Dolphins, Porpoises, and Whales - IUCN

at the population, and possibly subspecific, level for dolphins
from the southeastern Pacific, New Zealand, and
southwestern Africa (Van Waerebeek 1993). Dusky dolphins
are found in large herds and can be considered abundant
overall. However, recent catches off western South
America have been large enough to cause serious concern.
The small-cetacean fishery in Peru, which involves capture
in gillnets as well as by harpooning, removes thousands
of dusky dolphins annually (Read et al. 1988, Van
Waerebeek and Reyes 1990). Although the Peruvian government
announced a ban on the directed fishery for small
cetaceans in November 1990, the ban has been ineffective.
A sample of the catch between August 1991 and June 1993
suggested a total annual catch (direct and incidental combined)
of more than 7,000 dolphins and porpoises, approximately
half of them dusky dolphins (Van Waerebeek elal.
1993; also see IWC in press a).
The dusky dolphin is among the species that have been
taken for crab bait in southern Argentina and Chile
(Cardenas et al. 1987, Crespo 1991b, Lescrauwaet and
Gibbons 1994). It was only recently learned that dusky
dolphins are killed, in unknown numbers, by a multispecies
trawl fishery off Patagonia and in other Argentine
fisheries (Crespo 1991b).
Northern Right Whale Dolphin
{Lissodelphis borealis)
The northern right whale dolphin is widely distributed in
the cold-temperate North Pacific (Jefferson and
Newcomer 1993, Jefferson e< a/. 1994). Stock identity has
not been adequately studied, and only crude population
estimates for segments of the species' range are available.
These dolphins have never been exploited directly on a
significant scale, although they are taken occasionally in
the harpoon fishery mainly for Dall's porpoises in northern
Japan (Miyazaki 1983). They are also killed incidentally
in coastal gillnet fisheries.
Since the late 1970s large numbers of right whale dolphins
have died in the Japanese, Taiwanese, and Korean
high-seas driftnet fisheries for squid. Estimates of the total
kill in one year ranged as high as 50,000+. The IWC's
Subcommittee on Small Cetaceans called attention to this
mortality as a potentially serious conservation problem
(IWC 1992a), and the population(s) involved have probably
been depleted (Mangel 1993).
Southern Right Whale Dolphin
{Lissodelphis peronii)
This dolphin has a circumpolar range in cold-temperate
waters of the Southern Hemisphere (Jefferson et al. 1994).
Sf'
Like Lissodelphis borealis it is gregarious and oceanic. No
population estimates are available, but southern right
whale dolphins are probably reasonably abundant.
Although they are killed occasionally in fishing gear, no
large-scale incidental mortality has been documented. Of
greatest concern is the likelihood that these dolphins, like
their Northern Hemisphere counterparts, would be seriously
affected by drift gillnets deployed within their range,
particularly off Chile.
Irrawaddy Dolphin
{Orcaella brevirostris)
In spite of its vernacular name, which refers to a large river
system in southern Asia, this species is not limited to freshwater
habitats. Its distribution includes riverine, estuarine,
and coastal marine waters from the central east coast of
India in the west to the northeast coast of Australia in the
east (Marsh et al. 1989). It is uncertain whether the distribution
is continuous between areas of relative abundance.
There may be a number of separate stocks, some of
which are limited to particular river systems, estuaries, or
embayments. Several areas have been identified where the
population of Irrawaddy dolphins is considered to have
declined due to human activities: Chilka Lagoon in the
western Bay of Bengal (Dhandapani 1992), the Mahakam
River/Semayang Lake region of eastern Borneo (Tas'an
and Leatherwood 1984, A. Priyono, in litt., 8 November
1991), Segara Anakan Bay on the south coast of central
Java (A. Priyono, op. cit.), and inshore waters of Thailand
(M. Andersen and C.C. Kinze in IWC 1994).
A directed net fishery for Irrawaddy dolphins (and
Sousa chinensis) has developed in Thailand to supply live
animals to oceanaria; this fishery apparently evolved from
the accidental capture of dolphins in nets, which has a considerably
longer history locally (Smith 1991). The bycatch
of Irrawaddy dolphins in the Mekong River system of
Laos and Cambodia is also feared to be substantial (Baird
etal. 1994).
Nothing is known about the situation in Bangladesh
except that some mortality in fishing nets occurs there
(Haque 1982). Some mortality of Irrawaddy dolphins has
also occurred in shark-meshing and other fishing operations
off Australia (Mitchell 1975, Australia progress
reports to IWC), and small numbers have been taken deliberately
for captive display in both Indonesia (Tas'an and
Leatherwood 1984) and Australia (Klinowska 1991). A
relatively large population of Irrawaddy dolphins is known
to be present in coastal waters of Australia's Northern
Territory, where no serious conservation problem is
known to exist at present (Freeland and Bayliss 1989).
As pointed out by Klinowska (1991:262), dams and
barrages constructed in rivers could fragment Irrawaddy