Selection of waterbirds by Geoffroy's cat: Effects of prey abundance, size, and distance

In spite of its wide distribution, Geoffroy's cat (Oncifelis geoffroyi) has been recently upgraded from Least Concern IUCN category to Near Threatened because of lack of knowledge. In this study, we examine at the Mar Chiquita Biosphere Reserve (37° 46`S, 57° 27`W; Argentina) their seasonal diet, and their feeding preference in relation to waterbird abundance, size, and distance of waterbird prey before attack. The diet, evaluated by feces analysis, was comprised of 42% waterbirds and 40% small mammals. The relative importance of waterbirds in the diet changed throughout the year associated with seasonal fluctuations in their availability. Predation on waterbirds increased from autumn to summer, while predation on small mammals decreased during this period. Trophic-niche breadth for prey occurrence was higher in autumn and lower in spring. We found that abundance, distance of waterbird prey before attack, and prey size were significant predictors of waterbird consumption by the Geoffroy's cat. This small cat appears to change its kill rate in relation to waterbird abundance changes. The overconsumption of prey close to vegetation and big prey indicates selective predatory behavior by this cat.     

Diet of the invasive piscivorous fish <Emphasis Type="Italic">Fistularia commersonii</Emphasis> in a recently colonized area of the eastern Mediterranean

The composition of the diet of the Indo-Pacific cornetfish Fistularia commersonii from the SE Aegean Sea is described. The stomach contents of 245 specimens collected between September 2004 and March 2005 were examined. Dietary comparisons were made reflecting the relationship between diet composition, time of year, and fish size. Correlation between predator length and prey length was significant. The diet of the blue cornetfish consists of 96% by number and 99.95% by weight of fish. Size classification and habitat of prey groups (benthic, supra-benthic, and pelagic) showed that with increased body length the blue cornetfish extended its diet to larger prey and more generalist feeding. Spicara smaris, Boops boops, and Mullidae spp. were the most abundant prey by weight whereas a variety of small benthic fish (especially gobiids) and newly hatched fish constituted the largest number of prey items. Length–weight relationships for the cornetfish were investigated.     

Prey utilization by Chaoborus punctipennis Say in a small,eutrophic reservoir

Prey selection by 2nd-, 3rd-, and 4th-instar larvae of Chaoborus punctipennis was evaluated by comparing larval crop contents to the species structure of the zooplankton community in a small, eutrophic lake. The rotifers, Brachionus caudatus and Trichocerca similis, were positively selected by and comprised most of the diet of 2nd- and 3rd-instar larvae. Rotifers comprised 67% of all prey items identified in the crops of even 4th-instar larvae. Whereas 2nd-and 3rd-instar larvae selected the two rotifers with equalfrequency, 4th-instar larvae selected Trichocerca significantly more frequently than they did Brachionus. Although copepods comprised only 8% of all prey identified in 3rd-instar crops, they comprised 33% of the crop contents of 4th-instar larvae. Both 3rd and 4th instars exhibited a positive electivity for Cyclops vernalis significantly more frequently than for Diaptomus pallidus. We conclude that the larvae of Chaoborus punctipennis can, and do, select between Trichocerca and Brachionus and between Cyclops and Diaptomus.The paper by Brooks and Dodson (1965) triggered a flurry of studies on aquatic predators and their ability to discriminate between available prey species. Although the original work dealt with vertebrate predators, it has become increasingly apparent that invertebrate predators may also exhibit considerable selectivity in choosing between prey categories. The larval stages of the various species of Chaoborus are ubiquitous lentic predators, especially in mesotrophic or eutrophic systems. Although there have been a number of recent publications which deal with the food habits and preferences of several species of Chaoborus, only a few studies have included analyses of larval crop contents and none of these have included Chaoborus punctipennis. This species is of particular interest because it is one of the smaller species in the genus, and perhaps for this reason, because it is frequently present in lakes which support large populations of planktivorous fish (von Ende 1979). The purpose of our research was to characterize the food habits and preferences of Chaoborus punctipennis in a small, eutrophic reservoir which supports a rather depauperate number of species of zooplankters.     

