Aquatic ecosystem responses to fire and flood size in the Okavango Delta: observations from the seasonal floodplains

The frequency of fires in the Okavango Delta seasonal floodplains peaked at an intermediate frequency of flooding. Floodplains are commonly burnt every 3–5 years. This study showed fundamental changes in ecosystem properties due to burning. A burnt seasonal floodplain in the aquatic phase had oxygen levels well above saturation, 100–200%, while the levels in the un-burnt control site were below saturation and, at night, could decline to 10–40% saturation. The total phosphorous and total nitrogen concentrations were similar on both floodplains but considerably enriched relative to inflowing water, due to nutrient release from the flooded soil-sediment and animal droppings. Zooplankton biomass was very high in both systems although the abundance of fish fry was ten times higher on the un-burnt floodplain. In a low flood year the un-burnt floodplain water had high nutrient levels, primary production, methane emission, and subsequent uptake of methane in biota, as well as a high zooplankton biomass. The very high flood the following year showed the opposite with much lower production at all levels owing primarily to greater dilution of nutrients. The abundance of fish, however, was much higher during the high flood year. Macrophytes and litter provide direct shelter for fish fry but also promote low oxygen levels when decaying. Large flooded areas result in high fish production by removing obstacles related to congestion. This interplay between hydroperiod and fire may be crucial for the maintenance of high biological productivity both in the aquatic and terrestrial phases in a very nutrient poor wetland landscape. Understanding these interactions is crucial for optimal management.     

Connectivity and complexity of floodplain habitats govern zooplankton dynamics in a large temperate river system

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Predation pressure induced by seasonal fishing moratorium changes the dynamics of subtropical Cladocera populations

Seasonal fishing moratorium with selective fish harvesting is a common means of increasing fish production in Asia. Such manipulation might be expected to lead to a seasonal variation in abundance and composition of fish and predation pressure on zooplankton, and consequently a seasonal change in the Cladocera populations. In this study, we examined the seasonal dynamics of cladocerans in a subtropical plateau lake in southwestern China, Lake Erh, in which a fishing moratorium was implemented in spring and early summer. Cladocerans showed a bimodal seasonal distribution linked to variations in predation pressure induced by the seasonal fishing moratorium. When predation was low in winter because of cool water temperatures and decreasing fish density, Daphnia galeata appeared in the water column and increased towards spring. The cladoceran peaked in the middle of the fishing moratorium, coinciding with a clear water phase. The feeding rate increased with temperature in the late moratorium, allowing planktivorous fish to strongly suppress large daphnids. Small cladocerans benefited from the reduced competition with large daphnids by increasing their numbers rapidly, which resulted in a second peak of cladocerans in the fishing season.     

Diel variations in the assemblage structure and foraging ecology of larval and 0+ year juvenile fishes in a man‐made floodplain waterbody

This study investigated diel variations in zooplankton composition and abundance, and the species composition, density, size structure, feeding activity, diet composition and prey selection of larval and 0+ year juvenile fishes in the littoral of a man‐made floodplain waterbody over five 24 h periods within a 57 day period. There was a significant difference in the species composition of diurnal and nocturnal catches, with most species consistently peaking in abundance either during daylight or at night, reflecting their main activity period. There were no consistent diel patterns in assemblage structure or the abundance of some species, however, most likely, respectively, due to the phenology of fish hatching and ontogenetic shifts in diel behaviour or habitat use. There were few clear diel patterns in the diet composition or prey selection of larval and 0+ year juvenile roach Rutilus rutilus and perch Perca fluviatilis, with most taxa consistently selected or avoided irrespective of the time of day or night, and no obvious shift between planktonic and benthic food sources, but dietary overlap suggested that interspecific interactions were probably strongest at night. It is essential that sampling programmes account for the diel ecology of the target species, as diurnal surveys alone could produce inaccurate assessments of resource use. The relative lack of consistent diel patterns in this study suggests that multiple 24 h surveys are required in late spring and early summer to provide accurate assessments of 0+ year fish assemblage structure and foraging ecology.     

