REVIEW ON THE THREATS AND CONSERVATION STATUS OF FRANCISCANA, PONTOPORIA BLAINVILLEI (CETACEA, PONTOPORIIDAE) - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 329

used by Secchi (2006) in his projections. In addition, other sources of potential threat as
described above were not considered in Secchi's study.
Since the projections suggest a population decline of more than 30% over three
generations considering actual and potential levels of fishing-related mortality as well as
potential effects of environmental stochasticity (Secchi, 2006), the species qualified to be
classified as VU under criterion A3d of the World Conservation Union's Red List of
Endangered Species of Fauna and Flora (IUCN, 2008). The rate of decline is probably
underestimated because a period of only 25 years was considered and other sources of non-
natural mortality were not incorporated into the analysis. The causes of the inferred
population decline have not ceased and are likely increasing because of fishery expansion
(causing higher bycatch and also potentially reducing prey base) and lack of mitigation
actions. In southern Brazil, for example, both gillnet and trawl fishing effort have been
increasing since the early 1980s (Haimovici et al., 1997). The very high fishing effort has led
to the stock depletion of many bottom-dwelling fish species of the family Sciaenidae because
they are targeted by gillnet fisheries (Reis, 1992; Haimovici, 1998). The natural reaction of
fishermen is to further increase fishing effort to compensate for lower catches per unit of
effort until a profitable level is reached. Since the mid 1990s, the mean net length of most of
the coastal gillnet fleet has increased fourfold in this area (Secchi et al., 1997; 2004, Ferreira,
2009). Unfortunately, perspectives for action to mitigate bycatch on a short-term basis are
minimal (see below).
Figure 2. The species distribution range showing the four Franciscana Management Areas (FMA -
sensu Secchi et al., 2003 a ).