Relationships among invasive common carp,native fishes and physicochemical characteristics in upper Midwest (USA) lakes

Abstract – Common carp Cyprinus carpio is a widespread invasive species that, in high abundance, can impose numerous deleterious effects in aquatic ecosystems. Common carp increase turbidity and nutrient availability while reducing invertebrate prey resources and aquatic macrophytes, transforming shallow lakes from the clear‐ to turbid‐water state. However, potential effects of common carp on native fish communities have received limited attention. We evaluated the relationships among relative abundances of nine native fishes and common carp for 81 lakes in eastern South Dakota and their associated physicochemical characteristics. Inverse threshold relationships among relative abundances of native fishes and common carp were identified for black bullhead Ameiurus melas, black crappie Pomoxis nigromaculatus, bluegill Lepomis macrochirus, white bass Morone chrysops and northern pike Esox lucius, while marginally significant relationships were detected for largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu. Lakes where common carp relative abundance exceeded 0.6 fish per net night had low abundance of native fishes, whereas lower abundance of common carp resulted in variable abundance of native fishes. Lakes with abundance of common carp surpassing 0.6 fish per net night were also characterised by larger surface areas and watersheds and impaired water quality (higher dissolved solids and chlorophyll a concentrations and lower secchi depth). Our results are consistent with the biotic‐abiotic constraining hypothesis that proposes biotic factors can regulate fish populations regardless of abiotic conditions. Thus, common carp abundance may need to be reduced and sustained below ecological thresholds to improve water quality and increase abundance of native fishes.     

Effects of predator species,vegetation and prey assemblage on prey preferences of predators with emphasis on vulnerability of age‐0 common carp

Abstract Predation is an important force structuring aquatic communities, but predator–prey interactions are complex and regulated by multiple factors. Invasive fishes may interact with native fishes to alter predator–prey preferences and community dynamics. For example, common carp, Cyprinus carpio L., is an invasive species that can become abundant and negatively affect aquatic ecosystems. Juvenile common carp are occasionally found in predator diets, but predator preferences for common carp compared with alternative prey remains unknown. Prey selection and feeding behaviour of five piscivores (flathead catfish, Pylodictis olivaris (Rafinesque); largemouth bass, Micropterus salmoides (Lacepède); smallmouth bass, M. dolomieu Lacepède; walleye, Sander vitreus (Mitchill); and northern pike, Esox lucius L.) foraging on juvenile common carp and two alternative prey (fathead minnow, Pimephales promelas Rafinesque, and yellow perch, Perca flavescens Mitchill) at variable densities and habitats were evaluated. Common carp and fathead minnow were generally selected for or neutrally selected across predator species, habitat types and prey assemblages. By contrast, yellow perch was generally selected against. Common carp were easily captured but difficult to manipulate and ingest compared with other prey. These results reveal that common carp are vulnerable to a variety of predators, suggesting control of this detrimental invader may be possible through biomanipulation.     

Spatio‐temporal,ontogenetic and interindividual variation of age‐0 diets in a population of yellow perch

Dietary niches of fishes have traditionally been evaluated at the population level, with diet pattern central tendencies compared spatio‐temporally among habitats and populations. More recently, however, studies have emphasised the importance of within‐population diet variation and niche partitioning. Several studies have examined diets of young yellow perch (Perca flavescens) at the population level and have described an ontogenetic transition from zooplankton to benthic prey during the first year of life. However, independent of ontogenetic diet shifts, intrapopulation variation of young yellow perch diets remains largely unexplored. We quantified patterns of diet composition in age‐0 yellow perch collected from Saginaw Bay, Lake Huron, USA during July–October, 2009 and 2010. We observed substantial variation in diet composition among individuals across and within sites, but found relatively weak evidence indicating an ontogenetic diet shift. Zooplankton were the dominant prey for age‐0 yellow perch on most occasions, and individual diets were composed primarily of either zooplankton (e.g. Daphnia spp., Calanoida) or benthic (i.e. Chironomidae larvae, Chydoridae) prey. These patterns were not simply attributable to differences in prey availability and ontogenetic diet shifts, because a) not only diet composition, but also prey selectivity (Chesson's α) varied among sites and b) individual and spatial diet differences were evident independent of ontogeny. Within‐cohort differences in diet composition may be an important, but often overlooked, phenomenon with implications for cumulative trophic interactions and intracohort growth and survival among young fish.     

