Abstract The rio da Dona is an important water body in the Recôncavo Sul basin used as a water supply for the neighboring towns and for agriculture, recreation and subsistence fishing. The knowledge about the ichthyofauna of this river is scarce. In this paper, an inventory of the fish fauna from rio da Dona basin and an identification key for the species recorded are presented. Additionally, taxonomic and conservationist issues are discussed. The specimens were collected in different sites along the upper, middle and lower courses of the rio da Dona. The fishes were anesthetized, fixed in formalin, conserved in ethanol, and identified. In addition to the material collected, specimens previously deposited in the ichthyological collection of the Museu de História Natural da Bahia were also analyzed. Twenty species, distributed into 16 genera, ten families, and four orders were recorded. One of these species, Aspidoras kiriri, is endemic to the rio da Dona. Four species, Cichla pinima, Coptodon rendalli, Poecilia reticulata and Serrasalmus brandtii, have been introduced into the river. Higher richness of native species has been recorded in the upper course of the rio da Dona, while in the middle and lower parts non-native species were also representative. Along the river, a series of anthropic impacts were observed, such as deforestation of native forest including the riparian vegetation, silting and dams, which can probably compromised the resident ichthyofauna.

A resposta da fotossíntese e crescimento de Egeria najas (Hydrocharitaceae) a baixas intensidades de radiação luminosa (0-124 µM m-2 s-1 RFA) foi medida em exemplares coletados no reservatório de Itaipu. A fotossíntese aproximou-se da saturação nas intensidades de radiação utilizadas e o ponto de compensação foi atingido a aproximadamente 6-22 µM m-1 RFA, indicando que esta espécie apresenta um baixo requerimento de radiação subaquática para crescimento. A radiação subaquática estimulou as taxas de crescimento relativas das porções fotossintéticas (caules e folhas) e das raízes, mas não houve relação entre a radiação e a razão entre as taxas de crescimento relativo das partes fotossintéticas e raízes. Observações de laboratório indicaram que: i. tanto as raízes como as porções fotossinteticamente ativas foram estimuladas pela radiação subaquática e ii. o baixo requerimento por radiação de E. najas pode explicar a incidência desta espécie no reservatório de Itaipu, onde a turbidez biogênica e abiogênica é elevada.

Photosynthesis and growth of Egeria najas (Hydrocharitaceae) from a subtropical reservoir (Itaipu Reservoir, Brazil-Paraguay) were measured in response to low light intensities (0-124 µM m-2 s-1 PAR) in the laboratory. Photosynthesis approached saturation in the range of light intensities used and light compensation point was reached at ca. 6-22 µM m-2 s-1 PAR, indicating that this species had a low light requirement for growth. Light stimulated shoot and root relative growth rates (RGR) but it was not related to ratios between root:shoot RGR. Laboratory observations indicated that (i) both shoot and root growth were simultaneously stimulated by light and (ii) the low light requirements of E. najas may explain its incidence in the Itaipu Reservoir, where biogenic as well as abiogenic turbidity is high.