Total Prey Volume Research Articles

Non-native earthworms increase the abundance and diet quality of a common woodland salamander in its northern range.

The online version contains supplementary material available at 10.1007/s10530-023-03168-3.

Diet composition: A proximate mechanism explaining stream salamander declines in surface waters with elevated specific conductivity

Changes in land use, such as mountaintop removal mining with valley fills (MTR-VF), often results in headwater streams with elevated specific conductivity (SC). Stream salamanders appear to be particularly sensitive to elevated SC, as previous studies have shown occupancy and abundance decline consistently among all species and life stages as SC increases. Yet, the proximate mechanism responsible for the population declines in streams with elevated SC have eluded researchers. We sampled salamander assemblages across a continuous SC gradient (30–1966 μS/cm) in southeastern Kentucky and examined the diet of larval and adult salamanders to determine if the ratio of aquatic to terrestrial prey (autochthony), total prey volume, aquatic prey importance (Ix), and body condition are influenced by SC. Further, we asked if threshold points for each diet component were present along a gradient of SC. Larval salamanders experienced a 12–fold decline in autochthony at 153 μS/cm, a 4.2–fold decline in total prey volume at 100 μS/cm, a 2.2-fold decline in aquatic Ix at 135 μS/cm, and a rapid decline in body condition as SC increased. Adult salamanders experienced a 3–fold decline in autochthony at 382 μS/cm, no change in prey volumes, a 2-fold decline in aquatic Ix at 163 μS/cm, and a decline in body condition as SC increased. Our results indicate that SC indirectly affects stream salamander populations by changing the composition of diet, which suggests that food availability is a proximate mechanism that leads to reduced population occupancy, abundance, and persistence in streams with elevated SC.

Feeding habits and dietary overlap during the larval development of two sandperches (Pisces: Pinguipedidae)

Two species of sandperch (Pinguipedidae: Perciformes), Prolatilus jugularis and Pinguipes chilensis, inhabit the coastal waters of the South Pacific. Both species have pelagic larvae with similar morphology, but their diet preferences are unknown. Diet composition, feeding success, trophic niche breadth and dietary overlap were described during larval stages for both species. In the austral spring, larval P. jugularis (3.83-10.80 mm standard length [SL]) and P. chilensis (3.49-7.71 mm SL) during their first month of life had a high feeding incidence ( > 70%) and fed mostly on copepod nauplii ( > 80% IRI), Rhincalanus nasutus metanauplii and Paracalanus indicus copepodites. The number of prey ingested was low (mean: 4-5 prey per gut) and independent of larval size; total prey volume and maximum prey width increased as larvae grew. Mouth opening and ingested prey were greater in larval P. jugularis than in P. chilensis, leading to significant differences in prey composition among larval species, in terms of prey number and volume. Pearre’s trophic niche breadth was narrow for both species (0.159±0.07 for P. jugularis; 0.156±0.03 for P. chilensis) and independent of larval size. Dietary overlap was high inter- and intra-species in larvae with a mouth gape < 900 μm. These results suggest the relative importance of both larval species as primary consumers of the pelagic web in nearshore environments of rocky temperate areas.

Feeding ecology of the common sun skink, Eutropis multifasciata (Reptilia: Squamata: Scincidae), in the plains of central Vietnam

We studied the feeding ecology of Eutropis multifasciata in the tropical plains of central Vietnam to understand better the foraging mode, spatiotemporal and sexual variation in dietary composition, and rarefaction curves of prey-taxon richness for males and females. Stomach contents (n = 161) were collected from October 2013 to May 2014 using a nonlethal stomach-flushing technique. A total of 680 food items (624 animal items and 56 plant items) was found in 161 stomachs of skinks, representing 19 unique animal categories. We found that the diet of E. multifasciata is composed mainly of small, sedentary and clumped prey and that this skink specialises on spiders, insect larvae, snails, grasshoppers and crickets (with a combined importance index of 60%). Dietary composition, prey size and total prey volume in E. multifasciata changed between dry and rainy seasons and among regions. The total volume of food items consumed by males was larger than that of females, and the diversity and evenness index of prey categories were larger in males than in females. However, using rarefaction curves revealed that females have the higher prey-taxon richness after points between 130 and 140 prey items for frequency, and between 160 and 170 prey items for number of items, and the differences were not statistically significant. The foraging behaviour of E. multifasciata best fits a ‘widely foraging’ model.

