Network analysis reveals contrasting effects of intraspecific competition on individual vs. population diets

Optimal foraging theory predicts that individuals should become more opportunistic when intraspecific competition is high and preferred resources are scarce. This density-dependent diet shift should result in increased diet breadth for individuals as they add previously unused prey to their repertoire. As a result, the niche breadth of the population as a whole should increase. In a recent study, R. Svanb?ck and D. I. Bolnick confirmed that intraspecific competition led to increased population diet breadth in threespine stickleback (Gasterosteus aculeatus). However, individual diet breadth did not expand as resource levels declined. Here, we present a new method based on complex network theory that moves beyond a simple measure of diet breadth, and we use the method to reexamine the stickleback experiment. This method reveals that the population as a whole added new types of prey as stickleback density was increased. However, whereas foraging theory predicts that niche expansion is achieved by individuals accepting new prey in addition to previously preferred prey, we found that a subset of individuals ceased to use their previously preferred prey, even though other members of their population continued to specialize on the original prey types. As a result, populations were subdivided into groups of ecologically similar individuals, with diet variation among groups reflecting phenotype-dependent changes in foraging behavior as prey density declined. These results are consistent with foraging theory if we assume that quantitative trait variation among consumers affects prey preferences, and if cognitive constraints prevent individuals from continuing to use their formerly preferred prey while adding new prey.     

Nodularin concentrations in Baltic Sea zooplankton and fish during a cyanobacterial bloom

Toxic cyanobacterial blooms, dominated by Nodularia spumigena, are a recurrent phenomenon in the Baltic Sea during late summer. Nodularin, a potent hepatotoxin, has been previously observed to accumulate on different trophic levels, in zooplankton, mysid shrimps, fish as well as benthic organisms, even in waterfowl. While the largest concentrations of nodularin have been measured from the benthic organisms and the food web originating from them, the concentrations in the pelagic organisms are not negligible. The observations on concentrations in zooplankton and planktivorous fish are sporadic, however. A field study in the Gulf of Finland, northern Baltic Sea, was conducted during cyanobacterial bloom season where zooplankton (copepod Eurytemora affinis, cladoceran Pleopsis polyphemoides) and fish (herring, sprat, three-spined stickleback) samples for toxin analyses were collected from the same sampling areas, concurrently with phytoplankton community samples. N. spumigena was most abundant in the eastern Gulf of Finland. In this same sampling area, cladoceran P. polyphemoides contained more nodularin than in the other areas, suggesting that this species has a low capacity to avoid cyanobacterial exposure when the abundance of cyanobacterial filaments is high. In copepod E. affinis nodularin concentrations were high in all of the sampling areas, irrespective of the N. spumigena cell numbers. Furthermore, nodularin concentrations in herring samples were highest in the eastern Gulf of Finland. Three-spined stickleback contained the highest concentrations of nodularin of all the three fish species included in this study, probably because it prefers upper water layers where also the risk of nodularin accumulation in zooplankton is the highest. No linear relationship was found between N. spumigena abundance and nodularin concentration in zooplankton and fish, but in the eastern area where the most dense surface-floating bloom was observed, the nodularin concentrations in zooplankton were high. The maximum concentrations in zooplankton and fish samples in this study were higher than measured before, suggesting that the temporal variation of nodularin concentrations in pelagic communities can be large, and vary from negligible to potentially harmful.     

Feeding opportunities of larval and juvenile cod (Gadus morhua) in a Greenlandic fjord: temporal and spatial linkages between cod and their preferred prey

Feeding of fish depends on a spatial and temporal match with prey, and since larval and juvenile feeding can be highly selective, their preferences for given prey sizes and taxa should be considered when quantifying the actual availability of potential prey. We investigated the diet and prey preferences of the early-life stages of Atlantic cod (Gadus morhua) to quantify the availability of prey during a spring-summer season in a West Greenlandic fjord. We hypothesized that abundances of larval and juvenile cod at size were synchronized to optimal availability of preferred prey in space and time. The present analysis is based on nine cruises each covering 5 stations visited between 24 May and 5 August 2010 comparing zooplankton abundance, cod gut content and distribution patterns. Cod 4–25 mm in length preferred prey of about 5 % of their own length. During ontogeny, their preferences changed from calanoid nauplii towards Pseudocalanus spp. and Calanus spp. copepodites. The larvae/juvenile had an exceptionally high dietary contribution from cladocerans, which were highly preferred by cod larger than 9 mm, while the abundant Metridia longa and the non-calanoid copepods contributed less. These findings stress the importance of focusing on abundance of preferred prey when assessing the actual prey availability to young fish. We found a spatio-temporal overlap between cod and their preferred prey, and observations suggest that advection of both zooplankton and cod contributed to this overlap. Hence, the larval feeding opportunities might be sensitive to climate-related changes affecting the circulation patterns in this fjord.     

