Translocations of freshwater crayfish: contributions from
life histories, trophic relations and diseases of three species
in Western Australia
Stephen John Beatty
This thesis is presented for the Doctor of Philosophy
2
DECLARATION
I declare that the information contained in this thesis is the result of my own research unless otherwise cited
........................................................................ Stephen John Beatty
Frontispiece: Elizabeth Gratwick
3
Abstract By examining Western Australian freshwater crayfishes, this thesis aims to further our
understanding of how life-history strategies, trophic relationships and disease introductions
contribute to the threats posed by introduced species. Reproductive and population biology
of two species of freshwater crayfish endemic to Western Australia (the marron Cherax cainii
and gilgie Cherax quinquecarinatus) and the introduced yabbie Cherax destructor were
described. Multiple stable isotope analysis was employed to determine the trophic positions
of sympatric populations of C. cainii and the invading. A serious microsporidian disease of
freshwater crayfishes was also discovered in a wild population of C. destructor. These data
were used to determine the potential threat that C. destructor poses to the endemic crayfishes
of Western Australia.
Cherax cainii supports an iconic recreational fishery that has been in steady decline
for three decades. It is likely that considerable plasticity in the biology of C. cainii exists
amongst the ca 100 populations and that this may result in the current fishery management
regulations being not effective in protecting all stocks. To test these hypotheses, the biology
of C. cainii were described from populations occurring in an impoundment dam (Lake
Navarino) at the approximate centre of its current range and in the Hutt River at the
northernmost point of its range and compared with those from a previous study near the
southernmost point of its distribution. The study confirmed these hypotheses. For example,
the onset of spawning was later in the more southerly Lake Navarino population (August)
than in the northerly Hutt River population (July). Furthermore, the respective orbital
carapace lengths (OCL) at which C. cainii reached maturity in the two populations studied
here differed markedly. The lengths at which 50% of female and male C. cainii matured in
Lake Navarino were 32.1 mm and 28.6 mm OCL for females and males, respectively,
compared with 70 mm and 40 mm OCL for females and males in the Hutt River, respectively.
Therefore, these data clearly demonstrate that the current minimum legal size limit of 76 mm
4
CL (~55 mm OCL) is ineffective in allowing females to undertake a spawning event prior to
legal capture. It is therefore recommended that the minimum legal size limit be increased to
98 mm CL in the Hutt River to allow 50% of females to reach maturity prior to exploitation.
Furthermore, as the spawning rate of mature female C. cainii in the Hutt River was low
(10%) compared with those mature females in the more southerly Lake Navarino (96%), this
increase in minimum legal size of capture is of particular importance should fisheries
managers wish this translocated population to be exploited sustainably.
It is proposed that the much larger lengths at first maturity and low spawning rate in
the Hutt River were due to faster growth rates likely caused by relatively high water
temperatures and in response to competition with the sympatric, introduced crayfish, C.
destructor, respectively. This highlights the plasticity of the biology of C. cainii and has
considerable implications for effective management of the size-regulated recreational fishery.
Cherax quinquecarinatus, a south-western Western Australian endemic: occupies a
broad range of aquatic systems, is likely to be an important component to those aquatic food
webs, and is also subject to recreational fishing pressure. Cherax quinquecarinatus was
found to mature at a relatively small size (cf C. cainii) with the L50s for females and males
being 18.8 and 24.5 mm OCL, respectively, with the majority of C. quinquecarinatus first
spawning at the end of their second year of life. The potential (ovarian) and pleopodal
fecundities of C. quinquecarinatus were relatively low compared to other freshwater
crayfishes, being 81.7 (±5.93 s.e.) and 77.1 (±13.76 s.e.), respectively. Cherax
quinquecarinatus underwent an extended spawning period, from late winter to late summer
(i.e. August to February). Three spawning events were facilitated by short brood and rapid
gonadal recovery periods, traits consistent with other crayfish species able to exist in
temporary environments.