Factors influencing the abundance of three common nearshore fishes in south‐west Lake Michigan

Variation in the distribution and abundance of nearshore fishes is critical to understand food web processes and fishery management issues in Lake Michigan. This study characterised patterns in abundance of three common nearshore species, yellow perch Perca flavescens (Mitchell), round goby Neogobius melanostomus (Pallas) and alewife Alosa pseudoharengus (Wilson), in relation to spatio‐temporal, abiotic and biotic factors using gillnet sampling conducted across 5 years at multiple locations representing different substrates. Significant variations were observed in alewife and round goby catches between locations. A negative relationship between round goby and age‐0 yellow perch catch was observed, indicating potential competition between the two species. This study demonstrates that variability in nearshore fish communities can be driven by factors including substrate and interspecific interactions. Given the prominent role these species play in Lake Michigan's food web and thus their importance to fishery production, a thorough understanding of these factors is warranted.     

Factors influencing recruitment and growth of age‐0 yellow perch in eastern South Dakota glacial lakes

Variation in recruitment and growth of age‐0 yellow perch, Perca flavescens (Mitchill), was modelled across a range of nine eastern South Dakota glacial lakes to: (i) estimate factors influencing recruitment and growth dynamics during early ontogeny; and (ii) determine the relative importance of biotic versus abiotic processes in regulating recruitment and growth dynamics. Results provide a framework for future investigations and suggest that abiotic factors were more important in regulating recruitment of age‐0 yellow perch, whereas biotic factors were more important in regulating growth. Recruitment was positively related to springtime water levels and temperature and negatively related to spawning stock biomass and springtime wind conditions. By contrast, growth was negatively related to abundance of conspecifics and potential competitors (i.e. bluegill, Lepomis macrochirus Rafinesque) and positively related to abundance of potential predators [i.e. walleye, Sander vitreus (Mitchill) and northern pike, Esox lucius Linnaeus].     

Diet dynamics of the juvenile piscivorous fish community in Spirit Lake, Iowa, USA, 1997–1998

Abstract – We assessed temporal dynamics and variation among species and age-classes in the diets of age 0 and age 1 piscivorous fish species in Spirit Lake, Iowa, USA during 1997 and 1998. Species included walleye Stizostedion vitreum , yellow perch Perca flavescens , smallmouth bass Micropterus dolomieui , largemouth bass Micropterus salmoides , black crappie Pomoxis nigromaculatus and white bass Morone chrysops. Thirty taxa were identified in diets, including 12 species of fish. We found dramatic differences in diets among species, among age-classes within species and over time. Walleye, largemouth bass, smallmouth bass and white bass were piscivorous at age 0. Black crappie began piscivory at age 1. Yellow perch also began piscivory at age 1, but fish were a very small fraction of age-1 diets. The primary temporal pattern, seen in several species and age-classes, was an increase in piscivory from spring to fall. This pattern was due to the lack of small, age-0 prey fish in spring. Although some patterns were evident, the taxonomic composition of the diets of all species was highly variable over time, making generalizations difficult. A surprising result was the absence of yellow perch in the diet of age-0 walleye, despite their abundance in Spirit Lake and prominence in diets of age-1 walleye and other age 1-piscivores. Age-0 yellow perch were consistently too large to be eaten by age-0 piscivores, which preyed primarily on invertebrates and smaller fish such as johnny darters Etheostoma nigrum and age 0 bluegill Lepomis macrochirus. This finding suggests that predator-prey interactions and resulting population dynamics may be quite different in Spirit Lake than in other systems dominated by walleye and yellow perch.     

Diet overlap of non‐native alewife with native yellow perch and spottail shiner in nearshore waters of southwestern Lake Michigan, 2000–2007

Abstract – Lake Michigan has experienced many ecological changes as a result of introductions of non‐native species. Arguably the most significant was that of alewife (Alosa pseudoharengus), yet studies on diet overlap with native species are lacking. We analysed diet trends of alewife, spottail shiner (Notropis hudsonius) and yellow perch (Perca flavescens) collected in summer and fall 2000–2007 near Waukegan, IL, in 3–10 m depths. Mean percentage composition by dry weight for 23 prey taxa was used in multivariate analysis to test whether diet differed across species and size classes. We also tested whether zooplankton and benthic invertebrate community composition changed over time. Fish diets were similar over all years but differed seasonally. In summer, diets of large alewife were similar to both small alewife and small yellow perch, with Bosminidae, chironomid larvae and copepods as primary common prey. During fall, alewife and yellow perch size classes exhibited strong intraspecific diet overlap, while there was low diet overlap between species. Primary distinctions between species’ diets in fall were higher consumption of amphipods by yellow perch and dreissenids by spottail shiners compared to alewife, which consumed higher proportions of zooplankton. Overall, high yellow perch diet overlap with alewife during summer and with their larger conspecifics during fall could lead to negative implications for yellow perch growth before the critical overwintering period. Detailed insights into diet overlap and prey availability are critical first steps in understanding competitive interactions between native and non‐native fish that dominate the nearshore community in southwestern Lake Michigan.     

