Biotic resistance of impact: a native predator (<Emphasis Type="Italic">Chaoborus</Emphasis>) influences the impact of an invasive predator (<Emphasis Type="Italic">Bythotrephes</Emphasis>) in temperate lakes

Introduced predators have caused some of the largest documented impacts of non-native species. Interactions among predators can have complex effects, leading to both synergistic and antagonistic outcomes. Complex interactions with native predators could play an important role in mediating the impact of non-native predators. We explore the role of the native predator context on the effect of the introduced predatory cladoceran Bythotrephes longimanus. While post-invasion impacts have been well described, studies have largely ignored the role of native predators. We used a field mesocosm experiment to determine whether Bythotrephes’ impact on prey communities is influenced by the presence of the ubiquitous native predatory insect larvae Chaoborus. The two predators exhibited niche complementarity as no change in total zooplankton prey abundance was detected across predator treatments. Rather, copepod abundances increased with decreasing abundances of Chaoborus, while cladocerans decreased with increasing abundances of Bythotrephes. Thus, the replacement of Chaoborus with Bythotrephes led to changes in the overall community structure of the zooplankton prey, but had little effect on prey total abundance. More interestingly, we found evidence of biotic resistance of impact, that is, the impact of Bythotrephes on the cladoceran community was altered when the two predators co-occurred. Specifically, the predation effect of Bythotrephes was more restricted to the shallower regions of the water column in the presence of Chaoborus, leading to a reduced impact on deeper dwelling prey taxa. Overall, our results demonstrate that the native predator context is important when trying to understand the effect of non-native predators and that variation in native predator abundances and assemblages could explain variation in impact across invaded habitats.     

Latitude and elevation as factors controlling occurrence of calanoid copepods in marginal lotic waters in New South Wales,Australia

Freshwater calanoid copepods develop abundant populations in lentic water bodies such as lakes, reservoirs and lagoons. In this study, we examined the potential habitat value of edges in lotic systems such as creeks and rivers where waters tend to stagnate, providing lentic-like environments. We examined a total of 353 edge samples collected from 321 sites across the state of New South Wales, Australia, with latitudes in the range 28.3–37.4°S and elevations in the range 2–1834 m above sea level. Of the total samples examined, calanoid copepods were found in 94 samples, with the frequency of occurrences of species decreasing in the order: Boeckella fluvialis Henry, B. triarticulata (Thomson), Gladioferens spinosus Henry, G. pectinatus (Brady), B. major Searle, B. minuta Sars, and Calamoecia lucasi Brady. The probability of occurrence of the calanoid copepods was related negatively to both latitude (as absolute values) and elevation, based on logistic regression models. We conclude that the edges of many lotic systems provide additional habitats for some species of freshwater calanoid copepods, with constraints on their distributions along latitudinal and elevational gradients.     

Life table demography of <Emphasis Type="Italic">Asplanchna brightwellii</Emphasis> Gosse, 1850 fed with five different prey items

We conducted life table experiments on the freshwater rotifer Asplanchna brightwellii to analyze its demography when fed with prey items from several taxonomic groups (cladocerans, protozoans, and rotifers) and under two different temperature regimes (20 and 25°C); the aim of the study was to determine the preferred prey for A. brightwellii in terms of fitness (evaluated as reproductive success) among five cladoceran, protozoan, and rotifer preys, and to test which temperature (20 or 25°C) is better for life table parameters of Asplanchna. Our analysis identified Brachionus calyciflorus as the preferred prey for A. brightwellii based on life table statistics, ingestion rate and electivity indices. The greatest values for net reproductive rate and intrinsic growth rate were achieved when A. brightwellii was fed B. calyciflorus. Greater reproductive values (R _o and r) were found at 25°C than at 20°C for A. brightwellii across the five prey species. We found significant differences in the ingestion rate and electivity index among zooplanktonic and benthic preys. The influence of temperature, the cost of predation, and how prey selection by A. brightwellii is influenced by: biomass, size, and swimming speed; they are discussed hoping to gain a better understanding of trophic transfers in zooplankton communities.     

