Júlio César Sá-Oliveira

Diet and niche breadth and overlap in fish communities within the area affected by an Amazonian reservoir (Amapá, Brazil)

We investigated the niche breadth and overlap of the fish species occurring in four environments affected by the Coaracy Nunes reservoir, in the Amapá Brazilian State. Seasonal samples of fishes were taken using a standard configuration of gillnets, as well as dragnets, lines, and cast-nets. Five hundred and forty stomach contents, representing 47 fish species were analyzed and quantified. Niche breadth and overlap were estimated using indexes of Levins and Pianka, respectively, while interspecific competition was evaluated using a null model (RA3). ANOVA and the Kruskal-Wallis test were used, respectively, to evaluate differences in niche breadth and overlap between areas. The data indicate that the majority of the fish species belong to the piscivore, omnivore, and detritivore guilds. These species have likely colonized the environments due to the availability of suitable feeding resources, and the favorable physical conditions created by the river damming. Overall, few species have ample niches, but most of them are highly specialized. Resources seasonal variation had little effect on the feeding behavior of most species in the study areas. The null models indicated that competition was not a factor determining on community structure.

Atividade de limpeza e clientes de Elacatinus figaro (Pisces: Gobiidae) nos recifes de coral dos Parrachos de Muriú, Nordeste do Brasil

Peixes limpadores removem ectoparasitas, tecido doente ou ferido, muco e escamas da superficie corporal de outros peixes, sendo portanto de fundamental importância para a manutencao do equilibrio e da saude dos peixes do ecossistema recifal. Na costa brasileira sao registradas 24 especies de peixes limpadores, das quais se destaca Elacatinus figaro, uma das especies de limpadores mais especializada. Este estudo registrou a diversidade de clientes e o periodo de atividade de limpeza de Elacatinus figaro nos recifes de coral dos Parrachos de Muriu, Rio Grande do Norte. Foram registradas 21 especies de clientes pertencentes a 11 familias, das quais 15 especies (68,4% do total de especies) sao ativas durante o dia, cinco (25,3%) tem atividade noturna e uma (5,3%) atividade diurna e noturna. Os clientes mais frequentes de E. figaro foram especies de Haemulidae (25,6%) e Pomacentridae (22,8%) e a categoria trofica planctofago/invertivoro foi a mais representativa (23,6%). A atividade de limpeza teve inicio entre 05h14 e 06h28 e termino entre 17h13 e 17h25. Os tamanhos dos clientes de E. figaro variaram de 7-40 cm com media de 12-30 cm de comprimento total. Um total de 127 ± 3 interacoes de limpeza e 34 ± 1,7 minutos utilizados na limpeza por estacao por dia (2-6 individuos de E. figaro) foi registrado

Fecundidade e tipo de desova do tamuatá, Hoplosternum littorale Hancock (Osteichthyes, Siluriformes) no Rio Curiaú, Macapá, Amapá

During June 1999 to June 2000 one hundred and forty seven females of Hoplosternum littorale Hancock, 1828 were collected from the Curiau River, Macapa, Amapa, Brazil. The objective of this study was to determine the fecundity and the type of spawning of H. littorale. Analysis of the percentage distribution of the oocyte diameter softh e females, in five different stages of gonadal development, showed that this species is a total spawner. There were two different size graups of oocytes with synchranic development. The total fecundity varied from 9, 144 to 31, 698 mature oocytes.The fecundity, when related to total length and weight, showed that it increases with the enhance in total length and weight.

DIETA, AMPLITUDE E SOBREPOSIÇÃO DE NICHO ENTRE Hypostomus plecostomus (LINNAEUS, 1758) E Hypostomus emarginatus (VALENCIENNES, 1840) (SILURIFORMES) DO RESERVATÓRIO DA UHE COARACY NUNES, FERREIRA GOMES, AMAPÁ-BRASIL

The stomach contents of 172 individuals of Hypostomus plecostomus and 94 specimens of Hypostomus emarginatus from the Coaracy Nunes reservoir in northern Brazil were analyzed in order to evaluate the feeding ecology of the two fish species from this site. Data were collected in eight campaigns conducted every two months between May, 2010 and July, 2011, four in the dry season and four during the flood period. The analysis of the stomach contents was based on the volumetric frequency (VF%) and frequency of occurrence (FO%), combined with the feeding index (FI). Nine different dietary items were identified: detritus, plant fragments, zooplankton, arthropods, chlorophytes, bacillariophytes, cyanobacteria, dinophytes, and unidentified material. Detritus was the principal component of the diet during both seasons, with all the other items representing only complementary or accidental portions of the diets of both species. Niche breadth was low overall, but slightly greater in H. plecostomus in comparison with H. emarginatus. Niche overlap was accentuated in both seasons, which indicates that seasonality is not a major factor influencing the characteristics of the niches of these species, possibly because of the marked abundance of detritus in the study area, specifically in the impounded sector. The two species can be characterized as detritivores, which share dietary resources with no clear evidence of any negative effects of interspecific competition on the coexistence of the two populations.

