 mm SL. The dominance of benthic meiofauna in the diet of round goby fry expands upon the prior narrative of nocturnal, pelagic foraging, and demonstrates the flexibility of this species to thrive in diverse nursery habitats.

Mobulid rays feed on euphausiids in the Bohol Sea.

Mobulid rays have a conservative life history and are caught in direct fisheries and as by-catch. Their subsequent vulnerability to overexploitation has recently been recognized, but fisheries management can be ineffective if it ignores habitat and prey preferences and other trophic interactions of the target species. Here, we assessed the feeding ecology of four mobulids (Manta birostris, Mobula tarapacana, M. japanica, M. thurstoni) in the Bohol Sea, Philippines, using stomach contents analysis of fisheries specimens landed between November and May in 2013–2015. We show that the mobulids feed heavily on euphausiid krill while they are in the area for approximately six months of the year. We found almost no trophic separation among the mobulid species, with Euphausia diomedeae as the major prey item for all species, recorded in 81 of 89 total stomachs (91%). Mobula japanica and M. thurstoni almost exclusively had this krill in their stomach, while M. tarapacana had a squid and fish, and Ma. birostris had myctophid fishes and copepods in their stomachs in addition to E. diomedeae. This krill was larger than prey for other planktivorous elasmobranchs elsewhere and contributed a mean of 61 364 kcal per stomach (±105 032 kcal s.e., range = 0–631 167 kcal). Our results show that vertically migrating mesopelagic species can be an important food resource for large filter feeders living in tropical seas with oligotrophic surface waters. Given the conservative life history of mobulid rays, the identification of common foraging grounds that overlap with fishing activity could be used to inform future fishing effort.

Radiocesium contamination of aquatic organisms in the estuary of the Abukuma River flowing through Fukushima

AbstractIn the summer of 2013, we measured the radiocesium (134Cs and 137Cs) concentrations in aquatic organisms inhabiting the estuary of the Abukuma River, which flows through the Fukushima and Miyagi Prefectures. Radiocesium concentrations in four muscle‐tissue samples of blackhead seabream (Acanthopagrus schlegeli) [1240, 914, 202 and 106 Bq kg−1 wet weight (w.w.)] and two whole‐body samples deriving from multiple individuals of flathead grey mullet (Mugil cephalus) (129 and 110 Bq kg−1 w.w.) exceeded the Japanese standard limit for radiocesium levels in foods (100 Bq kg−1 w.w.). However, radiocesium concentrations in the other fish samples were lower than the Japanese standard limit. In addition, radiocesium concentrations in crustaceans, major prey items of omnivorous and carnivorous fish species in the Abukuma River estuary, were generally low (0.444–15.1 Bq kg−1 w.w.). Stable isotope analysis indicated that the feeding habit of the three heavily contaminated blackhead seabream, which the radiocesium concentrations were about several times or more higher than the Japanese standard limit, were similar to those of other individuals collected from the same sampling site. Therefore, the difference in the radiocesium level between the three heavily contaminated individuals and the less‐contaminated individuals of blackhead seabream was not because of a recent feeding habit in the Abukuma River estuary. Environmental conditions in the Abukuma River estuary in the summer of 2013 would not have had the potential to increase radiocesium concentrations in the muscle tissues of fish inhabiting the estuary to levels greater than 100 Bq kg−1 w.w.

Combined gut-content and stable isotope trophic analysis of the pelagic stingray Pteroplaytrygon violacea (Bonaparte, 1832) diet from the western North Atlantic Ocean

The understanding of trophic relationships is vital for correctly modeling ecosystems and ecosystem effects of fisheries removals. The pelagic stingray is found in epipelagic sub-tropical and tropical waters worldwide and is a common bycatch in pelagic longline fisheries. Between August 2008 and November 2011, 156 specimens (81 males; 75 females) were collected during pelagic longline fishing operations in the US South Atlantic Bight and Gulf of Mexico. Stomach content analyses found that the major prey items were cephalopod molluscs (59.18%), followed by actinopterygiian fishes (37.75%), and decapod crustaceans (35.71%). These concentrations of prey items found in the stomachs coincide with previous studies done in the Pacific Ocean. In contrast to previous studies that found high percentages of empty stomachs (63%), the current percentage of empty stomachs was much lower (25.6%), likely due to shorter times between collection and inspection. Stable isotope analysis (δ13C and δ15N) was performed on white muscle in order to correlate the trophic position with gut-content analysis. The δ13C values ranged from -18.81‰ to -16.70‰, while the δ15N ranged from 6.11‰ to 11.88‰. Modeling of stable isotope data suggest that while squid are occasionally an important part of the pelagic stingray diet, prey usually consist of shrimp and other pelagic crustaceans. Pelagic stingrays fed within two trophic levels, but their prey appeared to feed on different carbon sources than those found in other pelagic elasmobranchs. A deeper understanding of the pelagic stingray diet sources can help fisheries management as it begins to transition into ecosystem-based management.

