Presence Of Predatory Fish Research Articles

Benthic community zonation from mesophotic to deep sea: Description of first deep-water kelp forest and coral gardens in the Madeira archipelago (central NE Atlantic)

The Madeira archipelago has a unique underwater landscape that is characterised by narrow shelves, steep slopes and a large submarine tributary system that boosts primary productivity in oligotrophic waters and thus offers a potential for hotspots of biodiversity. Despite this, there have been limited deep-water exploration activities with less than five expeditions since the 1960s. Here, we investigated the seabed on the southern side of the Madeira-Desertas Ridge using a manned submersible along a 3.8 km long transect starting at 366 m depth up the ridge shelf until its top at 73 m. Benthic habitats and community composition were documented with video along a depth gradient from mesophotic to deep sea. Six distinct biotopes were recognised (three deeper, and three shallower than 115 m depth). Our results showed a rich biodiversity with deep biotopes characterised by sponges and non-reef-building corals (e.g., Pachastrella monilifera, Viminella flagellum, Eunicella verrucosa) and shallow biotopes comprising macroalgae and the gorgonian Paramuricea cf. grayi. The pronounced benthic zonation reflects the steep environmental gradient that includes high topographic variation, heterogeneous substrates, and bidirectional regular wave-motion at the shallow mesophotic part. Together with biotic factors, such as low density of sea urchins and presence of predatory fish, this environment with unusual deep light penetration, a mesoscale cyclonic eddy, and deep wave-motion, has allowed the establishment of a mature deep-water kelp population of Laminaria ochroleuca in the plateau (max. >100 individuals p/100 m2). At the same time, a conspicuous coral fauna was observed on a wide range of soft to hard bottoms with several species taking advantage of the favourable hydrodynamic regime and seawater properties together with substratum availability to create coral gardens. These habitats were previously not known from Madeira, and their newfound discovery in the archipelago merit further investigation and protection.

Community variability in pond metacommunities: interactive effects of predators and isolation on stochastic community assembly

In the absence of environmental heterogeneity, spatial variation among local communities can be mostly attributed to random dispersal, demographic stochasticity and species interactions causing historical contingency in colonization (e.g. priority effects). The consequences of demographic stochasticity and random dispersal are highly dependent on community size, regional richness and local richness, which, along with historical contingency can be strongly affected by spatial isolation and the presence of predators. Here, we tested whether and how the presence of a generalist predatory fish and spatial isolation can change spatial community variability in artificial ponds by manipulating the presence/absence of fish (redbreast tilapia) at three different distances from a source wetland. We then used null models to compute how much the observed community variability within treatments deviates from the expected from randomly reassembled communities (i.e. beta‐deviation). We found that spatial isolation can have both negative and positive effects on community variability, and their importance may depend on the presence of predatory fish. Negative effects likely occurred because predatory insects cannot always successfully colonize highly isolated ponds, causing the abundance of herbivores and detritivores to increase, consequently increasing community size, which is known to decrease the importance of demographic stochasticity. However, when fish are absent, the more isolated communities exhibit more community variability than is expected from random community assembly. We believe that such an increase in variability is most likely due to an increase in the importance of historical contingency in colonization, generating more distinct communities in isolated ponds. Such effects were absent in the presence of generalist predatory fish, likely because fish prevented any early colonizing taxa from becoming too abundant. Our findings show that the presence of generalist predators can change how community variability responds to spatial isolation.

Late-Season Movement and Habitat Use by Oregon Spotted Frog (Rana pretiosa) in a Large Reservoir in Oregon, USA

Dam-created reservoirs are common landscape features that can provide habitat for amphibians, but their water level fluctuations and nonnative predators can differ markedly from more natural habitats. We compared fall movement and habitat use by the Oregon Spotted Frog (Rana pretiosa) in the reservoir pool with nearby river and pond habitats at Crane Prairie Reservoir in central Oregon, USA. Movement rate of frogs in the river and ponds declined as water temperature cooled. Reservoir frogs moved further than those in the river or ponds, and their movement rate increased as water temperature cooled. Most frog locations across all site types were in aquatic herbaceous vegetation. We did not find shifts in habitat between early and late fall. Increased movement and the lack of habitat shift in our reservoir frogs deeper into fall contrast with R. pretiosa in non-reservoir sites in this study and others. Consistent use of vegetation by reservoir frogs throughout the fall could indicate cover use in presence of fish predators. Our study provides additional detail on the range of habitats used by R. pretiosa in fall and suggests areas for further work to improve survival in constructed sites with abundant fish predators.

