Distribution,habitat and conservation status of desert pupfish (Cyprinodon macularius) in the Lower Colorado River Basin,Mexico

In order to better determine the currentstatus of desert pupfish populations (Cyprinodon macularius macularius) in the LowerColorado River Basin of Mexico, bimonthly fishsampling and habitat evaluations were carriedout from September 1996 to August 1997 in sixlocalities of Baja California and Sonora.Desert pupfish were collected using minnowseines and traps. Four sampling sites are inSonora, in shallow marginal habitats of theCiénega Santa Clara (Hunters' Camp, Outletof the Welton-Mohawk channel, El Doctor andFlor del Desierto) and two are in BajaCalifornia (Cerro Prieto and streams south ofCerro Prieto). The most abundant fish speciessampled was native desert pupfish (C.macularius, 59%) followed by sailfin molly(Poecilia latipinna, 19%), redbellytilapia (Tilapia cf. zilli, 10%) and western mosquito fish (Gambusiaaffinis, 7%). Significant temporalfluctuations in distribution and abundance ofdesert pupfish populations, as previouslyreported for these populations, was againdocumented. The main anthropogenic factorsaffecting distribution and abundance of desertpupfish populations in the Mexican portion ofthe Lower Colorado River Basin are progressivealteration of aquatic and riparian habitats, aswell as presence of exotic fishes that havecaused the displacement or elimination ofnative fish populations. Both habitat andpresence of the desert pupfish populations inthe study area are controlled by theperiodicity, quality and volume of dischargesinto the Mexican portion of the basin from theUnited States.     

Habitat Restoration as a Means of Controlling Non-Native Fish in a Mojave Desert Oasis

Non‐native fish generally cause native fish decline, and once non‐natives are established, control or elimination is usually problematic. Because non‐native fish colonization has been greatest in anthropogenically altered habitats, restoring habitat similar to predisturbance conditions may offer a viable means of non‐native fish control. In this investigation we identified habitats favoring native over non‐native fish in a Mojave Desert oasis (Ash Meadows) and used this information to restore one of its major warm water spring systems (Kings Pool Spring). Prior to restoration, native fishes predominated in warm water (25–32°C) stream and spring‐pool habitat, whereas non‐natives predominated in cool water (≤23°C) spring‐pool and marsh/slack water habitat. Native Amargosa pupfish (Cyprinodon nevadensis) and Ash Meadows speckled dace (Rhinichthys osculus nevadensis) inhabited significantly faster mean water column velocities (MWCV) and greater total depth (TD) than non‐native Sailfin molly (Poecilia latipinna) and Mosquitofish (Gambusia affinis) in warm water stream habitat, and Ash Meadows speckled dace inhabited significantly faster water than non‐natives in cool water stream habitat. Modification of the outflow of Kings Pool Spring from marsh to warm water stream, with MWCV, TD, and temperature favoring native fish, changed the fish composition from predominantly non‐native Sailfin molly and Mosquitofish to predominantly Ash Meadows pupfish. This result supports the hypothesis that restoring spring systems to a semblance of predisturbance conditions would promote recolonization of native fishes and deter non‐native fish invasion and proliferation.     

Conservation and conflict between endangered desert fishes

Conservation of naturally sympatric endangered species requires unique considerations. While impacts of invasive species garner much attention, interactions between endangered species must also be managed. The endangered Leon Springs pupfish, Cyprinodon bovinus, has suffered a population decline due to decreasing natural habitat. As breeding habitat is lost, C. bovinus is also adversely affected by the sympatric, endangered Pecos gambusia, Gambusia nobilis. Here, we document interactions between these species, finding significantly more G. nobilis accumulated at pupfish spawning events than randomly distributed on breeding grounds in the absence of spawning. As a known egg predator, our results suggest that G. nobilis presence at spawnings may further decrease pupfish numbers while also altering the evolutionary dynamics of C. bovinus breeding tactics. Habitat restoration may decrease Gambusia concentrations or influence C. bovinus breeding behaviour and increase the number of territorial males resulting in viable population sizes for both critically endangered fishes.     