Assessing diet compositions of Lake Ontario predators using fatty acid profiles of prey fishes

Abstract Fatty acid profiles are used in food web studies to assess trophic interactions between predator and prey. The present study provides the first comprehensive fatty acid dataset for important prey and predator species in Lake Ontario. Three major prey fish (alewife, rainbow smelt, and round goby) were collected at three sites along the southern shore of Lake Ontario during the spring and fall of 2013, and predator species were collected in similar locations during the summer of 2013. Fatty acid compositions were compared among all prey species, all predator species, and information from both predator and prey was used to infer foraging differences among predators. Seasonal differences in fatty acids were found within each prey species studied. Differences among prey species were greater than any spatio-temporal differences detected within species. Fatty acids of predators revealed species-specific differences that matched known foraging habits. Chinook and Coho salmon, which are known to select alewife as their dominant prey item, had relatively little variation in fatty acid profiles. Conversely, brown trout, lake trout, yellow perch and esocids had highly variable fatty acid profiles and likely highly variable diet compositions. In general, our data suggested three dominant foraging patterns: 1) diet composed of nearly exclusively alewife for Chinook and Coho Salmon; 2) a mixed diet of alewife and round goby for brown and lake trout, and both rock and smallmouth bass; 3) a diet that is likely comprised of forage fishes other than those included in our study for northern pike and chain pickerel.

Environmental influence on the secondary productivity and fish abundance in coastal fishing grounds off Mangalore, south-eastern Arabian Sea

Environmental parameters influence the productivity and abundance of fish in marine ecosystems. In this study, we attempted to analyse the relationship between environmental parameters and abundance of fish in trawling grounds in south-eastern Arabian Sea along the coast of Karnataka. Among the 85 species of finfishes and shellfishes caught in the trawling grounds, 41 finfish species, 24 crustaceans, 18 molluscs and two echinoderms were recorded. Seasonal differences were seen in biomass with the highest biomass during the post-monsoon period (October-January). Water temperature and nutrients were the key contributing factors of seasonal differences in the biotic communities studied. Season specific diagnostic species were identified using SIMPER analysis. Squilla which formed the major prey item of most of the demersal fishes dominated (&gt;40%) coastal grounds throughout all seasons. This could be considered as a fishery indicator of the region. The dominance and abundance of copepods was found to be influenced by sea surface temperature (SST) and nutrients. The results of the study have implications on the fishery, knowledge on environmental factors influencing the abundance and importance of non-commercial species in sustaining the fishery in the region.

Diet composition and foraging ecology of U.S. Pacific Coast groundfishes with applications for fisheries management

Determining the prey composition and foraging habitats of U.S. Pacific Coast groundfishes are specified management directives that have not received much scientific attention. To address this knowledge gap, we conducted a meta-analysis of the feeding ecology of 18 commercially important species and their life stages during a recent review of Pacific Coast groundfish essential fish habitat. A Major Prey Index was developed to evaluate relative importance among 47 prey taxa. Based on this metric, unidentified teleosts, euphausiids, and brachyuran crabs were the most important prey groups. When 14 generalized prey categories were used, fishes represented the dominant taxon (mean % weight or volume = 32.3) followed by shrimps (11.5), crabs (10.0), and euphausiids (9.5). PERMANOVA results indicated that species-specific differences were the primary source of dietary variability among tested variables (life stage, functional group, taxonomic group). Pacific Coast groundfishes mainly were characterized as mesopredators with estimated trophic levels ranging from 3.4 to 4.2. Foraging habitats differed significantly among functional (benthic, demersal, pelagic) and taxonomic (elasmobranch, roundfish, rockfish, flatfish) groups. Using hierarchical agglomerative cluster analysis, we identified a significantly distinct trophic guild that consumes mainly polychaetes and hard-shelled molluscs (juvenile, juvenile–adult Dover Sole; juvenile–adult English Sole) and another that specializes on euphausiids (juvenile Pacific Hake; juvenile–adult Darkblotched Rockfish). Our findings filled substantial data gaps in the trophic ecology and habitat-based management of commercially important species and can be used to inform future reviews of Pacific Coast groundfish essential fish habitat.