The seasonal von Bertalanffy growth curve, fitted for the first 14 months of life for
female and male C. quinquecarinatus, had respective K and OCL∞s of 0.29 and 59.6 mm
5
OCL for females, and 0.25 and 73.8 mm OCL for males, respectively. At 12 months of age,
the OCLs of females and males were 14.7 and 14.1 mm, respectively. Estimates of total
mortality (Z) were relatively high at 2.34 and 1.95 year-1 based on an age-converted catch
curves for females and males, respectively, with a considerable proportion of this attributed to
fishing mortality (exploitation rates of 0.76 and 0.75 for females and males, respectively).
Cherax quinquecarinatus exhibited traits of both an r- and a K-strategist, which has likely to
have aided the success of this species across a wide range of permanent and temporary
systems.
During this study, C. destructor was found in many wild aquatic systems in the
southern Pilbara and Southwest Coast Drainage Divisions of Western Australia. This is of
great concern as all native freshwater crayfishes in Western Australia are restricted to the
southwest while the aquatic systems of the Pilbara Division do not naturally house freshwater
crayfish.
Despite the reported impacts that invasive freshwater crayfish species may have on
native crayfish species and food webs, the biology and ecology of C. destructor in wild
systems in Western Australia was unknown and therefore an assessment of their potential
impact has not previously been possible. Cherax destructor was collected monthly from the
Hutt River (Pilbara Drainage Division) for determination of life-history and reproductive
biology in a wild aquatic system in Western Australia. Proliferation in that system was
attributed to specific traits including: a small size at first maturity with 50% (L50) of females
and males maturing at 21.6 and 26.5 mm OCL, respectively, a size attained at the end of their
first year of life; a protracted spawning period (July to January); high mean ovarian fecundity
of 210.2 (±9.24 s.e.); and a rapid growth rate that was comparable to the larger sympatric C.
cainii in this system. Life-history characteristics of C. destructor in the Hutt River were
typical of many other invasive crayfish species and were likely to have aided in its
establishment.
6
This study is the first to examine the diet and trophic position of sympatric
populations of two species of freshwater crayfish in Australia. By determining temporal
changes in the assimilated diet and trophic positions of sympatric populations of C. destructor
and C. cainii, this study tested the hypothesis that C. destructor has the potential to compete
with C. cainii for food resources. This was tested using multiple stable isotope analyses with
samples of C. cainii, C. destructor and a wide variety of their potential food sources analysed
in the Hutt River in summer and winter, 2003. Summer samples indicated that these species
occupied similar predatory trophic positions when their assimilated diet consisted of a large
proportion of Gambusia holbrooki (either when the fish were alive or deceased due to a
presumably large natural mortality rate). Although C. cainii continued to assimilate animal
matter based on winter signatures, those of C. destructor appeared to shift towards more of
herbivorous trophic position. It appeared that C. destructor and C. cainii were keystone
species in the Hutt River and were likely to be important in the cycling of nutrients and in
structuring the aquatic food web that may have been considerably altered by their
introduction into this system.
As C. destructor has the ability to switch trophic positions, when an otherwise
abundant, high protein food sources (i.e. fish) becomes limited (as was the case in winter in
the Hutt River), it was able to co-exist with C. cainii. Furthermore, the ability of C.
destructor to switch from a diet of fish in summer to a predominantly herbivorous/detrital
diet in winter suggests that it may compete for food resources with the other smaller native
freshwater crayfishes (such as C. quinquecarinatus) in the small, unproductive lotic and
lentic systems common to south-western Australia, which often lack fish during summer.
The recently described Thelohania parastaci was identified in C. destructor in the
Hutt River and Vavraia parastacida, previously recorded from C. cainii and C.
quinquecarinatus populations elsewhere in the region, appeared to be infecting C. cainii.
Although not confirmed to have infected C. cainii, the presence of T. parastaci in the
sympatric C. destructor is of serious concern as there is the potential that the disease may be
7
able to be transmitted to the native congeners of the region, particularly as C. destructor
establishes itself in other natural waterbodies.
This thesis has addressed major gaps in the understanding of the biology, ecology
and threats to the unique freshwater crayfish fauna of Western Australia. The results of
this research highlight the plasticity of the biology and ecology of freshwater crayfishes
and enabled an initial assessment to be made of the potential ecological impacts of an
invading species. Considerable implications for fisheries and other natural resource
management agencies ensuing from this research are detailed. The conclusions drawn
from this study are also discussed in the broader context of invasive species in general and
important future investigations stemming from these results are identified.