Prey selection by the larvae of three species of littoral fishes on natural zooplankton assemblages

The prey selection of larvae of three common littoral fish species (pike, Esox lucius; roach,Rutilus rutilus; and three-spined stickleback, Gasterosteus aculeatus) was studied experimentally in the laboratory by using natural zooplankton assemblages. Zooplankton prey was offered at four different concentrations to study the functional responses of the planktivores. The diets of pike and sticklebacks were formed mainly of copepod juveniles and adults, which dominated the prey communities, although sticklebacks ate also cladocerans. The diet of roach larvae consisted of rotifers, cladocerans and copepods, without prey selection, in equal proportions indicating a more omnivorous diet. All fish larvae were able to feed selectively although in sticklebacks prey selection was less pronounced. Pike and roach larvae preferred large prey to smaller prey types. Patterns of prey selection are discussed in the context of size-selection theory and apparent vs. true selection.     

The diet of pygmy sperm whales, Kogia breviceps, stranded in New Zealand: implications for conservation

The stomach contents of 27 pygmy sperm whales, Kogia breviceps, stranded on New Zealand beaches between 1991 and 2003 are reported. These individuals comprise 16 males, 10 females, and one for which no sex information is available. The diet was found to include fish and crustaceans, but is comprised primarily of cephalopods, with 0–526 lower beaks, representing an estimated maximum of c. 60 kg of cephalopod prey consumed by any one whale. Cephalopod prey is attributed to 23 species from 13 families, and is dominated by juvenile individuals of the families Histioteuthididae and Cranchiidae (adults of which usually occur at depths exceeding 400 m). Perceived threats to this whale, particularly those affecting distribution and abundance of prey species, are also discussed. These are the first data reporting the diet of this whale species in New Zealand waters. A comparison of the diet of K. breviceps is made with that of the sperm whale, Physeter macrocephalus from New Zealand waters, and with the diet of Kogia known elsewhere.     

Vertebrate Predation and Food-Sharing in Cebus and Pan

Capuchins and chimpanzees are the only nonhuman primates apart from baboons known to prey systematically upon relatively large vertebrates. Vertebrate predation is common and well documented in Pan troglodytes, rare in Pan paniscus, and commonly reported but infrequently studied in Cebus. Food-sharing is common in both Pan species but rarely reported for wild capuchins. I present data on vertebrate predation and food-sharing by white-faced capuchins (Cebus capucinus) from ongoing field studies at Santa Rosa National Park, Costa Rica. We have observed 106 successful predation events resulting in the capture of 156 prey items during 2929 observation hr (5.35 prey per 100 hr). Squirrels and nestling coatis comprised half of the prey taken; the remainder were mainly nestling birds and eggs. Adult males took 52% of all prey and 67% of squirrels. Squirrels are actively hunted and about 65% of them are adults. I estimated that the average capuchin group kills 43–50 squirrels annually, mostly during the dry season. Capuchins hunt squirrels in groups 81% of the time, and 17% of hunts are successful. There is no evidence for cooperative hunting, but occasional collaboration is suggested. Rates of food-sharing were low (1.7 per 100 hr), and meat was the only food shared between adults. I compare predation and food-sharing in C. capucinus with published data for Pan troglodytes, primarily in Gombe and Taï National Parks. I discuss sex differences, hunting strategies, the relationship between hunting and food-sharing, and various ecological and social factors that may promote vertebrate predation in Pan and Cebus.     