Fish mediate high food web connectivity in the lower reaches of a tropical floodplain river

High levels of hydrological connectivity during seasonal flooding provide significant opportunities for movements of fish between rivers and their floodplains, estuaries and the sea, possibly mediating food web subsidies among habitats. To determine the degree of utilisation of food sources from different habitats in a tropical river with a short floodplain inundation duration (~2 months), stable isotope ratios in fishes and their available food were measured from three habitats (inundated floodplain, dry season freshwater, coastal marine) in the lower reaches of the Mitchell River, Queensland (Australia). Floodplain food sources constituted the majority of the diet of large-bodied fishes (barramundi Lates calcarifer, catfish Neoarius graeffei) captured on the floodplain in the wet season and for gonadal tissues of a common herbivorous fish (gizzard shad Nematalosa come), the latter suggesting that critical reproductive phases are fuelled by floodplain production. Floodplain food sources also subsidised barramundi from the recreational fishery in adjacent coastal and estuarine areas, and the broader fish community from a freshwater lagoon. These findings highlight the importance of the floodplain in supporting the production of large fishes in spite of the episodic nature and relatively short duration of inundation compared to large river floodplains of humid tropical regions. They also illustrate the high degree of food web connectivity mediated by mobile fish in this system in the absence of human modification, and point to the potential consequences of water resource development that may reduce or eliminate hydrological connectivity between the river and its floodplain.     

Zooplankton dynamics in the upstream part of Stratos reservoir (Greece)

The investigation of the zooplankton community in the upstream part of Stratos reservoir during a 24 months survey (September 2004–August 2006) revealed 26 invertebrate species (14 rotifers, 6 cladocerans, 5 copepods and one mollusk larva). The mean abundance of the total zooplankton was higher in the first sampling period (2004–2005) and ranged between 8.81 and 47.74 ind. L⁻¹, than the second period (2005–2006) when fluctuated between 1.91 and 43.09 ind. L⁻¹. The seasonal variation was strongly influenced by the presence of rotifers, which accounting on average for 68.4% in total. Among them Keratella cochlearis and the order Bdelloidea were numerically the most important, while Macrocyclops albidus prevailed among the copepods and Bosmina longirostris among the cladocerans. Dreissena polymorpha was the only mollusk found in the zooplankton community. Rotifers, copepods and cladocerans showed a seasonal succession with the former preceding in the abundance having their first maximum in spring, while copepods and cladocerans followed, having peaks of abundance in early summer and in autumn, respectively. No seasonal succession among the cladoceran species was observed. The intense water flow in the upstream part of the reservoir, as well as temperature, conductivity, DO, pH, phosphates and silicates, were significant parameters controlling abiotic and biotic elements of the ecosystem and consequently influencing the seasonal variation and the dynamics of the zooplankton community.     

Seasonal plankton cycles in a temperate fjord and comments on the match-mismatch hypothesis

As a field test of the ‘match-mismatch hypothesis’(Cushing, 1972, 1975, 1990), we sampled the ichthyoplanktonand different size fractions of zooplankton at two stationsin a temperate fjord (Dabob Bay, Washington, USA) between May1985 and October 1987. We present the results of this studytogether with historical data on seasonal abundances of phytoplanktonand invertebrate predators. The peak abundance of fish larvaein late winter/early spring preceded the peak abundance of preyorganisms by an average of 3 months. Correlation analysis resultedin one negatively significant and three non-significant correlationsbetween ichthyoplankton and appropriately sized prey organisms.These field observations, showing a distinct temporal lag betweenabundances of larval fish and their zooplankton prey, do notsupport the match-mismatch hypothesis as originally formulated.We use these field data and a simulation model of the growthof young fish to discuss the role of two alternative processes—foodlimitation during late larval/juvenile stages and predation—thatmay constrain the timing of spawning of marine fish and whichmay have implications for recruitment variability as well. Thisleads us to propose that the match-mismatch hypothesis be extendedto include a ‘critical period’ that lasts longerand occurs later in the life history of marine fish than haspreviously been supposed.     