Shoaling as an anti-ectoparasite mechanism in juvenile sticklebacks (Gasterosteus spp.)

Summary In laboratory experiments, we tested the hypothesis that by living in larger shoals, juvenile threespine (Gasterosteus aculeatus) and blackspotted (G. wheatlandi) sticklebacks lower their risk of being parasitized by the crustacean ectoparasite Argulus canadensis. An increase in shoal size resulted in a lower average number of attacks received by individual fish, but had no negative effect on the attack performance (attack rate and attack success) of the parasites. In addition, more fish formed shoals and shoal sizes were larger in the presence of parasites. We conclude that ectoparasitism may have been a strong selective factor in the evolution of social behaviour in juvenile sticklebacks.     

Prey selection by the hogchoker, Trinectes maculatus (Pisces: Soleidae), along summer salinity gradients in Chesapeake Bay, USA

We investigated feeding by the hogchoker, Trinectes maculatus (Bloch and Schneider), in freshwater, oligohaline, mesohaline, and polyhaline regions of Chesapeake Bay, USA, and examined prey selection in relation to food availability. Otter trawling for fish and Van Veen grab sampling for benthic macrofauna occurred in July and August 1992 and August and September 1993. Hogchokers exhibited both opportunistic and selective feeding patterns along the estuarine salinity gradient in four tributaries (Potomac, Rappahannock, York, and James Rivers) and in the mainstem Chesapeake Bay. Major prey taxa included annelids, arthropods, and tellinid siphons. In polyhaline habitat, polychaetes dominated both the benthos and gut contents numerically and gravimetrically. On the other hand, oligochaetes were numerically dominant in freshwater/oligohaline areas but were rarely eaten, perhaps because of their burial depth. Arthropods (mostly amphipods) occurred at most salinities, were common in gut contents in low-salinity areas, and were replaced as prey by larger proportions of polychaetes in polyhaline regimes. Although hogchokers ate tellinid siphons, they rarely consumed whole bivalves or gastropods. These diet patterns (and especially the importance of siphon nipping) are similar to those of juvenile or small flatfish elsewhere in Europe, Africa, and North America. A size–salinity relationship for hogchokers occurred along the summer salinity gradient, with smaller fish predominating upstream and larger fish downstream. It was not clear from our data if variation in diet composition reflected changes in prey composition along the salinity gradient rather than changes in fish size. Received: 14 June 1997 / Accepted: 27 June 1997     

Threat-sensitive foraging by larval threespine sticklebacks (Gasterosteus aculeatus)

Summary The threat-sensitive predator avoidance hypothesis predicts that prey can assess the relative threat posed by a predator and adjust their behaviour to reflect the magnitude of the threat. We tested the ability of larval threespine sticklebacks to adjust their foraging in the presence of predators by exposing them to conspecific predators of various sizes and recording their foraging and predator avoidance behaviours. Larvae (<30 days post-hatch) displayed predator escape behaviours only towards attacking predators. At 3 weeks post-hatch larvae approached the predator after fleeing, a behaviour which may be the precursor to predator inspection. Larvae reduced foraging and spent less time in the proximity of large and medium-sized predators compared to small predators. The reduction in foraging was negatively correlated to the predator/larva size ratio, indicating that larvae increased their foraging as they increased in size relative to the predator. We conclude that larval sticklebacks can assess the threat of predation early in their ontogeny and adjust their behaviour accordingly.Correspondence to: J.A. Brown     

Within- and transgenerational effects of ocean acidification on life history of marine three-spined stickleback (Gasterosteus aculeatus)

