Piscivorous Species Research Articles

Mercury Concentrations in Birds from Two Atmospherically Contaminated Sites in North Texas, USA.

Mercury (Hg) is a ubiquitous and highly toxic contaminant that can have negative effects on wildlife. Only a few studies have measured Hg concentrations in birds from the south central United States, and the potential threat of Hg contamination to birds in this region is largely unknown. In the present study, we assess Hg concentrations in blood and feathers from five bird species [eastern bluebird (Sialis sialis), Carolina wren (Thryothorus ludovicianus), wood duck (Aix sponsa), great egret (Ardea alba), and great blue heron (Ardea herodias)] that occupy different trophic levels at Caddo Lake and Lewisville Lake, located in northeast and north central Texas, respectively. Both sites are contaminated with Hg from the atmosphere. Adult passerines had higher Hg concentrations in their blood than conspecific nestlings. Mercury concentrations in feathers differed between species by more than an order of magnitude with large piscivorous species having higher concentrations than smaller insectivorous species. Mercury concentrations in eastern bluebirds were higher at Caddo Lake than Lewisville Lake. The present study represents one of the first studies of Hg concentrations in multiple bird species in north Texas and suggests that Hg concentrations in birds from atmospherically polluted sites in this region may be high enough to compromise fitness in those species.

Trends and stability of inland fishery resources in Japanese lakes: introduction of exotic piscivores as a driver.

Although many studies have focused on marine resources, few studies have considered the resources of inland fisheries. Inland fishery resources are typically either monitored on the basis of catch data alone or are not assessed quantitatively at all, despite their social, economic, and ecological importance. Because freshwater ecosystems have been severely degraded by human activities, evaluating the trends and current status of fishery resources and assessing their drivers are urgent tasks. We compiled long-term data on the annual catch, fishing effort, and fishing power of 23 Japanese lakes, using two sets of government statistics that date back to the 1950s, which were previously neglected because of the large number of missing values. Using Bayesian state-space models, we examined the trajectories of the catch per unit effort (CPUE) of entire communities, considering changes in fishing effort and fishing power, and quantified both changes in the CPUE over the 10-, 20-, and 30-year periods preceding 2008 and the temporal detrended stability of the CPUE over the three periods. We also investigated the relationships among the CPUE changes and stability, anthropogenic drivers, and lake morphometric characteristics. The CPUE declined in 17, 19, and 15 of the 23 lakes over the past 10-, 20-, and 30-year periods, respectively. Our macroecological analyses demonstrate that the functional group richness of exotic piscivores was the most important predictor of changes in the CPUE among the drivers we considered. The stability of the CPUE was positively related to lake area; larger lakes have more stable CPUE. The functional group richness of exotic piscivores also negatively affected the stability of the CPUE. The effect of overfishing was considered to be small because both fishing effort and power declined in almost all of the lakes. Thus, our findings suggest that increasing exotic piscivore species may diminish the resources and their stability, particularly in Japanese lakes where native piscivores are rare. This might lead to a substantial decline in ecosystem services. Our study highlights the importance of assessing inland fishery resources in a comprehensive manner and the need for restoration strategies to mitigate the effects of exotic piscivores.

Diets and trophic-guild structure of a diverse fish assemblage in Chesapeake Bay, U.S.A.

Dietary habits and trophic-guild structure were examined in a fish assemblage (47 species) of the Chesapeake Bay estuary, U.S.A., using 10 years of data from >25 000 fish stomachs. The assemblage was comprised of 10 statistically significant trophic guilds that were principally differentiated by the relative amounts of Mysida, Bivalvia, Polychaeta, Teleostei and other Crustacea in the diets. These guilds were broadly aggregated into five trophic categories: piscivores, zooplanktivores, benthivores, crustacivores and miscellaneous consumers. Food web structure was largely dictated by gradients in habitat (benthic to pelagic) and prey size. Size classes within piscivorous species were more likely to be classified into different guilds, reflecting stronger dietary changes through ontogeny relative to benthivores and other guilds. Relative to predator species and predator size, the month of sampling had negligible effects on dietary differences within the assemblage. A majority of sampled fishes derived most of their nutrition from non-pelagic prey sources, suggesting a strong coupling of fish production to benthic and demersal food resources. Mysida (predominantly the opossum shrimp Neomysis americana) contributed substantially to the diets of over 25% of the sampled predator groups, indicating that this species is a critical, but underappreciated, node in the Chesapeake Bay food web.