Diet of the Bannan CaecilianIchthyophis bannanicus(Amphibia: Gymnophiona: Ichthyophiidae) in the Mekong Delta, Vietnam

Abstract Ichthyophis bannanicus is a terrestrial caecilian, and little is known about many aspects of the ecology of this species. We investigated the correlation between diet and body size, spatiotemporal variation in dietary composition, diversity index of prey, and size dimorphism among populations for this species. Specimens (N = 135) were collected from May 2010 to April 2011 in the Mekong Delta, Vietnam. We found 178 prey items representing 11 unique families and discovered that the diet of I. bannanicus is composed mainly of small prey; the most important were Achatinidae, Lumbricidae, and Formicidae, with a combined importance index of 77%. Diet composition, prey size, and total prey volume in I. bannanicus changed between dry and rainy seasons and among regions (P < 0.001). Mean prey volume increased with body size and showed positive correlations (P < 0.001) between total length and mouth width and prey size consumed. The total dietary breadth of I. bannanicus was 4.52, and all six populations o...

Breeding Dynamics, Diet, and Body Condition of the Hong Kong Newt (Paramesotriton hongkongensis)

Paramesotriton hongkongensis has a highly restricted distribution in southern China, and a comprehensive study of the species' basic ecology in aquatic and terrestrial habitats has not been previously undertaken. Using mark-recapture methods, we assessed seasonal patterns of breeding populations in four streams in Hong Kong every 3 wk over 18 mo (2007–2009). We examined diet and body condition of newts in the four focal and six additional streams. We surveyed transects radiating outward from breeding pools to determine the extent of terrestrial habitats used. In the four focal streams, we made 3436 captures of adult newts, comprising 1312 unique individuals. Breeding occurred primarily during the dry, cool season and extended over 8 mo. Individuals remained in breeding pools for an average of 45 days, suggesting that populations in pools were changing throughout the breeding season and that most individuals had a 10-mo terrestrial phase. Sex ratio changed across the breeding season, with males making up larger proportions of populations earlier in the season. Breeding site fidelity averaged 24% and was density-dependent. Among the 47 identified prey types identified in the diet of 406 newts, the most important prey were Brotia snails, Caridina shrimp, newt eggs, baetid mayflies, and calamoceratid caddisflies, in composite making up 63% of total prey volume and 82% of total prey abundance. Cannibalism of eggs and larvae, primarily by females, largely explained differences in diet between sexes. We documented no systematic difference in adult body condition (size-weight relationship) among streams. Fifteen individuals were found in forested habitats within 100 m of the nearest stream, except a single individual located 228 m away. Our work demonstrates that P. hongkongensis occurs at relatively high densities in stream pools during a protracted breeding season, in which individuals show site fidelity but probably do not breed every year. The species appears to be a generalist predator in most aquatic habitats. Although individuals spend most of the year on land, we still have little understanding of the spatial extent of terrestrial habitat use by the species. Future investigations should focus on the species' ecology in terrestrial habitats and on determining the amount of forest cover around breeding sites necessary to protect P. hongkongensis populations in Hong Kong.

ESTUDO PRELIMINAR DA ECOLOGIA TRÓFICA DA Sardinella brasiliensis NA COSTA SUDESTE DO BRASIL

The feeding ecology of the brazilian sardine Sardinella brasiliensis was studied on the Brazilian continental shelf, from 22°S to 29°S. Based on the Index of Relative Importance (IRI) the diet S. brasiliensis was analysed qualitatively and quantitatively in autumn, winter and spring. An indirect volumetric analysis (called individual volume method) was also performed where food items were classified as geometric bodies and mean volumes were calculated for each food item. The length distribution of sardine in the bulk of the samples varied mainly between 170 and 200 mm. S. brasiliensis prey on a broad variety of phytoplankton and zooplankton organisms, including diatoms, dinoflagellates, tintinnids, copepods, decapods and amphipods. In the stomach contents of S. brasiliensis 27 different taxa were identified; 11 phytoplankton and 16 zooplankton taxa. The zooplankton fraction represented 74,2% of the total prey volume in the sardine stomachs in autumn, 36,8% in winter and 99,8% in spring. The diatom Coscinodiscus spp. and copepods were volumetrically the most important taxa in the diet. Among copepods, the cyclopoid Oncaea sp., the harpaticoid Microsetella norvegica, calanoids Centropages sp., Temora stylifera and Candacia curta were the most important species in the diet. Larvae of Brachyura and the amphipod Lestrigonus sp. constituted a large volume in the stomach contents. S. brasiliensis was found to be an omnivore species, which preys on zooplankton, but that is able to switch to filter-feeding on phytoplankton and microzooplankton.