Spatial and temporal variations in densities of small fishes across different temporary floodplain types of the lower Okavango Delta,Botswana

Small-sized and juvenile fishes as well as physicochemical water parameters in various primary, secondary and rarely flooded temporary floodplains of the Okavango Delta were assessed during the different hydrological phases of the 2009–2010 flooding season. Small fishes were sampled in the marginal zone of the floodplains using a throw-trap net and a suite of physicochemical properties were measured. Both physicochemical water quality parameters and densities of small fishes showed spatiotemporal variations across the temporary floodplain types. Turbidity, dissolved oxygen, conductivity, woody debris and chlorophyll a were all highest in rarely flooded floodplains compared to both primary and secondary floodplains (ANOVA, p < 0.05). Fish from 38 fish taxa belonging to 11 families were identified and classified during the study. The fish families Cichlidae (dominated by tilapias), Poeciliidae (Aplocheilichthys spp.) and Cyprinidae (Barbus spp.), were the most abundant across the study floodplains. The poeciliids were most abundant in frequently flooded primary and secondary floodplains, whereas juvenile cichlids dominated in rarely flooded floodplains. During high floods the rarely flooded portions of the delta function as important nursery habitats for juvenile cichlids, implying that a significant reduction in flooding may have negative effects on the delta's tilapia stocks due to reduced recruitment success.     

Feeding ecology of pelagic fish species in the Gulf of Riga (Baltic Sea): the importance of changes in the zooplankton community

The feeding ecology of four pelagic fish species was studied in relation to their prey availability in the Gulf of Riga (Baltic Sea) during the summer 1999-2006. The zooplankton community was dominated by the cladoceran Bosmina longispina, rotifers Keratella cochlearis and K. quadrata and the copepod Eurytemora affinis, with the highest interannual variability in abundance recorded for B. longispina. The last influenced the diet of adult sprat Sprattus sprattus, juvenile smelt Osmerus eperlanus and three-spined stickleback Gasterosteus aculeatus as these were strongly selecting for B. longispina. The fish feeding activity did not match the abundance dynamics of their preferred prey, suggesting that fishes may switch to consume other prey in case the preferred diet was limited. A considerable dietary overlap indicated high potential competition between pelagic fish species. While herring Clupea harengus membras and G. aculeatus were relying on very different food, the diets of young O. eperlanus and G. aculeatus were very similar. Interannual variability in zooplankton composition and abundance significantly affected the diet composition of fishes, but those changes were insufficient to exert a consistent influence upon fish feeding activity and total amounts of zooplankton consumed.     

The foraging ecology of larval and juvenile fishes

Knowledge of the foraging ecology of fishes is fundamental both to understanding the processes that function at the individual, population and community levels, and for the management and conservation of their populations and habitats. Furthermore, the factors that influence the acquisition and assimilation of food can have significant consequences for the condition, growth, survival and recruitment of fishes. The majority of marine and freshwater fish species are planktivorous at the onset of exogenous nutrition and have a limited ability to detect, capture, ingest and digest prey. Improvements in vision, development of fins and associated improvements in swimming performance, increases in gape size and development of the alimentary tract during ontogeny often lead to shifts in diet composition. Prey size, morphology, behaviour and abundance can all influence the prey selection of larval and juvenile fishes. Differences in feeding behaviour between fish species, individuals or during ontogeny can also be important, as can inter- and intraspecific interactions (competition, predation risk). Temporal (diel, seasonal, annual) and spatial (microhabitat, mesohabitat, macrohabitat, regional) variations in prey availability can have important implications for the prey selection, diet composition, growth, survival, condition and, ultimately, recruitment success of fishes. For fish populations to persist, habitat must be available in sufficient quality and quantity for the range of activities undertaken during all periods of development. Habitats that enhance the diversity, size ranges and abundance of zooplankton should ensure that sufficient food resources are available to larval and juvenile fishes.     

Consumption of zooplanktonic organisms by Astyanax fasciatus Cuvier, 1819 (Osteichthyes,Characidae) in Lobo (Broa) reservoir,São Carlos,SP, Brazil

The consumption of zooplanktonic organisms by young and adult fish of Astyanax fasciatus in Lobo Reservoir was studied from October 1978 to September 1979 by analysing the abundance of zooplankton in the gut of fishes and relating it to the variation of the zooplankton community in the lake. To analyse the diet the following methods were used: numeric frequency of occurrence, and frequency rate. Astyanax fasciatus showed a large spectrum of feeding. The young stage feeds mainly on zooplankton and macroinvertebrates (insect larvae) but the adults also consume algae and detritus. Even in relation to the zooplankton the young stage showed a food preference different from that of the adults, selecting copepods over cladocerans, while the adults consumed more cladocerans.     

