Hector's Dolphin
description
Transcript of Hector's Dolphin
The Hector’s DolphinEndangered Animal Report 2010
Name: Hector’s dolphin
Scientific Name: Cephalorhynchus Hectori
Habitat: Coastal Waters
Location: North And South Island
Population: Approximately 7270
Hector’s dolphins are the world’s smallest and rarest
dolphins which are only found in New Zealand. The
Hector’s dolphin is the smallest in the delphinidae
family as well as the rarest oceanic species.
Hector’s dolphin was named after Sir James Hector
(1834 – 1907). He was the curator of the Colonial
Introduction
Museum in Wellington, Te Papa. He examined the
first specimen found of the dolphin. The species was
scientifically described by Belgian zoologist Pierre
Joseph van Beneden in 1881.
Primarily grey, black and white with a distinctive stripe
running across its belly, this cetacean, air breathing,
water living mammal, is most recognizable by its lack
of discernible beak and its round dorsal fin.
The dolphin is classified as a vulnerable threatened
species in the most recent IUCN, World Conservation
Union, listings of globally threatened animal species.
The problem
Unprotected distribution
Hector’s dolphins are endemic to the coastal
regions of New Zealand and they have a patchy
distribution around the entire South Island. The
species has a preference for shallow, coastal
waters less than 100m deep. This means they are
most commonly seen close to shore, although
in shallow regions they have been sighted up to
34km from the coast.
In some areas, there is a pronounced seasonal
difference in distribution, with dolphins being
sighted further offshore
and in deeper water in winter, presumably in
response to movements of their prey species.
The main populations are found between Motunau
and Timaru on the East Coast of the South Island,
on the West Coast of the South Island, and in
Foveaux Strait Te Waewae Bay area in Southland.
Currently they are trapped accidentally in trawls
and gill nets. Some parts of their habitat have
been protected, but to save this declining species,
more areas around New Zealand will have to be
declared no-go zones for coastal gill nets.
Hector’s dolphin’s distribution
1/3 offshore distribution protected(Population continues to decline)
Unprotected areas(Population continues to decline)
‘Over the last thirty years New Zealand has lost on average 570 endangered Hector’s dolphins a year, that’s over 5,000 deaths each decade.’
WWF, 2010
Population decrease
Scientists estimate that more than 26,000 Hector’s
dolphins lived around New Zealand’s shores in the
1970s. Today, it is thought that just 7270 remain
which is less than one third of the 1970s’ population.
The Hector’s dolphin was given ‘threatened species’
status by the Department of Conservation in
December 1999.
Today, Hector’s dolphins are listed on the World
Conservation Union’s Red List as endangered, and
are among the most rare of the world’s 32 marine
dolphin species. The Cetacean Specialist Group of
the Species Survival Commission of IUCN, the world
scientific experts on cetacean conservation, have
assessed Hector’s dolphin as a threatened species
of vulnerable status using the agreed threatened
species criteria. Research shows that even if all
available actions were implemented today, by 2055
the population would still be smaller than it was
in 1970. The most likely outcome is that they will
continue to decline, just at a slower rate than before.
2010
2001
1985
1970
5000
10000
15000
14000
18500
23000
27500
Pop
ulat
ion
of H
ecto
r’s d
olp
hin
Decrease of population from 1970–2010
25
Hector’s dolphin’s mortality (1969–2009)
50
75
100
125
1969
–197
9
Num
ber
of d
olp
hins
1979
–198
9
1989
–199
9
1999
–20
09
Mortality
Mortality of Hector’s dolphin in gill-net fisheries is a
threat to local populations throughout its range. This
population viability analysis extends previous work by
exploring a wider range of fishing levels and population
growth rates, by incorporating year to year and
environmental variability and by reporting results for
smaller population units.
Ten of the 16 populations are likely to continue to
decline, five are indefinite, and one is likely to increase.
All populations subjected to high fishing effort are
declining. The only population predicted to increase
is partly protected by a marine mammal sanctuary
that was created in 1988, which reduces the amount
of gill net fishing. Conservation measures are most
urgently needed for the highly threatened North Island
population, in particular the dolphins at the northern
and southern end of this range.