Differences in feeding selectivity and efficiency between young-of-the-year European perch (Perca fluviatilis) and roach (Rutilus rutilus) — field observations and laboratory experiments on the importance of prey movement apparency vs. evasiveness

Feeding selectivity and efficiency of young-of-the-year European perch and roach were compared under field and laboratory conditions. In laboratory experiments, the importance of prey evasiveness versus prey movement conspicuousness for fish selectivity was evaluated with respect to changing Cladocera/Copepoda prey ratio. Feeding efficiency was additionally investigated in relation to feeding time (5, 10, 20 min) and prey density (approx. 50, 200, 700 ind. L⁻¹). In Říov Reservoir, the diet of both fish species was nearly exclusively composed of crustacean zooplankton. In roach, diet shifted from rotifers and bosminids in May, towards Daphnia sp. and Leptodora kindtii in June and July. Daphnia contributed almost exclusively to the roach diet since June, composing on average more than 94% of total prey. Cyclopoid copepods, occurred in the roach’s diet only on the first sampling date; later on both cyclopoid and calanoid copepods were completely absent. On the other hand, copepods played an important role in the diet of perch. In early and mid-June when their share in the zooplankton was particularly high, copepods contributed by more than 50% to the diet of perch. Although their contribution dropped with their decline in zooplankton in June/July, by the end of July they again comprised about one third of perch’s diet. In both fish species, the increase in numbers of cladocerans in their diet was related to increase in SL. In roach, the numbers of consumed prey were doubled every twenty days during the investigated period. In perch the increase was not so consistent, but significantly higher efficiency of perch was reported on three out of six sampling dates. In laboratory experiments, roach showed a distinct avoidance for copepods and a preference for cladocerans. Both prey categories were only fed non-selectively when they dominated the prey mixture. Perch selectivity was more diversified. Contrary to roach, perch were fed copepods non-selectively on a balanced prey ratio. Further, with an increasing share of Cladocera, a situation resembling that of roach and Copepoda was avoided. However, when the share of copepods in the prey mixture dropped below ten percent, they were consumed non-selectively and with their ongoing decline in the prey mixture their preference even increased. Feeding efficiency differed significantly between perch and roach when foraging on copepods exclusively or on a prey mixture where copepods predominated. In the short time feeding experiment (5 min) with copepods, perch consumed on average 5.9 times more prey than roach. Although roach increased their success with increasing time it was still 1.7 times greater than for perch in the long time feeding experiment (20 min). Total numbers of prey consumed were positively affected by prey density and feeding time. With increasing feeding time, the consumption rate generally declined. With a fourfold increase in feeding time, the numbers of consumed prey increased on average only two times. Only in roach feeding on copepods did the numbers of prey consumed per minute of feeding increase with increasing feeding time. However, the overall numbers were low. Differences in feeding selectivity and efficiency between perch and roach juveniles were found to be significant both in the field and laboratory experiments. In roach, selectivity was determined solely by prey evasiveness. By contrast, perch’s selectivity was influenced by prey movement conspicuousness; prey escape abilities did not play an important role. Perch were more efficient foragers on evasive prey, but its feeding efficiency for non-evasive prey was not lower than that of roach. According to our observations, we suggest feeding behaviour to be responsible for the roach’s inefficiency in capturing evasive copepods.     

Polymorphism and size-pairing in the harvester antPogonomyrmex badius: a test of the ecological release hypothesis

Summary The role of caste polymorphism in the foraging strategy ofPogonomyrmex badius was studied in the field by measuring food items collected by foragers, and correlating food item size variables with forager size variables. The diet ofP. badius included seeds and insects. In two colonies examined, these food types comprised different proportions of the diet sample.Although some forager size variables showed close or significant correlations with food item size variables, we could identify no overall significant relationship between worker size and seed or prey size. Polymorphism inP. badius may be associated with omnivory. However, since minor workers serve as foragers and represent a portion of the total worker size variation, dietary expansion through caste proliferation appears to be only one aspect of the functional significance of polymorphism in this species.     

Diet comparison among demersal marine fish from the Canadian Arctic

Summary The diets of 12 species of demersal marine fish from various locations in the Canadian Arctic comprised a grand total of 267 prey species, mainly invertebrates. The total number of prey species taken by a single fish species ranged from 9 to 91, and the mean number per stomach from 2.0 to 9.4. The most important prey were Crustacea, most frequently epibenthic or planktonic species; Polychaeta, mainly the larger species; and Mollusca, notably the cropped siphons of Macoma calcarea. Generally, only a few species comprised the bulk of the food. Most of the fish had a predominantly benthic or epibenthic diet, a notable exception being Triglops pingeli which ate zoo plankton almost exclusively at the three sites from which it was collected. To a lesser extent, Triglops murrayi, Icelus spatula and Liparis gibbus also fed planktonically. No significant correlations in diet were found among sympatric fish populations, implying a division of resources and reduced interspecific competition.     