Habitat segregation of plate phenotypes in a rapidly expanding population of three‐spined stickleback

AbstractDeclines of large predatory fish due to overexploitation are restructuring food webs across the globe. It is now becoming evident that restoring these altered food webs requires addressing not only ecological processes, but evolutionary ones as well, because human‐induced rapid evolution may in turn affect ecological dynamics. We studied the potential for niche differentiation between different plate armor phenotypes in a rapidly expanding population of a small prey fish, the three‐spined stickleback (Gasterosteus aculeatus). In the central Baltic Sea, three‐spined stickleback abundance has increased dramatically during the past decades. The increase in this typical mesopredator has restructured near‐shore food webs, increased filamentous algal blooms, and threatens coastal biodiversity. Time‐series data covering 22 years show that the increase coincides with a decline in the number of juvenile perch (Perca fluviatilis), the most abundant predator of stickleback along the coast. We investigated the distribution of different stickleback plate armor phenotypes depending on latitude, environmental conditions, predator and prey abundances, nutrients, and benthic production; and described the stomach content of the stickleback phenotypes using metabarcoding. We found two distinct lateral armor plate phenotypes of stickleback, incompletely and completely plated. The proportion of incompletely plated individuals increased with increasing benthic production and decreasing abundances of adult perch. Metabarcoding showed that the stomach content of the completely plated individuals more often contained invertebrate herbivores (amphipods) than the incompletely plated ones. Since armor plates are defense structures favored by natural selection in the presence of fish predators, the phenotype distribution suggests that a novel low‐predation regime favors stickleback with less armor. Our results suggest that morphological differentiation of the three‐spined stickleback has the potential to affect food web dynamics and influence the persistence and resilience of the stickleback take‐over in the Baltic Sea.

Mosquito oviposition and larvae development in response to kairomones originated by different fish.

Predator-released kairomones indicating the presence of predatory fish are known to alter the behaviour and life-history traits of several aquatic herbivores. Culex mosquitoes (Diptera: Culicidae) respond to such cues by altering oviposition habitat selection and larval development time. These responses differ among fish species indicating composition differences among fish-released cues, but the recognition pattern is not clear. This study tested the dependence of fish recognition to co-evolution and the level of threat to larvae. We compared Culex responses to three fish, the invasive larvivorous Gambusia affinis (Cyprinodontiformes: Poeciliidae), the native larvivorous Aphanius mento (Cyprinodontiformes: Cyprinodontidae) and the native algivorous Garra rufa (Cypriniformes: Cyprinidae). The effects of cues released by the three fish on Culex oviposition and life-history shifts were compared in field mesocosms and lab tests. Our results showed that ovipositing females were significantly repelled only by cues originated from G. affinis, while developing larvae response was a more general one. Our results support the idea that fish-released kairomones differ in composition or quantities among different species.

Effects of Fish Predators on the Mass-Related Energetics of a Keystone Freshwater Crustacean.

Little is known about how predators or their cues affect the acquisition and allocation of energy throughout the ontogeny of prey organisms. To address this question, we have been comparing the ontogenetic body-mass scaling of various traits related to energy intake and use between populations of a keystone amphipod crustacean inhabiting freshwater springs, with versus without fish predators. In this progress report, we analyze new and previously reported data to develop a synthetic picture of how the presence/absence of fish predators affects the scaling of food assimilation, fat content, metabolism, growth and reproduction in populations of Gammarus minus located in central Pennsylvania (USA). Our analysis reveals two major clusters of ‘symmorphic allometry’ (parallel scaling relationships) for traits related to somatic versus reproductive investment. In the presence of fish predators, the scaling exponents for somatic traits tend to decrease, whereas those for reproductive traits tend to increase. This divergence of scaling exponents reflects an intensified trade-off between somatic and reproductive investments resulting from low adult survival in the face of size-selective predation. Our results indicate the value of an integrated view of the ontogenetic size-specific energetics of organisms and its response to both top-down (predation) and bottom-up (resource supply) effects.

