Analyses of the sediment toxicity of Monjolinho River, São Carlos, São Paulo State, Brazil, using survey, growth and gill morphology of two fish species (Danio rerio and Poecilia reticulata)

The objective of this work was to evaluate the toxicity of the sediments of the Monjolinho River (São Carlos - São Paulo/Brazil), through partial chronic toxicity bioassays with juveniles of D. rerio and P. reticulata. Histological analyses of the gills and biometric measurements were conducted to detect the possible deleterious effects that caused the death. In all points the sampled the alterations were found in the gills (hyperplasia, fusion of secondary lamellas and dilation of blood vessels), with the most intense lesions (second stage) occurring at the point two. The biometric analysis pointed to inadequate conditions for the growth of the test-organisms when exposed to the sediment samples. These results showed that the conditions of these environments were not suitable for the survival and growth of these fishes.Este trabalho teve como objetivo avaliar a toxicidade dos sedimentos do rio Monjolinho (São Carlos - São Paulo/Brasil), por meio de bioensaios de toxicidade crônicos parciais com juvenis de D. rerio e P. reticulata. Foram realizadas análises histológicas das brânquias dos organismos para detectar possíveis efeitos deletérios que antecedam a mortalidade. Em todos os pontos amostrados, foram verificadas alterações nas brânquias (hiperplasia, fusão de lamelas secundárias e dilatação de vasos sanguíneos), sendo no ponto dois foram encontradas lesões mais acentuadas (segundo estágio). A análise biométrica dos indivíduos expostos em amostras de sedimento demonstrou condições inadequadas para o crescimento e desenvolvimentos dos organismos-teste em todo o ambiente estudado. Os sedimentos apresentaram maior toxicidade no período chuvoso, sendo estes resultados confirmados por meio das análises histológicas das brânquias dos organismos expostos, as quais demonstraram lesões mais acentuadas no mesmo período. Tal situação possivelmente decorre dos impactos antrópicos os quais o sistema está suscetível (efluentes domésticos, industriais e agrícolas), que foram constatados pelas análises físicas e químicas dos sedimentos.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Induced reproduction and reproductive characteristics of Rhinelepis aspera Agassiz, 1829 (osteichthyes: Siluriformes, Loricariidae)

Rhinelepis aspera is the largest Loricariidae species found in the São Francisco river basin where it is now rarely caught. Brooders kept in tanks were hypophysed with crude carp pituitary extract (CCPE). Approximately 82% of the females responded positive to the treatment. The egg was opaque, demersal, round, yellow and adhesive. Egg stripping was done at 212 hour-degrees (= 8.2 h) after application of the second dose of CCPE (water temperature = 25-26 ºC). Hatching of the larvae occurred at 1022 hour-degrees (= 42.2 h), after fertilization of the eggs (water temperature =24-25 ºC). Fertilization rate of the eggs was 72%. Absolute fecundity (AF), initial fertility (IF) and final fertility (FF) in relation to the females' body weight are expressed, respectively, by the equations: AF = - 33993 + 122308 Wt (r² = 0.88), IF = - 14823 + 58619 Wt (r² = 0.71) and FF = - 6553 + 29741 (r² = 0.61

Stream-dwelling fish communities from an Atlantic rain forest drainage

Twenty-two species were registered in the Ubatiba system with a predominance of Characiformes and Siluriformes followed by Cyprinodontiformes, Perciformes and Synbranchiformes. Among these species four were occasional with one or two sampled individuals and restricted to one or two of the nine studied sites; the other 18 species were constant with high densities in at least one site. Most of the sampled sites presented between 11 and 18 species, all largely distributed; except for the uppermost site, located right over a waterfall 4m high, which showed at least four species and for the confluence site that presented 18 species. Canonical Correspondence Analysis indicated that environmental variables explained a great part of the density and distribution patterns of the fish species, showing that community structure of each locality was independent from the longitudinal succession, theoretically expected by the River Continuum Concept, and hardly explained by local environmental characteristics

Population structure and reproductive biology of Cichla kelberi (Perciformes, Cichlidae) in Lobo Reservoir, Brazil

The structure of Cichla kelberi population was characterized regarding the sex ratio, total length composition and some reproductive characteristics. The specimens were collected in two periods, from November 2002 to November 2003 and from December 2004 to May 2006. The sex ratio was significantly different than 1:1. The total length varied from 3.4 to 40.1 cm, with individuals in the shortest length classes occurring throughout the year, but with greater incidence in the warmer periods. Females and males reached similar lengths and there was no difference between the sexes regarding the length-weight relationship. The estimated values of condition factor were near the central value of 1.0 and decreased during the cooler months, coinciding with periods of lower reproductive activity. Individuals with mature or semi-spent gonads occurred from November to April, indicating that Cichla kelberi reproduces for a long period of time. The spawning is partitioned, with an average absolute fecundity of 6072 oocytes (from 5220 to 6908 oocytes). The high relative condition factor values, long reproductive period, large output of fingerlings and high fecundity are biological conditions that indicate the species is well adapted in this reservoir