saving the marron from extinction - riversymposium 2011 marron from extinction ... 5-6% hybrids 9...
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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…
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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
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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