PREDICTING FACTORS THAT INFLUENCE FISH GUILD COMPOSITION IN FOUR COASTAL RIVERS (SOUTHEAST IVORY COAST) USING ARTIFICIAL NEURAL NETWORKS

The present study is focused on small coastal rivers in southeast Ivory Coast, aimed to predict species richness of fish guilds and to test contribution of environmental variables for explaining guild structure with Self-Organizing Map (SOM) and Backpropagation (BP) algorithms. The former method was applied to pattern the samples based on the richness of six major fish guilds observed (benthivores, invertivores, detritivores, piscivores, herbivores and omnivores). Four clusters were identified: cluster I was characterised by benthivores, cluster II was distinguished by invertivores, detritivores, piscivores and omnivores, cluster III had high richness of benthivores, invertivores and herbivores, and cluster IV had high numbers of omnivore, detritivore and piscivore species. The BP showed high predictability (0.89 for benthivores, 0.85 for omnivores and Odonata, 0.84 for herbivores). There was high correlation between observed and estimated values for piscivores (0.77) and detritivores (0.72); the poorest fit was for invertivores (0.63). The frequency histogram of residuals showed that most residuals lie around zero for all guilds. The most contributing variables in predicting the six fish trophic guilds were water temperature, conductivity, total dissolved solids, dissolved oxygen, depth, width, canopy and distance from source. This underlines the crucial influence of both instream characteristics and riparian environment.

Diet of Mediterranean moray, Muraena helena (Actinopterygii: Anguilliformes: Muraenidae), from the north-eastern Tunisian coast (central Mediterranean)

Background. The feeding behaviour of Mediterranean moray, Muraena helena Linnaeus, 1758, from the coast of Tunisia (central Mediterranean) is poorly know and this study is a first step in determining prey consumption by M. helena as main information for improving fishery monitoring and management in the study area. Materials and methods. Of the 411 sampled Mediterranean morays, 237 were males and 174 females. The stomach contents were removed, sorted, identified to the lowest possible taxon, counted, and weighed. For diet description, we calculated vacuity index (VI), abundance (mean number of preys) (NM), frequency of occurrence (F%), relative abundance (N%), and frequency by weight  (W%). The contribution of each prey in the diet was also estimated with Index of Relative Importance (IRI) and its standardized value (%IRI). The trophic level (TROPH) was calculated for total sample to determine the diet of the species, but it was also related to the sex, size, and seasons. Results. The relation between the total length and the total body weight showed a positive allometry for both males and females. VI presented high values, for total sample, sex, size, and season. Muraena helena under study consumed a variety of prey items including 3 higher taxa, 13 families, and 20 species. Osteichthyans were the dominant preys with 15 taxa, representing 96.84% of weight, 78.83% of number, 84.21%, of frequency, and %IRI = 98.51. Crustaceans and cephalopods and sea grass were also ingested by M. helena, with lower %IRI (0.65, 0.66), and no ontogenetic changes in the diet were recorded related to sex, size, and seasons. The most common prey species were Diplodus annularis (Linnaeus, 1758) and D. vulgaris (Geoffroy Saint-Hilaire, 1817) with  %IRI = 28.52 and 7.45, respectively while Serranus cabrilla (Linnaeus, 1758) was also consumed with %IRI = 1.84. The calculated TROPH was 4.27 (SE = 0.74); changes were recorded with seasons but not significantly different. Conclusion. Muraena helena is a carnivorous species feeding on prey items representing three higher taxa, osteichthyans being the most common in stomach contents and such findings suggest that it should be considered as a piscivorous species. The high value of trophic level pointed out that M. helena is a top predator.

Estudo da dieta natural da ictiofauna de um reservatório centenário, São Paulo, Brasil

Este estudo teve como objetivo caracterizar e comparar a alimentação de 13 espécies de peixes em três zonas (zona de influência fluvial, zona de transição e zona lacustre) do reservatório de Itupararanga. Foram analisados 436 estômagos, sendo encontrados 17 recursos alimentares, todos de origem autóctone. As dietas predominantes das espécies foram: peixe, inseto, material vegetal e detritos na zona de influência fluvial, peixe, sedimento e material vegetal na zona de transição e inseto, escama e peixe na zona lacustre. Através do Índice Alimentar, as espécies foram categorizadas nas guildas: piscívora, insetívora, detritívora e carcinófaga. O Cluster indicou separação da guilda insetívora em espécies generalistas (insetos diversos) e especialista (Chironomidae) o que aumenta para cinco guildas. Na zona fluvial foram verificadas quatro guildas; na zona de transição três guildas e na zona lacustre duas guildas. Observou-se ainda uma dominância de espécies piscívoras que pode estar relacionada à idade do reservatório. Este estudo ampliou o conhecimento dos hábitos alimentares dos peixes em reservatórios antigos e suas diferenças, comparando as zonas existentes.

