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 327

decline of some shark stocks (see Chiaramonte, 1998) or due to depredation and damage of
caught fish and nets by southern sea lions ( Otaria flavescens ) (Cappozzo et al., 2000).
Although this decline of gillneting activities might have positive outcomes for franciscanas,
recent trawling for shrimps has been responsible for high by-catch around Ingeniero White
and Puerto Rosales, southern Buenos Aires Province and is an additional reason for concern
(Cappozzo et al., 2000).
Figure 1. Franciscanas incidentally caught in coastal gillnetting in southern Brazil.
Assessing the Species Conservation Status
The franciscana is possibly the cetacean species most seriously and immediately affected
by human activities in the western South Atlantic, especially incidental mortality in fisheries.
Mortality due to incidental entanglement in coastal gillnets is suspected to be by far the greatest
threat to the franciscana. Regrettably, despite the collapse of some fish stocks ( e.g. Haimovici,
1998), fishing effort is increasing and the number of franciscanas annually caught remains high
in some areas ( e.g. Secchi et al. 2004, Ferreira, 2009). Nevertheless, the actual effect of bycatch
on the chances of population persistence is likely to vary geographically. This is because both the
level of bycatch (Ott et al., 2002; Secchi et al., 2003 b ) and the life history strategies differs along
the species range ( e.g. Secchi et al., 2003 a ; Secchi, this volume). Some life history parameters
such as age at the attainment of sexual maturity, fecundity and survival rates influence the
population's potential to respond to non-natural removals and on its likelihood for long term
persistence (Caughley, 1977; Caswell, 2001; Morris & Doak, 2003). Therefore, for a proper
assessment on the species conservation status to be possible, management units ( i.e. discrete
populations) need to be identified. Once these units are identified, abundance, removal rates due
to bycatch (or other causes) and population-specific biological rates ( e.g. reproductive and
survival) can be estimated and changes of long-term persistence, with or without non-natural
removal may be assessed.