Saving the Margaret River Hairy Marron from Extinction

Cameron Hugh, Martin de Graaf and Craig Lawrence

© Simon Visser

Marron Cherax cainii

Endemic to the south-west of Western Australia

Third largest FreshwaterThird largest Freshwater crayfish in the world.

Maximum size 2 kgMaximum age ?? g

Distribution

Margaret River

Inhabits permanent freshwater rivers, lakes and dams.

Widely translocated since EuropeanWidely translocated since European settlement.

Morphological DifferencesDifferences

Median carina extends to cervical groovecervical groove

Carapace covered in tuffs of hair (setae)of hair (setae)

Decline of the Hairy Marron

90

100 Upper reaches Middle reaches

50

60

70

80

y M

arro

n (%

) Lower reaches

10

20

30

40

50

Pro

porti

on H

airy

0

10

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

19…

20…

20…

20…

20…

20…

20…

20…

20…

20…

20…

20… de Graaf et al.

2009

Possible Replacement Mechanisms:

Displacement Mechanisms

Diseaseexample: “crayfish plague” decimated European species after introductionAmerican speciesp

Susceptibility to predators

Faster growth, superior ability to compete for food and shelterexample: USA replacement of mid-western species by eastern species O. rusticus

Susceptibility to predatorsexample: USA replacement of mid-western species by eastern species O. rusticus

Habitat degradation/alteration

Hybridization and Introgressionl USA l t f id t i b t i O ti

example: removal spring water for agricultural, industrial and urban use caused extinction of Mexican freshwater crayfish species

example: USA replacement of mid-western species by eastern species O. rusticusO. rusticus x O. virilis NO HybridsO. rusticus x O. propinquis Hybrids, no true species under biological concept

not diverged to point of permanent

Crucial importance to understand mechanisms responsible for replacement

not diverged to point of permanent sympatric co-existence

mp m m p f p mof hairy marron by smooth marron to develop successful management arrangements to protect Margaret River biodiversity

DISPLACEMENT MECHANISM: HYBRIDIZATION

Bunn (2004) widespread hybridization between hairy marron and smooth marron

lower section 4 out of 8 locations

middle section 2 out of 4

upper section 9 out of 9 locations4 out of 8 locations

1-17% hybrids2 out of 4 locations

5-6% hybrids

9 out of 9 locations2-21% hybrids

70%

80%

90%

100%

VI

SMOOTH

39 11 15 1 00 0 0

REPLACEMENT MECHANISM: HYBRIDIZATION

20%

30%

40%

50%

60% VIVIIIIII

HYBRIDIZATION

Craig Lawrence ( lt )

0%

10%

20%

2 S

EP

2 O

CT

29 O

CT

20 N

OV

18 D

EC

13 J

AN

10 F

EB

10 M

ar

80%

90%

100%HAIRY

14 3 10 0 0 0 0

(aquaculture):No hairy male X smooth female Only hairy female X smooth

40%

50%

60%

70%VIVIVIIIIII

Only hairy female X smooth male

Phil Vercoe (genetics):

0%

10%

20%

30%

2 SEP 2 OCT 29 OCT 20 NOV 18 DEC 13 JAN 10 FEB 10 M

IPhil Vercoe (genetics):All hybrids hairy mother

2 SEP 2 OCT 29 OCT 20 NOV 18 DEC 13 JAN 10 FEB 10 Mar

50

60

%)

Smooth MarronHairy Marron 63

FEMALE

MALE

Smooth Hairy

20

30

40

cent

age

Mat

ure

Mal

es (%

102

119

97

75

TIME

MALE

0

10

2 SEP 2 OCT 29 OCT 20 NOV 18 DEC 13 JAN 10 FEB 10 MAR

Per

c

96

55 43

3170

104

9160

433626de Graaf and Hugh, in prep

DISPLACEMENT MECHANISM: HYBRIDIZATION

Austin & Ryan (2002) elevated Hairy & Smooth Marron to species level based on the assumption of

‘minimal interbreeding’.

Large and significant body of evidence exists that a) interbreeding and hybridization are common b) hybrids are fertile and viable.b) hybrids are fertile and viable.

Hairy & smooth marron do not appear to be reproductively isolated entities,presumably have not diverged to the point that they can coexist in sympatrypresumably have not diverged to the point that they can coexist in sympatry

whileretaining their integrity. EVOLUTION NIPPED IN THE BUD!!

More accurate to view hairy and smooth marron as geographical subspecies (Austin & Knott, 1996), hybridization key role in the displacement

Regardless of precise taxonomical status, hairy marron clearly adivergent and distinct population enriching the freshwater crayfish biodiversitydivergent and distinct population enriching the freshwater crayfish biodiversity in an area already recognized as a global biodiversity ‘hotspot’ (Myers et al., 2000), and as such requires careful management and protection.

Management and Recovery PlanDepartment of Fisheries

li i i ith C t Cliaising with Cape to Cape NRM Group.Recreational fishing

prohibited in upper Margaretprohibited in upper Margaret RiverIntensive fishouts involving

landowners removinglandowners removing smooth marron. Over 4000 smooth marron

removed from hairy marronremoved from hairy marron habitat.

Captive Breeding ProgramProgram

Selected Hairy Marron (Cherax tenuimanus) were removed from Margaret Riverremoved from Margaret River.

Genetically tested to confirm as “pure” Hairy Marron.

Captively bred at PembertonCaptively bred at Pemberton Freshwater Research Centre PFRC.Restocking of Hairy MarronRestocking of Hairy Marron

juveniles into upper reaches of Margaret River

2500 tagged animals gg

Management Plan Results

90

100 Upper reaches

Middle reaches

60

70

80

y M

arro

n (%

) Lower reaches

40

50

60

Prop

ortio

n H

airy

10

20

30

P

0

1979

1980

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1991

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1993

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1995

1996

1997

1998

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2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

Intensive removal of smooth marron

Decline has stabilised since intensive trapping commenced

Future Management of the Margaret River Hairy Marron

Continued removal of smooth marronContinued removal of smooth marron.Captive breeding program.More research to confirm mechanisms of hybridization.C ti d it i l t dContinued community involvement and awareness.Genetic testing to confirm a hairy genotype is always expressed as a hairy

phenotype.Continued research and monitoring.

Thankyouy