Fertilizer Leakage to the Marine Environment, Ecosystem Effects and Population Trends of Waterbirds in Denmark

Leakage of nutrients from farmland to freshwater and marine environments results in fertilization that increases primary production with cascading effects in the ecosystem. Leakage of fertilizers may initially increase availability of food for primary and secondary consumers, although part of this effect may subsequently be followed by a reduction in food abundance caused by hypoxia. We hypothesized that leakage of nutrients from farmland increased primary and secondary production and subsequently the population size of waterbirds. The amount of phosphorus in the marine environment in Denmark during 1975–2010 increased with fertilizer use on farmland and this effect was stronger when winter precipitation was high. Leakage of fertilizer had ecosystem effects on phytoplankton, zooplankton, and ultimately biodiversity in the marine environment. We found linear relationships between fertilizer use and population size of breeding and wintering waterbirds, with additional quadratic relationships with fertilizer use and linear effects of temperature. The linear effect of fertilizer use depended on the diet of waterbirds with stronger effects in herbivorous and piscivorous species than in species eating benthos. These findings have implications for management of waterbird populations because a reduction in fertilizer use should result in increasing populations of herbivores and piscivores.

Eating the competitor: a mechanism of invasion

The success of predators in species invasion will depend on their interactions with their own predators and competitors. The present study examined whether the predation of piscivorous fish among other piscivorous fish could be an active mechanism in species invasion. The diet of eleven piscivorous fish found in the upper Parana River basin was analyzed during eight years. Seven of the fish species were native to the river basin, and four were invasive species. The diet composition of the studied species did not differ from each other, and a high value of niche overlap was found among invasive species with native species. Invasive species consumed higher amounts of piscivorous species, mainly Hoplias sp. 1 and C. kelberi.Salminus brasiliensis was the only native species with high values of predation over piscivorous fish. There were no significant differences between the consumption of piscivorous fish and their abundance. Overall, the consumption of piscivorous fish by invasive species can act as a mechanism for their success and maintenance in a new environment. Piscivorous invaders radically change the composition of their new environment more than other trophic levels; therefore, we recommend special care with the introduction of piscivores.

An investigation into fisheries interaction effects using Atlantis

Abstract Fisheries management is commonly based on the outputs of single-species stock assessment models. While such models are appropriate for tactical issues such as quota setting, they typically omit explicit trophic interactions between different parts of the ecosystem. To successfully manage multiple fisheries in the same ecosystem, we need to understand how fishing one species may indirectly affect other species. In this paper, we used a simulation model of the southern Benguela ecosystem, built in the Atlantis framework, to explore fisheries interaction effects. We first measured the impact of fishing different stocks individually at FMSY, the hypothetical level of fishing effort which produces maximum sustainable yield (MSY) in a single-species modelling context. We then applied FMSY to all stocks simultaneously and compared the simultaneous yield with the sum of yields from the individual applications of FMSY. Contrary to expectations, the total catch was higher under the simultaneous scenario. We explored our results by studying the influences of trophic interaction between species at different levels of the foodweb, and found that our overall result was driven by two key factors: volumetric dominance of small pelagic fish in the total catch, and asymmetric influences of competition and predation between piscivorous and planktivorous species. The simultaneous increase in fishing pressure across multiple species in the model led to increased effective carrying capacity for small pelagic species (due to reduced competition), but reduced carrying capacity for piscivorous species (due to reduced small pelagic prey). This work has important implications for the design of tactical multispecies models for use in ecosystem-based fisheries management.

Contaminant exposure of birds nesting in Green Bay, Wisconsin, USA.