8
Acknowledgements
I feel very fortunate to have had the guidance of Drs David Morgan and Howard Gill who
have both inspired me throughout my studies and fostered my passion for freshwater
biology and ecology and for whom I have the utmost respect. Great appreciation is
expressed to Drs Simon de Lestang, Alex Hesp and Norm Hall for their helpful discussions
regarding modelling the growth and maturity of crustaceans. Thanks also to Dr Brett
Molony for earlier inspirational discussions on many aspects of the unique and precious
freshwater fauna of this region, and is a scientist whom I respect greatly. I would like to
express gratitude to Dr Jenny Davis, an aquatic ecologist who has done much to shape my
research direction.
Many thanks to other members of Murdoch University’s Centres for Fish and
Fisheries Research and Aquatic Ecology, in particular Mark Allen, Mark Maddern, Suzie
Wild, Simon Hambleton, Megan McGuire and Dean Thorburn for help in sampling and
discussions on all things underwater. The expertises of Gordon Thomson in help with the
histological preparations, Simon Visser with photography, and Dr Brian Jones regarding
nasty diseases, have all been greatly appreciated. Thanks to Murray Angus for his help at
the ALCOA Willowdale marron farm. I would also like to pay tribute to the late Dr Luke
Pen, a greatly admired biologist and ecologist whose large body of work greatly inspired
many aquatic researchers in Australia, not least I.
Many thanks to the following organisations who provided funding to David Morgan,
Howard Gill and myself for various aspects of this study: Murdoch University, the Natural
Heritage Trust, the Department of Fisheries, Government of Western Australia, Fisheries
Research Development Corporation, the Water Corporation of Western Australia, Water
and Rivers Commission of Western Australia and ALCOA Australia.
I would finally like to thank my friends who have supported me on this journey and
my brother David, father Ken, and mother Jan whose patience, love and support I could
never express in words what have meant to me. Right, let the world keep turning!
9
Table of contents
Abstract.............................................................................................................................. 3
Acknowledgements......................................................................................................... 8
Table of contents............................................................................................................. 9
Publications....................................................................................................................... 15
Chapter 1
General Introduction............................................................................................... 16
1.1 Phylogeny and zoogeography of freshwater crayfishes........................................ 16
1.1.1 Origin of freshwater crayfishes................................................................................. 16
1.1.2 Interrelationships and evolution within the Astacida................................................ 17
1.1.3 Australian freshwater crayfishes............................................................................... 19
1.1.4 Taxonomy of Cherax: the current state of play......................................................... 21
1.1.5 Western Australian freshwater crayfishes................................................................. 23
1.2 Biology and ecology of freshwater crayfishes....................................................... 23
1.2.1 Life-history strategies................................................................................................ 23
1.2.2 Ecological roles of freshwater crayfishes.................................................................. 24
1.2.3 The biology and ecological role of freshwater crayfishes in Western Australia....... 25
1.3 Impacts of introduced species on freshwater crayfishes...................................... 28
1.3.1 Worldwide aquatic introductions.............................................................................. 28
1.3.2 Impacts of freshwater crayfish introductions............................................................ 29
1.3.3 Threats posed by the yabbie Cherax destructor in Western Australia...................... 32
1.4 Aims of this thesis.................................................................................................... 34
Chapter 2
Reproductive biology of the large freshwater crayfish Cherax
cainii in south-western Australia..................................................................... 36
2.1 Introduction................................................................................................................ 36
2.2 Materials and methods............................................................................................ 38
2.2.1 Study sites.................................................................................................................. 38
10
2.2.2 Environmental variables............................................................................................ 38
2.2.3 Sampling.................................................................................................................... 38
2.2.4 Relationships of orbital carapace length, carapace length and weight.................... 39
2.2.5 Gonadosomatic indices (GSIs).................................................................................. 39
2.2.6 Macroscopic and histological descriptions of gonad development........................... 39
2.2.7 Potential and effective fecundities............................................................................. 40
2.2.8 Size at first maturity................................................................................................... 40
2.3 Results....................................................................................................................... 41
2.3.1 Environmental variables of Lake Navarino............................................................... 41
2.3.2 Sex ratios, OCL versus CL and weight versus OCL.................................................. 41
2.3.3 Histological and macroscopic gonad descriptions.................................................... 42
2.3.4 Temporal descriptions of female gonadal development............................................ 43
2.3.5 Gonadosomatic indices.............................................................................................. 45
2.3.6 Potential and effective fecundities............................................................................. 45
2.3.7 Size at first maturity................................................................................................... 45
2.4 Discussion................................................................................................................. 46
2.4.1 Sex ratios, carapace length, orbital carapace length and length-weight
relationships............................................................................................................... 46
2.4.2 Seasonal breeding cycle............................................................................................. 46