Changes in a Fish Community in a Small River Related to the Appearance of the Invasive Topmouth Gudgeon Pseudorasbora parva (Temminck & Schlegel, 1846)

In recent years, the topmouth gudgeon (Pseudorasbora parva) has been one of the most invasive fishes in Europe. Pseudorasbora parva can potentially affect ecosystems, fish communities, and particular fish species. Electrofishing was carried out over a five-year period at three study sites in the Ciemięga River (eastern Poland) before and after P. parva had been found in the river. Changes in the occurrence, abundance, and density of native fish species after the appearance of the invader were determined. Changes in the species’ richness were calculated, and correlations were estimated between the occurrence and density of P. parva and particular fish species and richness indices. The presence of P. parva has not affected the density of native species but coincides with a significant increase in estimated species richness and the total density of fish. There was a significant relationship between the presence of this invasive species and the fish community’s composition, though the PERMANOVA result was unclear with regards to site-specific effects. Moreover, tench and bleak were associated positively, whereas Eurasian perch and sunbleak were associated negatively with the occurrence of P. parva. Pseudorasbora parva density was highly correlated with Cyprinidae density (excluding P. parva), species richness, and the Margalef diversity index. Thise study has shown that the presence of predatory fish in the river (Salmo trutta L.) may reduce the numbers of invasive P. parva.

Combined Effects of Environmental Drivers on Marine Trophic Groups – A Systematic Model Comparison

The responses of food webs to simultaneous changes in several environmental drivers are still poorly understood. As a contribution to filling this knowledge gap, we investigated the major pathways through which two interlinked environmental drivers, eutrophication and climate, affect the biomass and community composition of fish and benthic macrofauna. For this aim, we conducted a systematic sensitivity analysis using two models simulating the dynamics of benthic and pelagic food webs in the Baltic Sea. We varied environmental forcing representing primary productivity, oxygen conditions and water temperature in all possible combinations, over a range representative of expected changes during the 21st century. Both models indicated that increased primary productivity leads to biomass increase in all parts of the system, however counteracted by expanding hypoxia. Effects of temperature were complex, but generally small compared to the other drivers. Similarities across models give confidence in the main results, but we also found differences due to different representations of the food web in the two models. While both models predicted a shift in benthic community composition towards an increased abundance of Limecola (Macoma) balthica with increasing productivity, the effects on deposit-feeding and predatory benthic groups depended on the presence of fish predators in the model. The model results indicate that nutrient loads are a stronger driver of change for ecosystem functions in the Baltic Sea than climate change, but it is important to consider the combined effects of these drivers for proper management of the marine environment.

Distribution of migratory fish in the stream (depth, velocity, body size, predators)

In order to supplement the available information for the eco-hydraulic approach to designing fish passages, taking into account the taxonomic, dimensional structure, as well as taking into account the presence of predatory fish in the stream, the distribution of migratory fish of the boreal plain faunistic complex (Russian Federation) was studied. Three depth-velocity sections from the shore to the midstream were investigated: 5 m and 27.8 cm/s, 8 m and 44.4 cm/s, 11 m and 55.6 cm/s. Analysis of the migration distribution of fish showed that in the direction from the shore to the midstream, the proportion of representatives of Cyprinidae decreases from 41.8–24.3% and that of Percidae decreases from 25.0–18.4%. For individuals of two groups: the Acipenseridae and Lotidae, Coregonidae and Esocidae, patterns of distribution in the structure of migratory fish are opposite – their share increases with increasing speed and depth characteristics: 23.0–40.2% and 10.2–17.1%, respectively. An assessment of the dimensional structure revealed a feature of increase in the size range of fish from the shore to the midstream: the dominance of small individuals (<10 cm) in the shore area is replaced by the dominance of large fish (> 30 cm) in the area of higher speeds and depths. A significant difference in the distribution for all studied taxonomic fish groups between the shore and the midstream was shown. Thus, it has been established that for Cyprinidae during the migration period, the choice shifts in favour of minimizing energy costs, and the choice to avoid the risk of predation from individuals of the groups: Coregonidae and Esocidae, and also Percidae, shifts in favour of the former. The distribution of perch is influenced by the reduction of energy costs and the simultaneous avoidance of predation and cannibalism. For the fish group Acipenseridae and Lotidae, their predominance in the deeper area is due to their less developed visual orientation mechanism in the stream because they are bottom-living fish species.