Some studies have demonstrated that elevated CO₂ concentrations in ocean waters negatively impact metabolism and development of marine fish. Particularly, early developmental stages are probably more susceptible to ocean acidification due to insufficient regulations of their acid-base balance. Transgenerational acclimation can be an important mechanism to mediate impacts of increased CO₂ on marine species, yet very little is known about the potential of parental effects in teleosts. Therefore, transgenerational effects were investigated on life history in juvenile three-spined sticklebacks Gasterosteus aculeatus by acclimating parents (collected in April 2012, 55°03′N, 8°44′E) and offspring to ambient (~400 µatm) and elevated (~1,000 µatm) CO₂ levels and measured parental fecundity as well as offspring survival, growth and otolith characteristics. Exposure to elevated CO₂ concentrations led to an increase in clutch size in adults as well as increased juvenile survival and growth rates between 60 and 90 days post-hatch and enlarged otolith areas compared with fish from ambient CO₂ concentrations. Moreover, transgenerational effects were observed in reduced survival and body size 30 days post-hatch as well as in enlarged otoliths at the end of the experiment, when fathers or both parents were acclimated to the high-CO₂ environment. These results may suggest that elevated CO₂ concentrations had rather positive effects on life-history traits of three-spined sticklebacks, but that parental acclimation can modify these effects without improving offspring fitness. Although the mechanistic basis of such transgenerational acclimation remains unclear, selective gradients within generations seem to determine the direction of transgenerational effects.     

Sympatric species of threespine stickleback differ in their performance in a spatial learning task

Increasing evidence suggests that cognitive function is under selection in diverse taxa and that this results in different cognitive abilities in taxa experiencing different selective environments. For example, species inhabiting spatially complex environments might be expected to have good spatial learning ability. We investigated whether local habitat conditions influence learning by comparing the performance of two recently diverged species of threespine stickleback (Gasterosteus aculeatus complex) in a spatial learning task. The two species reside sympatrically in several lakes. Benthics occupy the spatially structured vegetated littoral zone, whereas limnetics occupy the spatially homogenous open-water pelagic zone. We trained fish to locate a hidden reward in a T-maze and asked whether they did so by learning a body-centred pattern of movement (turn left or right) or by using plant landmarks. Both benthics and limnetics used turn and landmark cues, but benthics learnt the task almost twice as quickly as limnetics. This difference is consistent with the hypothesis that benthic and limnetic sticklebacks are equipped with spatial learning abilities well suited to the spatial complexity of their littoral and pelagic habitats. Our findings add to the understanding of the evolution of learning.     

Seasonal variations in the stable carbon and nitrogen isotope ratios (13C/12C and 15N/14N) of primary producers and consumers in a western Mediterranean coastal lagoon

Stable carbon and nitrogen isotope ratios (¹³C/¹²C and ¹⁵N/¹⁴N) of primary producers and consumers were investigated seasonally throughout 1999, in order to describe the food web in a western Mediterranean coastal lagoon (Lake of Sabaudia, central Italy). Particulate organic matter and algal material (seagrass epiphytes and macroalgae) seem to constitute the main food sources for primary consumers (zooplankton and small benthic invertebrates, respectively) throughout the sampling year, while the seagrass Cymodocea nodosa appears to play a negligible trophic role. As regards the ichthyofauna, carbon stable isotopes differentiated between planktivore and benthivore fish species. However, a benthic-pelagic coupling seems to occur, with some fish of higher trophic levels feeding both on benthic and pelagic materials. Analysis of variance showed that the interaction between the three main factors (species2size2season) significantly affects the isotopic composition of fish, suggesting the presence of intra- and inter-specific resource partitioning. Wide seasonal variations in the isotopic composition were observed in organic matter sources, invertebrates and fish, with a general trend towards depleted values in winter and enriched values in summer. The winter depletion of organic matter sources may be due to several environmental factors and seems to be mirrored in the upper trophic levels. Primary producers and invertebrates are known to have shorter time-integrated isotopic signatures than vertebrates, yet fish also exhibited seasonal isotopic differences. We concluded that the examined fish species can assume a new muscle isotopic signature relatively quickly in response to changes in the isotopic composition of their diet and/or diet shifts.     