Studies on the zooplankton community of a shallow lagoon of the Southern Baltic Sea: long-term trends,seasonal changes,and relations with physical and chemical parameters

The Darß-Zingst Lagoon, a coastal inlet of the southern Baltic Sea, was subject to extended monitoring. The biomass data of zooplankton from 1969 to 2001 were used to analyze long-term trends and to correlate zooplankton biomass with abiotic factors. The dominant species in the lagoon were the calanoid copepods Eurytemora affinis and Acartia tonsa, and the rotifer Keratella cochlearis f. tecta. In the long-term trend, two pronounced changes in zooplankton biomass and species composition were observed. They are discussed in connection with a shift in dominance from macrophytes to phytoplankton and the invasion of a polychaet species into the lagoon. Significant relations between zooplankton data and abiotic parameters were found. While temperature, precipitation and NAO winter index correlated positively with copepods and negatively with rotifers, the relationships were inversely for pH-value and duration of ice cover.     

Predation potential of <Emphasis Type="Italic">Rhynocoris marginatus</Emphasis> (Hemiptera: Reduviidae) against three mealybug species of agricultural importance

The predation potential of a generalist predator Rhynocoris marginatus (Fab.) (Hemiptera: Reduviidae) against three important mealybug pests of cotton, Phenacoccus solenopsis Tinsley, Maconellicoccus hirsutus Green, and Coccidohystrix insolita Green (Hemiptera: Pseudococcidae) was evaluated under laboratory conditions. The specific objective of the study was to determine the prey capturing time, prey handling time, and prey preference among the three mealybug species for different developmental stages of R. marginatus. The number of prey consumed/predator/24 h by R. marginatus was dependent on the mealybug species and the predator developmental stage. Rhynocoris marginatus showed a decrease in prey capturing time and handling time as the predator grew older. After evaluating the prey stage preference, results indicated that the developmental stages of R. marginatus preferred adult mealybugs over the younger stages. In a choice-test bioassay including the three mealybug species, no significant difference in prey species selection was observed for the various R. marginatus developmental stages. However, the mortality of P. solenopsis was observed to be highest among the mealybugs, followed by M. hirsutus and C. insolita. This supports the idea that R. marginatus can be effectively utilized for the management of one of the most destructive mealybug pests of cotton, P. solenopsis. Results from this study are important for the development of a knowledge-based management program for cotton agroecosystems affected by various mealybug pests.     

Predator-induced plasticity does not alter the pathway from evolution to ecology among locally adapted populations of <Emphasis Type="Italic">Daphnia</Emphasis>

In the growing field of eco-evolutionary dynamics, evidence for an influence of rapid shifts in phenotype on ecological processes is accumulating, yet, the contributions of phenotypic plasticity versus genetic change to these observed ecological changes are unclear. In one of the best studied ecosystems in terms of eco-evolutionary dynamics, landlocked versus anadromous alewife (Alosa pseudoharengus) have caused strong evolutionary divergence in their key zooplankton prey (Daphnia ambigua). We previously showed that such evolutionary differences have cascading ecological effects on consumer-resource dynamics and primary production. Yet, these locally adapted populations of Daphnia also differ in trait plasticity, which may, in turn, modify the pathway from evolution to ecology. Here we compared Daphnia from lakes with landlocked versus anadromous alewife for differences in rates of population growth in the presence and absence of predator cues over the course of a 39-day experiment. We predicted that predator-induced shifts in life history traits would facilitate faster rates of population growth. Contrary to our expectations, predator cue exposure did not alter rates of population growth. We instead found that Daphnia from lakes with landlocked alewife ultimately attained higher population densities (and exhibited faster population growth) when compared with Daphnia from lakes with anadromous alewife. Based on our previous work, these population level responses were unexpected, as Daphnia from lakes with landlocked alewife exhibit slower rates of somatic growth and delayed maturation. We discuss our results in lieu of the known differences in plasticity and how the population growth patterns may be influenced by resource limitation.     

