Dolphins, Whales and Porpoises: 2002-2010 Conservation - IUCN

effort, imposing spatial and/or temporal fishing closures,
or introducing alternative fishing methods.
Such modifications may be pursued not only to reduce
franciscana mortality, but also to conserve economically
valuable fish stocks that are depleted or
rapidly declining. Government agencies, the fishing
industry, fishery and marine mammal biologists, and
representatives of local fishing communities will need
to work together to design and promote appropriate
conservation measures in particular areas.
� Existing fishery regulations should be enforced, and
additional regulations considered. Some fish stocks
have declined because of inadequate policing; for example,
extensive trawling close to shore has had a
large impact on benthic fauna and on juveniles of
target fish species (some of which are important prey
of franciscanas). One regulatory approach might be to
impose limits on the allowable length of gillnets. For
example, in Rio Grande do Sul, southern Brazil, the
coastal gillnet fleet (about 175 boats) uses nets with an
average length of 5–6km (some boats use nets more
than 10km long). Lowering the allowable net size
could bring benefits both to franciscanas and to fish
stocks.
� While acoustic deterrents (“pingers”) have the
potential to contribute to bycatch mitigation, it is essential
that their effectiveness be demonstrated
through controlled scientific experimentation before
their widespread use in fisheries is authorized
(Bordino et al. 2002), and that such use is monitored
to confirm continuing effectiveness and to detect unforeseen
consequences. This applies equally to other
gear changes and alternative fishing methods.
� The people of the region should be made aware of the
risks that gillnet fishing poses to the franciscana, and
of the ways in which the conservation of franciscanas
might be related to that of more general marine resource
conservation, including valued teleost and
elasmobranch stocks. Education programs in schools
are one obvious mechanism, but broader efforts to
publicize the franciscana’s existence, as well as its
vulnerability to bycatch, may be appropriate.
� The three range States should engage in discussions
aimed at an agreement for bilateral or trilateral management
for conservation of franciscanas. The species
is migratory, as defined by the Bonn Convention, and
its ecosystem is influenced by factors within the jurisdictions
of more than one state (e.g., river runoff). The
concept of shared responsibility for franciscana conservation
among the three range states is viewed by
the CSG as a priority.
Hector’s dolphin
History: Hector’s dolphin is endemic to New Zealand,
where there are at least four genetically distinct populations
87
(Pichler et al. 1998; Pichler and Baker 2000) and evidence
of additional local populations with very limited dispersal
(Martien et al. 1999). The total size of all populations is
estimated at around 7400, with 7270 (CV 16.2%) distributed
around South Island (Slooten et al. 2002) and some
100 individuals off the west coast of North Island (Russell
1999). The species is listed as Endangered and the North
Island population as Critically Endangered.
Hector’s dolphins have been by-caught in gillnets
throughout most of their range since gillnetting became
widespread in New Zealand waters in the early 1970s
(Dawson 1991; Slooten and Lad 1991; Taylor 1992). Based
on the best estimate of maximum population growth rate
(�max = 1.018) ( Slooten and Lad 1991), gillnet mortality is
anticipated to cause continuing declines in all of the
populations (Martien et al. 1999). The Banks Peninsula
Marine Mammal Sanctuary was created in 1988 to reduce
bycatch off the Canterbury coastline on the east side of the
South Island. Independent observers were first placed on
gillnet vessels fishing north and south of Banks Peninsula
during the 1997–1998 season. The estimated bycatch by
commercial gillnetting vessels during that season was 16
Hector’s dolphins (CV 39%) (Baird and Bradford 2000).
These were caught outside the sanctuary in an area with an
estimated 300 Hector’s dolphins (CV 36.5%)(Du Fresne et
al. 2001). While there are no quantitative estimates, several
dolphins are killed each year in recreational gillnets, and
there are at least occasional catches in trawl nets (Baird and
Bradford 2000). The commercial gillnet fishery, on its own,
seriously threatens local populations (Martien et al. 1999;
Slooten et al. 2000).
In view of continued recreational and commercial bycatch
north and south of the sanctuary (Baird and Bradford 2000)
and continued low survival rates (Slooten et al. 2000),
regulations were recently introduced to prohibit recreational
gillnetting along the Canterbury coastline from 1 October to
31 March. Commercial fishermen have developed a voluntary
code of practice (COP) for reducing bycatch in the
Canterbury area, as an interim measure while a management
plan for the species is prepared. Acoustic deterrents
(“pingers”), specially developed for Hector’s dolphin based
on field studies of this species (Stone et al. 2000), are being
used by Canterbury gillnet fishermen as part of the COP.
Although there have been no reports of catches of Hector’s
dolphins in any of these fishermen’s nets (G. Stone, pers.
comm.), the fishery is too small for a statistically robust
study of effectiveness to be carried out (cf. Dawson et al.
1998). Therefore, uncertainty remains concerning the effectiveness
of pingers and other components of the COP.
Even in the absence of human impacts, the North Island
population of Hector’s dolphins may be vulnerable to extinction
for decades because it has been reduced to such a
low level (Martien et al. 1999; Dawson et al. 2001). A
meeting of fishermen, conservation groups, scientists, and
government officials concluded in May 2000 that mortality
due to human activities must be reduced to zero to allow the