Reducing fisheries mortality to levels approaching zero
shows the strongest promise of meeting national and
international guidelines for managing dolphin bycatch,
with a 59% probability of reaching 50% of estimated
1970 population size by 2050.
‘Such very small population of Hector’s dolphins have a high extinction risk simply due to stochastic factors.
Marine and Freshwater research, 2010
Striped dolphin
Hourglass Dolphin
Atlantic spotted Dolphin Whiteside dolphin
Risso’s Dolphin
Hector’s Dolphin
1.5m
1.8m
2.5m 2.5m 2.5m
3.5m
Shorter length, shorter life
Hector’s Dolphins are one of the smallest
dolphins in the world. As adults the Hector’s
Dolphin has a length of 1.5 meters and weigh
in at only 50 kilograms.
Hector’s dolphins do not live as long as others,
the smaller the species, the shorter the lifespan.
Out of more than 80 Hector’s which have been
dissected some of them caught in fishing nets,
the oldest recorded ages have been 19 years for
a female and 20 for a male. Some individuals may
live longer than this, but the ages are comparable
to those recorded for other Cephalorhynchus
species. By contrast, larger dolphins such as the
bottlenose live to between 25 and 50 years.
A dolphin’s age is estimated from the layers in a
cross section of tooth. Because of their small size,
they do not have enough reserves to make long
journeys through fish starved oceans, to either
populate other coasts or to mix with other of their
kind. The lungs of a Hector’s dolphin are about
the size of a human’s, and when trapped in one,
it takes about the same length of time for them to
drown as it would a person.
10,000
50,000
100,000
500,000
1,000,000
1,500,000
2,000,000At
lant
ic S
potte
d D
olph
in
Num
ber o
f dol
phin
s
Population of different breeds
Ris
so’s
Dol
phin
Whi
tesi
de D
olph
in
Strip
ed D
olph
in
Hou
r gla
ss D
olph
in
Hec
tor’s
Dol
phin
‘New zealand Hector’s dolphin populations are more susceptible to extinction than other species.’
Zoology and wildlife conservation, 1998
The causes
Humpback Whale
Life expectancy
Number of reproductions
Hooker’s Sea Lion
Hector’s Dolphin
20 yrs
23 yrs
50 yrs4–8 yrs
3–4 yrs
7–8 yrs
Breeding ovulation
The slow rate of Hector’s dolphin’s reproduction
makes their populations vulnerable. Females aren’t
sexually mature until they are between seven
and nine years old, that would be equivalent to a
human not being able to reproduce until they are
about 30 years old.
They produce just one calf every two to four years.
One female might only produce four calves in her
20 year lifetime and this is just enough to replace
the number of dolphins that die naturally. Hector’s
dolphins are having a very difficult time replacing
members of their population as fast as they are
losing them.
The gestation period for Hector’s Dolphin is believed
to be about a year. Calves are born in spring and early
summer, November to February. The calf starts eating
solid food at about 6 months of age, but stays with its
mother for a full year. Minimum calving intervals range
from 2 – 4 years, but the mother does not conceive
again until the calf is independent.
Life expectancy of endangered species
Year 3
Year 1
Year 2
Calves areborn
Calves are oldenough to live on
their own
JanFeb
Mar
Apr
May
JunJuly
Aug
Sep
Oct
Nov
NovDec
Nov
Mating season
Breeding ovulation
73% Set net
5% Natural
0.5%Boat strike
6.5%Trauma
1.5%Cray pot
13.5%Trawler
Population declining threats
Dolphins and people have shared our shores and
bays for centuries. In recent years, there has been a
worldwide increase in awareness of marine mammals
and a greater desire to protect them.
Set net fishing poses a major threat to Hector’s
dolphins. Like all marine mammals they need to
come to the surface regularly to breathe. If they
become tangled in set nets, they will hold their
breath until they suffocate.