Continued feeding on <Emphasis Type="Italic">Diporeia</Emphasis> by deepwater sculpin in Lake Huron

Monitoring changes in diets of fish is essential to understanding how food web dynamics respond to changes in native prey abundances. In the Great Lakes, Diporeia, a benthic macroinvertebrate and primary food of native benthivores, declined following the introduction of invasive Dreissena mussels and these changes were reflected in fish diets. We examined the diets of deepwater sculpin Myoxocephalus thompsonii collected in bottom trawls during 2010–2014 in the main basin of Lake Huron, and compared these results to an earlier diet study (2003–2005) to assess if their diets have continued to change after a prolonged period of Dreissena mussel invasion and declined Diporeia densities. Diporeia, Mysis, Bythotrephes, and Chironomidae were consumed regularly and other diet items included ostracods, copepods, sphaerid clams, and fish eggs. The prey-specific index of relative importance calculated for each prey group indicated that Mysis importance increased at shallow (≤55 m) and mid (64–73 m) depths, while Diporeia importance increased offshore (≥82 m). The average number of Diporeia consumed per fish increased by 10.0% and Mysis decreased by 7.5%, while the frequency of occurrence of Diporeia and Mysis remained comparable between time periods. The weight of adult deepwater sculpin (80 mm and 100 mm TL bins) increased between time periods; however, the change in weight was only significant for the 80 mm TL group (p?<?0.01). Given the historical importance of Diporeia in the Great Lakes, the examination of deepwater sculpin diets provides unique insight into the trophic dynamics of the benthic community in Lake Huron.     

Feeding behavior,ration and size structure of a population of the predatory gastropod <Emphasis Type="Italic">Cryptonatica janthostoma</Emphasis> in Vostok Bay,Sea of Japan

The relationships between the shell height of the predatory gastropod Cryptonatica janthostoma and the shell length of its typical prey, the bivalve Ruditapes philippinarum, and the diameter of the borehole on the prey shell resulting from a successful attack of the predator were experimentally found and assessed statistically. The shell height of C. janthostoma calculated retrospectively from the borehole diameter using the obtained relationships was 17–52 mm. The prey of C. janthostoma are burrowing bivalves, whose populations are affected by the predator to a varying degree. In populations of medium-sized mollusks (R. philippinarum, Protothaca euglypta, P. jedoensis, and others), C. janthostoma feeds on mollusks larger than 7–10 mm; in species with a shell length greater than 100 mm (Callista brevisiphonata, Saxidomus purpuratus), it eats specimens of 10–58 mm. C. janthostoma apparently has no effect on populations of small-sized mollusks (Anisocorbula venusta) and mollusks with an active avoidance response (Clinocardium californiense).     

Variation in the population demographics of <Emphasis Type="Italic">Scolopsis bilineatus</Emphasis> in response to predators

Predatory fishes play critical roles in the trophodynamics of coral reefs, and the biomass of predatory fish can be a strong determinant of the structure of reef fish assemblages. In this study, we used variations in predator biomass between management zones on the Great Barrier Reef to examine how predators influence the biomass, mortality, condition, and reproductive potential of a common prey species Scolopsis bilineatus (bridled monocle bream; Nemipteridae). Despite no numerical differences in biomass or mortality, we found significant differences in a variety of demographic traits for S. bilineatus between multiple areas of high and low predator biomass. The size-at-age, condition, and reproductive potential of fish were reduced in marine reserves where predator biomass was high. The response of fish to predators was highly sex dependent; females suffered the greatest reductions in condition and reproductive potential. This study supports the notion that predators can play important roles in regulating prey dynamics and emphasises the importance of understanding top-down control by predators when considering fisheries management techniques and conservation strategies.     