Effects of Feeding Rate on Habitat Quality in Fish Rearing Ponds

Manufactured feeds are commonly added to earthen ponds to enhance growth and survival of juvenile fish. However, excessive feeding may decrease fish production efficiency and yields by causing hypoxia (dissolved oxygen, DO < 2 mg/L) and stimulating excessive phytoplankton, filamentous green algae, and vascular plant growth. In this study, we quantified the effects of manufactured feed addition (no feeding, 1%, or 3% body‐weight/day, BW/d) on DO and inorganic phosphorus (P) and nitrogen (N) concentrations, plant abundance, and invertebrate prey production in ponds stocked with age‐0 channel catfish, Ictalurus punctatus. We found that the 3% BW/d ponds had lower DO concentrations and greater infestation by filamentous green algae (Rhizoclonium spp.) as compared to the 1% BW/d and no‐feeding ponds. Using stable N and carbon (C) isotopes to trace the fate of feed‐derived N and C in ponds, as well as analysis of zooplankton abundance, we determined that the supplied feed did not support or enhance production of natural invertebrate prey. To improve fish production efficiency, we recommend that managers leverage natural prey support of growth during early life, then adjust feeding levels to enhance growth of older fish and maintain suitable habitat quality.     

Interactions between juvenile roach or perch and their invertebrate prey in littoral reed versus open water enclosures

Abstract – Structural complexity offered by submerged macrophytes was shown to have fundamental effects on interactions between fish and their prey. However, less information is available for littoral reed (Phragmites spp.) stands. A previous field study found juvenile roach and perch to coexist within the reed stands. It was suggested that reed serves mainly as refuge against littoral piscivores, such that coexistence of perch and roach in the reed was externally forced. Several hypotheses were raised to explain why roach nevertheless showed good growth performance. Three of the hypotheses were tested experimentally. In particular, we were interested in how the confinement of fish to one of the reed or open water habitats alters feeding and growth patterns of juvenile age‐1 perch and roach. Fish were stocked separately into littoral enclosures for a 3‐week period in densities which had been found in the surrounding lake. Development of zooplankton and macroinvertebrate biomasses was observed by sampling the enclosures three times over the experimental period. Individual consumption of prey groups by the fish was calculated with a bioenergetics model, and was compared with prey group biomass in the enclosure treatments. The confinement of fish to one littoral habitat had clear effects on diet composition and growth rates. Roach fed less zooplankton and partially switched to macroinvertebrates in the reed enclosures when compared with the open water treatments, and consequently their growth rates were lower in the reed. Perch preferred macroinvertebrates in both habitats, without any difference in growth rates between the habitats. Effects of fish predation on both zooplankton and macroinvertebrate biomass were low in open water and reed enclosures. Daily consumption rates were only in a few cases higher than 40% of the available biomass of the respective prey group, but mainly were below 10% of available biomass. Therefore, we argue that both the diel horizontal migrations of roach and the relatively low consumption rate of fish when compared with the available resource biomass allow the coexistence of juvenile roach and perch in littoral reed stands.     

Potential direct and indirect effects of climate change on a shallow natural lake fish assemblage