2.4.3 Size at first maturity................................................................................................... 49 2.4.4 Factors influencing effective and potential fecundity................................................ 49
Chapter 3
Biology of a translocated population of the large freshwater
crayfish Cherax cainii, in a Western Australian river....................... 52 3.1 Introduction.............................................................................................................. 52
3.2 Materials and methods............................................................................................ 54
3.2.1 Sampling.................................................................................................................... 54
3.2.2 Gonadal development................................................................................................ 54
3.2.3 Gonadosomatic indices (GSI).................................................................................... 54
3.2.4 Size at first maturity................................................................................................... 55
3.2.5 Length-frequency and growth rates........................................................................... 56
11
3.2.6 Mortality.................................................................................................................... 57
3.3 Results....................................................................................................................... 58
3.3.1 Environmental variables and catch data................................................................... 58
3.3.2 Temporal descriptions of gonad development of Cherax cainii................................ 59
3.3.3 GSI............................................................................................................................. 59
3.3.4 Size at first maturity................................................................................................... 60
3.3.5 Growth....................................................................................................................... 60
3.3.6 Mortality.................................................................................................................... 61
3.4 Discussion................................................................................................................. 61
3.4.1 Reproductive biology................................................................................................. 62
3.4.2 Biological plasticity................................................................................................... 62
3.4.3 Management implications.......................................................................................... 66
3.4.4 Conclusions................................................................................................................ 67
Chapter 4
Life-history and reproductive biology of the south-western
Australian endemic gilgie Cherax quinquecarinatus........................... 69 4.1 Introduction............................................................................................................. 69
4.2 Materials and methods............................................................................................ 70
4.2.1 Sampling regime........................................................................................................ 70
4.2.2 Morphological relationships...................................................................................... 71
4.2.3 Reproduction.............................................................................................................. 71
4.2.4 Temporal Pattern in hepatosomatic Indices.............................................................. 73
4.2.5 Growth....................................................................................................................... 73
4.2.6 Mortality.................................................................................................................... 74
4.2.7 Density....................................................................................................................... 75
4.3 Results....................................................................................................................... 76
4.3.1 Environmental variables........................................................................................... 76
4.3.2 Morphological relationships..................................................................................... 77
4.3.3 Reproductive biology................................................................................................. 77
4.3.4 Temporal pattern in hepatosomatic indices............................................................... 79
4.3.5 Growth....................................................................................................................... 80
4.3.6 Mortality.................................................................................................................... 81
4.3.7 Density....................................................................................................................... 81
12
4.4 Discussion................................................................................................................. 81
4.4.1 Reproductive biology................................................................................................. 83
4.4.2 Temporal pattern in hepatopancreatic indices.......................................................... 85
4.4.3 Growth and mortality................................................................................................. 86
4.4.4 Conclusions................................................................................................................ 89
Chapter 5
Role of life-history strategy in the colonisation of Western
Australian aquatic systems by the introduced crayfish Cherax
destructor......................................................................................................................... 90
5.1 Introduction.............................................................................................................. 90
5.2 Materials and methods............................................................................................ 92
5.2.1 Distribution of Cherax destructor in Western Australia........................................... 92
5.2.2 Hutt River study site and sampling regime................................................................ 93
5.2.3 Environmental variables ........................................................................................... 93
5.2.4 Reproductive biology................................................................................................. 93
5.2.5 Growth and mortality................................................................................................. 95
5.3 Results....................................................................................................................... 97
5.3.1 Present distribution in Western Australia................................................................. 97
5.3.2 Environmental variables........................................................................................... 97
5.3.3 Reproductive biology................................................................................................. 98
