Visualizar Tese - Instituto de Biociências - Unesp

Four years of study were done and in the three first ones (1998,1999
and 2000) 30.201 samples were shown in the fish landings belonging to 71 species of
fishes being these grouped into 19 families, 47 genera and four orders
(Characiformes, Siluriformes, Gymnotiformes and Perciformes). Of all these species
the ten found in more abundance were: The corvine (Plagioscion squamosissimus),
the taguara (Schizodon nasutus), the acarajéu (Satanoperca pappaterra), the pacuprata
(Metynnis mola), the piranha (Serrasalmus maculatus), the mandi (Pimelodus
maculatus), the caborja (Hoplosternum littorale), the cascudo-amazonas
(Pterygoplichthys anisitsi), the traíra (Hoplias malabaricus) and the cascudos claros
(Hypostomus sp.1), representing 76,23% from the total samples.
Still between these ten species, the exotic/introduced represented half
of the most abundant ones, being P. squamosissimus,
S. pappaterra, M. mola,
H.littorale and P. anisitsi. In the last year of work in 2006, only 2.486 samples were
shown, also including a new species that was found : the porquinho (Geophagus
proximus), making it 72 species and 48 registered genera in the four years of study
totalizing 32.687 shown species.
Within the four years, the introduced species P. squamosissimus leaded
the ranking in numbers of individual and biomass; and in this last year it was
responsible alone for 47% of the fish landings.
Capture data per unit of effort and the ecological attributes show a very
critical and worrying situation, for it’s clearly noticed that there was a drastic decrease
in the number of species, as well as in the number and in the biomass of the last
collected samples in the last year of study.
The most plausible hypothesis to this serious situation would be the
great number of exotic/introduced species which are competing with the native ones,