Foraging impact on zooplankton by age-0 walleye pollock (<Emphasis Type="Italic">Theragra chalcogramma</Emphasis>) around a front in the southeast Bering Sea

The waters around the Pribilof Islands in the southeast Bering Sea are a center of abundance for age-0 walleye pollock (Theragra chalcogramma). Each spring and summer a tidal front is formed around the islands separating a well-mixed inshore habitat from a stratified offshore habitat. The objective of this study was to assess the foraging impact on zooplankton by age-0 pollock in the vicinity of this frontal structure. A bioenergetic model was used to estimate age-0 pollock food consumption from field estimates of water temperature, age-0 pollock density, diet and growth. Sampling of field variables took place over three hydrographic habitats along an inshore–offshore transect located north of the islands. The bioenergetics analysis was applied for a 2-week period during the late summer of four consecutive years, 1994–1997. Model results of age-0 pollock food consumption indicated variable levels of food depletion, changing with prey type, year and habitat. The foraging impact of age-0 pollock on copepods and euphausiids (most common prey) ranged from about 3% to 77% of the biomass available at the start of the simulation. Copepod depletion was typically greater than euphausiid depletion. Consequently, juvenile pollock <60 mm in standard length were more likely to experience food limitation due to the greater proportion of copepods in their diet. We present evidence of severe foraging impact during 1996, when one of the primary prey items of juvenile pollock (i.e. large copepods) was scarcely represented both in their diet and in the water column. In all years, most instances of prey depletion were found at the inshore and front habitats; age-0 pollock densities were too low relative to their prey to severely impact the offshore zooplankton populations. We discuss these results with respect to modeling assumptions and in the context of previously acquired knowledge of fish behavior around frontal regions.Communicated by T. Ikeda, Hakodate     

Diel trophic interactions between vertically-migrating zooplankton and their fish predators in an eelgrass community

Diel changes in the composition of crustacean zooplankton and the diets of fish predators from an intertidal eelgrass flat were monitored concurrently. The zooplankton is characterized by two major components. The obligate zooplankters (holoplanktonic calanoid copepods and meroplanktonic decapod larvae) appear to exhibit vertical migration, being present in higher densities near the surface of the water column at night. The facultative zooplankton (amphipods and ostracods) are benthic during the day, but move up into the water column at night. Planktivorous midwaterdwelling fish consume calanoid copepods and decapod larvae during the day and cease feeding or switch their diet to amphipods at night. Benthic-dwelling fish consume some amphipods during both day and night. The factors important in prey selection by fish and the functional significance of vertical migration in both components of the zooplankton are discussed in the light of the changing patterns of fish predation.This paper is Publication No. 183 in the Ministry for Conservation of Victoria, Environmental Studies Series.     

Limitations to colour-based sexual preferences in three-spined sticklebacks (Gasterosteus aculeatus)

Female three-spined sticklebacks (Gasterosteus aculeatus) are suggested to select mates based on their red nuptial coloration, males with a redder display being more preferred. Although there are both laboratory and field data to support this view, there are also published accounts where females do not show a preference for the redder male. Here we report the results of a series of 19 trials where receptive gravid female three-spined sticklebacks were allowed to choose between two size-matched rival males. We used photographic and image analysis techniques to quantify male nuptial coloration to investigate how the magnitude of the colour difference between the two alternative males influenced female preferences. Using the amount of time a female spent oriented towards each male as a measure of his attractiveness to her, females were not always found to select the redder of the two presented males. We did, however, find that that the relative difference in coloration of the two males in each pair was important in determining the level of coloration-based preference, with females only selecting redder males consistently when the difference in coloration was sufficiently large. Received: 26 October 1999 / Received in revised form: 10 January 2000 / Accepted: 13 February 2000     

Effects of increased vegetation cover on nesting behavior of sticklebacks (Gasterosteus aculeatus)

To maximize reproductive success, reproductive behaviors have to be adjusted to environmental conditions. The breeding habitats of the threespine stickleback Gasterosteus aculeatus are presently changing in the Baltic Sea due to eutrophication and enhanced growth of filamentous green algae. Earlier studies show that high algae density reduces mate encounter rate and the intensity of selection on a few sexually selected traits, but the willingness of males to nest under the new conditions, and their investment into reproduction, have not been investigated. Here, we investigated the effect that increased algae growth has on nesting behavior of sticklebacks. We allowed males to build nests in aquaria with either a sparse or a dense vegetation structure and recorded male nest building behavior and nest characters. Males that nested in dense vegetation showed a longer latency before commencing nest building and also completed nest building later since there was no difference in time spent building. There was no effect of vegetation cover on nest characters. These results suggest that males prefer to nest in sparser vegetation, but that they eventually nest in dense vegetation if more open habitats are not available. This may arise from a negative effect of vegetation on visibility and mate encounter rate and thus on expected reproductive success. This implies that human-induced changes in the environment may force sticklebacks to breed in non-preferred habitats. Since the intensity of sexual selection is reduced in these areas, this could influence the further evolution of the population.     