Much uncertainty exists around how fish communities in shallow lakes will respond to climate change. In this study, we modelled the effects of increased water temperatures on consumption and growth rates of two piscivores (northern pike [Esox lucius] and largemouth bass [Micropterus salmoides]) and examined relative effects of consumption by these predators on two prey species (bluegill [Lepomis macrochirus] and yellow perch [Perca flavescens]). Bioenergetics models were used to simulate the effects of climate change on growth and food consumption using predicted 2040 and 2060 temperatures in a shallow Nebraska Sandhill lake, USA. The patterns and magnitude of daily and cumulative consumption during the growing season (April–October) were generally similar between the two predators. However, growth of northern pike was always reduced (?3 to ?45% change) compared to largemouth bass that experienced subtle changes (4 to ?6% change) in weight by the end of the growing season. Assuming similar population size structure and numbers of predators in 2040–2060, future consumption of bluegill and yellow perch by northern pike and largemouth bass will likely increase (range: 3–24%), necessitating greater prey biomass to meet future energy demands. The timing of increased predator consumption will likely shift towards spring and fall (compared to summer), when prey species may not be available in the quantities required. Our findings suggest that increased water temperatures may affect species at the edge of their native range (i.e. northern pike) and a potential mismatch between predator and prey could exist.     

Comparison of food availability and performances of first-feeding alevins through spring with the occurrence of a flood

Climate change will increase the temperature of rivers and will lead to more extreme events, such as floods. Temperature increases and floods will likely alter the phenology of freshwater species differently and have the potential to significantly disturb prey–predator interactions. In spring, an increase in temperature triggers an increase in primary production and controls the timing of the emergence in brown trout (Salmo trutta L.). Hydrology regulates the abundance of invertebrates, which are the main food source for newborn alevins. As such, climate change may desynchronise the relationship between fish emergence and invertebrate production, resulting in a negative impact on the performance of newly emerged alevins. In the present study, we quantified the abundance of invertebrates and the performance (survival and growth) of newborn alevins in early spring (March) compared to late spring (April/May) in 8 enclosures in a semi-natural channel. In addition, we simulated a flood in 4 enclosures in late spring. Our results revealed that survival and growth of alevins in early spring were limited due to low invertebrate abundance. In late spring, there was a decrease in the survival of alevins placed in the flooded enclosures, likely due to the reduction of food availability. However, the growth of survivors increased, probably because of the increase in the abundance of Chironomidae after the flood and a reduced competition between congeners. Our results demonstrate that when emergence and flooding happen simultaneously, they can limit resources which will impact the survival and growth of young salmonids in running waters.     

Comparison of exploited and unexploited yellow perch Perca flavescens (Mitchill) populations in Nebraska Sandhill lakes

Exploitation can have a pronounced effect on fish populations. Yellow perch, Perca flavescens (Mitchill), populations in Nebraska Sandhill lakes were sampled in 1998 and 1999. Three of the 29 lakes containing yellow perch have been closed to fishing for at least 10 years. Unexploited yellow perch populations had fast growth rates, but age structure was similar to exploited populations. For unexploited lakes combined, mortality and condition were not different from exploited lakes. However, one unexploited lake, Marsh Lake, had the fastest growth, highest proportion of older fish and highest condition of all populations sampled. This lake had low interspecific competition and high invertebrate abundance, which likely resulted in fast growth and high condition. However, size structure and growth were also related to lake productivity. Although exploitation may affect yellow perch populations, other factors (food availability, predators and lake productivity) also play an important role in structuring these populations. Regardless, these results indicate the potential of yellow perch in Nebraska Sandhill lakes given no exploitation.     

Growth standards for nine North American fish species

Abstract  Standard methods for comparing population characteristics within and among fish populations greatly enhance communications among fisheries scientists, improve the efficiency of data analysis, and provide insight that helps guide management actions. Although standard methods are available for comparing some fish population characteristics (e.g. length structure, body condition), similar methods are lacking for comparing growth. The purpose of this study was to provide standards (i.e. percentiles and a standard growth model) for nine ecologically and recreationally important fish species. Percentile distributions of mean back-calculated length at age were estimated using data obtained from the published literature and from data solicited from state and federal agencies throughout North America. Percentiles of growth were estimated for bluegill, Lepomis macrochirus Rafinesque, common carp, Cyprinus carpio Linnaeus, flathead catfish, Pylodictis olivaris (Rafinesque), largemouth bass, Micropterus salmoides (Lacepède), sauger, Sander canadensis (Griffith & Smith), smallmouth bass, Micropterus dolomieu Lacepède, white bass, Morone chrysops (Rafinesque) and yellow perch, Perca flavescens (Mitchill). Standard growth models (i.e. von Bertalanffy models) were developed for these species and for channel catfish, Ictalurus punctatus (Rafinesque). These results provide tools that will help scientists compare growth of fishes across North America.     