Habitat and life history differences between two species of Gambusia

Life history strategies reflect trade-offs that tend to maximize fitness, such as investment in a few large or many small offspring. We compared life histories of two temperate livebearing fishes Gambusia affinis and G. nobilis, an endangered species which is virtually unstudied. The two species persist in environments that differ widely in abiotic and biotic factors in the same local area. Gambusia affinis were typically found in habitats with high productivity and wide fluctuations in temperature, salinity and dissolved oxygen, whereas G. nobilis occurred in more stable spring-fed habitats. We collected data on life-history traits: embryo mass, brood size (number of embryos), total maternal reproductive effort, population sex ratios, and size (mass and length) distributions of adults and juveniles. There was no difference between species in reproductive effort per brood, but they differed in investment strategy. Gambusia affinis females produced large broods with small embryos, whereas G. nobilis females produced broods of fewer, larger embryos. These differences in life history strategies reflect a tradeoff between individual productivity and differential mortality rates in different environments. At our field site G. affinis persists as an annual species with relatively high growth rates and corresponding reproductive patterns, whereas G. nobilis females have a slower reproductive tempo and may live multiple years.     

Sex Differences in Mate Preference Between Two Hybridizing Species of Poeciliid Fish

When hybridization between two species in secondary contact is costly, natural selection should favor pre‐mating isolation barriers. The invasive Gambusia affinis has been introduced to habitats of a closely related species, the endangered Gambusia nobilis. Although other Gambusia species readily hybridize in secondary contact, previous studies in this system found low abundance of hybrids in sympatry. To examine whether hybridization is limited by behavioral pre‐mating isolation that may have evolved in allopatry, I examined each species’ mating preferences using individuals from allopatric populations in male and female visual/olfactory association preference tests as well as open mating tests with and without male–male competition. Gambusia affinis and G. nobilis males had significant association preference for conspecific females in visual/olfactory tests. Only G. nobilis females had statistically significant preference for conspecific males. In open mating tests, males of both species had lower chase times overall when in competition, but there was no difference in number of copulation attempts. Males of both species had higher copulatory success rates with conspecific females when in competition, suggesting females may exert some control over copulation success of males. These results suggest that there are differences in mating preferences between these species. This mate choice may act as a pre‐mating isolating barrier to reduce hybridization in sympatry, a proposed threat to the endangered G. nobilis.     

Zooplankton response to flooding of a drought refuge and implications for the endangered fish species Craterocephalus fluviatilis cohabiting with alien Gambusia holbrooki

Disruption to a river’s natural flow regime changes its ecological character, which becomes unfavourable for previously adapted biota. The zooplankton particularly are affected, and survival of larval and juvenile fish is largely determined by their availability. Alien fishes can also impact on recruitment in native fishes, sometimes through competition. In this regard, the invasive eastern Gambusia Gambusia holbrooki is linked to the decline of several fish species. It can have a substantial influence in shaping plankton communities, which implies that it competes with native fish that rely on the microfauna. The effects of river regulation and over abstraction of water in the Murray–Darling Basin, south-eastern Australia, were exacerbated by drought from 1997 to 2010. Consequently, the endangered Murray hardyhead Craterocephalus fluviatilis underwent substantial population decline and extirpations. The purpose of this study is to determine if a link exists between zooplankton response to flooding of a drought refuge and the recruitment success of C. fluviatilis in the presence of G. holbrooki. Flooding triggered sharp and substantial increases in the zooplankton and their eggs, which was the sole food of C. fluviatilis. This apparently benefitted the recruitment of C. fluviatilis, and sometimes alleviated diet overlap with G. holbrooki. Conversely, the zooplankton in a nearby non-flooded refuge was low in abundance and diversity, and all fish species were extirpated. The findings indicate that the flooding of drought refugia with relatively small volumes of water can be timed with ecological cues that would otherwise be desynchronized in highly regulated rivers, particularly during drought.     

Development of a technique for quarantining Great Artesian Basin springs from colonisation by the invasive fish Eastern Gambusia (Gambusia holbrooki)

A species recovery project for the endangered fish Red‐finned Blue‐eye (Scaturiginichthys vermeilipinnis) commenced in 2009 at Edgbaston Reserve in central western Queensland. To date, the project has included relocations and control of alien Eastern Gambusia (henceforth Gambusia, Gambusia holbrooki), using the piscicide rotenone. Preventing Gambusia colonising springs where Red‐finned Blue‐eye occur or have been relocated is crucial to the success of the project. As such, this study tested the use of porous silt fences that were installed around five springs from 2012. Results indicate that silt fencing is a suitable barrier material and that provided installed silt fences are serviced regularly, the material is an effective method of quarantining populations of endangered species in isolated aquatic environments. Four of the five installed fences were effective, and maintenance consisted of small repairs at regular intervals (quarterly) followed by replacement after 2 years. As such, silt fencing may have wider application in the conservation of endangered fish and other organisms, particularly in areas where isolated waterbodies occur and where their size renders exclusion fencing a practical recovery action.     