Social recognition in sticklebacks: the role of direct experience and habitat cues

The social organisation of animals relies on recognition. However, there are many means by which animals may recognise one another and a variety of cues are available to any individual at any one time. We tested the effects of cues based on direct experience and of cues based on habitat and diet on association decisions in the three-spined stickleback (Gasterosteus aculeatus). Our results show that sticklebacks rapidly acquire association preferences for novel con- and heterospecifics (nine-spined sticklebacks, Pungitius pungitius) which had experienced the same habitat and diet conditioning as themselves over novel con- and heterospecifics which had experienced a different habitat and diet conditioning, a preference which may be based on self-referent matching. Association preferences were observed after only 24 h and were independent of the number of tank mates (treatments with 20 and 100 fish). Evidence for the influence of direct social experience on association preferences was weak and may be confounded by other factors.Communicated by K. Lindström     

Terrestrial, benthic, and pelagic resource use in lakes: results from a three-isotope Bayesian mixing model

Fluxes of organic matter across habitat boundaries are common in food webs. These fluxes may strongly influence community dynamics, depending on the extent to which they are used by consumers. Yet understanding of basal resource use by consumers is limited, because describing trophic pathways in complex food webs is difficult. We quantified resource use for zooplankton, zoobenthos, and fishes in four low-productivity lakes, using a Bayesian mixing model and measurements of hydrogen, carbon, and nitrogen stable isotope ratios. Multiple sources of uncertainty were explicitly incorporated into the model. As a result, posterior estimates of resource use were often broad distributions; nevertheless, clear patterns were evident. Zooplankton relied on terrestrial and pelagic primary production, while zoobenthos and fishes relied on terrestrial and benthic primary production. Across all consumer groups terrestrial reliance tended to be higher, and benthic reliance lower, in lakes where light penetration was low due to inputs of terrestrial dissolved organic carbon. These results support and refine an emerging consensus that terrestrial and benthic support of lake food webs can be substantial, and they imply that changes in the relative availability of basal resources drive the strength of cross-habitat trophic connections.     

Courting virtual rivals increase ejaculate size in sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>)

Sperm competition occurs when sperm of two or more males compete to fertilize a given set of eggs. Game-theory models of sperm competition predict that males, which face an increased risk of sperm competition, will invest more sperm in a mating. In the pair-spawning three-spined stickleback ( Gasterosteus aculeatus), males attempt to steal fertilizations (i.e. to sneak) when they are in the courting phase, but not when they are parental. The behaviour of neighbouring males may therefore indicate the risk of sperm competition. We visually confronted males before spawning with computer animations of the same virtual stickleback showing two different behaviours: either courting (high risk of sperm competition) or brood-caring (low risk of sperm competition). We show that males invest significantly more sperm (absolutely and relatively with respect to available sperm in the testes) after the courting stimulus. The relative investment ratio between the courting and the brood-caring treatment was on average 1.75. Three-spined sticklebacks thus seem to assess the risk of sperm competition by the behaviour of neighbours and to adjust their ejaculate accordingly. This result suggests that the evolutionary force of sperm competition has led to precise mechanisms of future risk assessment.     

Threat-sensitive feeding strategy of immature sticklebacks (Gasterosteus aculeatus) in response to recent experimental infection with the cestode Schistocephalus solidus

Threat-sensitive decision-making might be changed in response to a parasitic infection that impairs future reproduction. Infected animals should take more risk to gain energy to speed up their growth to achieve early reproduction and/or to strengthen their immune response. To avoid correlational evidence, we experimentally infected and sham-infected randomly selected immature three-spined sticklebacks with the cestode Schistocephalus solidus. For 7 weeks we determined the threat-sensitive foraging decisions and growth of individual sticklebacks in the presence of a live pike (Esox lucius). The experimenters were blind with respect to the infection status of the fish. In contrast to previous studies, our recently infected fish should have been almost unconstrained by the parasite and thus have been able to adopt an appropriate life history strategy. We found a strong predator effect for both infected and uninfected fish: the sticklebacks’ risk-sensitive foraging strategy resulted in significantly reduced growth under predation risk. Infected fish did not grow significantly faster under predation risk than uninfected fish. Since infected fish consumed much less prey in the presence of the predator than did infected fish in its absence, they obviously did not use the opportunity to maximize their growth rate to reach reproduction before the parasite impairs it. Received: 21 June 1999 / Revised: 27 November 1999 / Accepted: 5 September 2000     