In earlier studies, elevated concentrations of polychlorinated biphenyl (PCB) and p,p'-dichlorodiphenyldichloroethylene (DDE) were reported in double-crested cormorant (Phalacrocorax auritus) eggs and tree swallow (Tachycineta bicolor) eggs and nestlings collected from lower Green Bay (WI, USA) in 1994 and 1995 and black-crowned night-heron (Nycticorax nycticorax) eggs collected in 1991. Comparable samples collected in 2010 and 2011 indicated that concentrations of PCBs were 35%, 62%, 70%, and 88% lower than in the early 1990s in tree swallow eggs, tree swallow nestlings, double-crested cormorant eggs, and black-crowned night-heron eggs, respectively; concentrations of DDE were 47%, 43%, 51%, and 80% lower, respectively. These declines are consistent with regional contaminant trends in other species. Concentrations of PCBs were higher in herring gull (Larus argentatus) than in black-crowned night-heron eggs collected from Green Bay in 2010; PCB concentrations in double-crested cormorant and tree swallow eggs were intermediate. The estimated toxicity of the PCB mixture in eggs of the insectivorous tree swallow was the equal to or greater than toxicity in the 3 piscivorous bird species. A multivariate analysis indicated that the composition percentage of lower-numbered PCB congeners was greater in eggs of the insectivorous tree swallow than in eggs of the 3 piscivorous species nesting in Green Bay. Dioxin and furan concentrations and the toxicity of these chemicals were also higher in tree swallows than these other waterbird species nesting in Green Bay.

Comparative study of mercury speciation in commercial fishes of the Brazilian Amazon

Mercury is responsible for serious episodes of environmental pollution throughout the world, especially in the Amazon. This toxicity has led regulatory agencies to focus on fish as the target organism for protecting the health of humans and other sensitive organisms. Unfortunately, in the Amazon area, different sampling strategies and the wide variety of sampling areas and fish species make it extremely difficult to determine relationships across geographic regions or over time to ascertain historical trends. Thus, the aim of this work was to achieve three main objectives: a comparative study of mercury contamination in fish of Itaituba (Tapajós, located downstream of the largest gold-mining region in Amazon) and Belém (an area non-exposed to mercury pollution of anthropogenic origin), perform an analysis of inorganic mercury (IHg) versus monomethylmercury (MeHg) contents, and, finally, compare mercury contamination in Tapajós over time. Five piscivorous species were obtained in Itaituba and Belém. Also, four non-piscivorous species were collected in Itaituba. For the first time, mercury speciation showed that (1) current MeHg levels in piscivorous species in Tapajós are higher than those of the non-exposed area, (2) piscivorous species from Itaituba (dourada, filhote, and sarda) contained mercury levels above the World Health Organization safety limit (~17%) and/or above the US Environmental Protection Agency tissue residue criterion (40%), (3) increased MeHg is usually accompanied by increased IHg, and (4) the mean total mercury concentrations for piscivorous species in Itaituba were within the same range and, associated uncertainties as those previously reported, although a remarkable decreasing trend over time was observed for mean total Hg concentrations in non-piscivorous species from Itaituba. The present study supports the importance of continuous monitoring of both populations in the Amazon Rivers. Our results will better assist the development of preventive strategies and governmental actions to confront the problem of mercury contamination in the Amazon.

Urohyal size versus body-length and weight relationships for thirteen mojarras species (Perciformes: Gerreidae) in Mexican waters

Given that it has been shown that urohyal bones can be used to identify gerreid fish to the species level, predictive regression equations between urohyal size and fish standard length and weight of thirteen species of Gerreidae living along the coasts of Mexico, were calculated. All regressions were statistically significant with coefficients of variation and coefficient of determination values around 0.90 in most of cases. These regression equations could provide a reliable tool in trophic ecology and other studies by estimating the original body size and weight of fish from measuring urohyal bone lengths. Information provide from the urohyal bone-fish length and weight relationships also facilitates the assessment of the potential role of gerreid fish found in the diet of piscivorous species from Mexican waters.

A simplified approach for estimating age-0 gizzard shad prey supply and predator demand

Gizzard shad, Dorosoma cepedianum (Lesueur), often compose a majority of the prey biomass in southern US reservoirs. Previous studies suggest prey limitation frequently occurs in these systems, suggesting that fisheries managers need tools to evaluate the production potential of the populations they manage. Bioenergetics modelling was used to quantify the abundance of age-0 gizzard shad necessary to sustain multiple piscivore species with diverse growth rates, population sizes, mortality rates and diets. Gizzard shad biomass at the 50th percentile of published values was insufficient to support seven piscivore species in 69% of the simulations, suggesting that above-average prey biomass is required to support multiple piscivore populations at high abundance and growth rates. To help guide management, estimates of the gizzard shad biomass needed to sustain piscivore communities are provided for management situations in which coarse-scale (low, medium or high) growth, population size and percent of shad in diet data are available.