5.3.4 Growth and mortality................................................................................................ 100
5.4 Discussion................................................................................................................. 102
5.4.1 Distribution of Cherax destructor in Western Australia............................................102
5.4.2 Reproductive biology................................................................................................. 103
5.4.3 Growth....................................................................................................................... 105
5.4.4 Mortality.....................................................................................................................107
5.4.5 Conclusions................................................................................................................ 107
Chapter 6
The diet and trophic positions of sympatric populations of Cherax
destructor and Cherax cainii in the Hutt River, Western Australia:
evidence of resource overlap............................................................................... 109
13
6.1 Introduction.............................................................................................................. 109
6.2 Materials and methods............................................................................................ 112
6.2.1 Sampling regime........................................................................................................ 112
6.2.2 Sample preparation....................................................................................................113
6.2.3 Sample analysis..........................................................................................................114
6.2.4 Determination of trophic position.............................................................................. 114
6.2.5 Mixing model: IsoSource........................................................................................... 115
6.2.6 Comparison of assimilated diets between species, season and maturity................... 116
6.3 Results....................................................................................................................... 117
6.3.1 Summer δ13C and δ15N signatures............................................................................. 117
6.3.2 Winter δ13C and δ15N signatures............................................................................... 119
6.3.3 Differences in the δ13C and δ15N signatures between groups of freshwater
crayfishes................................................................................................................... 120
6.3.4 Trophic position of Cherax cainii and Cherax destructor in the Hutt River............. 120
6.3.5 Assimilated diet of Cherax cainii and Cherax destructor in the Hutt River............. 121
6.3.6 Classification and ordination of the dietary data...................................................... 122
6.3.7 Similarities and differences in the assimilated diets of freshwater crayfishes.......... 122
6.4 Discussion................................................................................................................. 123
6.4.1 Assimilated diets and trophic positions of Cherax cainii and Cherax destructor in the
Hutt River.................................................................................................................. 123
6.4.2 Trophic and functional roles of freshwater crayfishes.............................................. 124
6.4.5 Conclusions................................................................................................................ 127
Chapter 7
First evidence of microsporidian infection of sympatric wild
populations of Cherax cainii and Cherax destructor in Western
Australia.......................................................................................................................... 128
7.1 Introduction.............................................................................................................. 128
7.2 Materials and methods............................................................................................ 133
7.2.1 Study site................................................................................................................... 133
7.2.2 Sampling regime........................................................................................................ 133
7.2.3 Laboratory techniques............................................................................................... 133
7.3 Results....................................................................................................................... 134
7.3.1 Spore concentration technique.................................................................................. 134
14
7.3.2 Genetic testing........................................................................................................... 136
7.4 Discussion................................................................................................................. 136
7.4.1 What species of microsporidians are infecting Cherax cainii and Cherax destructor in
the Hutt River?........................................................................................................... 136
7.4.2 Microsporidian infection rates.................................................................................. 138
7.4.3 The introduction and spread of Thelohania sp. in Western Australia....................... 140
7.4.4 Potential impacts of Thelohania parastaci................................................................ 141
7.4.5 Conclusions................................................................................................................ 142
Chapter 8
Summary and General Conclusions.............................................................. 144
8.1 Plasticity of the biology of Cherax cainii............................................................... 145
8.2 Comparison of the biology of wild populations of C. cainii, C. destructor and
Cherax quinquecarinatus in Western Australia.................................................... 146
8.3 Trophic positions of translocated populations of C. cainii and C. destructor..... 147
8.4 The threat of Cherax destructor to the aquatic fauna and ecosystems of Western
Australia................................................................................................................... 148
8.5 Future research arising from this thesis................................................................ 149
References...................................................................................................................... 154
15
Publications
The following publications form the basis of many of the chapters in this thesis.
Beatty, S. J., Morgan, D. L., and Gill, H. S. (2003). Reproductive biology of the large
freshwater crayfish Cherax cainii in south-western Australia. Marine and
Freshwater Research 54, 597-608.
Beatty, S. J., Morgan, D. L., and Gill, H. S. (2004). Biology of a translocated population of
the large freshwater crayfish, Cherax cainii Austin and Ryan, 2002 in a Western
Australian river. Crustaceana 77 (11), 1329-1351.