Experimental analysis of the predation impact of the larvae of pond smelt (<Emphasis Type="Italic">Hypomesus transpacificus nipponensis</Emphasis>) on zooplankton populations established in mesocosms

The predation impact of the larvae of pond smelt Hypomesus transpacificus nipponensis on a zooplankton community was studied using mesocosms. The fish significantly depressed the abundances of copepod nauplii and rotifers, especially Hexarthra mira. The vulnerabilities of these prey might be determined by their swimming behavior and population density, suggesting that larval fish selectively prey on zooplankton that have a high encounter rate with the predator. The larvae did not have a negative effect on the densities of cladocerans, but fish predation altered the cladoceran community structure from the dominance of B. longirostris to that of B. fatalis. This result suggests that larval fish predation is an important factor that shifts the species composition of Bosmina in some lakes, the shift occurring in the season when fish larvae are abundant. Our results have shown that predation by the larval fish would control not only the abundance, but also the community structure of the small-sized zooplankton prey.     

Predictability of littoral-zone fish communities through ontogeny in Lake Texoma,Oklahoma-Texas,USA

Synopsis We sampled larval, juvenile and adult fishes from littoral-zone areas of a large reservoir (Lake Texoma, Oklahoma-Texas) (1) to characterize environmental factors that influenced fish community structure, (2) to examine how consistent fish–environment relationships were through ontogeny (i.e., larval vs. juvenile and adult), and (3) to measure the concordance of larval communities sampled during spring to juvenile and adult communities sampled at the same sites later in the year. Larval, juvenile and adult fish communities were dominated by Atherinidae (mainly inland silverside, Menidia beryllina) and Moronidae (mainly juvenile striped bass, Morone saxatilis) and were consistently structured along a gradient of site exposure to prevailing winds and waves. Larval, juvenile and adult communities along this gradient varied from atherinids and moronids at highly exposed sites to mostly centrarchids (primarily Lepomis and Micropterus spp.) at protected sites. Secondarily, zooplankton densities, water clarity, and land-use characteristics were related to fish community structure. Rank correlation analyses and Mantel tests indicated that the spatial consistency and predictability of fish communities was high as larval fishes sampled during spring were concordant with juvenile and adult fishes sampled at the same sites during summer and fall in terms of abundance, richness, and community structure. We propose that the high predictability and spatial consistency of littoral-zone fishes in Lake Texoma was a function of relatively simple communities (dominated by 1–2 species) that were structured by factors, such as site exposure to winds and waves, that varied little through time.     

Seasonal Patterns of Abundance: Do Zooplankton in Small Ponds do the Same Thing Every Spring–Summer?

Small ponds ( ≤ 2 ha) are often a common landscape feature, but their ecology has been less well studied than that of lakes. Studies of some lakes and reservoirs show among-year repeatability in the seasonal abundance of different zooplankton (i.e., succession). For small ponds the seasonal dynamics of zooplankton community structure are relatively unstudied, as are any mechanisms underlying these dynamics. We took a community-level approach to studying the spring–summer abundance of zooplankton in two small Ohio ponds. In particular we wanted to know if repeatable patterns exist for zooplankton community structure in these ponds. We surveyed the spring–summer zooplankton communities in the ponds from 2001 to 2003 and used community-level ordination techniques (i.e., non-metric multidimensional scaling, NMDS) to characterize the assemblages. For both ponds the seasonal pattern of total zooplankton abundance differed significantly among years. We found that the proportional abundance of taxa across the season also varied among years. Elements of the zooplankton community, as described by the NMDS dimensions, showed among-year variation in the spring–summer trajectories that developed. Some of the variation in these zooplankton communities was associated with seasonal changes in water temperature. This among-year variation in the seasonal pattern of zooplankton community structure suggests that community dynamics in these small ponds may not be very repeatable. These complex dynamics of zooplankton thus challenges us to improve our characterization of zooplankton communities in small ponds such that we can better understand the factors that drive the patterns we observe.     