Abiotic and biotic correlates of yellow perch recruitment to age‐2 in southern Lake Michigan, 1984–2007

Abstract Seven abiotic and biotic variables were tested to determine whether they influence the recruitment to age two of yellow perch, Perca flavescens (Mitchill), in waters of southern Lake Michigan, USA. Recruitment was analysed using a Ricker stock‐recruitment relationship that accounts for density dependency. Significant model variables tested individually and ranked by total variance explained included the abundance of sexually mature yellow perch, alewife, Alosa pseudoharengus (Wilson) and spottail shiner, Notropis hudsonius (Clinton). Variables found unrelated to recruitment or generally less explanatory included the abundance of round goby, Neogobius melanostomus (Pallus), mean water temperature, variation in water temperature and water clarity. The best‐fitting multivariable model explained 69% of the recruitment variability and included abundances of sexually mature yellow perch, alewife and spottail shiner. These results suggest that yellow perch recruitment in southern Lake Michigan is regulated in part by biotic interactions with other species of the near‐shore community, including alewife and spottail shiners, in addition to the abundance of reproductively mature yellow perch.     

Species‐specific effects of subdaily temperature fluctuations on consumption,growth and stress responses in two physiologically similar fish species

Fluctuations in water temperature can have important physiological consequences for fishes. Effects of daily thermal cycles are well studied and can be beneficial, increasing prey consumption and growth rates when mean and maximum temperatures of the fluctuations are at or below the species’ optimum temperature. While less studied, subdaily temperature fluctuations are also common in many aquatic habitats and can be caused by both natural and anthropogenic processes. We performed laboratory experiments to examine how two fish species (yellow perch, Perca flavescens, and walleye, Sander vitreus) with similar thermal preferences respond to chronic exposure to subdaily temperature variability. We selected temperature treatments that reflected observed thermal variation after examining water temperature data from multiple aquatic systems. We then separately exposed yellow perch and walleye to a stable 23 °C treatment and 12‐h cycles of 23 ± 2 °C or 23 ± 4 °C for 45 days. Adult yellow perch exposed to fluctuations of 23 ± 4 °C over 12 h expressed higher consumption, growth and food conversion efficiency than fish experiencing stable 23 °C. Temperature fluctuations, though, resulted in mortalities and the development of skin ulcers in yellow perch that did not occur under stable temperatures. In contrast, the same 12‐h temperature fluctuations did not result in mortalities or stress responses in juvenile walleye. Moreover, unlike yellow perch, growth rates of walleye were lower under 12‐h temperature fluctuations compared with the stable 23 °C treatment. Our results indicate that species with similar thermal preferences can respond differently to the same subdaily temperature fluctuations.     

Temperature,plankton and conspecific density influence dynamics of age‐0 gizzard shad: implications for a gape‐limited piscivore

Age‐0 gizzard shad Dorosoma cepedianum are the main prey fish for white crappies Pomoxis annularis in many US reservoirs. However, these prey fish commonly outgrow their vulnerability to white crappie predation in some, but not all, northern Missouri reservoirs. Potential variables that could influence abundance, growth and mortality of age‐0 gizzard shad were examined in three reservoirs that differed with respect to age‐0 gizzard shad growth rates. Because of thermal effluent from a power plant, gizzard shad spawned earlier in Thomas Hill Lake and initial densities of larvae were greater than in the other reservoirs. Larval and juvenile gizzard shad grew slowest in Thomas Hill Lake, followed by Mark Twain Lake and Long Branch Lake. Growth rate of larvae increased with increasing water temperature and food abundance, but decreased with increasing conspecific density. Similar relationships were found for juvenile growth, except that growth declined with increasing temperature. The slower growth of larvae and juveniles in Thomas Hill Lake was probably a consequence of their greater densities relative to their food abundance and higher water temperatures during the juvenile stage. Conversely, both larvae and juvenile gizzard shad grew more rapidly and juveniles attained large sizes in Long Branch Lake owing to their lower densities relative to their available food. Mortality of larvae and juveniles was mostly similar among the reservoirs. Because of their greater abundance and slower growth, gizzard shad were available as prey for white crappies for a longer period in Thomas Hill Lake than in the other reservoirs.     