Alterations in foraging behavior of Coccinella septempunctata and Propylea japonica mediated by a novel defended prey affect their predatory potential

Generalist aphidophagous coccinellids have to cope with novel prey aphids in environments that are changing rapidly because of anthropogenic activity. The goldenrod aphid, Uroleucon nigrotuberculatum (Olive) (Hemiptera: Aphididae), is a noxious prey, which was recently introduced into Japan. It is a major prey for the native Japanese predators Coccinella septempunctata bruckii Mulsant and Propylea japonica (Thunberg) (both Coleoptera: Coccinellidae) in early summer on patches of solidago, Solidago altissima L. (Asteraceae). Prey preference of these coccinellids between this aphid and a native suitable prey aphid, Megoura crassicauda Mordvilko (Hemiptera: Aphididae), as well as their foraging behavior were studied for a better understanding of the negative impacts of the noxious novel aphid. Coccinella septempunctata initially preferred the novel prey, but later switched to the native prey, M. crassicauda; P. japonica had no preference for either prey. Feeding time of the first instars of C. septempunctata on U. nigrotuberculatum was significantly longer than that of P. japonica. The foraging bouts of fourth instars of C. septempunctata were significantly longer on U. nigrotuberculatum than on M. crassicauda, whereas only the feeding time of fourth instars of P. japonica on U. nigrotuberculatum was significantly longer than on M. crassicauda. Both coccinellids consumed less of U. nigrotuberculatum than of M. crassicauda. Thus, solidago patches infested by U. nigrotuberculatum may present an ecological trap, especially for C. septempunctata.

Nestling diet optimization and condition in relation to prey attributes and breeding patch size in a patch-resident insectivorous passerine: an optimal continuum and habitat constraints

Direct observational studies are needed to address dietary adjustment in species breeding in isolated non-forest habitat islands with respect to the energy demands of growing nestlings and breeding patch size. Using new dietary records determined for nestlings of Whinchat Saxicola rubetra, a dramatically declining insectivorous passerine and an indicator species of the cessation of agricultural activity, we investigated the relationships between changes in the main dietary characteristics, numerical and biomass contributions of major taxonomic and functional prey groups (expressing chitin content, vertical distribution, habitat preference and vagility within the landscape) and brood age, nestling condition and size of abandoned fields (i.e. breeding patches). Broods from larger abandoned fields received more sedentary and heavier prey like Orthoptera and soil-dwelling invertebrates, whereas the proportion of caterpillars, aerial insects and prey from vegetation decreased with increasing patch size. Nestling condition was positively correlated with the proportion of caterpillars and Orthoptera or sedentary prey taxa, but negatively with the proportion of Coleoptera or vagile prey taxa in the diet, though not with patch area. This suggests that parent Whinchats can overcome the habitat constraints resulting from the small area of an abandoned field by interchangeably incorporating the two major prey groups (Orthoptera or Lepidoptera) into the diet they feed to their nestlings. This implies a continuum in dietary optimization that is a trade-off between a brood’s nutritional demands and the parents’ ability to deliver top-ranked invertebrates present mostly within the breeding patch.

Diel diet of fantail darter in a tributary to Lake Ontario, New York, USA

ABSTRACTThe foraging behavior of benthic fishes in streams is seldom examined but is vital to the health of the aquatic community. We examined the feeding ecology of the fantail darter (Etheostoma flaballere) in Trout Brook, a tributary of the Salmon River in central New York, USA. Of the six time periods examined, fantail darters fed most intensely from 1600–2000 h, with ephemeropterans the major prey consumed during all time periods except for 2000 where chironomid larvae were consumed the most. Fantail darter diet composition was similar across all time periods except during the night which appeared to be uniquely different. According to the prey selection analysis, fantail darters appear to prefer dipterans and ephemeropterans but also demonstrated an opportunistic behavior feeding on what was available in the brook.