Érica Pellegrini Caramaschi

Electrofishing as a sampling technique for coastal stream fish populations and communities in the Southeast of Brazil

Electrofishing adequacy was tested as a technique to obtain quantitative data of coastal stream fish populations and communities in the Southeast of Brazil. Seven field trips, between July/94 and July/95, were done in 5 localities of the Ubatiba fluvial system (Maricá, RJ). Seventeen species, among the 22 collected, had their numbers estimated through the Zipping method, the model used to test the sampling methodology. At each field trip, three removals with electrofishing were done in each locality and, according to the number of obtained species at each locality/field trip, we analysed 315 cases. Nineteen cases, among 315, showed failure condition. Estimates were significant (p < 0.01) in 96% of the studied cases. Non-significant cases were obtained for rare species due to over and randomly efficient electrofishing in 63.3% and 36.4% of the cases, respectively. No correlation was found between catchability and the estimated number of individuals and/or environmental characteristics. High values for sampling efficiency (> 85%) were found for all estimates. An experimental analyses were done for one locality and, the comparison between the estimates for 3 and 6 successive removals showed a mean error and a standard deviation of 5.5% and 2.1% respectively. Therefore, it can be concluded that electrofishing was an efficient method for quantitative data analysis of fish populations and communities in the Ubatiba fluvial system.

Temporal and spatial distribution of the ichthyofauna in two streams of the upper Rio Parana basin

The temporal and spatial distribution of the ichthyofauna was assessed in two streams, Caracu and Sao Pedro, affluents of the Rio Parana, from March 1991 through February 1992. Samples were taken along the streams, using sieves (three sites on the Caracu and two on the Sao Pedro), and gill nets (two sites on the Sao Pedro). A total of 6,664 specimens belonging to 71 species were captured. CPE was calculated for each fishing gear. The data for cumulative frequency indicated that only the mouths of streams did not reach an asymptote. Constancy analysis showed that occasional and accessory species predominated. The spectrum of spatial diversity indicated that diversity increased toward the mouth of streams and temporal diversity increased in the high water season. The results of correspondence analysis for sieved fishes and Sorensen similarity for netted ones showed that the sites located at the same position on the streams were more similar than between adjacent sites in the same stream.

Estrutura populacional, aspectos da reprodução e alimentação dos Cyprinodontiformes (Osteichthyes) de um riacho do sudeste do Brasil

The population structure, reproductive aspects and feeding of Phalloceros caudimaculatus (Hensel, 1868), Poecilia vivipara Bloch & Schneider (1801), Phalloptychus januarius (Hensel, 1868) e Jenynsia lineata (Jenyns, 1842) were studied in five sampling stations in the Ubatiba stream, municipality of Marica (State of Rio de Janeiro, Brazil). In relation to the population structure, P. caudimaculatus was more representative upstream; P. vivipara mid-stream and downstream; P. januarius and J. lineata downstream. The species presented preponderance of females, except in the intermediate length classes. The occurence of imatures and females with young pointed out a long reproductive period and favoured areas for reproduction of the four species. The young forms of P. caudimaculatus were more abundant in station 1 (upstream), P. vivipara in station 4 (downstream) and P. januarius and J. lineata in station 5 (Marica coastal lagoon). The higher occurences of females with young belong to P. caudimaculatus, in station 1 (upstream) and P. vivipara and P. januarius in station 5 (Marica lagoon). The four studied species presented herbivorous diet and the differences found in the feeding may reflect the differences in the food availability in the microhabitats used by the species. So, we concluded that the studied species presented evident segregation in several levels of the different available resources in the environment.

Feeding Ecology of Leporinus friderici (Teleostei; Anostomidae) in the Upper Tocantins River, Central Brazil, before and after Installation of a Hydroelectric Plant

The feeding ecology of Leporinus friderici Bloch, 1794 was investigated in the upper Tocantins River, before and after its impoundment by the Serra da Mesa Hydroelectric Dam. Leporinus friderici was classified as an euryphagic, omnivorous species. Allochtonous food items formed a high proportion of its diet in all periods analysed, except in the later stages of reservoir formation. Its diet did not vary significantly between high-water and low-water seasons in the riverine environment, although it differed qualitatively. Leporinus friderici was very opportunistic, rapidly changing its diet to profit from the abundant terrestrial food sources when the reservoir started to flood the surrounding land, and shifting again when terrestrial food items became exhausted. Resumo A ecologia alimentar de Leporinus friderici Bloch, 1794 foi investigada no alto rio Tocantins antes e após seu represamento pelo AHE Serra da Mesa. A espécie foi classificada como onívora e eurifágica. Um consumo maior de itens alóctones foi observado em todos os períodos analisados, exceto em estágios posteriores de formação do reservatório. A dieta não variou significativamente entre as estações de águas altas e águas baixas no ambiente de rio, embora a composição qualitativa tenha sido diferente. Leporinus friderici demonstrou um comportamento claramente oportunista, mudando sua dieta rapidamente para aproveitar a abundância de itens de origem terrestre quando o reservatório começou a inundar as margens, e depois alterando novamente conforme esses itens foram se tornando escassos.