Beatty, S. J., Morgan, D. L., and Gill, H. S. (2005). Life-history and reproductive biology of
the gilgie Cherax quinquecarinatus, a freshwater crayfish endemic to south-western
Australia. Journal of Crustacean Biology 25 (2).
Beatty, S. J., Morgan, D. L., and Gill, H. S. (in press). Role of life-history strategy in the
colonisation of Western Australian aquatic systems by the introduced crayfish
Cherax destructor. Hydrobiologia.
Additional publication produced from this research:
Beatty, S. J., Molony, B. W., Rhodes, M., and Morgan, D. L. (2003). A methodology to
mitigate the negative impacts of dam refurbishment on fish and crayfish values in a
south-western Australian reservoir. Ecological Management and Restoration 4 (2),
147–49.
Lake Navarino
1000 200 km
Hutt River
Warren River
Margaret River
Canning River(Bulls Creek)
Geraldton
Albany
Perth
Esperance
WesternAustralia
Pilbara DrainageDivision
Southwest CoastDrainage Division
Zone of UncoordinatedDrainage
Northampton
Moore River
Fig. 1.1 South-western Western Australia showing the main study sites (blue
points) in the current thesis. N.B. The major Drainage Divisions of
the region are shown (after Allen et al. 2002) as are the aquatic
systems, cities and towns that are referred to in this study.
(Bull Creek)
A
B
C
Plate 1.1 Freshwater crayfishes examined in the current thesis: A) marron
Cherax cainii, B) gilgie Cherax quinquecarinatus, and C) yabbie
Cherax destructor (an introduced species).
A
B
Plate 2.1 Lake Navarino (Waroona Dam) in south-western Western Australia. A)
Aerial photograph of Lake Navarino during partial drainage (see Beatty
et al. 2003), and B) view from the Dam wall during the current study
(prior to drainage).
Lake Navarino
Swan Coastal Plain
Darling Scarp
Plate 2.2 The basin of Lake Navarino during draining in 2003 (see Beatty et al.
2003). Note the absence of heterogeneous benthic habitat.
Plate 2.3 Redfin perch, Perca fluviatilis; a major predator of endemic freshwater
crayfishes and fishes in south-western Australia.
F
10
30
550
900
Rai
nfal
l (m
m)
Day
-leng
th (m
in)
Mean rainfall (1951-2000)Rainfall during sampling period
Maximum
Minimum
(a)
(c)
(d)
(b)
Month
T
empe
ratu
re (
C)
0
M A M J J A S O N D J
5
35
0
250
Rai
nfal
l (m
m)
Tem
pera
ture
(°C
)D
ay-le
ngth
(min
)
250
0
900
A
B
550
35C
5
D30
10
Maximum
Minimum
M
Month
MA J J A S O N D J F
Mean rainfall(1951-2000)Rainfall duringSampling period
Fig 2.1 A) Mean (1951 to 2000, + 1 s.e.) and actual monthly rainfall, B) duration
of day, C) mean monthly maximum and minium air temperatures (± 1
s.e.), and D) mean monthly water temperatures (± 1 s.e.) for Lake
Navarino.
Fig. 2.2 Microscopic appearance of the different gonadal developmental stage of
female Cherax cainii in Lake Navarino. N.B. N = nucleus; NI =
nucleoli; YG = yolk granule; YV = yolk vesicle; POF = post-ovulatory
follicle; FC = follicle cell; Og = Oogonia; PN = perinucleolar oocyte;
ED = developing embryo. N.B. Magnification 1 : 0.025.