The role of refugia for fishes during drought: a review and synthesis

• 1 Drought is a natural disturbance of aquatic ecosystems and can be a major factor in structuring aquatic communities. For individuals, populations and communities to persist in disturbed environments, they must have refuge from disturbance or disturbance must be minimal. Refugia convey spatial and temporal resistance or resilience in the face of disturbance, but the role of refugia in aquatic systems remains poorly understood. 2. We review available literature on aquatic refugia for fishes in order to synthesise current knowledge and provide suggestions for needed research. Our objectives were to clarify definitions of disturbance and refugia in the context of drought in aquatic systems, review how refuge habitats influence fish community structure, and consider the potential impact of refugia on fish population and community dynamics during drought. 3. Droughts cause a decrease in surface area/volume and an increase in extremes of physical and chemical water quality parameters. These conditions are linked with biotic interactions that structure the community of fishes residing in low‐flow or dry season refugia by increasing mortality rates, decreasing birth rates and/or increasing migration rates. Many aquatic organisms seek refuge from disturbance and/or have adaptations (e.g. physiological tolerance) that provide refuge. 4. Drought in aquatic systems leads to shifts in refugia spacing and connectance at multiple spatial and temporal scales. Refuge size, disturbance intensity, and mobility of organisms is predicted to play a large role in population persistence. We expect that refuge habitats will experience net immigration during drying and net emigration after rewetting, with the opposite occurring in surrounding habitat patches. Population dynamics of fishes using refugia during drought are best modelled by modified source‐sink dynamics, but dynamics are likely to change with spatial scale.

     

Incorporating asymmetric movement costs into measures of habitat connectivity to assess impacts of hydrologic alteration to stream fishes

Aim

Hydrologic alterations are widespread in freshwater ecosystems worldwide and often detrimentally impact fish populations. Habitat suitability models are commonly used to assess these impacts, but these models frequently rely upon observed fish–habitat relationships rather than more mechanistic underpinnings. The aim of this study was to demonstrate how to incorporate swim performance into a measure of habitat connectivity at a fine scale, providing a method for assessing the availability of suitable habitat for stream fishes.

Location

We applied this technique to an endangered species, the Western Silvery Minnow Hybognathus argyritis, in the Milk River of southern Alberta, Canada. The Milk River is an augmented system, where a diversion in nearby St. Mary River augments flow by a factor >3 × (from 1–5 m³/s to 15–20 m³/s).

Methods

We used laboratory measured swim performance of Western Silvery Minnow to develop a movement cost function that was used in conjunction with a habitat suitability model to assess habitat availability via a recently developed graph‐theoretic metric, equivalent connected area (ECA).

Results

Stream augmentation altered not only habitat suitability but also habitat connectivity for this species. During augmentation, suitable habitat area declined by 81.3%. Changes in habitat connectivity were site dependent. Movement costs between habitat patches were lower during augmentation due to current‐assisted dispersal and increased distance to patches during natural flows from dried streambeds. When movement costs were incorporated into ECA, ECA decreased by 78.0% during augmentation.

Main conclusions

With changing climate and increasing anthropogenic impacts on aquatic ecosystems, understanding how freshwater fishes relate to their habitat is critical for appropriate management. In many cases, such as the Western Silvery Minnow, mitigating habitat suitability may not be sufficient, as species are unable to reach suitable habitat. The incorporation of swim performance into habitat connectivity assessments, as carried out here, can be easily adapted to other species and situations and can improve the understanding of impacts to stream fishes and increase the effectiveness of mitigation efforts.     

A review of changes in the fish assemblages of Levantine inland and marine ecosystems following the introduction of non-native fishes

