Harvesting of plant and animal species in an unsustainable
fashion, here referred to as overharvesting, is the
most significant historical driver of Amazon freshwater
ecosystem degradation. Despite a lack of basin-wide data
on overharvesting of freshwater timber resources, selective
logging is thought to already have reached unsustainable
levels for several economically important species in
floodplain forests (e.g., Ceiba pentandra; Albernaz & Ayres
1999). Data also are sparse on the overharvesting of animal
communities, but an analysis of available population
assessments reveals the “fishing-down” process of
Welcomme (1999; Castello et al. 2011a). In the fishingdown
process, historical increases in exploitation reduce
the mean body size of harvested animals through the
progressive depletion of high-value, large-bodied species.
Mean maximum body length of the main species harvested
in the basin in 1895 was %206 cm, while for
all 18 species dominating fishery yields in 2007 it was
only %79 cm (Figure 3). The three main species harvested
in the early 1900s are now considered endangered;
and of the 18 species that now dominate fishery
yields, one is considered to be endangered and four
have been found to be overexploited in at least one region
of the basin (Figure 3; Ver´ıssimo 1895; Barthem
& Goulding 2007). Although the depletion of large,
commercially important species has decreased mean
maximum body length of the main species harvested
(Figure 3), it must be noted that this reduction also occurs
due to the natural tendency of expanding fisheries
to increase harvests of small-bodied, highly abundant
species (e.g., Prochilodus spp). Overharvesting of freshwater
ecosystem plant and animal species has multiple
adverse impacts. Whereas the impacts caused by loss
of plant species are similar to those caused by riparian