Alimentação de peixes piscívoros antes e após a formação do reservatório de Salto Caxias, Paraná, Brasil

Abstract

(post-impoundment period) within the reservoir. Stomach contents of 549 individuals were analyzed and the diet was described as occurrence and volumetric percentage of each item combined in a feeding index. The piscivorous habit was, overall, more evident in H. malabaricus, O. longirostris and R. voulezi. However, for R. branneri mollusks and crabs were more important than fish. After the impoundment, most consumed prey was Astyanax sp. b and Cyphocharax modestus for three of the predators. These prey species were more abundant after the impoundment. Then, there are evidences that the availability, abundance and vulnerability of prey in the reservoir environment are the most important factors influencing predator's choice.Keywords

Ecomorphological differences between Rhamdia (Bleeker, 1858) populations from the Iguaçu River basin

“…On the other hand, other authors (Cassemiro et al 2005, Novakowski et al 2007 found dietary differences between R. branneri and R. voulezi. However, patterns in the diet of these fishes were not clearly defined, occurring local variations (Cassemiro et al 2005).…”

“…The ecomorphological indices related to occupation of lentic habitats probably favored R. voulezi to feed on prey that explore the bottom, such as Cyphocharax modestus (Fernández-Yépez 1948), and fishes that can forage in shallow waters, such as some species of Astyanax ). These two prey types were the most consumed by piscivores in Salto Caxias Reservoir (Novakowski et al 2007). The ecomorphological characteristics related to benthic fishes (depressed body) in R. branneri may have favored the ingestion of benthic crustaceans as Aegla sp.…”

“…Cassemiro et al (2005) verified that, in Salto Caxias Reservoir, Rhamdia species fed exclusively on fishes after the impoundment, differently from the previous phases when invertebrates and crustaceans were also consumed. Other authors recorded significant differences in diet in the impoundment phases with R. voulezi consuming fishes, and R. branneri feeding on crustaceans and terrestrial insects (LoureiroCrippa & Hahn 2006, Novakowski et al 2007). The dietary changes can be certainly related to environmental changes caused by impoundments, since fishes and insects are abundant food resources in reservoirs .…”

Effects of river damming in Neotropical piscivorous and omnivorous fish: feeding, body condition and abundances

“…The high availability of allochthonous resource in the environment, may cause a positive effect in the production of all trophic levels, an event known as the trophic upsurge period (Kimmel & Groeger, 1986;O'Brien, 1990;Gubiani et al, 2011). The high availability of small body size species in the new environment should increase the frequency of fish with a carnivorous fish diet (Novakowski et al, 2007) or even lead some omnivorous species to piscivory (Luz- Agostinho et al, 2006;Delariva et al, 2007). Although the nutritional quality of a fish-based diet should be higher than one based on other items, such as invertebrates, due to its high protein (Anthony et al, 2000) and energy content (Davis et al, 1998), the organism's response to this consumption should differ according to the species diet in the natural environment.…”

Piscivory by Hoplias aff. malabaricus (Bloch, 1794): a question of prey availability?

“…Several studies investigated the role of predation on population dynamics (e.g. Novakowski et al, 2007). Some of the well known positive effects of predation come about from the selective pressure directed to weaker prey individuals, and the control of dominant species, therefore maintaining appropriate levels of diversity (Popova, 1978).…”