Because these dolphins swim close to the shores
and harbours, they are at risk of being injured by
boats. Newborn dolphins are particularly
vulnerable as they swim relatively slowly, close to
the surface. Some have been killed by boat
propellers, when unwary boats have run them over.
Other potential threats to their survival include
trawling, marine pollution, disease and impacts
of tourism and aquaculture. They are also
harmed by boat strikes, pollution and coastal
developments which degrade their habitat, and
future threats may arise from climate change,
overfishing and aquaculture.
Death causes
‘Fishing nets continue to kill Hector’s dolphins faster than they can breed.’
Global Voice for Wildlife, 2009
Net sets
Hector’s dolphins use echo-location to locate their
prey. Dolphins send out a stream of high frequency
clicking noises and when the sound strikes an object
it bounces back and the dolphin can tell by listening
what the object is, what kind of fish it is, how far
away it is and how fast it is moving.
The dolphins cannot easily detect the nets, even
when using echolocation. This enables them to see
the hard parts of prey, or solid objects like rocks,
but because nets are soft and flexible they do not
bounce sounds back to the dolphin.
Set nets are the single most significant threat to
the survival of Hector’s dolphins as the dolphins
get entangled in these nets and drown. Without
restrictions placed on commercial fishing, the risk of
extinction of Hector’s dolphins would be very high.
A 2008 report by the National Institute of Water
and Atmospheric Research (NIWA) estimates that
110 to 150 Hector’s dolphins die in commercial set
nets every year.
Reported net entanglements
Commercial net
Recreational net
Unknown net
12
10
8
6
4
2
1985
Num
ber
of d
olp
hins
1990
1995
2000
2005
What needs to be done
Specific ways in which protection could be improved
includes protection from gill nets and set nets,
allowing the Hector’s dolphins to recover. Better
protection of harbours are needed.
Extending protection is needed on the west coast
South Island to 6 nautical miles offshore, year-round.
Also extending protection at Banks Peninsula area
offshore to 15 nautical miles as Hector’s dolphins
are found well beyond the 4 nautical mile protection
boundary in this relatively shallow area. Increased
protection from trawl fisheries and observers on all
gill net and trawl fisheries continuing, in areas where
Hector’s dolphins are found need to be considered.
We need to have a nationwide ban on gill nets in
order to save the dolphins from extinction. This
means banning trawl fishing in waters less than 100
meters deep in areas where Hector’s dolphins are
found. Full protection is needed for dolphins across
their entire range and for areas where they historically
ranged in the past.
Strategy
1970s
2010
‘Hector’s dolphin’s population today, is less than one-third of the 1970’s population.’
WWF, 2010
What has already been done
On 15 November 2007, the World Wide Fund for
Nature launched an online petition asking Helen
Clark, New Zealand’s Prime Minister at the time,
to introduce emergency measures to protect the
Hector’s dolphins. New measures were introduced
by the Ministry of Fisheries in 2008 effectively
banning gill netting within 4 of the majority of the
South Island’s east and south coasts, regulating
gill netting on the South Island’s west coast out to
3.7km offshore and extending the gillnet ban on
the North Island’s west coast to 13 km offshore.
There are also restrictions on trawling in some of
these areas.
The New Zealand Marine Mammals Protection Act
has made the deliberate killing or injury of marine
mammals illegal. Under this act, the Department of
Conservation designated the Banks Peninsula Marine
Mammal Sanctuary in 1988, effectively prohibiting
commercial gillnetting and restricting recreational
gill netting.
These were surpassed by new Ministry of Fisheries
regulations in 2008 which ban gillnetting to four
nautical miles off the majority of the South Island’s
east and south coasts, regulate gillnetting on the
South Island’s west coast to two nautical miles (3.7
kilometres) offshore. Five marine mammal sanctuaries
were designated around the coastline in 2008 to
provide additional protection from non fisheries
related impacts
Protected distributions
‘The only population predicted to increase is partly protected by a marine mammal sanctuary which reduces the amount of gill net fishing.’
WWF, 2010
‘Total protection is the only way to give the dolphins the chance to recover so they are no longer at risk of extinction.’
Forest and Bird, 2010
Lisa Park | 06196330
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