Stage I/II: Immature / recovering spent
Stage III: Developing (yolk vesicle)
Egg
Stage V: Mature / gravid
Stage IV: Developed (late yolk vesicle)
Stage VI: Ripe / spawning
Stage VII: Spent
N
N
N
N
N
N
FC
FC
YV
YG
YG
FC
NI
NI
NI
NI POF
ED
YV
NI
PN
500µm
Og
20
20
0
50
0
0
20
0
0
20
0
30
0
Freq
uenc
y (%
)
Oocyte diameter (µm)
1000 2000 3000
Stage I / II (immature/recovering) n = 11 (254)
Stage IV (late yolk vesicle) n = 10 (187)
Stage III (yolk vesicle) n = 10 (190)
Stage V (mature/gravid) n = 10 (149)
Stage VI (ripe/spawning) n = 11 (254)
Stage VII (spent) n = 8 (170 oocytes, 80 eggs)
Fig. 2.3. Mean oocyte diameters of the different gonad stages of female Cherax
cainii. N.B. n = number of C. cainii (number of oocytes measured is in
parenthesis). For the individuals possessing stage VII ovaries (i.e.
ovigerous females), the diameters of pleopodal eggs are also included
(unfilled columns).
0
20
0
20
0 400 800 1200 1600 2000 2400 2800 3200
Oocyte diameter (µm)
June n = 18 (192)
July n = 9 (68)
0
40
0
30
0
30
0
30
August n = 15 (169)
September n = 14 (254)
November n = 26 (611)
December n = 31 (734)
January n = 29 (661)
February n = 27 (429)
0
30
0
20
0
20
0
20
March n = 10 (105)
May n = 11 (121)
Freq
uenc
y (%
)
Fig. 2.4. Monthly distributions of the diameters of oocytes in ovaries
(histologically examined) of Cherax cainii. N.B. n =
number of C. cainii (number of oocytes is in parentheses).
I/II III IV V VI VII
Gonad stage
Augustn = 18
Septembern = 32
Novembern = 24
Decembern = 34
Januaryn = 25
Februaryn = 27
Per
cent
age
(%)
Marchn = 27
Mayn = 28
Junen = 32
Julyn = 10
Octobern = 6
0
1000
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Fig. 2.5 Monthly percentage contributions of female Cherax cainii at the
different gonadal developmental stages in Lake Navarino.
0
25
50
75
100
A S O N D J F M A M J J
Month
Per
cent
age
berr
ied
(%)
Fig. 2.6 Percentage of mature (i.e. gonads of recovering stage II, or
III-VII) female Cherax cainii in Lake Navarino that were
berried in each month of the study.
0
1
2
3
4
5
A S O N D J F M A M J J
Month
Gon
ados
omat
ic in
dex
Fig. 2.7 Mean monthly gonadosomatic indices (± 1 s.e.) for female Cherax
cainii in Lake Navarino with immature (i.e. stages I/II, continuous
line) and maturing/mature (III-VII, broken line) gonad stages.
Females 4 4 5 12 28 30 18 12 5 2 2 1
Orbital carapace length (mm)
20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Perc
enta
ge (%
)
0
25
50
75
100
Stages III - VII (females)Stages III - V (males)Stages I / II
Males 2 7 9 10 11 11 8 2 1
Orbital carapace length (mm)
20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Perc
enta
ge (%
)
0
25
50
75
100
Fig. 2.8 Percentage contributions of gonad development stages I/II (i.e. immature females
and males), III-VII (i.e. maturing/mature females) and III-V (i.e. mature males) in
sequential 5 mm OCL intervals of female and male Cherax cainii in Lake
Navarino during the breeding season, i.e. August to December. The logistic
curve was fitted to the percentage of female C. cainii with gonads at stages III–
VII or male C. cainii with gonads at stages III–V. The number of C. cainii in
each length interval is given.
Table 2.1 Macroscopic and histological descriptions of the oocytes of the different stages of ovarian development for
female Cherax cainii in Lake Navarino
Ovarian stage Macroscopic description Maximum oocyte
diameter (µm)
Histological description
I/II
Immature/recovering
Ovaries thin strand-like and white. Recovering spent gonads thickened and orange/white with some larger unspent oocytes present.
400 Oogonia and perinucleolar oocytes dominate. Post-spent ovaries also contain atretic oocytes and post-ovulatory follicles.
III
Developing (yolk vesicle)
Ovaries thickened, dark grey, with larger unspent orange oocytes present. Oocytes within ovary discernable.
800 Oocytes undergoing primary development with a band of cytoplasmic yolk vesicles appearing around the nucleus in larger oocytes. Follicle cells starting to envelop oocytes.
IV
Developed (late yolk vesicle)
Ovaries further thickened and very dark grey in colour with some unspent orange oocytes visible. Oocytes clearly visible in ovary.
