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

Larissa Strictar Pereira,Rosilene Luciana Delariva,Angelo Antonio Agostinho

doi:10.1590/1982-0224-20150044

Larissa Strictar Pereira, Rosilene Luciana Delariva + Show 1 more

Open Access

https://doi.org/10.1590/1982-0224-20150044

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Abstract

ABSTRACT The increase in abundance of small-sized fishes is common after a reservoir is formed. There is an increase in the consumption of fish, from typically piscivorous fish to opportunistic species that take advantage of abundant resources. This study aims to evaluate the effects of diet changes induced by damming on the feeding activity and condition factor of typically piscivorous (Hoplias aff. malabaricus and Oligosarcus longirostris ) and opportunistic (Astyanax lacustris (ex Astyanax altiparanae ) and Pimelodus britskii ). Sampling was conducted before and after the impoundment in the Iguaçu River in the region of Salto Caxias, Paraná State, Brazil. Stomach contents were analysed by the volumetric method. Feeding activity and body condition were inferred by the mean stomach repletion index and the mean condition factor. Typically piscivorous species presented a general tendency of decreased feeding activity and increased condition factor, while opportunistic species, presented a decrease in condition and feeding activity in the most affected sites. The increase in the condition factor of piscivorous fish suggests that these species benefit by the increased abundance of small size prey fish. Some opportunist species that do not have adjustments for the piscivorous diet, regardless of the intensity of consumption and resource availability, can suffer negative reflex when adopting a piscivorous diet.

Highlights

Piscivorous fish impact the aquatic community and water quality (Nowlin et al, 2006) contributing to the stabilisation of food webs (Rooney et al, 2006)
All species considered in this study presented significant increases in abundance (CPUE), after damming
This was observed in the present study as the sites that presented the higher increases in prey abundance (DO and RE) presented the higher increases in piscivorous abundance, as observed for H. aff. malabaricus and O. longirostris, specialist piscivorous (Hahn & Fugi, 2008), that do not change their diet despite environmental changes, and for A. lacustris and P. britskii, in which the fish consumption was sporadic or even inexistent (Cassemiro et al, 2005; Luz-Agostinho et al, 2006)

Summary

Introduction

Piscivorous fish impact the aquatic community and water quality (Nowlin et al, 2006) contributing to the stabilisation of food webs (Rooney et al, 2006). The new environment is colonised largely by those species with pre-adaptations for the lentic condition (Fernando & Holcik, 1991) and those with opportunistic strategies. Dominant species in a new reservoir are small-sized, with feeding plasticity, low longevity and high reproductive performance (opportunist strategy, sensu Winemiller, 1989), denoting advantages in the colonisation process (Agostinho et al, 1999). This small sized species become an abundant resource and explains the success of piscivores after impoundments (Luz-Agostinho et al, 2006; Hahn & Fugi, 2007; Bennemann et al, 2011)

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