The reservoir of UHE Coaracy Nunes in Araguari is located between the cities of Porto
Grande and Ferreira Gomes in the state of Amapá, Brazil, lying 200 km from the Atlantic
Ocean. The Coaracy Nunes was the first dam to be built in the Brazilian Amazon, with its
works started in 1967. The Araguari river is the main of the state of Amapá and represents a
source of income generation through fishing, farming activities in their floodplain, navigation,
mining, power generation and recreation. The present study aimed to assess the changes
imposed by the construction of the reservoir of UHE Coaracy Nunes, through the fish
assemblages of four areas of direct influence of this plant. For this, from May 2009 to July
2010, fish collections were made bimonthly, with standardized mesh networks ranging from
1.0 to 10.0 cm between knots and other technical aids. From these collections, in the Chapter
1 was investigates the composition, abundance (CPUEn) and biomass (CPUEp) on the fish
fauna, sampling efficiency (collector curve, rarefaction curves and Jacknife) and descriptors of
ecological communities (richness, diversity, evenness and dominance) of the assemblages of
the four areas. We conducted analyzes of variance (ANOVA: factorial), Kruskal-Wallis, t-test
and Mann-Whitney test to see if there were significant differences between the descriptors of
the areas and seasons. These analyzes were corroborated by multivariate analysis of
grouping (cluster), spatial (MDS) and ANOSIM Simper. In chapter 2, the ecological status of
the four areas were verified using as indicators: species abundance curves, curves and Kdominance
curves ABC, as well as species-abundance models geometric series, log series,
log normal and broken stick, and regression model linear size spectra. In chapter 3, the trophic
structure was estimated from the categorization of species in each area five guilds:
piscivorous, omnivorous, detritivorous, carnivorous and herbivorous. The abundance, biomass
and ecological indexes of these guilds were estimated and verified their spatial and temporal
variations, by analysis of variance (ANOVA: factorial and Kruskal-Wallis) and Student t test. In
chapter 4, the diet of most abundant species assemblage of each area was checked and their
spatial and temporal variations detected by analysis of variance (ANOVA: factorial and
Kruskal-Wallis). Also estimated the breadth and niche overlap of the most abundant species,
as well as the existence of competition between species through modeling zero. In chapter 5
was evaluated four areas of the ecosystem through flow models of biomass in the ecosystem
food web, using as a tool for modeling software Ecopath. These analyzes were designed to
describe the changes in ecological attributes that quantify the properties of maturity, stability
and resilience ecosystem that could reflect the ecological status of these areas. The model
included functional compartments from primary producers to top predators. In general, all
analyzes indicated significant changes in fish fauna attributed to the implementation of UHE
Coaracy Nunes, reflected in the three organizational levels: ecosystem, community (assembly)
and guild. The results indicated the capture of 1977 fish divided into two classes, 9 orders, 23
families, 73 genera and 108 species. The species accumulation curves and rarefaction curves
showed that samples areas were sufficient to Reservoir and Lacustrine areas. The results
showed that the area downstream was more rich, diverse and equitable in relation to other
areas and did not influence the seasonal variation in these rates. The relative abundance
(CPUEn) was higher in areas Reservoir and Lacustrine and relative biomass (CPUEb) was
higher in the downstream, with no seasonal differences for these descriptors in all areas. The
cluster analysis (cluster) and spatial (MDS) of the fish fauna permitted to identify the formation
of three distinct assemblies: Downstream, Upstream and an assembly comprising Reservoir
and Lacustrine areas, confirming the similarity of these two areas. The results of the curves
whitake-plot, ABC and K-dominance, as well as the satisfactory adjustment of the broken stick
model and the patterns of currvas spectrum size to the assembly area downstream indicate
that this area was the most balanced in terms of ecology. Reservoir and Lacustrine areas, the
results of both the model adjust geometric series, as the results of the curves whitake-plot,
ABC and K-spectrum dominance and size as well as the results of the curves and adjustments
to the model spectrum and lower logserie size for the assembly of the reservoir area, reflect that fish these areas, most of them are little guys with high dominance and low evenness,
featuring typical of communities impacted areas. The trophic structure of fish assemblages in
areas dammed (Reservoir and Lacustrine) formatted according to the bus of the river, which
was isolated and fragmented environment, determining their physical modification, requiring
the establishment of a fish fauna species pre-adapted to environmental conditions
impoundment, different, in part, the structure of the pre-river ichthyofauna bus, highlighting the
piscivores, omnivores and detritivores that were the richest and most abundant in the
availability in the two areas of food resources of your choice. The results showed that the diets
of the assemblies of all areas were similar to the prevalence of consumption of fish and debris,
followed by allochthonous plant food, revealing a pattern with a few large clusters and a higher
concentration of species with narrower niches. However, the pattern of low amplitude was
evidenced by trophic guild dominance of piscivores, added to the detritivore and herbivore
guilds. Seasonality little influence on the supply of most species in all areas. The comparative
patterns of diet among the areas upstream and downstream to the Reservoir and Lacustrine
areas indicate that most species of impoundment areas belonged to guilds piscivorous,
omnivorous and detritivorous bus before the river, which colonized these environments,
influenced mainly by abundance of food resources on their preferences and physical
conditions are favorable. Competitive interactions were evidenced by the null model,
suggesting that competition was also an important factor in structuring assemblages.
Ecossistemicamente, the four flow models represent ecosystems with high biomass
production primári coming from the riparian forest and filamentous algae, which are partially
used. The detritus-based food chain had to be more important than that is based on primary
aprodução Reservoir and Lacustrine areas. Most flow occurs in compartments lower trophic
levels. The properties area downstream ecosystem indicate that this environment is further
developed and couple, characterized by a high resilience and entropy. The area presented
Reservoir ecosystem attribute features that conferred less resilient and more stable, but less
than the couple areas of the river. The Lacustrine area presented attributes characterizing an
environment of intermediate resilience, stable immature and at the same time. The Upstream
area showed a pattern intermediate amount of resilience, stability and maturity.
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