The arrival of non‐native fishes in the Levant Basin began in the late 19th century. Whereas the presence of most of the 40 non‐native freshwater fishes stem from intentional introductions, either for aquaculture or pest control, the 62 species of non‐native marine fishes arrived by natural dispersal via the Suez Canal. Of the non‐native freshwater species, five have established successful breeding populations (mosquitofish Gambusia affinis, common carp Cyprinus carpio, crucian carp Carassius carassius, swordtail Xiphophorus hellerii and rainbow trout Oncorhynchus mykiss), and seven are regularly stocked in natural habitats (thinlip mullet Liza ramada, flathead mullet Mugil cephalus, European eel Anguilla anguilla, grass carp Ctenopharyngodon idella, Asian silver carp Hypophthalmichthys molitrix, bighead carp Aristichthys nobilis, black carp Mylopharyngodon piceus). Some non‐native species appear to have out‐competed native species. Gambusia affinis may have caused the extirpation of two native cyprinid fishes from the Qishon River basin (Levant silver carp Hemigrammocapoeta nana and common garra Garra rufa) and the southern Dead Sea (endemic Sodom's garra G. ghoerensis). The opening of the Suez Canal in 1869 allowed entry into the eastern Mediterranean of Indo‐Pacific and Erythrean biota, with the latter now dominating the community structure (50–90% of fish biomass) and function (altered native food web) of the Levantine littoral and infra‐littoral zones. The process has accelerated in recent years concurrent with a warming trend of the seawater. Record numbers of newly discovered non‐native species is leading to the creation of a human‐assisted Erythrean biotic province in the eastern Mediterranean.     

Floating-leaved and emergent vegetation as habitat for fishes in a eutrophic temperate lake without submerged vegetation

Although submerged vegetation is considered to be the most suitable refuge against predators and form of foraging habitat for small fishes, submerged plants are often scarce or lacking in turbid eutrophic lakes. To evaluate emergent (Zizania latifolia) and floating-leaved (Nelumbo nucifera) vegetation as refuge areas against predators and as foraging habitats for small fishes, we investigated the fauna, abundance, and size distribution of the fish community as well as the abundance of possible prey for small fishes in beds of each vegetation type in a eutrophic shallow lake: Lake Teganuma in Japan. The leaves and stems of N. nucifera occupied an area 4.2 times larger than that of Z. latifolia. The high coverage of the water surface with plants most likely induced the hypoxia found in the N. nucifera bed. The diversity of small fishes was greater in the Z. latifolia bed with piscivorous fish than in the N. nucifera bed without piscivorous fish. The diversity of fish species in the vegetation was enhanced when there was an increased diversity of possible food sources rather than an absence of predators. Some aquatic insects of the same species had a much lower δ¹³C signature at hypoxic locations than at less hypoxic locations in the N. nucifera bed. Such site differences within a bed were not observed in the organisms caught in the Z. latifolia bed. The insects in hypoxic zones with a δ¹³C signature lower than ?30 ‰ were more depleted in ¹³C than the surface sediment or attached algae, suggesting that the larvae in the hypoxic zones incorporated the organic materials generated by methane-oxidizing bacteria. We can therefore conclude that floating-leaved vegetation, especially a N. nucifera bed, is not suitable as a replacement for submerged vegetation because of its potential to induce hypoxia, which can decrease the diversity of the fish fauna.     

Colonization of abandoned swimming pools by larval mosquitoes and their predators following Hurricane Katrina

Thousands of flooded swimming pools were abandoned in New Orleans following Hurricane Katrina and provided a natural experiment to examine colonization of a novel aquatic habitat by mosquito larvae and their aquatic predators. We conducted a randomized survey of flooded swimming pools in two neighborhoods in January 2006 and found that 64% contained mosquito larvae, 92% contained predatory invertebrates, and 47% contained fishes. We collected 12,379 immature mosquitoes representing five species, primarily Culiseta inornata, and secondarily, the arboviral vector Culex quinquefasciatus. Dragonfly nymphs in the families Aeshnidae and Libellulidae were the most common predatory invertebrates collected among a total of 32 non-mosquito invertebrate species. Eleven species of fishes were collected, with Gambusia affinis accounting for 76% of the catch. Diversity of fishes in swimming pools was positively correlated with proximity to a levee breach and the fish assemblage found in swimming pools was similar to that found along shorelines of Lake Pontchartrain and drainage canals that flooded the study area. Mosquito larvae were rare or absent from pools containing fishes; however, path analysis indicated that the presence of top predators or abundant competitors may somewhat mitigate the effect of Gambusia affinis on mosquito presence.     

Role of Fish in Structuring Invertebrates on Stromatolites in Cuatro Ciénegas, México

Stromatolites, the dominant Precambrian life form, declined in the Phanerozoic to occur today in only a few sites. This decline has been attributed to evolution of metazoan grazers, but stromatolites in our study site, Cuatro Ciénegas, Coahuila, México, harbor diverse macroinvertebrates. Drawing on food chain theory, we hypothesized that fish predation on invertebrates controls invertebrate populations, allowing stromatolites to flourish in Cuatro Ciénegas. Our experiment used small mesh (1 mm) cages to exclude all but larval fishes, and larger (6.5 mm) cages to exclude all larger fishes (including the molluscivorous and omnivorous endemic polymorphic cichlid, Herichthys minckleyi), but allow access to all sizes of the abundant endemic pupfish, Cyprinodon bifasciatus. No effects of treatments on invertebrate densities were noted at 6 week, but significant effects were observed on specific taxonomic groups after 3 month. In absence of fishes, hydrobiidae snails and ceratopogonids increased 3- and 5-fold, respectively, and invertebrate assemblage composition varied among treatments. Algal biomass was not affected by treatments, but algal species composition appeared to change. Overall results suggest that fish assemblages structure invertebrate assemblages, and that fishes may also be factors in determining algal communities.     