Reproductive biology of Astyanax janeiroensis (Osteichthyes, Characidae) from the Ubatiba River, Maricá, RJ, Brazil

Aspects of the reproductive biology of Astyanax janeiroensis in the Ubatiba river in Maricá, RJ, Brazil were evaluated in order to ascertain whether the strategy adopted by the species is causally related to environmental variables. Specimens were collected on a monthly basis from October 1994 to September 1995, through electrofishing. The Sex ratio was not significantly different from the expected frequency of 1:1 (G = 1.29; p > 0.50); nonetheless, considering three standard length classes, significantly larger numbers of females were recorded for the higher SL class (G = 11.07; p < 0.01). Size at first maturation showed no significant differences between sexes. Length-weight ratio analyses showed negative allometry for males and isometry, for females. Length structure was significantly different between sexes, suggesting that females are larger than males (D = 0.027, p < 0.01). Reproductive specimens were recorded during nine months of the annual cycle. Seasonal variations of reproductive specimens belonging to two different standard length classes displayed an asynchronous behavior, with larger specimens having a longer reproductive period and smaller ones reproducing for fewer months during the annual cycle. High values of fecundity (F), varying from 3169 to 18714 oocytes, were recorded for fish of 9.1 and 10.2 cm lengths, respectively. The correlation between weight and number of oocytes/unit of weight was positive, indicating that larger specimens produced more eggs.

Ocupação espacial, alimentação e época reprodutiva de duas espécies de Corydoras Lacépède (Siluroidei, Callichthyidae) coexistentes no rio Alambari (Botucatu, São Paulo)

Patterns of spatial occupation, feeding, and reproductive period of two species, Corydoras aeneus and Corydoras gr. carlae (Siluroidei, Callichthyidae), coexistents in the Alambari River (Botucatu, Sao Paulo), were studied. High diet overlap, partial spatial segregation, and well differentiated reproductive strategies were verified. These findings do not permit to evidence the occurrence of competitive interactions between the analysed species.

Reproductive biology of a characidiinae (osteichthyes, characidae) from the Ubatiba river, Maricá -- RJ

The Ubatiba river is a coastal stream subject to stochastic spates all over the year and, Characidium sp.n. is among the twenty-two species that compose its ichthyofauna. In this study we analyse some traits of its reproductive biology and discuss whether the adopted strategy has causal relationship with the environmental variables. Specimens were collected in the upper Ubatiba river. Samplings, were carried out monthly by electrofishing, between Oct./94 and Sep./95. Some differences between male and female strategies were observed. Females were significantly (p < 0.05) bigger than males; length--weight relationship was different (p < 0.05) between sexes with the onset of sexual maturity occuring at smaller sizes among males. Reproductive investment is high for both males and females but higher for males, maximum Gonadosomatic Index for females and males were 40.97% and 44.90%, respectively. Reproductive specimens were registered all over the year, suggesting continuous reproduction. High values of fecundity were also registered varying from 1342 to 5535 eggs for ripe females of 4.4 and 7.0 cm, respectively and an amount of 1105 oocytes per grams of fish. We suggest that differences in the reproductive strategy, between sexes, determine the observed patterns in the size structure; the absence of males in the higher SL classes could be a consequence of high mortality rates and/or reduction in the growth rates as a precocity consequence in the onset of reproduction and/or high reproductive investment. Relationship between continuous reproduction and environmental condition could be explained as an adaptation to maximise supervivency of the young fishes that is: guarantee the species maintenance in a stochastic environment.

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.

Effects of Artificial Canal Openings on Fish Community Structure of Imboassica Coastal Lagoon, Rio deJaneiro, Brazil

ABSTRACT The embankment of the Imboassica River formed the Imboassica Lagoon located to north of the State of Rio de Janeiro by the coastal sandbank, which separates it permanently from the sea. Formerly, the lagoon used to be connected to the sea naturally when waves broke the sandbar. Presently, connection is established artificially to prevent roads and houses from flooding. Such action increases the diversity of fish species living in the lagoon and therefore expands the fishing activity. This study investigated the effects of such openings on the structure of local fish community. Among the 26 species collected by gillnets, Hoplias malabaricus, Paralichythys brasiliensis, Gerres aprion, Genidens genidens, Strongylura timucu, Mugil curema, and Geophagus brasiliensis were the most abundant during the study. Lycengraulis grossidens, Archosargos probatocephalus, Tilapia rendalli, and Micropogonias furnieri were dominant before the canal was opened, whereas Anchovia clupeoides and Trachinotus carolinus were dominant in the period after the canal opening. Species diversity and evenness were practically constant during the months before the canal opening. Although both indices decreased substantially while the sea connection remained open, they returned to the same level as before when the canal was closed again. Cluster and detrended correspondence analyses showed similar patterns of two distinct groups of months before and after the canal opening supporting the idea that distinct fish assemblages occupied that environment before and after the event. Our results show that artificial canal opening is a factor that affects the structure and species composition of the fish community in the Imboassica Lagoon.

Ovary maturation stages and oocyte features in three species of the neotropical fish Hemiodus (Müller, 1842)

Macro- and microscopic ovarian features of Hemiodus microlepis, H. ternetzi and H. unimaculatus were analyzed. Based on these features we proposed an ovarian maturation scale. The nine stages of the preliminary macroscopic fieldwork scale were reduced to five after microscopic analysis of ovaries. The microscopic analysis indicated a group-synchronous oocyte development common to the three species that were characterized as iteroparous synchronous spawners with a total spawning type. The remarkable thickness of the zona radiata layer and the large size of vitellogenic oocytes of Hemiodus ternetzi distinguished this species from the others.