Trophic ecology of the Southern Grey Shrike (Lanius meridionalis) in insular environments: the influence of altitude and seasonality

The seasonal diet and prey selection of the Southern Grey Shrike (Lanius meridionalis) was studied in two different insular habitats: shrub environments of the Canary Islands in coastal and high mountain zones. We measured, in each season, food availability and prey size in order to determine prey size selection of shrikes along an altitudinal gradient. Moreover, we compared the diet patterns observed with those documented on the continent, to determine if Southern Grey Shrikes in the islands’ high mountain zone (which has a continental climate) showed seasonal diet variation similar to those in northern continental areas. We analysed a total of 1,139 shrike pellets collected in 1 year and identified 10,179 prey items. Numerically arthropods (91%), and in terms of biomass lizards (70%) were the main prey consumed by the shrikes. The proportions of the main prey items differed significantly between seasons and habitats. Diet in the coastal areas was less variable than in the high mountain zone. The greater seasonal climatic variation in the high mountain zone was associated with diet patterns similar to those found in some northern continental areas, such as the Iberian Peninsula and southern France. Finally, shrikes selected the largest prey in the high mountain habitat. This suggests that foraging behaviour in this species is related to climatic conditions, as the biggest and most profitable prey were consumed in the most harsh habitats.     

Experience affects performance of ten-spined sticklebacks foraging on zooplankton

To study the effects of short-term experience on prey size-selection ten-spined sticklebacks (Pungitius pungitius) were fed 7–13 days with five differing diets of novel prey, Daphnia magna. The diets consisted either of a mixture of two prey size classes (1.7 and 2.2 mm) or of single-sized (1.7 and 2.2 mm) prey. Before and after the diets, the sticklebacks' prey size selection was tested with a 1:1 ratio of 1.7 and 2.2 mm D. magna. Sticklebacks made more attempts to capture large than small prey, but their foraging success was better for small than for large prey. Sticklebacks fed with a diet of both prey sizes chose significantly more large prey on the 13th day than on the 7th day or at the beginning of the experiment. Handling times for both Daphnia size classes decreased slightly with increasing foraging experience. Inexperienced sticklebacks made more unsuccessful strikes on large prey than did experienced fish. Foraging success on large prey improved somewhat with increasing experience in all but one diet group. The results indicate that experience affected ten-spined sticklebacks' prey selection.     

Effect of cassava exudate and prey densities on the survival and reproduction of Typhlodromalus limonicus (Garman & McGregor) s.l. (Acari: Phytoseiidae), a predator of the cassava green mite,Mononychellus tanajoa (Bondar) (Acari: Tetranychidae)

The effects of cassava exudate and prey densities on reproduction and survival of the predatory mite, Typhlodromalus limonicus (Garman & McGregor) (Acari: Phytoseiidae), were investigated in the laboratory. Females were provided either cassava exudate ad lib. daily, low or high numbers of the cassava green mite prey, Mononychellus tanajoa (Bondar) (Acari: Tetranychidae) daily, or exudate for 5 or 10 days before switching to a low or high prey diet. Females fed only exudate laid no eggs. Females fed exudate before prey experienced a significant decrease (30%) in the number of eggs laid compared to females fed high numbers of prey daily. The reduction in fecundity was the result of prolonged preoviposition periods (2.0 days on prey daily vs 4.0 days on exudate before prey) and reduced number of eggs laid per female per day (1.7 eggs per female per day on prey daily vs 0.4 eggs per female per day on exudate before prey). Females fed only exudate had a greater survival rate and longevity than females fed prey daily or females fed exudate before a diet of prey. These results suggest that T. limonicus can survice for a limited period on cassava exudate during periods of low prey availability, but requires prey to complete oögenesis and propagate the population.     