Few But Relatively Large Prey: Trophic Ecology of <Emphasis Type="Italic">Chauliodus sloani</Emphasis> (Pisces: Stomiidae) in Deep Waters of the Central Mediterranean Sea

The trophic ecology of Chauliodus sloani (Stomiidae) was thoroughly investigated by stomach content analysis for the first time in the Mediterranean. Overall 206 individuals (64.0–260.0 mm SL) were collected from 2013 to 2015. C. sloani can be defined a specialist predator which feeds exclusively on mesopelagic fish belonging to Gonostomatidae, Myctophidae, Paralepididae, Phosichthyidae, Sternoptychidae and Stomiidae. Gonostomatidae (%IRI = 26.02), Myctophidae (%IRI = 24.77) and Sternoptychidae (%IRI = 24.35) were important food items for C. sloani. Maurolicus muelleri (%IRI = 36.43), Cyclothone braueri (%IRI = 28.26) and Vinciguerria attenuata (%IRI = 12.97) were the most important prey. Cases of cannibalism were also observed. The examination of food size spectrum, in relation to predator length, demonstrated that C. sloani developed a feeding strategy aimed to maximizing energy input and based on the capture of few and relatively large prey: more than 50% of prey items exceeded the value of 20% for ratio between prey and predator size (SL) and the 5.4% of prey measured more than 50% of predator size. Differences in food composition across seasons were found; C. braueri and M. muelleri were more abundant in autumn, V. attenuata during spring. Prey items mainly belongs to weakly vertical migrating fauna, usually concentrated at 400 m Deep Scattering Layer.     

Suitability of Different Prey Aphids on the Growth,Development and Reproduction of <Emphasis Type="Italic">Chrysoperla zastrowi sillemi</Emphasis> (Esben-Petersen) (Chrysopidae: Neuroptera)

The prey preference of polyphagous predator, green lacewing (Chrysoperla zastrowi sillemi (Esben-Petersen)) was evaluated against five prey aphids viz., mustard aphid (Lipaphis erysimi), green peach aphid (Myzus persicae), cabbage aphid (Brevicorynebrassicae), black bean aphid (Aphis craccivora), spirea aphid (Aphis spiraecola) of agriculture importance and compared with eggs of Corcyracephalonica (Stainton). Lacewing larvae preferred Myzus persicae most followed by Brevicorynebrassicae. The highest growth index (8.31), larval survival (94.50 %), larval weight (10.45 mg), pupal weight (8.78 mg), faster multiplication rate (0.051) and fecundity (183.4 per gravid female) of the predator were recorded on M. persicae. However, the chrysopid reared on Corcyra eggs performed best in all biological parameters and fitness, than on aphid preys. This study explores the possibilities of selecting the most suitable prey aphid species for its exploitation as supplement for mass multiplication of chrysopid during off-season or unavailability of Corcyra eggs.     

Feeding patterns of the black-striped pipefish <Emphasis Type="Italic">Syngnathus abaster</Emphasis> in an invaded freshwater habitat

Syngnathus abaster is an euryhaline species, which has penetrated freshwaters in Europe and its range is expanding. The goal was to investigate the feeding patterns of this species in an invaded freshwater habitat, where it first appeared at the beginning of 1990s, with implications for assessing its possible effects on invaded ecosystems. In total, 36 prey items were identified in the diet of S. abaster. The most important prey were zooplanktonic organisms, among which copepods predominated significantly. The second most important prey were cladocerans, represented by 20 species/genera. The diet composition of this species showed clear seasonal dynamics but copepods remained the predominant prey item throughout the year. Significant positive relationships between the abundance of zooplanktonic organisms in the gut contents of S. abaster and their abundance in zooplankton samples were found for copepods and Ceriodaphnia sp. S. abaster showed a significant positive electivity for copepods throughout all months. It also positively selected some large cladocerans, which probably shared the same habitat. S. abaster also consumed fish items including gobiid larvae and its own juveniles, when they were abundant in May and especially in June. The possible effect of S. abaster on native ecosystems may include the shaping of zooplanktonic communities through selective predation on copepods. This species is unlikely to be a serious food competitor for native fish inhabiting European freshwaters, the majority of which are cyprinids. Nevertheless, it can have effects on some native fish through predation on their juveniles, which might share the same habitats.     