Relative feeding specialization may depress ontogenetic, seasonal, and sexual variations in diet: the endemic lizard Cnemidophorus littoralis (Teiidae).

We investigated the feeding habits of the teiid lizard Cnemidophorus littoralis in the markedly seasonal habitat of Restinga da Barra de Maricá (22 degrees 57'S, 43 degrees 50'W), Rio de Janeiro State, Brazil, to evaluate to what extent its diet is ontogenetically, sexually, and/or seasonally conservative. Lizard stomach contents were analyzed, identified, counted, estimated for volume (in mm3), and grouped in four classes (active, sedentary, and clumped preys, and plant material). The relative contribution of each food class to the total prey volume consumed by adult males and females and juveniles was compared in three ways: between juveniles and adults, sexes, and seasons (wet and dry). Sexual dimorphism in head size was tested by comparing head width and jaw length using analysis of covariance (ANCOVA). Isopterans were the most important prey item, occurring in 93% of the lizard stomachs examined and corresponding to 96.4% of total prey content and 69.7% of total prey volume. They occurred in high frequencies in the stomachs of C. littoralis throughout all study months. We found no sexual, ontogenetic, or seasonal differences in C. littoralis diet although the sexes differed significantly in head width. We concluded that isopterans are the main item in the diet of C. littoralis in Restinga da Barra de Maricá, both for juveniles and adults. The lack of seasonal, sexual, or ontogenetic variation in its diet results from the massive consumption of these insects. Isopterans are small, occur in clumps, and are available year-round, and thus are an advantageous food item for the active forager C. littoralis. We also found sexual dimorphism in the head size of C. littoralis: males have wider heads than females. This dimorphism, however, does not seem to be related with the diet of the species, and is probably a result of sexual selection.

Spatial and temporal variability in the distribution and diet of the gudgeon (Eleotridae: Hypseleotris spp.) in a subtropical Australian reservoir

The diurnal distribution and diet of Hypseleotris spp. was examined over a 14-month period in Maroon Dam, a productive subtropical reservoir in south-east Queensland, Australia. Three distinct size classes of Hypseleotris were observed. The smallest (&lt;16 mm standard length (SL)) fish undertake a vertical diurnal migration in the pelagic throughout the year, spending daylight hours near the surface and night hours in deeper waters. The diet of this size class consists almost exclusively of zooplankton (98.6% total prey volume), with cladocera and copepoda dominating the identifiable prey items. A larger (12–20 mm SL) size class group of subadult/adult fish occupies the near-shore littoral throughout the daylight hours but moves out of the sampled area during the night. The diet of this size class is more diverse (zooplankton 58.5%, macro-invertebrate 25.0%, other 16.5%). The largest size class (&gt;20 mm SL) of adult Hypseleotris remains in the near-shore littoral throughout seasonal and diurnal cycles and has a more eclectic diet than the other two size classes (zooplankton 28.8%, macro-invertebrate 28.9%, other 42.3%). Spatial and temporal differences in the distribution and diet of these three size class groups are discussed with reference to the abundance and availability of suitable prey, intraspecific competitive exclusion, predator avoidance and water quality.

Relationships among vertically structured in situ measures of turbulence, larval fish abundance and feeding success and copepods on Western Bank, Scotian Shelf