Effects of seed size and emergence time on tree seedling establishment: importance of developmental constraints

Arafura filesnakes (Acrochordus arafurae) are large (up to 2.5 m, 5 kg) aquatic nonvenomous snakes that feed entirely on fishes. A 10-year field study in the Australian wet-dry tropics revealed strong correlations between rainfall patterns, fish abundance, and snake population dynamics. All of these characteristics showed considerable annual variation. High rainfall late in the wet season (February–March) caused prolonged inundation of the floodplain. Following such years, dry-season sampling revealed that fishes were abundant, filesnakes were in good body condition, and a high proportion of adult female filesnakes were reproductive. Annual variation in recruitment to the population (as judged by the relative abundance of yearling snakes) was also correlated with fish abundance and thus, with rainfall patterns in the late-wet season. Our results fit well with those from other studies on a diverse array of aquatic and terrestrial species within the wet-dry tropics. Annual variation in rainfall patterns, via its effects on prey abundance, may drive the population dynamics of many tropical predators. Received: 28 June 1999 / Accepted: 29 February 2000     

Significance of a floodplain in the formation of fish communities in small rivers of Ryazan oblast

In total, 37 fish species from 30 genera and 10 families are registered in small rivers of the Ryazan oblast. In addition to other significant factors, the floodplain width is important for the formation of species structure of fish communities. In the rivers with small floodplains (less than 0.2 km in width), mainly small and short-lived fishes are represented in the catches. In the rivers or in their parts with wide floodplains (0.2–0.5 km), the dominant complex (in addition to short-lived fish species) includes roach Rutilus rutilus and/or perch Perca fluviatilis. In the rivers with wider floodplains (more than 0.5 km), long-lived phytophils represented by mainly the limnophilous group prevail.     

Zooplankton,fish and fisheries in tropical freshwaters

About 40% of all fish species occur in freshwater, although only 1% of the globe is occupied by freshwaters. The tropics harbour a high percentage of these fishes. Freshwater zooplankton on the other hand is far less diverse than its marine counterpart and the tropics do not harbour a markedly high percentage of freshwater species either. The antecedents of freshwater zooplankton appear to have come from riverine and terrestrial habitats via temporary habitats (ponds, floodplains). The present zooplankton composition has also been shaped by, among other factors, the highly efficient zooplanktivorous modern teleosts which have restricted the formerly widespread Branchiopoda mainly to fishless freshwaters. Those Branchiopoda frequently co-existing with fishes (Cladocera) have their size composition strongly influenced by fish predation. Circumstantial evidence indicates that pelagic zooplankton (Cladocera, Copepoda, Rotifera) appear to provide a relatively scarce food supply relative to the littoral region for the early stages of fishes. Also, unpredictability of zooplankton may be involved here. These factors have led to the loss of planktonic eggs and the siting of fish breeding in shallow littoral situations, where other animal foods besides zooplankton are also available, especially for later stages of juvenile fish. The Ostariophysi breed in the shallow expanses of flood waters while the Cichlidae, some of which breed like Ostariophysi, also breed in standing waters in the littoral of lakes or floodplains. In all these locations zooplankton and benthic organisms, especially insects, are available. The cichlids are, in addition, provided with parental care. Predation on young fishes is also reduced by these strategies. Young fishes may also be adapted to feed on patches of zooplankton and other food in their breeding grounds. Tropical pelagic clupeids and cyprinids may breed continuously. Some of these clupeids in rivers breed at low water.Zooplankton, supplemented by other animal food is more critical to achieving the potential fish yields in the tropics than in temperate freshwaters because fish yields in the tropics can be very high indeed. The high metabolic rate of young fishes in the tropics adds to the demand for food. Tropical freshwaters have a relatively high primary production but a low zooplankton/phytoplankton ratio. Zooplankton is kept small in size and biomass by continuous predation. Herbivorous fishes can sustain very high fish yields in the tropics but they must have a high fecundity and high survival of young produced seasonally, mainly in rivers or even continuously as in lakes and reservoirs to weather predation. Rich littoral zooplankton and benthos combined with omnivory and a higher efficiency in the use of the available animal food by newly hatched fishes may be critical factors linking fish yields to zooplankton in tropical freshwaters. The ability of herbivorous tilapias to give very high fish yields in shallow tropical lakes may also be due to their efficient use of animal food, algae and microphagy in young stages besides other favourable adaptations like opportunistic feeding on detrities and the ability to feed on and digest cyanobacteria, abundant in the tropics.     