Restoration Effects of the Riparian Forest on the Intertidal Fish Fauna in an Urban Area of the Amazon River

Urbanization causes environmental impacts that threaten the health of aquatic communities and alter their recovery patterns. In this study, we evaluated the diversity of intertidal fish in six areas affected by urbanization (areas with native vegetation, deforested areas, and areas in process of restoration of vegetation) along an urban waterfront in the Amazon River. 20 species were identified, representing 17 genera, 14 families, and 8 orders. The different degrees of habitat degradation had a major effect on the composition of the fish fauna; the two least affected sectors were the only ones in that all 20 species were found. Eight species were recorded in the most degraded areas. The analysis revealed two well-defined groups, coinciding with the sectors in better ecological quality and degraded areas, respectively. The native vegetation has been identified as the crucial factor to the recovery and homeostasis of the studied ecosystem, justifying its legal protection and its use in the restoration and conservation of altered and threatened environments. These results reinforce the importance of maintaining the native vegetation as well as its restoration in order to benefit of the fish populations in intertidal zones impacted by alterations resulting from inadequate urbanization.

Resource Partitioning between Two Piranhas (Serrasalmus gibbus and Serrasalmus rhombeus) in an Amazonian Reservoir

The exploitation of resources by closely related species with similar niches may be mediated by differences in activity patterns, which may vary in nycthemeral scale and seasonal scale. Piranhas Serrasalmus gibbus and Serrasalmus rhombeus are Neotropical predators that occur sympatrically in many environments of the Amazon basin. To evaluate the strategies adopted by these two species in a restricted environment (a reservoir), nycthemeral and seasonal samples were made, identifying the composition of the diet and their activity patterns. A total of 402 specimens were collected: 341 S. gibbus and 61 S. rhombeus. Both species fed themselves primarily on fish, with some seasonal variation being found in S. gibbus during the flood season, when plant material was consumed. There was considerable temporal overlap in the foraging behavior of the two species, although S. rhombeus presented a bimodal pattern of abundance over the 24-hour cycle. S. rhombeus was more active during the nighttime, between dusk and early morning, whereas S. gibbus was active throughout the nycthemeral cycle. These findings indicate low levels of competition between the two species, which allowed for a considerable overlap in nighttime foraging, following distinct nycthemeral patterns of foraging activity and allowing their coexistence.

Factors Structuring the Fish Community in the Area of the Coaracy Nunes Hydroelectric Reservoir in Amapá, Northern Brazil

The objective of this study was to document the structure of the fish assemblages found in the aquatic environments affected by the Coaracy Nunes hydroelectric reservoir in Ferreira-Gomes, Amapá (Brazil) and the principal factors that determine this structure. In order to do this, standardized samples were collected of the fauna and the environmental parameters in the four principal sectors of the reservoir (upstream, the reservoir, the lake, and downstream). Fish species richness, abundance, and biomass were estimated for each sector. The abundance data were analyzed using null models of co-occurrence. A multivariate BIO-ENV analysis was used to examine the relationship between biological and environmental factors. The relationship between species richness and biomass of both prey and predator species was analyzed to determine whether predation was affecting community structure. Size spectrum analysis was conducted to verify whether fishing has influenced community structure. The results indicated contrasting seasonal patterns of deterministic processes in the downstream and lake sectors, suggesting that competition or abiotic factors may play a role in community structure. Stochastic patterns were recorded in the other sectors. Environmental factors, such as water transparency and depth, and the reservoir level were also closely related to the relative abundance of species in the communities. The relationship between the species richness and the biomass of predators and prey indicated that predation was an important determinant of community structure, which was interrupted by selective fishing. Despite the stochastic nature of most processes, deterministic factors were fundamental to the structure of the assemblages found in the downstream and lake sectors.

PREFERÊNCIA CLARO/ESCURO EM Danio rerio : EFEITOS DO HORÁRIO DA COLETA E DE REGIME DE LUZ

gland cells contain photoreceptors and the suprachiasmatic nucleus seems to be involved in biological rhythm just like in other vertebrates. This work aims to describe the role of luminosity and day periods in Danio rerios Light/Dark preference. For this purpose 160 naive adult undetermined sex Zebrafish were divided into 5 groups of 32 subjects and kept in isolated aquaria with light control. Afterwards, each fish was tested in the Light/Dark aquaria, with water column of 5 centimeters. There was an habituation period of 5 minutes (300 seconds) followed by removal of the sliding doors, allowing the subjects to explore the apparatus for 15 minutes (900 seconds). Tests were performed in different day periods, as follows: Morning (06:00 – 12:00 h); Afternoon (12:00 – 18:00 h); Night (18:00 – 24:00 h); Late Night (24:00 – 06:00 h). Our results show that the time of permanence is sensitive to day period. The number of crossings and latency were not influenced by the period of the day. Further studies regarding biological basis of Light/Dark Preference should be carried out in order to understand the role of circadian function in Danio rerios behavior.