Continuing influences of introduced hedgehogs <Emphasis Type="Italic">Erinaceus europaeus</Emphasis> as a predator of wader (Charadrii) eggs four decades after their release on the Outer Hebrides,Scotland

Non-native predators can cause major declines or even localised extinctions in prey populations across the globe, especially on islands. The removal of non-native predators can, therefore, be a crucial conservation management tool but there can be challenges when they are viewed as charismatic in their own right. Four decades after their introduction to islands in the Outer Hebrides, Scotland, European hedgehogs Erinaceus europaeus continue to be an important nest predator for a declining population of breeding waders. Where hedgehogs were rare, clutch survival rates (assessed using nest temperature loggers) of five species of waders (dunlin Calidris alpina, lapwing Vanellus vanellus, redshank Tringa totanus, snipe Gallinago gallinago and ringed plover Charadrius hiaticula) were higher than where hedgehogs were relatively more abundant. Hedgehogs were the most frequent nest predator identified using cameras. However, factors influencing population sizes of breeding waders are complex and unlikely to be attributable to a single species of predator. The interactions between predation, land use, habitat and the changes in each deserve further attention.     

Increased abundance of the non-indigenous zooplanktivore, <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis>, is strongly correlated with greater spring prey availability in Canadian Shield lakes

The non-indigenous zooplanktivore, Bythotrephes longimanus, is a large Palaearctic cladoceran that is spreading rapidly in the Great Lakes watershed in North America. As a voracious predator, Bythotrephes can reduce herbivorous cladoceran abundance and diversity; however, the variables that affect its abundance are not well understood. To determine what bottom-up factors are associated with the abundance and seasonal dynamics of established Bythotrephes populations, two Bythotrephes datasets from lakes in south-central Ontario, Canada, were analysed using multiple regression and multivariate analyses: a multi-lake dataset of nine lakes sampled in 2003 and a multi-year dataset of one of these lakes, Harp Lake, sampled from 1994–1998 and 2001–2004. Bottom-up variables tested were Secchi disk depth, epilimnetic temperature, cladoceran (prey) density, total phosphorus, dissolved organic carbon and Chlorophyll a, as well as maximum depth for the multi-lake dataset. In both analyses and datasets, springtime abundance of herbivorous cladocerans was consistently found to be a significant factor associated with Bythotrephes (June–September) abundance; Bythotrephes annual abundance was significantly and positively associated with mean May and June prey abundance, along with mean Secchi disk depth for the multi-lake dataset, and groups of lakes or years with similar Bythotrephes seasonal abundance patterns were predicted by June prey abundance. Additionally, prey availability was the dominant contributor towards changes in weekly Bythotrephes birth rates calculated for two of the study lakes. Our study suggests that prey availability influences Bythotrephes abundance, which provides evidence that Bythotrephes establishment success is affected by the abundance of its prey.     

The plankton community of Lake Matano: factors regulating plankton composition and relative abundance in an ancient,tropical lake of Indonesia