Influence of plant habitat types and the presence of fish predators on macroinvertebrate assemblages in southern Brazilian highland wetlands

Influence of plant habitat types and the presence of fish predators on macroinvertebrate assemblages in southern Brazilian highland wetlands

Partitioning tadpole beta diversity in highland ponds with different hydroperiods

Pond hydroperiod and other aspects of environmental heterogeneity play important roles in metacommunity organization in freshwater systems. We examined tadpole species richness and dissimilarities among assemblages at different hydroperiods (3, 7, and 13 mo) in highland ponds in the Araucaria moist forest ecoregion of southern Brazil. We also investigated whether β diversity components changed in accordance with spatial and environmental factors. We sampled tadpoles at 18 ponds between September 2012 and April 2013. Tadpole species richness was lower in permanent than in temporary ponds, but pond hydroperiod was not associated with tadpole abundance and species dissimilarities. β diversity was almost completely caused by species replacement associated with pond area, presence of predatory fish, and type of margin. Despite its small contribution, the nestedness component was associated with water depth and geographic patterns. Our study suggests that tadpole communities in the highlands of Araucaria moist forests are niche structured.

Environmental predictors for annual fish assemblages in subtropical grasslands of South America: the role of landscape and habitat characteristics

Annual fishes (AF) are ecologically unique assemblage with major conservation concern. Several AF species are found in temporary waters of South American subtropical grasslands, an ecoregion largely neglected by conservation policies. We applied a broad-scale approach to understand distribution pattern of the AF and tested the effects of environmental predictors on occurrence, abundance and assemblage structure of this diverse Neotropical group of threatened endemic aquatic fauna. We recorded 23 AF species. AF assemblage was strongly spatially structured and many individual species formed discrete units. AF presence was negatively associated with altitude at the landscape scale, and negatively associated with maximum pool depth and presence of predatory fish at the local scale. We found negative association between AF abundance and water depth. Assemblage composition was spatially structured, differed among hydrographic regions and was influenced by altitude, temperature and monthly precipitation. AF inhabits highly vulnerable habitats currently located in livestock and agricultural landscapes. Habitat maintenance through wildlife-friendly practices should be considered as an alternative to promote AF conservation.

Effects of fish predators and litter pack size on leaf breakdown in a subtropical stream

Many studies have examined trophic cascades in allochthonous lotic systems of temperate streams, but few have examined those in subtropical and tropical streams. Many subtropical and tropical streams are characterised as detritivore-poor stream systems, which might result in a fundamental difference in the trophic cascades of brown food webs. We performed an in situ experiment to test the effects of the presence or absence of a small-bodied endemic benthic fish and of the mass of litter packs (five levels), arranged in a full factorial design (10 treatments), on macroinvertebrate detritivore assemblages and invertebrate-mediated breakdown rates and to identify possible trophic cascades. Fish slightly reduced the invertebrate-mediated breakdown rates by depressing detritivore abundance. Effects of fish predators and litter pack size on detritivore abundance were species dependent. Nemouridae (Plecoptera), a non-camouflage detritivore (without a casing), was highly sensitive to the presence of fish predators. By contrast, camouflaged detritivores, such as Stenochironomus spp. (Diptera), which mine decayed leaves, and Anisocentropus sp. (Trichoptera), a case-building caddisfly, were able to avoid being preyed upon and thereby buffered the effect of predation on litter processing. These results suggest that ecosystem functioning of detritus-based stream systems could be regulated by the traits of dominant detritivores.

