Biology Reference
In-Depth Information
Chapter 11
F
ISHERY
A
CTIVITY
I
MPACT ON THE
S
OTALIA
P
OPULATIONS FROM THE
A
MAZON
M
OUTH
Sandra Beltran-Pedreros
1
and Miguel Petrere
2
1
Instituto Nacional de Pesquisas da Amazônia (INPA), Coordenação de Pesquisas em
Biologia Aquática, Rua Ajuricaba, Manaus, Brazil
2
Universidade Estadual de São Paulo (UNESP),
Departamento de Ecology, Rio Claro, Brazil
A
BSTRACT
This chapter describes and analyzes the bycatch of
Sotalia guianensis
, in gillnets by
an artisan fishing fleet within the Amazonian estuary during two time periods: 1996-1997
and 1999-2001. Number, size and gender data, as well as dolphin specimens were
obtained from fishermen at Brazilian ports and analyzed. Fishing capacity and effort were
determined via simple linear regression and bycatch, fishing trip and fishing effort data
were analyzed between time-periods, among climatic (seasonal) periods and between
strata (based on vessel length). Results indicated that the stratum two fishing fleet not
only had larger vessels but longer fishing trips, used longer nets and had larger fishing
crews compared to stratum one's fleet. Bycatch increased in both strata between periods
but to a greater extent in stratum two. Although there was an increased percentage of
fishing trips with bycatch across time, there was a reduced mean number of dolphins per
bycatch. There were also differences in the bycatch by sexual maturity with an
indiscriminately larger number of sexual-reproducing adults caught in stratum two.
Collectively, these results in conjunction with other anthropogenic factors combined with
dolphins being a k-selected species, suggest that dolphin mortality from bycatch may
seriously affect
Sotalia guianensis
in the Amazonian estuary. Furthermore, the fishery-
dolphin interaction was characterized and determined to be indirectly predatory.
Keywords:
Amazonian estuary,
Sotalia guianensis
, bycatch, fishing-dolphin interaction.
beltranpedreros@hotmail.com.
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