Effects of a top invertebrate predator (<Emphasis Type="Italic">Dytiscus alaskanus</Emphasis>; Coleoptera: Dytiscidae) on fishless pond ecosystems

We investigated the predatory effects of Dytiscus alaskanus, a large predaceous diving beetle, on the biomass, species composition and diversity of fishless pond communities. The effects were tested using presence and absence treatments of D. alaskanus in 24 mesocosms distributed among six ponds. We sampled phytoplankton, zooplankton and macroinvertebrates every two weeks for a six week period. Periphyton was sampled from the mesocosm walls on the final day. Total macroinvertebrate biomass decreased in the presence of dytiscids while species richness was not affected. Macroinvertebrate predators, snails and Gammarus lacustris decreased in the dytiscid treatments. Laboratory feeding experiments confirmed feeding preferences consistent with the mesocosm results. Periphyton biomass was six times greater in the dytiscid enclosures, concomitant with the decreased grazing by gastropods and other invertebrate primary consumers indicating a benthic trophic cascade. Top–down effects of dytiscids on other predatory invertebrates led to increased total zooplankton biomass, largely due to increased abundances of large and small cladocerans. Zooplankton species richness increased in the dytiscid enclosures. Inconsistent with trophic cascade theory, phytoplankton did not respond to top–down effects of D. alaskanus within the study period. Overall, the results show D. alaskanus predation caused trophic effects via two distinct food chains, a dytiscid–snail–periphyton trophic cascade, and a dytiscid–predatory macroinvertebrates–zooplankton partial trophic cascade.     

Feeding of Arapaima sp.: integrating stomach contents and local ecological knowledge

The giant arapaima (Arapaima sp.) has been described as a fish of change in Amazonia because of its important role in the conservation of floodplains, food security and income generation for rural communities. Nonetheless, despite the cultural, ecological and economic importance of arapaima, data on diet are scarce. Aiming to expand knowledge about arapaima diet in western Amazonia, scientific knowledge was integrated with the knowledge of local dwellers. During the low-water period (September 2018) and the falling-water period (June 2019), arapaima stomachs were collected from 11 floodplain lakes in the middle Juruá River. All fishes were measured [TL (total length)] and sexed. Food items from each stomach were categorized as fishes, invertebrates, plants and bone remains and weighed. Also, in the latter period, experienced local fishers were interviewed about arapaima feeding. This integrated approach revealed that young arapaima eat fish and invertebrates but adult arapaima eat fish of a wide range of species, which were mainly of low and intermediate trophic positions. This study reports the first case of cannibalism for arapaima and also shows that during the low-water period, many individuals had empty stomachs or only some small fish-bone remains and/or plant material. Arapaima sex and TL had no influence on the absence of prey in stomach contents. Overall, it can be concluded that local people had consistent ethnobiological knowledge of arapaima feeding ecology that could be useful within management projects in the region.     

Utilization of the exotic cladoceran Daphnia lumholtzi by juvenile fishes in an Illinois River floodplain lake

Daphnia lumholtzi comprises a substantial component of the zooplankton community during mid‐ to late‐summer in Lake Chautauqua, a floodplain lake along the Illinois River near Havana, Illinois. In order to quantify the utilization of D. lumholtzi by juvenile fishes, diet analyses were conducted for seven juvenile fish species collected from Lake Chautauqua during the 2001 annual drawdown period. Freshwater drum Aplodinotus grunniens and emerald shiner Notropis atherinoides demonstrated negative selectivity for D. lumholtzi relative to native zooplankton species whereas four species of fish (bluegill Lepomis macrochirus, white bass Morone chrysops, white crappie Pomoxis annularis and black crappie Pomoxis nigromaculatus) consumed substantial amounts of D. lumholtzi. Although selectivity values for D. lumholtzi varied among these fish species, positive selection for D. lumholtzi increased similarly among larger size classes of each fish species, and corresponded with ontogenetic shifts in diet. Mean body length of D. lumholtzi consumed by 20–69 mm L_T juvenile fishes ranged from 0·75 to 0·99 mm with a calculated total length range of 2·0–2·6 mm. Results from this study provide evidence that high abundances of D. lumholtzi in mid‐ to late‐summer provide an additional food source for several juvenile fish species during a time when abundances of large native cladoceran species (i.e. Daphnia) are low, and juvenile fishes are searching for larger prey associated with ontogenetic shifts from zooplankton to macroinvertebrates and fishes. Because zooplankton production is typically lower in rivers than in lakes, survivorship of juvenile fishes produced in floodplain lakes may be higher in riverine systems if they are not reliant on zooplankton as a primary food resource. Therefore, high abundances of D. lumholtzi may benefit juvenile fishes in managed floodplain lakes, such as Lake Chautauqua, by increasing growth and facilitating the transition from zooplanktivory to insectivory or piscivory.