The Spatial Pattern of the Small Fish Community in the Biandantang Lake – A Small Shallow Lake Along the Middle Reach of the Yangtze River, China

The spatial pattern of the small fish community was studied seasonally in 1996 in the Biandantang Lake. Based on plant cover, the lake was divided into five habitats, arranged in the order by plant structure complexity from complex to simple: Vallisneria spiralis habitat (V habitat), Vallisneria spiralis–Myriophyllum spicatum habitat (V–M habitat), Myriophyllum spicatum habitat (M habitat), Nelunbo nucefera habitat (N habitat), and no vegetation habitat (NV habitat). A modified popnet was used for quantitative sampling of small fishes. A total of 16 fish species were collected; Hypseleotris swinhonis, Ctenogobius giurinus, Pseudorasbora parva, Carassius auratus and Paracheilognathus imberis were the five numerically dominant species. In both summer and autumn, the total density of small fishes was about 10indm^–2. Generally, Ctenogobius giurinus, a sedatory, benthic fish, was distributed more or less evenly among the five habitats, while the other four species had lower densities in the N habitat and NV habitat, which had the simplest structures. The distribution of the small fish species showed seasonal variations. In winter, most species concentrated in the V habitat, which had the most complex structure. In spring, the fish had low densities in the N and NV habitat, and were more or less evenly distributed in the other habitats. In summer, the fish had a low density in the NV habitat, and were evenly distributed in the other habitats. In autumn, the fish had higher densities in the V–M and M habitats than in the others. Generally, spatial overlaps between the dominant species were higher in winter than in the other seasons. It was suggested that the variations in the importance of predation risk and resource competition in habitat choice determined the seasonal changes of spatial patterns in the small fishes in the Biandantang Lake.     

Preliminary evidence for a two‐for‐one deal: Wetland restoration for a threatened frog may benefit a threatened bat

Habitat restoration is an integral feature of wildlife conservation. However, funding and opportunities for habitat restoration are limited, and therefore, it is useful for targeted restoration to provide positive outcomes for non‐target species. Here, we investigate the possibility of habitat creation and management benefitting two threatened wetland specialists: the Green and Golden Bell Frog (Litoria aurea) and the Large‐footed Myotis (Myotis macropus). This study involved two components: (i) assessing co‐occurrence patterns of these species in a wetland complex created for the Green and Golden Bell Frog (n = 9) using counts, and (ii) comparing foraging activity of Large‐footed Myotis in wetlands with low and high aquatic vegetation (n = 6 and 7, respectively) using echolocation metres. Since Large‐footed Myotis possesses a unique foraging behaviour of trawling for aquatic prey, we hypothesised that foraging activity of this species would be higher in wetlands with low aquatic vegetation coverage. Additionally, we provide observations of its potential prey items. We identified one created wetland where both species were found in relatively high numbers, and this wetland had a permanent hydrology, was free of the introduced fish Gambusia (Gambusia holbrooki) and had low aquatic vegetation coverage. We also found that Myotis feeding activity was significantly higher in low aquatic vegetation coverage wetlands (x? = 65.72 ± 27.56 SE) compared to high (x? = 0.33 ± 0.33 SE, P = 0.0000). Although this is a preliminary study, it seems likely that Green and Golden Bell Frog and Large‐footed Myotis would gain mutual benefit from wetlands that are constructed to be permanent, that are Gambusia free, low in aquatic vegetation coverage, and are located in close to suitable roosting habitat for Large‐footed Myotis. We encourage adaptive aquatic vegetation removal for Green and Golden Bell frog as this may have benefits for Large‐footed Myotis. The evidence suggests that the former may be a suitable umbrella species for the latter.     

