|
SECTION
4 ECOLOGICAL RESOURCES CAPITAL STOCK
| 4.2 |
Existing
Capital Stock and Trends |
| |
|
|
|
| Marine
Mammals
|
| |
|
| 4.2.2.14 |
Of
the fifteen species of cetaceans recorded
in Hong Kong waters, either as live sightings
or strandings, five are whales, including
three members of the Balaenopteridae (the
Minke whale, Balaenoptera acutorostrata,
Bryde's whale Balaenoptera edeni, and the
Fin whale, Balaenoptera physalus), one member
of the Physeteridae (the Pygmy sperm whale,
Kogia breviceps), and one member of the
Delphinidae (False Killer whale, Pseudorca
crassidens). However, none of these whales
is resident in Hong Kong waters and most
have only been recorded on one or two occasions.
|
| |
|
| 4.2.2.15 |
The
Indo-Pacific Humpback Dolphin or Chinese White
Dolphin (Sousa chinensis), and the Finless
Porpoise (Neophocaena phocaenoides), are the
only species of marine mammal regularly sighted
in Hong Kong waters (Parsons et al 1995).
Considerable information has been gathered
on the Chinese White Dolphin primarily by
AFCD's "Multi-Disciplinary Research Program
on the Indo-Pacific Hump-Backed Dolphin Population"
(Jefferson 1998b), and studies undertaken
by the Swire Institute of Marine Science and
The University of Hong Kong (Parsons et al
1995; Porter et al 1997) commissioned by AFCD.
In contrast, little is known about the distribution
or basic biology of the Finless Porpoise (Parsons
et al 1995, ERM 1998e), although studies currently
underway by AFCD on this species (Jefferson
1998b, 1999), will assist in filling this
data gap. |
| |
|
| 4.2.2.16 |
The
local (Guangdong) population of Sousa chinensis
is reported to be centred around the Pearl
River Estuary and Hong Kong waters are thought
to represent the eastern portion of its
range. There were an estimated 967 Chinese
White Dolphin in the eastern Pearl River
estuary during the winter of 1997, and a
Pearl River estuary population of 1054 individuals.
Dolphins residing in the large western portion
of the Pearl River estuary were not surveyed
and may have been excluded from this estimate
(Jefferson 1998a). The population in Hong
Kong waters varied seasonally from about
92 individuals in winter to about 163 individuals
in autumn. It is speculated that heavy Pearl
River flow during the summer might contribute
to the higher numbers of dolphins dispersing
into typically oceanic waters in Hong Kong
(Jefferson 1998a).
|
| |
|
| 4.2.2.17 |
Chinese
white dolphins in Hong Kong waters are born
year-round, with peaks in late spring (May/June)
and late summer (August), after an estimated
gestation period of 11 months (Jefferson
1998a). This species feeds mainly on fish
(Jefferson 1998a, Parsons 1997) and has
often been recorded feeding behind pair
and shrimp trawlers. When feeding was not
associated with trawlers, it usually was
close to shore or near rock outcrops.
|
| |
|
| 4.2.2.18 |
Annual
strandings of Chinese white dolphins were
less than 3 per year through 1985 and then
increased rapidly to 15 strandings in 1996.
It was reported that 59% of the 22 strandings
that occurred between January 1996 and March
1998 were neonates, suggesting the mortality
rates for newborns might be high, as is
the case for most cetaceans (Jefferson 1998a).
The cause of mortality may be related to
bacterial disease, as exhibited by several
strandings, or due to elevated levels of
organic contaminants which have been found
in stranded dolphins (Parsons 1997). This
latter finding has prompted concern that
Chinese White Dolphins are being adversely
affected by pollution in the environment.
|
| |
|
| 4.2.2.19 |
Sousa
chinensis is listed as Data Deficient in the
IUCN Red List (IUCN 1996) and the genus was
listed in the Convention on International
Trade in Endangered Species (CITES) Appendix
I in 1979 (CITES 1998). China granted the
Indo-Pacific hump-backed dolphin Class I Special
Protection, which prohibits it from being
caught (Lin and Wang 1997). Within Hong Kong,
the species also is protected from hunting,
possession, and trade by the Wild Animals
Protection Ordinance (Cap 170) and the Animals
and Plants (Protection of Endangered Species)
Ordinance (Cap 187) (Jefferson 1998a). |
| |
|
| 4.2.2.20 |
The
finless porpoise, Neophocaena phocaenoides,
is a small cetacean endemic to southern
and eastern Asia. In general, marine areas
around Lamma Island appear to be the most
important habitats for this species (ERM
1998e). The main areas used by the porpoises
around the island are the nearshore waters
off the southwestern coast although this
appears to vary on both a spatial and temporal
basis. Ongoing studies are providing information
on the population distribution, density,
habitat ecology and behaviour of the species
with a goal of establishing a long-term
conservation and preservation programme
for the species. Like Chinese White Dolphins,
Finless Porpoise are protected under the
Wild Animal Protection Ordinance (Cap 170),
the Marine Parks Ordinance (Cap 476) and
listed on Appendix 1 of CITES.
|
|
|
|