The release and regulation of rotifers: examining the predatory effects of invasive juvenile common and bighead carp

Ecosystem level effects of common (Cyprinus carpio) and bighead carp (Hypophthalmichthys nobilis) have generally focused on adult life stages. The objective of our mesocosm study was to investigate and contrast the roles of juvenile common and bighead carp in structuring planktonic invertebrate assemblages, with focus on rotifers. We examined whether predation by juvenile carp was indiscriminate or size-selective with respect to prey size. Furthermore, we examined how changes to large and small prey influenced the potential for compensatory increases of some taxa within prey assemblages. Both species of juvenile carp reduced large zooplankton taxa. However, rotifer responses were variable depending on the taxon and predator combination. Juvenile common carp enhanced abundance for Polyartha and Squatinella, but most taxa were unaffected. Juvenile bighead carp had a more varied effect on rotifer abundance, having no effect on most, reducing Keratella and enhancing Anuraeopsis. We also estimated net filtration volume of the zooplankton community for each of the treatments and found partial compensation in net filtration because of the increased abundance of a few rotifer taxa, but this reduction did not match the depletion of macrozooplankton. Rotifers that benefitted from the presence of fish predators likely responded positively because of reduced predation by mesopredators, because of their short generation times, and/or from reduced competition.

Trophic roles of tadpoles in tropical Australian streams

Abstract Tadpoles can be abundant consumers in stream ecosystems, and may influence the structure and function of streams through their feeding activities and interactions with other organisms. To understand the contribution of tadpoles to stream functioning, and the potential impact of their loss, it is necessary to determine their diets and how they might influence food‐web structure. Using gut‐content analysis and stable‐isotope analysis of N and C, we determined the main food sources and trophic positions of tadpoles of five native frog species, invertebrates, and fish in upland and lowland Australian Wet Tropics streams. Omnivory was prevalent among the tadpoles and invertebrates. Tadpoles consumed different food according to availability and nutrient quality, but assimilated mainly biofilm and algae. Most tadpoles and invertebrates assimilated the same high‐quality foods. Food webs in upland riffles were simplified by local extinction of tadpoles, and were probably simplified in pools in the cooler months by seasonal decline in tadpole abundance. Food‐web complexity was increased in some pools by the presence of predatory fish and a greater number of basal sources. As tadpoles are important seasonal components in stream food webs, their local extinction can greatly alter food‐web structure and complexity and, possibly, processes such as leaf litter breakdown and sediment accumulation.

The Interactive Effects of Fish Predation and Conspecific Density on Survival and Growth of Tadpoles ofRana sylvaticain a Subarctic Wetland

In nature, prey are often simultaneously exposed to predators and competitors, leading to conflicting demands between survival and growth. Larval amphibians are model organisms to investigate the balancing of life history trade-offs because individuals must metamorphose before a wetland dries. Therefore, we deployed enclosures in a natural wetland to investigate the interactive effects of Wood Frog (Rana sylvatica) density (50 or 100 tadpoles) and Brook Stickleback (Culaea inconstans) presence on survival and growth of tadpoles. We hypothesized that the effects of conspecific density on tadpole survival and growth would be dependent on the presence of fish predators. Stickleback predation significantly decreased Wood Frog survival; however, a trend of higher tadpole survival with fish was detected at high conspecific densities. Wood Frog time to and mass at metamorphosis was not significantly affected by either conspecific density or stickleback presence. Our results demonstrate that Brook Sticklebacks ca...

Tree Climbing and Temporal Niche Shifting: An Anti-Predatory Strategy in the Mangrove Crab <i>Parasesarma plicatum</i> (Latreille, 1803)

Parasesarma plicatum , a common sesarmid crab in mangrove habitats of India, always climbs onto the mangrove vegetation during high tide. We studied whether this temporal niche shifting of the crab is an anti-predatory strategy against potential predators that invade their habitat during high tide. We studied the difference in density of this crab on the forest floor and vegetation during low and high tides in three selected study sites. Ex situ experiments were also conducted using the crab and a predatory fish simulating the habitat. The study confirmed that all the crabs climbed onto the vegetation from the forest floor during high tide and came down to the forest floor during low tide. Regression analysis revealed a positive correlation between water level and the height climbed by crabs on vegetation. Crabs completely migrated from sites which were fully submerged during high tide to nearby areas where mangrove trees and the shrub Acanthus ilicifolius provided them ample refuge above water level. Ex situ experiments showed that though P. plicatum could remain under water and feed in starved conditions, they climbed onto the vegetation above water level so as to seek refuge in the presence of predatory fish, Lutjanus argentimaculatus . Therefore, it is inferred that the tree-climbing character exhibited by P. plicatum is a strategy to escape from predators that invade their habitats during high tide inundation and flooding.