Biases in determining the diet of jumbo squid <Emphasis Type="Italic">Dosidicus gigas</Emphasis> (D’ Orbigny 1835) (Cephalopoda: Ommastrephidae) off southern-central Chile (34°S–40°S)

The diet of jumbo squid (Dosidicus gigas) off southern-central Chile is described to examine potential biases in the determination of their main prey. Specimens were collected from catches using different fishing gear (jigging, trawl and purse-seine), from July 2003 to January 2004, and from December 2005 to October 2006. The stomach contents were analyzed in terms of frequency of occurrence, number, and weight of prey items and the diet composition was analyzed using Detrended Correspondence Analysis. In the industrial purse-seine fleet for jack mackerel (Trachurus murphyi), the dominant prey of D. gigas was T. murphyi. In the industrial mid-trawl fishery for Patagonian grenadier (Macruronus magellanicus), the dominant species in the diet of D. gigas was M. magellanicus. Similarly, Chilean hake (Merluccius gayi) was the main prey in the diet of D. gigas obtained in the industrial trawl fishery for Chilean hake; and, in both artisanal fisheries (purse-seine for small pelagics and jigging), small pelagic fish and D. gigas were the main prey in the stomach contents of D. gigas. Cannibalism in D. gigas varied between different fleets and probably is related to stress behavior during fishing. The Detrended Correspondence Analysis ordination showed that the main prey in the diet of D. gigas is associated with the target species of the respective fishery. Consequently, biases are associated with fishing gear, leading to an overestimate in the occurrence of the target species in the diet. We recommend analyzing samples from jigging taken at the same time and place where the trawl and purse-seine fleets are operating to avoid this problem, and the application of new tools like stable isotope, heavy metal, and fatty acid signature analyses.     

Prey preference and egg production of the carabid beetleAgonum dorsale

In order to elucidate whether the aphidRhopalosiphum padi is low quality food for the carabid beetleAgonum dorsale, as it has previously been found to be for cereal spiders, we performed a series of experiments using fruit fliesDrosophila melanogaster as a standard alternative prey (‘control prey’): 1) Prey preference, 2) Aphid consumption for satiated and starved beetles, 3) Egg production on different diets and 4) Preference experiments with fruit flies coated with a taste of different prey types. Other alternative prey types used were earthworms and sciarid midges, all potential prey in the field.A. dorsale has a low preference for aphids compared to fruit flies. Apparently there is an upper limit to the consumption of aphids independent of hunger and much below the beetles' total food demand. Egg production on a pure diet of aphids is lower than on a pure diet of fruit flies; it is extremely low on a pure diet of earthworms; the highest fecundity is found on a mixed diet. As fruit flies coated with a taste of aphids or sciarid midges are less prefered than flies covered with a taste of fruit flies there may be a chemical factor, acting through taste, involved in determining prey preference.     

The diet of the Imperial Shag Phalacrocorax atriceps at a colony on New Island, Falkland/Malvinas Islands combining different sampling techniques

The diet of the Imperial Shag Phalacrocorax atriceps was studied on New Island, Falkland/Malvinas Islands during the 2008/2009 breeding season, with some additional data from 2007/2008. The diet comprised a large variety of prey, mainly fish, crustaceans and squid. In contrast to other species of the blue-eyed shag complex, prey not only consisted of benthic organisms but also included pelagic prey. Different sampling techniques were combined in order to obtain a comprehensive overview of the diet. Pellets, regurgitations and stomach contents yielded different results. We discuss the causes for these variations including different sample availability over time. In particular, the stomach analyses seem to overestimate the importance of squid based on the occurrence of squid beaks. For the pellet analyses, lobster krill accounted for the majority of the prey remains except during the second half of December (i.e. when young chicks were being attended), when fish was more important.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Diet composition of the Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis> at the coast of the Guilan Province,Caspian Sea