Recent evidence reveals that food webs within the Malili Lakes, Sulawesi, Indonesia, support community assemblages that are made up primarily of endemic species. It has been suggested that many of the species radiations, as well as the paucity of cosmopolitan species in the lakes, are related to resource limitation. In order to substantiate the possibility that resource limitation is playing such an important role, a study of the phytoplankton and zooplankton communities of Lake Matano was implemented between 2000 and 2004. We determined species diversity, relative abundances, size ranges, and total biomass for the phytoplankton and zooplankton, including the distribution of ovigerous individuals throughout the epilimnion of Lake Matano in three field seasons. The phytoplankton community exhibited very low biomass (<15 μg l^?1) and species richness was depressed. The zooplankton assemblage was also limited in biomass (2.5 mg l^?1) and consisted only of three taxa including the endemic calanoid Eodiaptomus wolterecki var. matanensis, the endemic cyclopoid, Tropocyclops matanensis and the rotifer Horaella brehmi. Zooplankton were very small (<600 μm body length), and spatial habitat partitioning was observed, with Tropocylops being confined to below 80 m, while rotifer and calanoid species were consistently observed above 80 m. Less than 0.1% of the calanoid copepods in each year were egg-bearing, suggesting very low population turnover rates. It was concluded that chemical factors as opposed to physical or biological processes were regulating the observed very low standing crops of phytoplankton which in turn supports a very minimal zooplankton community restricted in both species composition and abundance. As chemical factors are a function of the catchment basin of Lake Matano, it is predicted that resource limitation has long played an important role in shaping the unique endemic assemblages currently observed in the food web of the lake.     

The Predation Strategy of the Recluse Spider <Emphasis Type="Italic">Loxosceles rufipes</Emphasis> (Lucas, 1834) against four Prey Species

Generalist predators have to deal with prey with sometimes very different morphologies and defensive behaviors. Therefore, such predators are expected to express plasticity in their predation strategy. Here we investigated the predatory behavior of the recluse spider Loxosceles rufipes (Araneae, Sicariidae) when attacking prey with different morphologies and defensive mechanisms. We expected L. rufipes to show different prey capture strategies and variable acceptance towards each prey type. Potential prey species were collected directly from the web or in the surroundings of the web-building site of L. rufipes. We collected and used the following in our experiments: termite workers (Nasutitermes sp.), lepidopteran larvae (Eurema salome), ants (Camponotus sp.) and isopods (Tylidae). We paired these prey with L. rufipes and recorded their behavior in captivity, quantifying acceptance rate, immobilization time and the sequence of behaviors by the predator. The acceptance rate was lower for isopods but not different among other prey. The immobilization time was higher for isopods than for termites and similar for the other pairwise comparisons. The behavioral sequence was similar for all prey except for isopods, which were also bit more often. Our combined results show plasticity in the behavior of L. rufipes and also show it subdues a potentially dangerous prey (ant) and an armored prey (isopod).     

Specific features of feeding in underyearlings of zander (<Emphasis Type="Italic">Sander lucioperca</Emphasis>) (Percidae) of the Rybinsk reservoir in various years

The results of the studies on feeding of zander (Sander lucioperca) underyearlings in the Rybinsk Reservoir in 2008-2010 and 2012 are presented. The study revealed that, at feeding on plankton, the assemblage of the organisms consumed by juvenile zander has not been changed compared to 1950. The underyearlings prefer to feed on large zooplankters—Daphnia longispina, Leptodora kindtii, and Bythotrephes longimanus—along with copepods. At some sampling stations, the species of macrozoobenthos were included in the young zander food. The piscine component of zander food was dominated by underyearlings of Azov-Black sea tyulka (Clupeonella cultriventris); the fries of perch (Perca fluviatilis) and cyprinids (Cyprinidae) were less important. The feeding strategy of zander underyearlings was unchanged in various years. At turning to predatory feeding, not only the ratio of sizes of predator versus prey but also the proportion of the densities of their populations plays an important role.     

