The reproductive strategy of Leporinus friderici (Characiformes, Anostomidae) in the Paraná River basin: the effect of reservoirs

Abstract

The reproductive strategy of a species depends upon the interaction between intrinsic and extrinsic factors. Examining the population of Leporinus friderici in two reservoirs of the Upper Paraná River basin in reference to first gonadal maturation and breeding season and sites, the present investigation tested whether the environment formed by damming promoted spatial and temporal changes in the reproductive strategy of this species. Analyses of sex ratios showed that females significantly predominated in Itaipu, while in Corumbá the sexes were about equal with a slight predominance of males. Size-associated sexual dimorphism was observed, that is females dominated the longer length categories, and males the shorter. The minimum size at which L. friderici initiated reproduction varied from year to year, and was larger in the periods soon after formation of both reservoirs. In Itaipu, stabilization between the maximum and minimum lengths at first maturation was also noted after year 6 following closure and continuing until year 15. In general, the breeding season lasted from October through April, although cyclic changes in the duration and intensity of this season were evident. Young individuals predominated during the entire study period in Corumbá. The formation of Itaipu Reservoir had a greater effect on the reproduction of L. friderici, where a gradual adaptation of the reproductive strategy of this species may possibly have been occurring. It is also possible that some of the characteristics of the Itaipu population will in the future be shown by the Corumbá population. It was concluded that reproductive strategies constitute ecological adaptations that are temporally and spatially altered and are fitted to resource availability and environmental pressure.

Reproductive and feeding biology of Acestrorhynchus pantaneiro Menezes, 1992 (Osteichthyes: Acestrorhynchidae) in areas under the influence of dams in the upper Uruguay River, Brazil

“…Mature and spent females were registered in the winters of 2001, 2003, and 2005, albeit in small numbers. Lopes et al (2000) also reported cyclical changes in the duration and intensity of the reproductive period for Leporinus friderici in the Itaipu Reservoir. Acestrorhynchus pantaneiro presented a long reproductive period, similar to other species of peixe-cachorro, such as Galeocharax knerii (Magalhães et al, 2004).…”

Reproductive tactics used by the Lambari Astyanax aff. fasciatus in three water supply reservoirs in the same geographic region of the upper Iguaçu River

“…In addition, the differentiated growth rates, the high mortality of males, the high longevity of females or even the susceptibility to the fishing equipment used may explain the predominance of females (Abilhoa & Agostinho, 2007). It could even be associated with the abundance of available food (a response of the species to this condition) (Lopes et al, 2000).…”

“…Initially, after the implementation of a reservoir, a restructuration of the fish community will contribute to the reduction and/or the disappearance of species, including reophilic ones, in addition to probably producing an increase in species adapted to lentic environments , which present a high physiological tolerance and behavioral adaptability, leading to plasticity and, consequently, reproductive success (Gray et al, 2000;Lopes et al, 2000;Mammoliti, 2002;Dias et al, 2005).…”

Population structure and reproduction of a migratory fish Leporinus piau (Characiformes: Anostomidae) in a semiarid tropical reservoir, Brazil

“…Differences in the length structure between females and males are common in fish populations and reflect growth rate differences between sexes (Sparre & Venema, 1997). These differences have been observed for other species of Leporinus in the Upper Paraná River basin reservoirs, such as Leporinus friderici in the Itaipu and Corumbá reservoirs (Lopes, Benedito-Cecilio, & Agostinho, 2000), and L. ambryrhynchus in the Miranda Reservoir (Vono, Silva, Maia, & Godinho, 2002). Significant differences in length structure were not observed between female and male L. piau at the Pau dos Ferros Reservoir, indicating that the growth rate was similar for both genders.…”