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The Hector’s Dolphin Endangered Animal Report 2010
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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

Infographic design | 222.408


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