Seasonal Abundance and Predatory Potential of <Emphasis Type="Italic">Stethorus aptus</Emphasis> Kapur (Coleoptera: Coccinellidae): A Biocontrol Agent of Tea Red Spider Mite <Emphasis Type="Italic">Oligonychus coffeae</Emphasis> Nietner (Acarina: Tetranychidae)

The tea red spider mite, Oligonychus coffeae Nietner is one of the major pests of tea plants in North-east India. The ladybird beetle, Stethorus aptus Kapur, is a newly reported predator of O. coffeae. Predatory efficiency study of S. aptus under laboratory conditions revealed that adult of S. aptus consumed significantly more mites than larvae. In free choice condition, the predator consumed within a range of 48–56 adults and 82–90 larvae of O. coffeae whereas the 3rd and 4th instar larvae of S. aptus consumed 20–26 adults and 50–60 larvae of O. coffeae per day respectively. Population dynamics of S. aptus was observed for 1 year under field conditions. The maximum density of the predator was recorded during January to March and it gradually declined from September onwards. Population of S. aptus showed positive correlation with its prey O. coffeae and relative humidity while effect of other factors was insignificant.     

Selective predation by crevalle jack <Emphasis Type="Italic">Caranx caninus</Emphasis> on engraulid fishes in the SE Gulf of California,Mexico

Feeding habits determine many aspects of living organisms, where it lives, the time of day that it is active, energy flow, biomass consumed and intra- and interspecific interactions, it which provides information to make predictions about the effects of fisheries on predator-prey relationships. Accurate predictions require a thorough understanding of predator diets and prey selection. In this study, specimens of the crevalle jack Caranx caninus were obtained between October 2012 and October 2014 in the SE Gulf of California, Mexico, in order to determine its feeding habits and prey selection. A total of 238 specimens were obtained, of which 94 (39.5%) had stomachs containing food and 144 (60.5%) had empty stomachs. A total of 10 prey items were identified, corresponding to seven families that included fishes, crustaceans and cephalopods. According to the Index of Relative Importance (IRI) the most important prey were Anchoa spp. (IRI = 91.2%), Engraulis mordax (IRI = 1.8%), and fish from the Clupeidae family (IRI = 1.0%). The crevalle jack’s diet did not change with the season (warm or cold). The crevalle jack was considered a tertiary predator (trophic level = 4.3) that tends to feed on a reduced number of prey, characterizing it as a specialist and selective predator of engraulid fishes (Levin’s index, Bi = 0.08; E = 0.6).     

Planktivory in the changing Lake Huron zooplankton community: Bythotrephes consumption exceeds that of Mysis and fish

1. Oligotrophic lakes are generally dominated by calanoid copepods because of their competitive advantage over cladocerans at low prey densities. Planktivory also can alter zooplankton community structure. We sought to understand the role of planktivory in driving recent changes to the zooplankton community of Lake Huron, a large oligotrophic lake on the border of Canada and the United States. We tested the hypothesis that excessive predation by fish (rainbow smelt Osmerus mordax, bloater Coregonus hoyi) and invertebrates (Mysis relicta, Bythotrephes longimanus) had driven observed declines in cladoceran and cyclopoid copepod biomass between 2002 and 2007. 2. We used a field sampling and bioenergetics modelling approach to generate estimates of daily consumption by planktivores at two 91‐m depth sites in northern Lake Huron, U.S.A., for each month, May–October 2007. Daily consumption was compared to daily zooplankton production. 3. Bythotrephes was the dominant planktivore and estimated to have eaten 78% of all zooplankton consumed. Bythotrephes consumption exceeded total zooplankton production between July and October. Mysis consumed 19% of all the zooplankton consumed and exceeded zooplankton production in October. Consumption by fish was relatively unimportant – eating only 3% of all zooplankton consumed. 4. Because Bythotrephes was so important, we explored other consumption estimation methods that predict lower Bythotrephes consumption. Under this scenario, Mysis was the most important planktivore, and Bythotrephes consumption exceeded zooplankton production only in August. 5. Our results provide no support for the hypothesis that excessive fish consumption directly contributed to the decline of cladocerans and cyclopoid copepods in Lake Huron. Rather, they highlight the importance of invertebrate planktivores in structuring zooplankton communities, especially for those foods webs that have both Bythotrephes and Mysis. Together, these species occupy the epi‐, meta‐ and hypolimnion, leaving limited refuge for zooplankton prey.