Distribution and diet of juvenile Patagonian toothfish on the South Georgia and Shag Rocks shelves (Southern Ocean)

The distribution and diet of juvenile (<750 mm) Patagonian toothfish are described from four annual trawl surveys (2003–2006) around the island of South Georgia in the Atlantic sector of the Southern Ocean. Recruitment of toothfish varies inter-annually, and a single large cohort dominated during the four years surveyed. Most juveniles were caught on the Shag Rocks shelf to the NW of South Georgia, with fish subsequently dispersing to deeper water around both the South Georgia and Shag Rocks shelves. Mean size of juvenile toothfish increased with depth of capture. Stomach contents analysis was conducted on 795 fish that contained food remains and revealed that juvenile toothfish are essentially piscivorous, with the diet dominated by notothenid fish. The yellow-finned notothen, Patagonotothen guntheri, was the dominant prey at Shag Rocks whilst at South Georgia, where P. guntheri is absent, the dominant prey were Antarctic krill and notothenid fish. The diet changed with size, with an increase in myctophid fish and krill as toothfish grow and disperse. The size of prey also increased with fish size, with a greater range of prey sizes consumed by larger fish.     

Foraging behavior of a generalist marine top predator,Japanese cormorants (<Emphasis Type="Italic">Phalacrocorax filamentosus</Emphasis>), in years of demersal versus epipelagic prey

To examine the behavioral adjustment of a generalist marine top predator to variability of their prey, we studied the foraging behavior of Japanese cormorants (Phalacrocorax filamentosus) breeding at Teuri Island, Hokkaido, in years of contrasting demersal and epipelagic prey composition. We used radio telemetry and ship-based surveys to determine behavior and at-sea distribution during three summers (1996–1998). The cormorants fed on epipelagic anchovy (Engraulis japonicus) and sandlance (Ammodytes personatus) in 1998 (year of epipelagic diet), while they fed on benthic rock fish (Sebastes spp.) and flatfish (Pleuronectidae) and nearshore-living naked sandlance (Hypophychus dybowskii), as well as epibenthic greenling (Hexagrammidae) in 1996 and 1997 (year of demersal diet). Cormorants engaged in larger feeding groups, visited more feeding sites, and stayed at each feeding site for a shorter period in the year of epipelagic diet than in the years of demersal diet. The cormorants made long foraging trips and fed in the mainland coastal habitat, distant from the colony, in the years of demersal diet. Individual radio-tracked birds fed over the wide area between the islands and mainland, in the year of epipelagic diet, while most individuals specialized in mainland or island coastal habitats in the years of demersal diet. Behavioral adjustment of Japanese cormorants might allow them to exploit both unpredictable epipelagic and predictable benthic prey efficiently.Communicated by T. Ikeda, Hakodate     

Subhabitat selection by foraging threespine stickleback (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>): previous experience and social conformity

Any mechanism that allows animals to increase their foraging efficiency is likely to be selected for, including the ability to learn to recognise and subsequently discriminate between habitat types based on their profitability. In a series of laboratory studies, we manipulated prey densities across two different experimental subhabitats and demonstrated that threespine stickleback (Gasterosteus aculeatus) can develop foraging preferences for subhabitats that have previously yielded prey. Fish were not recalling the spatial location of prey patches; rather, they were discriminating between subhabitats based on foraging experience there and allocating foraging effort accordingly. Foraging preferences took around 14 days to develop, and once established, they persisted independently of experimental prey density, suggesting that fish were using experience rather than real-time sampling to select foraging grounds. When we presented focal fish with social information cues, we found that they preferentially used local enhancement and current public information cues when they conflicted with previous experience, but that they did not use prior public information. This suggests that in the presence of conspecifics, individuals prioritise social conformity over the use of private information. We discuss our results in the context of optimal foraging and the trade-offs associated with balancing conflicting private and social information.