Fish community structure on coral habitats with contrasting architecture in the Tropical Eastern Pacific

Reefscape architecture, shaped by dominant coral morphologies, can play a major role in determining the structure and composition of fish assemblages by affecting niche and resource availability and mediating interspecific interactions. To explore the role of dominant coral morphologies on reef fish communities, we carried out a comparative study of the fish community associated with a Massive Coral Community (MCC) and a Branching Coral Community (BCC) at Gorgona Island, Tropical Eastern Pacific (TEP). On each community, the benthic substrate was assessed through the “chain transect method” while the fish assemblage was evaluated through visual surveys on belt transects. We found differences between both fish assemblages in terms of the abundance, diversity (H’), and evenness (J’). The BCC, despite being formed by morphologically complex pocilloporid colonies, had a simple and relatively flat architecture that attracted principally small and territorial fishes. Significant higher abundances of Chromis atrilobata and Thalassoma lucasanum at the BCC boosted the total fish abundance but caused low fish evenness and diversity. Conversely the MCC, composed of massive coral species with considerable sizes and diversity of shapes, held a complex and high-relief reefscape capable of sustaining a more diverse and even fish community, although with the same species richness as the BCC. Fishes with large sizes, roving behavior and piscivore-feeding preferences were especially attracted to the MCC. Although, massive coral species are important in determining a diverse and complex reefscape architecture, both dominant coral morphologies (massive and branching) attract and provide resources to different types of fish according to their size, mobility and trophic group. Our results suggest that a loss of massive coral species and a community shift towards stress-resistant taxa (such as Pocillopora spp.), could alter the structure and function of fish assemblages in the TEP due to the habitat loss for large, mobile and piscivore species. Rev. Biol. Trop. 62 (Suppl. 1): 343-357. Epub 2014 February 01.

New crania from Seymour Island (Antarctica) shed light on anatomy of Eocene penguins

Abstract Antarctic skulls attributable to fossil penguins are rare. Three new penguin crania from Antarctica are here described providing an insight into their feeding function. One of the specimens studied is largely a natural endocast, slightly damaged, and lacking preserved osteological details. Two other specimens are the best preserved fossil penguin crania from Antarctica, enabling the study of characters not observed so far. All of them come from the uppermost Submeseta Allomember of the La Meseta Formation (Eocene-?Oligocene), Seymour (Marambio) Island, Antarctic Peninsula. The results of the comparative studies suggest that Paleogene penguins were long−skulled birds, with strong nuchal crests and deep temporal fossae. The configuration of the nuchal crests, the temporal fossae, and the parasphenoidal processes, appears to indicate the presence of powerful muscles. The nasal gland sulcus devoid of a supraorbital edge is typical of piscivorous species.

Gill rakers in six teleost species: influence of feeding habit and body size

This study analyzed the structure of the gill rakers of Parapimelodus valenciennis and Parapimelodus nigribarbis (planktivorous), Serrasalmus maculatus and Hoplias malabaricus (piscivorous), Iheringichthys labrosus (benthophagous) and Hypostomus commersonii (detritivorous) and related it with the body size and feeding habits of these species. The species of Parapimelodus and H. commersonii showed long, filiform and closely spaced gill rakers, similar to those of species that use the gill rakers as a filter to assist in the retention of small particles. The widely spaced gill rakers of I. labrosus probably allow the retention of insect larvae, but not particles of inorganic matter. In H. malabaricus and S. maculatus the gill rakers are most likely related to prey capture and swallowing, as observed in other piscivorous species. In general, gill raker length and the distance between gill rakers have a positive relationship with fish length. The gill rakers show adaptations related to the diet of the fish, but morphological variation may occur even between species whose feeding habits are the same.

Commensal association of piscivorous birds with foraging otters in southeastern Brazil, and a comparison with such a relationship of piscivorous birds with cormorants

Associations of birds with foraging otters are restricted to four records in different regions of the world. We report herein on piscivorous birds associated with foraging otters (Lontra longicaudis) in a pool at an urban park in southeastern Brazil. We recorded up to ˜30 individuals of seven piscivorous bird species associated with a single otter. The mammals searched for fish prey in the pool, causing fish to surface or flee to the shallows, and the birds preyed on the disturbed fish. The bird assemblages we recorded associated with otters are the richest ones reported to date both in number of species and individuals. The bird species associated with otters were the same that followed cormorants (Phalacrocorax brasilianus) in a large pond adjacent to the pool. The foraging of cormorants and otters may be considered as functionally equivalent, because both predators chase prey underwater, surface periodically, and cause fish to flee.