Using vertically stratified data of the abundance of silver hake (Merluccius bilinearis) larvae and concentrations of copepods collected in the field, we examine relationships among the vertical distribution of larval fish, their potential prey, feeding success and water column turbulence. Water column turbulence and associated stratification parameters were estimated from: (i) in situ measures of turbulent kinetic energy dissipation (ɛ) provided by an EPSONDE profiler; (ii) in situ wind speed; (iii) the Richardson number (Ri); and (iv) the buoyancy frequency (N2). Small (&lt; 5 mm total length) silver hake were more abundant in the least turbulent waters (i.e. at a minimum in the rate of dissipation of turbulent kinetic energy, ɛ &lt; 10–7 W kg−1; Ri &gt; 0.25; N2 &gt; 0.001 (rad s–1)2). Partial correlations amongst ɛ, N2 and small hake larvae were significant only for N2. The abundance of larger (&gt; 5 mm total length) hake larvae was positively correlated with depth and was not associated with either ɛ or N2. Vertical distributions of three potential prey (classified by stage) were variable. Early stage copepodids were positively correlated with N2 and negatively correlated with ɛ. We found no evidence of diel distribution patterns for small (&lt; 5 mm total length) hake larvae or for any of the developmental stages of the copepods examined. Neither estimate of water column turbulence inferred from wind speed nor from Ri was meaningfully related to in situ estimates of ɛ or to larval fish abundance. Feeding success, measured either as prey items (gut)–1, average prey length, or total prey volume (gut)–1, was not related to predicted encounter rates between days. However, the average prey length (gut)–1 was significantly (P &lt; 0.01) related to water column turbulence. These conflicting results suggest that the relationship between larval feeding and the environment is more complicated than assumed. We conclude that without substantial high resolution in situ examination of the relationship between the vertical distributions of turbulence, larvae and their prey, the growing acceptance in the secondary literature that turbulence has a positive and biologically meaningful effect on trophic interactions between fish and their zooplankton prey (a generalization based largely on modelling and laboratory experiments) is premature.

Diet of the Mexican Fringe-Toed Lizard (Uma exsul)

Seasonal differences in environmental conditions, such as precipitation, appear to regulate food diversity and abundance, and thereby indirectly influence changes in the diet of some lizards (Ballinger and Ballinger, 1979). Whitford and Creusere (1977) showed that the availability of insect prey varied according to the distribution and amount of rain throughout the year, and Maury (1995) found that variability in prey diversity and abundance was correlated with the effect of precipitation on primary productivity. The diet of the genus Uma remains somewhat unclear (D. S. Turner and C. R. Schwalbe, unpbul.). Commonly, it has been considered a carnivore, or perhaps opportunistic omnivore, but the data are contradictory. In Sonora (Mexico), Ortega-Rubio et al. (1995) found no plant matter in the diet of Uma notata. They reported a purely insect diet. In sharp contrast, a study of the more distantly related Mexican species, Uma paraphygas, found plant parts in nearly 56% of the 153 lizards examined, providing more than 40% of the total prey volume for adult males in two of four seasons (Gadsden and PalaciosOrona, 1997). The purpose of our paper is to describe seasonal variation in the diet of an endemic Mexican lizard species, Uma exsul, and to investigate sexual differences in diet. The study was conducted in the sand dune systems within the Mapimian subprovince of the Chihuahuan Desert (25023'N, 103?30'W), in the dry Laguna de Viesca in southwestern Coahuila, Mexico (1100 m elevation; INEGI, 1988). The vegetation is dominated by Larrea tridentata and Suaeda nigrescens (Instituto Nacional de Estadistica, Georgrafia e Informatica, 1988). Average monthly temperature ranges from 13?C in January to 28?C during the summer. Average annual rainfall is 200 mm but varies greatly among years (Schmidt, 1979). In 1992, adult U. exsul were noosed or shot with BB rifles each month (8.3 + 4.0 individuals each month), immediately placed on ice, and subsequently preserved in 10% formalin. Lizards were collected between 1000 and 1600 h. Monthly samples for each season were combined (winter = January-March, spring = April-June, summer = July-September, and autumn = October-December). Stomach contents were removed, and food items

Stomach content analysis of minke whales Balaenoptera acutorostrata from the Lofoten and Vesterålen areas, Norway

Stomach contents from 15 minke whales Balaenoptera acutorostrata collected in the Lofoten and Vesterålen areas of Norway, August 1988, were analysed. All stomachs contained identifiable remains and constituted of fish only. Herring Clupea harengus was the dominant prey species found in all whale stomachs and constituted 92% of the total prey volume. Cod Gadus morhua was the second most abundant prey. In addition pollock Pollachius virens, haddock Melanogrammus aeglefinus, and great silver smelt Argentina silus were found in single whale stomachs. All fish species found in the whale stomachs in our investigations are of commercial importance, and the sizes of the herrings and cods in minke whale stomachs are of interest for commercial exploitation.