Sturgeons are one of the most important and valuable species in the Caspian Sea. This investigation (2000–2002) was aimed at determining the feeding habits and the main and secondary prey organisms consumed by the Persian sturgeon (Acipenser persicus Borodin, 1897) living at depths less than 10 m in the Caspian Sea (Guilan Province). The food spectrum of immature A. persicus was comprised of benthic invertebrates of seven genera and fishes of three genera. The main prey items of immature A. persicus were polychaete worms and the secondary prey were crustaceans. The study of stomach contents showed that polychaetes were the most important component of the diet of immature A. persicus of the length class up to 25 cm.     

Determinants of predation on phytophagous insects: the importance of diet breadth

To evaluate the role of predation in the evolution of diet specialization and to determine the effectiveness of various larval defenses, we offered lepidopteran larvae to colonies of the tropical ant Paraponera clavata. We recorded behavioral and physical characteristics of prey items and used log-linear models to analyze their importance as deterrents to predation by P. clavata. The most important determinant of probability of prey rejection by P. clavata was a prey's diet breadth; specialists were rejected by the ants significantly more than generalists. Other less important, but significant, predictors of prey rejection included ontogeny, morphology and chemistry. Late instar caterpillars were rejected more frequently than early instars, hairy caterpillars were rejected more frequently than caterpillars with other morphologies, and one caterpillar species with an unpalatable extract was rejected more frequently than two species with palatable extracts.     

Diet and foraging opportunism of the Guiana dolphin (Sotalia guianensis) in the Abrolhos Bank,Brazil

Diet analysis allows exploring how coastal dolphins interact with the environment and their role in the marine food webs. We studied the diet and feeding ecology of the Guiana dolphin, Sotalia guianensis, through analysis of stomach content from 42 animals stranded on the eastern coast of Brazil. A total of 1,336 semidigested prey items (fish, otoliths, cephalopod beaks, and crustaceans) were identified. Teleost fish comprised the most frequent food item (92% of the total), followed by cephalopods, and crustaceans. Prey belonged to 34 taxa and richness in individual stomachs varied from 1 to 15 prey taxa. Prey were generally small, but showed a significant trend to increase in size with dolphin length. The main prey of Guiana dolphins were demersal, estuarine, and sound-making fish such as catfish and sciaenids. No sex-related differences in diet were found. Diet composition varied seasonally and occurrence of prey items was coherent with breeding or high abundance periods of some fish species and squids. Our study shows the importance of demersal prey from estuarine and soft-sediment habitats to Guiana dolphin in the Abrolhos Bank and reveals that feeding habits are generalist and opportunistic, with diet reflecting the seasonal abundance and availability of prey.     

Use of enclosures to detect the contribution of particular zooplankton to growth of young-of-the-year yellow perch (Perca flavescens Mitchell)

Summary Densities of the cladoceran, Holopedium gibberum, were manipulated in 18 enclosures containing juvenile (age 0+) yellow perch (Perca flavescens) and mean-lake densities of other zooplankton. In enclosures, where nearlake densities of all zooplankton species including Holopedium were maintained, young-of-the-year perch grew significantly heavier and longer than in experimental enclosures where Holopedium was excluded. Holopedium comprised between 15–45% of the diet (wet weight) of perch in the first 2 weeks of July in the control treatment (Holopedium at or near ambient lake densities) and only 3–7% of total biomass ingested in the experimental treatment (Holopedium density selectively reduced). Predation on Holopedium decreased dramatically after the 2nd week of July in the control treatment after which Chaoborus, chironomids, and Sida became dominant prey items (by weight) of juvenile perch. These findings suggest that growth and survivorship of age 0+ perch in Precambrian Shield lakes may be coupled to Holopedium abundance. Thus, utilization of Holopedium by young-of-the-year yellow perch may affect recruitment of this species since overwintering survivorship, range of accessible prey sizes or species, and vulnerability of juvenile perch to predation by larger fish depend on body size, which is reduced when Holopedium is excluded from the diet.