Changes in yellow perch (Perca flavescens) growth associated with the establishment of a walleye (Stizostedion vitreum) population in Canadarago Lake, New York (USA)

Abstract – Piscivorous fish can affect prey growth in two ways: directly by reducing prey density and indirectly by inducing predator-avoidance behaviors. We investigated these two pathways in yellow perch ( Perca flavescens ) growth responses to walleye ( Stizostedion vitreum ) stocking in Canadarago Lake, New York (USA) using a 25-year time series. Before walleye stocking, yellow perch growth rate was low and independent of body size. As walleye abundance increased, yellow perch growth increased and became size-dependent. The switch to size-dependent growth occurred in 1 year, indicating a rapid behavioral response to predators. Mean growth rate increased more gradually and was linearly related to walleye density, indicating a slower numerical effect of walleye on yellow perch densities. Although the net effect was an increase in perch growth, small perch growth initially decreased as walleye became established. Therefore, the combination of numerical and behavioral effects produced a complex pattern of size-dependent changes in growth of yellow perch.     

Ontogenetic variability of maternal effects in an iteroparous fish

Maternal effects have been observed to interact with genotypic and environmental influences to structure offspring phenotypes across a wide variety of taxa. In fishes, maternal effects may be especially important due to their potential influence on development and survival during early ontogeny – a period with high potential for population regulation. While previous studies have confirmed that maternal effects on offspring phenotype are common in fishes, the consistency with which they positively affect offspring fitness throughout early ontogeny remains largely unknown. We examined maternal effects on offspring fitness by quantifying relationships between maternal (length, mass and age), egg (diameter, mass and density) and larval traits (length, yolk‐sac volume and survival) in yellow perch (Perca flavescens). Consistent with several past studies, positive relationships among maternal and egg traits were evident. While egg mass was positively related to larval size at hatching, direct relationships between maternal and larval metrics were not apparent. Larval survival appeared to have two critical periods; in contrast with expectations, survival in the first 5 days posthatch was strongly negatively related to female size and age, while survival over the following 9 days was unrelated to maternal traits. Throughout the study, survival was positively related to yolk‐sac volume. Our unexpected observation of a negative relationship between maternal size and age and initial larval survival indicates that maternal effects may not be consistent throughout larval ontogeny. In fact, maternal effects appear to be dynamic influences on offspring fitness, and may have complex effects on individual‐ and population‐level reproductive success.     

Effect of light intensity,prey density,and ontogeny on foraging success and prey selection of larval yellow perch (Perca flavescens)

Light intensity has been shown to influence the foraging success of larval fish. However, the effect of light intensity on larval foraging is likely variable and influenced by both the density and characteristics of planktonic prey. In this study we examined the influence of light intensity of 0.1, 2.0, and 60 μmol·s^?1·m^?2 Photosynthetically Active Radiation (PAR) on foraging of yellow perch (Perca flavescens) larvae at two prey densities. We fed them with a mixture of zooplankton taxa common to lakes inhabited by yellow perch. In addition to light intensity and prey density, the effect of larval yellow perch size was examined by using fish ranging from 9 to 15 mm. The results of our study indicated that yellow perch larvae are well adapted to feed at a wide range of light intensities, as there was no difference in foraging success at investigated light intensities. Increasing prey density from 25 to 150 (zooplankton·l^?1) significantly improved the foraging success of larval yellow perch. However, the influence of prey density on foraging success was dependent on fish length. Improved foraging success at increased prey densities occurred only for individuals with a total length >10 mm. Overall, prey selection by fish larvae was influenced by light intensity, prey density, and fish length. However, the factors that influenced selection for specific prey types differed. Our study, combined with evidence from other field and laboratory work, highlight the need for a better understanding of the influence of prey density on foraging throughout ontogeny.     

Prey abundance, channel structure and the allometry of growth rate potential for juvenile trout

Abstract  The application of a drift-foraging bioenergetic model to evaluate the relative influence of prey abundance (invertebrate drift) and habitat (e.g. pool frequency) on habitat quality for young-of-the-year (YOY) and yearling juvenile cutthroat trout, Oncorhynchus clarki (Richardson) is described. Experiments and modelling indicated simultaneous limitation of fish growth by prey abundance and habitat, where depth and current velocity limit the volume of water and prey flowing through a fish's reactive field as well as swimming costs and prey capture success. Predicted energy intake and growth increase along a depth gradient, with slower deeper pool habitat generating higher predicted growth for both YOY and yearling trout. Bioenergetic modelling indicated that fish are constrained to use progressively deeper habitats to meet increasing energy requirements as they grow. Sensitivity of growth to prey abundance identified the need to better understand how variation in invertebrate drift and terrestrial drop affects habitat quality and capacity for drift-feeding fishes.