Characteristics of fatty acid composition of Gammarus lacustris inhabiting lakes with and without fish.

The effect of a biotic factor--the presence of predatory fish in water--on the composition and content of fatty acids in crustaceans was studied in the populations of the lake amphipod Gammarus lacustris from two lakes with fish and three lakes without fish. It was found that, at an overall increase in the quantity and quality of food resources (namely, increase in the content of eicosapentaenoic acid and docosahexaenoic acid (DHA) in the biomass), the relative rate of DHA accumulation in gammarids in the lakes without fish is higher than in the lake with fish.

Allometric differences between two phenotypes of the amphidromous shrimp Xiphocaris elongata

The amphidromous shrimp Xiphocaris elongata (Guerin-Meneville, 1855) has a long rostrum in the presence of predatory fishes and a short rostrum above steep waterfalls where predatory fishes are absent, i.e., typically above waterfalls. Prior experiments showed that elongated rostrum in X. elongata is induced by chemical signals from the predatory fish Agonostomus monticola . We tested the hypothesis that in addition to rostrum length there are other morphometric differences between long-rostrum (LR) and short-rostrum (SR) X. elongata . We measured the post-orbital carapace length and pleon length of LR and SR shrimp and weighed both shrimp morphs. LR shrimp have significantly longer and heavier pleons than the SR shrimp. These allometric differences may affect the behavior of X. elongata shrimp in ways that, in turn, affect their interactions with predators and the environment. Our study demonstrates the importance of taking pleon measurements when studying crustaceans given that these measurements have been mostly overlooked, and may provide insight of environmental influences on crustacean morphology and behavior. This research provides data of the differences between prey phenotypes, which may alter their life-histories and interactions with the environment.

Exotic Fish in Exotic Plantations: A Multi-Scale Approach to Understand Amphibian Occurrence in the Mediterranean Region.

Globally, amphibian populations are threatened by a diverse range of factors including habitat destruction and alteration. Forestry practices have been linked with low diversity and abundance of amphibians. The effect of exotic Eucalyptus spp. plantations on amphibian communities has been studied in a number of biodiversity hotspots, but little is known of its impact in the Mediterranean region. Here, we identify the environmental factors influencing the presence of six species of amphibians (the Caudata Pleurodeles waltl, Salamandra salamandra, Lissotriton boscai, Triturus marmoratus and the anurans Pelobates cultripes and Hyla arborea/meridionalis) occupying 88 ponds. The study was conducted in a Mediterranean landscape dominated by eucalypt plantations alternated with traditional use (agricultural, montados and native forest) at three different scales: local (pond), intermediate (400 metres radius buffer) and broad (1000 metres radius buffer). Using the Akaike Information Criterion for small samples (AICc), we selected the top-ranked models for estimating the probability of occurrence of each species at each spatial scale separately and across all three spatial scales, using a combination of covariates from the different magnitudes. Models with a combination of covariates at the different spatial scales had a stronger support than those at individual scales. The presence of predatory fish in a pond had a strong effect on Caudata presence. Permanent ponds were selected by Hyla arborea/meridionalis over temporary ponds. Species occurrence was not increased by a higher density of streams, but the density of ponds impacted negatively on Lissotriton boscai. The proximity of ponds occupied by their conspecifics had a positive effect on the occurrence of Lissotriton boscai and Pleurodeles waltl. Eucalypt plantations had a negative effect on the occurrence of the newt Lissotriton boscai and anurans Hyla arborea/meridionalis, but had a positive effect on the presence of Salamandra salamandra, while no effect on any of the other species was detected. In conclusion, eucalypts had limited effects on the amphibian community at the intermediate and broad scales, but predatory fish had a major impact when considering all the scales combined. The over-riding importance of introduced fish as a negative impact suggests that forest managers should prevent new fish introductions and eradicate fish from already-occupied ponds whenever possible.