Diet of hoki larvae (Macruronus novaezelandiae) off Westland, New Zealand

Abstract The diet of hoki larvae, Macruronus novaezelandiae, was determined by examining the gut contents of larvae from plankton samples collected in July and August 1987 off Westland, New Zealand. The maximum size of prey consumed was similar for all sizes of hoki larvae examined, and the diet consisted primarily of the adults and copepodites of Clauso‐calanus, Oithona, and calocaianids. The size range of prey and composition of the diet appeared to change with larval development. First‐feeding larval stages fed on a diverse range of small prey, particularly phytoplankton, tintinnids, and copepod nauplii, whereas larger larvae consumed only copepod adults and copepodites. The small prey consumed by early larval stages was found to represent less than 3% of the total prey volume, however, and it is suggested that these prey were of little nutritional significance. The diet of hoki larvae is similar to that of larvae of other hake species.

Feeding chronology of juvenile piranhas, Pygocentrus notatus, in the Venezuelan llanos

During the 1988 rainy season, I studied the 24 h feeding chronology of juvenile (40–68 mm standard length) piranhas, Pygocentrus notatus (Characidae: Serrasalminae) from a natural population inhabiting a small savanna stream in Apure State, Venezuela. Stomach contents analyses, supported by laboratory determinations of digestion rate, showed that these fish are primarily diurnal carnivores. Predatory activity on 4–5 August 1988 increased markedly after sunrise, peaked around 1100 h, and essentially stopped after sunset. Means of stomach content weight-to-fish weight ratios among the periods sampled were significantly different. Small fish were the major prey at all hours (81% of total prey volume). Underlying factors responsible for the observed 24 h feeding patterns were not investigated, but avoidance of predation by adult piranhas, which were very active near sunset, may have been important.

Trophic Ecology of the Frecklebelly Madtom Noturus munitus in the Tombigbee River, Mississippi

Aspects of the trophic ecology of the frecklebelly madtom Noturus munitus, from a site on the Tombigbee River, Mississippi, are described. Aquatic insect larvae comprised the bulk of the diet. Noturus munitus differed little in gut content from a group of associated syntopic species. Males and females differed in mean prey length in autumn. Individual trophic diversity increased significantly in the autumn for both sexes and with standard length. Mean prey length and total prey volume did not increase with fish size. INTRODUCTION The mechanism of trophic resource allocation in fish communities may be complicated by ontogenetic, sexual, seasonal and diel differences within individual species. Because of the indeterminate nature of fish growth, changes in food habits that occur with age may be related to aspects of fish morphology and there may be seasonal changes in diet. Numerous studies have reported changes in diet with season and fish length in darters and madtoms (e.g., Turner, 1921; Daiber, 1956; Braasch and Smith, 1967; Page and Smith, 1970, 1971; Page, 1974, 1975, 1980; Mayden and Burr, 1981; Burr and Mayden, 1982). Northcote (1954) related diet changes to increasing size in Cottus. Werner (1974) studied the relationship between optimal prey size and predator mouth size, and variables such as trophic diversity and prey width have been shown to change ontogenetically (Nakashima and Leggett, 1978; Fahy, 1980). However, our knowledge about these relationships is limited for many species. This study focuses on ontogenetic and sexual differences in diet composition, prey size, prey volume and individual diet diversity of the frecklebelly madtom Noturus munitus, a little-studied, nocturnal, benthic species of the Tombigbee River, Mississippi. The numeric and volumetric characteristics of the gut composition are described and seasonal, sexual and size class differences in six attributes of the prey are considered. METHODS AND MATERIALS Specimens of Noturus munitus (N = 116) were collected between December 1979 and February 1980 from a site on the Tombigbee River N of Hwy. 50, 14.5 km NW of Columbus (Lowndes Co.), Mississippi. Specimens were collected between 1900 and 2200 hr at approximately 30-day intervals. Because of flooding, few madtoms were collected between April and early June of 1980. Specimens from the Tulane University Museum of Natural History (N = 43) that were collected at the same site and time of day in 1969 (G. H. Clemmer, pers. comm.) were used to estimate spring diets. Because few specimens were collected in some months, data are analyzed for two seasons, spring (February through July) and autumn (August through December). I obtained no specimens in January. The spring period coincides with the breeding period of the species (Trauth et al., 1981). Each specimen was measured for standard length (Hubbs and Lagler, 1958).