Fish fauna destruction after the introduction of a non-native predator (Cichla kelberi) in a Neotropical reservoir

In South America, the introduction of peacock-bass (Cichla), a voracious predator fish, has been an underestimated threat for native fish communities. Although this predator is widespread in many reservoirs, few studies have explored its impact on biodiversity. To investigate the relationship between invasion and fish diversity, the present study followed a natural experiment in the Rosana Reservoir (Paraná River basin), where Cichla kelberi were introduced in 2004. We monitored fish assemblages associated with submerged macrophytes between 2003 and 2007, using a 1 m² throw trap. In the years following the introduction, fish diversity dramatically changed. For example, in March 2007, mean fish density and richness were reduced by ca. 95 and 80%, respectively, and many small-sized species had vanished. One aspect was the gradual change of biodiversity, which unfolded at two times during each year: (1) impacts during summer/autumn periods, which coincided with large shoals of young C. kelberi in the patches; and (2) assemblage recovery during the spring. The sequence of extinction-colonization events, however, might not be able to maintain fish assemblages due to the decrease in recovery intensity each spring; assuming a constant decline rate in the coming years, we predict complete assemblage extinction by the summer of 2010. Results from this natural experiment provided evidence supporting the collapse of fish assemblages soon after the introduction of C. kelberi. Such rapid destruction (2 years) reveals an important homogenizing force behind this predator and stresses the need for control measures that prevent new transferences among South American basins.     

Recognition of non-native peacock bass, <Emphasis Type="Italic">Cichla kelberi</Emphasis> by native prey: testing the naiveté hypothesis

Prey naiveté is proposed as one of the main reasons behind species extinctions attributed to invasive predators. This study examined whether the naiveté hypothesis could explain extinctions after the introduction of peacock bass (Cichla kelberi) in Paraná River, Brazil. Our results show that prey responded to both visual and chemical cues of peacock bass. Displayed avoidance behaviors were equal to or greater than those observed with a native predator, Hoplias malabaricus. We conclude that lack of recognition was not responsible for the observed vulnerability of native species to this introduced predator. Finally, we discuss implications of these findings for the native biodiversity and convene other potential explanations for the observed effects of peacock bass on native prey.     

Comparative functional responses predict the predatory impact of the highly invasive fish Cichla kelberi

Hydrobiologia - Peacock basses (genus Cichla) are a group of Amazonian predatory fishes that invaded many systems worldwide. Severe ecological impacts have been reported, but no study investigated...     

Polychromatism in native populations of peacock basses Cichla kelberi and Cichla piquiti (Cichlidae)

Environmental Biology of Fishes - The present study described in detail the occurrence of polychromatism in two peacock bass species (Cichla kelberi and Cichla piquiti) endemic to the...     

Temporal organization of fish assemblages in floodplain lagoons: the role of hydrological connectivity

The present study evaluated the hypothesis that after flooding events, non-random patterns of species co-occurrence (segregation) are progressively intensified in fish assemblages inhabiting seasonally isolated lagoons. We sampled lagoons in the upper Paraná River floodplain between 1992 and 1993, and classified them into five hydrological phases, according to their surface connectivity. During the period of isolation (9 months), lagoons depth decreased progressively, but desiccation was reversed after 4 months (possibly due to groundwater infiltration and rainfall). A significant co-occurrence pattern (segregation) occurred in the last phase, supporting our initial hypothesis. However, richness, abundance and composition were significantly correlated with habitat depth, indicating that assemblage structure and organization is closely associated with dynamics of habitat retraction/expansion during isolation. Although environmental conditions of lagoons (absence of prolonged desiccation) prevented an adequate test of our hypothesis, our data suggests that, in addition to the importance of surface floods, the hydrological cycle as a whole has a crucial role shaping the organization of fish assemblages in floodplain lagoons seasonally isolated.     

The role of submerged trees in structuring fish assemblages in reservoirs: two case studies in South America

The importance of subaquatic structures in determining fish assemblages is well documented in the literature, but few studies have examined the influence of submerged vegetation resulting from river impoundments in which arboreal vegetation was not removed. The purpose of this study was to evaluate the role of submerged trunks determining abundance and composition of fish assemblages by comparing habitats with and without them in two reservoirs of different ages. The results of this study demonstrated the importance of structured areas (with submerged vegetation) to the abundance of fish in both reservoirs. However, the role of these structures in maintaining species richness and diversity was significant only during the initial years after the impoundment. The occupation of these habitats by small invertivorous fish indicates that the non-removal of arboreal vegetation in these reservoirs contributes to the increase of their biogenic capacity. In addition, vegetation provides shelter against predation. Considering the conservation of fishery resources, we conclude that the pre-removal of arboreal vegetation in new reservoirs should be allowed only to the extent necessary to maintain acceptable water quality, even considering transitory and localized hypoxic processes.     

First record of the mating behaviour of the spotted surubim Pseudoplatystoma corruscans in the Uruguay River

The spotted surubim Pseudoplatystoma corruscans is a large migratory catfish native to the La Plata and San Francisco basins. Nonetheless, its reproductive dynamics and behaviour remain poorly understood. This brief note provides the first record of the mating behaviour of P. corruscans in natural conditions. This behaviour was observed in the main channel of the Middle Uruguay River (Brazil). A school of approximately 25 fish, 5 females (with protruding abdomen and larger body size) and 20 males, were followed and videotaped. The largest female led the school, followed by other fish. Some males disputed repeatedly the posterior region of the females, whereas other males continuously repelled them. Eventually, some males, apparently exhausted, floated belly up. During this event, males were in a state of pronounced agitation, and some had abrasions in the head. Polygamy characterized the mating behaviour of P. corruscans.     

Riverine networks constrain β‐diversity patterns among fish assemblages in a large Neotropical river

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First record of pughead deformity in Cichla kelberi (Teleostei: Cichlidae), an invasive species in an estuarine system in south‐eastern Brazil

The first record of pughead deformity in a Neotropical freshwater fish not raised in captivity is provided, based on an adult male of Cichla kelberi introduced into an estuary of Rio de Janeiro State, south‐eastern Brazil. A general biological characterization of the specimen is provided and aspects of its aberrant anatomy are described. Environmental and biological factors that may cause pughead deformity in fishes are discussed.