Heavy metal and trace element bioaccumulation in target tissues of four edible fish species from the Danube River (Serbia)

Pikeperch (Sander lucioperca), European catfish (Silurus glanis), burbot (Lota lota), and common carp (Cyprinus carpio) were collected from the Danube River (Belgrade section, Serbia), and samples of liver, muscle, and gills were analyzed for Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, and Zn using inductively coupled plasma optical emission spectrometry (ICP-OES) to highlight the importance of species and tissue selection in monitoring research, contaminant studies, and human health research. The Kruskal–Wallis test revealed significant differences between fish species in regard to metal levels in liver, muscle, and gills. The principal component analysis (PCA) indicated that the studied fish species could be grouped on the basis of the level of analyzed elements in liver and gills. The Mann–Whitney test showed two subsets (one comprising two piscivorous species, pikeperch and catfish, and the other, two polyphagous species, burbot and carp) in regard to Cr and Hg levels in liver (higher levels in piscivorous species), as well as B, Fe, and Hg in gills (B and Fe with higher levels in polyphagous and Hg in piscivorous species), and As in muscle (higher levels in polyphagous species). Carp had distinctly higher levels of Cd, Cu, and Zn in liver in comparison to other three species. None of the elements exceeded the maximum acceptable concentrations (MAC). However, since Hg levels are close to the prescribed MAC levels, the consumption of these fishes can be potentially hazardous for humans.

Inverse mercury and selenium concentration patterns between herbivorous and piscivorous fish in the Tapajos River, Brazilian Amazon

We evaluated the levels of selenium and mercury in five fish species commonly eaten by local populations of the Brazilian Amazon. Fish specimens were sampled in two lotic and three lentic areas at two different phases of the hydrological cycle. Analyses of Carbon and Nitrogen stable isotopes allowed us to confirm the trophic levels of the fish species (one herbivorous, two omnivorous and two piscivorous) and verify that these levels remained unchanged with the habitats and the season. The levels of selenium and mercury in fish varied from 50ng/g to 1006ng/g and from 17ng/g to 3502ng/g respectively. For both seasons, fish from lotic ecosystems presented higher selenium concentrations. An inverse pattern was observed between selenium and mercury concentrations within the trophic chain, and this in both seasons. Indeed, the highest mean concentrations of selenium and lowest mean concentrations of mercury were measured in the herbivorous species and the opposite in the piscivorous species. Our results unequivocally demonstrate that local riverside populations will maximize the selenium health benefits of eating fish while minimizing their risk of being chronically exposed to mercury by preferentially consuming herbivorous species and to some extent omnivorous species, while avoiding piscivorous species.

Preference for Cannibalism and Ontogenetic Constraints in Competitive Ability of Piscivorous Top Predators

Occurrence of cannibalism and inferior competitive ability of predators compared to their prey have been suggested to promote coexistence in size-structured intraguild predation (IGP) systems. The intrinsic size-structure of fish provides the necessary prerequisites to test whether the above mechanisms are general features of species interactions in fish communities where IGP is common. We first experimentally tested whether Arctic char (Salvelinus alpinus) were more efficient as a cannibal than as an interspecific predator on the prey fish ninespine stickleback (Pungitius pungitius) and whether ninespine stickleback were a more efficient competitor on the shared zooplankton prey than its predator, Arctic char. Secondly, we performed a literature survey to evaluate if piscivores in general are more efficient as cannibals than as interspecific predators and whether piscivores are inferior competitors on shared resources compared to their prey fish species. Both controlled pool experiments and outdoor pond experiments showed that char imposed a higher mortality on YOY char than on ninespine sticklebacks, suggesting that piscivorous char is a more efficient cannibal than interspecific predator. Estimates of size dependent attack rates on zooplankton further showed a consistently higher attack rate of ninespine sticklebacks compared to similar sized char on zooplankton, suggesting that ninespine stickleback is a more efficient competitor than char on zooplankton resources. The literature survey showed that piscivorous top consumers generally selected conspecifics over interspecific prey, and that prey species are competitively superior compared to juvenile piscivorous species in the zooplankton niche. We suggest that the observed selectivity for cannibal prey over interspecific prey and the competitive advantage of prey species over juvenile piscivores are common features in fish communities and that the observed selectivity for cannibalism over interspecific prey has the potential to mediate coexistence in size structured intraguild predation systems.