Management of an ornamental pond as a conservation site for a threatened native fish species, crucian carp Carassius carassius

Ornamental ponds are important sites for conserving threatened native fish species (e.g. crucian carp Carassius carassius L.), but pond management plans rarely include considerations of native fishes. We developed and implemented a management plan for a small (0.8 h), ornamental estate pond in Hertfordshire (England) using historical information (aquatic plant and animal surveys) and a 9-year data set on climatic variables and crucian carp body condition. Crucian carp growth was not correlated with climatic variables, but body condition decreased with increasing temperature (in degree-days), which suggests that temperature influences on growth are counter-balanced by environmental factors. Management included the removal of one fish species (to eliminate hybridization with another species) and the introduction of two native species (to re-balance the fish assemblage), a reduction in floating aquatic plants (to reduce shading of the sediments) as well as the use of a chemical agent to compact the pond’s fine sediments and barley straw to enhance invertebrate habitat and thus fish prey production. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli and S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

Current distribution and ecology of the critically endangered <Emphasis Type="Italic">Valencia letourneuxi</Emphasis> in Greece

The current population status of the critically endangered Greek valencia Valencia letourneuxi (Sauvage, 1880), is presented, based on a thorough survey of low-altitude aquatic systems of Western Greece. The species’ historical geographical range appears to have been reduced, with the westernmost and southernmost populations being currently extinct or near extinction respectively, and the remaining ones in a vulnerable state. According to univariate and multivariate analysis, V. letourneuxi exhibits habitat specificity, with a strong affinity towards spring-fed wetlands with clear waters and rich surface vegetation, being thus vulnerable to human-induced habitat modifications and hydrological changes. The impact of the above threats, as well as of the introduction of alien species such as the mosquitofish Gambusia holbrooki is discussed.     

Aquatic faunal responses to an induced regime shift in the phosphorus‐impacted Everglades

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Importance of Shallow Water Habitats for Demersal Fishes and Decapod Crustaceans in Penobscot Bay, Maine

We characterized demersal fish and decapod crustacean habitats in 14 shallow (< 12m) areas in Penobscot Bay, Maine, by mapping the distribution of subtidal substrata with an acoustic sea bottom profiler. We identified the aquatic vegetation and the fishes and decapods associated with these habitats. Samples of fishes and decapods in each habitat were collected with a small beam trawl. The seabed at most of the stations sampled was composed of a mosaic of substrata. More species of fishes tow^-1 and higher abundances of fishes and decapods were found in stations with vegetation present, particularly eelgrass, Zostera marina. Decapod species richness tow^-1 was similar between vegetated and unvegetated habitats. Shallow habitats in Penobscot Bay were dominated by juvenile fishes and function as nursery areas. The greater species diversity and higher abundances of epibenthic fishes and decapod crustaceans observed in vegetated habitats, particularly beds of Zostera marina, compared with unvegetated areas in Penobscot Bay conform to the hypothesis that increased habitat complexity results in increased species richness and abundance.The first author is also senior author     

An experimental study of habitat choice by Daphnia: plants signal danger more than refuge in subtropical lakes

1. In shallow temperate lakes, submerged plants often provide refuge for pelagic zooplankton against fish predation, a mechanism with potential strong cascading effects on water transparency and on the entire ecosystem. In (sub)tropical lakes, however, the interaction between aquatic plants and predation may be more complex, particularly because fish density is high within the plant beds in such systems. 2. Using laboratory ‘habitat choice’ experiments, we determined the effects of three (sub)tropical free‐floating plants, Eichhornia crassipes, Pistia stratiotes and Salvinia auriculata and the cosmopolitan submerged Ceratophyllum demersum, on horizontal movement by the water flea Daphnia obtusa. We tested for avoidance of plants in the absence and presence of alarm signals from crushed conspecifics and chemical cues from the fish Cnesterodon decemmaculatus, the fish have been subjected to different feeding regimes. 3. In the absence of other stimuli, D. obtusa strongly avoided the plants and the crushed conspecifics, as expected. However, the response to fish was insignificant regardless of their previous feeding regime. The avoidance of free‐floating plants was more pronounced than that of the submerged plant. Contrary to predictions based on research in temperate lakes, Daphnia did not take refuge among the plants but rather swam away from them when exposed simultaneously to plants and alarm signals. 4. We hypothesise that the avoidance of plants by D. obtusa may ultimately be attributable to an expectedly higher predation risk within the plants than in the pelagic, because of a high density of associated zooplanktivorous fish in the former. In the (sub)tropics, therefore, aquatic plants and particularly the free‐floating ones, may not promote cascading effects via Daphnia grazing on phytoplankton as seen in temperate eutrophic lakes.