1100 Oocytes have a thickened distinct cytoplasmic yolk vesicle region. Larger oocytes contain yolk granules concentrated in a band peripheral to the vesicle region in the cytoplasm. Follicle cells envelop oocytes.
V
Mature or gravid (yolk vesicle)
Ovaries thickened and deep grey nearing black in colour and oocytes clearly visible.
1700 Yolk granules dominate the cytoplasm indicating further vitellogenesis. Follicle cells envelop oocytes.
VI
Ripe/spawning
Ovaries swollen and large black oocytes clearly visible in the ovary.
3000 Cytoplasm dominated by yolk vesicles and some hydration of oocyte evident. Follicle cells largely disintegrate from around the oocytes.
VII
Spent
Slightly thickened ovaries. Largely white with occasional unspent orange oocytes able to be distinguished.
700 Post-ovulatory follicles present along with unextruded ova and signs of atretic oocytes.
Table 2.2 Macroscopic descriptions of the different stages of testicular
development for male Cherax cainii in Lake Navarino
(adapted from Laevastu 1965; Aitken and Waddy 1980;
Hamr and Richardson 1994)
Testicular stage Macroscopic description
I
Virgin
Thin, clear vas deferens.
II
Maturing virgin
Thin, slightly milky opaque vas deferens.
III
Mature
Thickened, milky opaque vas deferens.
IV
Gravid
Swollen, milky opaque vas deferens.
V
Spawning
Swollen, milky vas deferens with distal (near the ejaculatory duct) end being less opaque than proximal and mid regions.
Hutt River
Yerina Springs site
Monthly sampling site
1 km
Box Rd site Trevenson Rd site
Ogilvie Rd site
Estuarine site
Indian Ocean
Plate 3.1 Aerial photo of the Hutt River showing the monthly sampling site for
Cherax cainii and Cherax destructor and those sampled to determine their
distributions in that system.
A
B
Plate 3.2 Contrasting water levels in the Hutt River during A) summer and
B) winter.
Wat
er te
mpe
ratu
re (o C
)
05
1015202530
A
B
600
700
800
900
Day
-leng
th (m
in)
C
Dis
char
ge (m
3 sec-1
)
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0.01
0.1
1
10
100
Fig. 3.1 Environmental conditions at the Hutt River study site.
A) Mean water temperature (± 1 s.e.), B) mean
instantaneous rate of discharge, and C) day-length.
0
100
0
100
0
100
0
100
Gonad stage
0
100
Julyn = 53
Augustn = 62
Septembern = 57
Octobern = 69
Novembern = 60
Decembern = 25
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Junen = 46
Januaryn = 25
Februaryn = 35
Marchn = 62
Apriln = 50
Mayn = 46
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Junen = 58
Julyn = 61
Augustn = 66
Januaryn = 22
Februaryn = 35
Marchn = 45
Apriln = 48
Mayn = 60
Septembern = 57
Octobern = 70
Freq
uenc
y (%
)
0
100
0
100
Novembern = 58
Decembern = 33
Females Males
I II III IV V VII II III IV V VI VII
Fig. 3.2 Monthly frequency of different gonad developmental stages of female
and male Cherax cainii in the Hutt River.
Month
J F M A M J J A S O N D
Gon
ados
omat
ic in
dex
0
1
2
3
4 ImmatureMature
Month
J F M A M J J A S O N D
Gon
ados
omat
ic in
dex
22 35 25 21 55 48 56 59 48 61 58 23
8
5
8
7
4
8
84
2
9
23
11
1913
23 3823
31
2647
22
0.25
0.5
0
Females
Males
1216
222923 33 30 25 20
24 34 19
Fig. 3.3 Mean gonadosomatic indices (+ or - 1 s.e.) for female and male
Cherax cainii in the Hutt River with immature (i.e. stages I/II) and
maturing/mature (i.e. stages III-VI) gonad stages.
Orbital carapace length (mm)
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Perc
enta
ge(%
)
0
20
40
60
80
100
Females
10 4932 4471 35 24 4034 35 28 24 14 12 3 1
Orbital carapace length (mm)
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90
Perc
enta
ge (%
)
0
20
40
60
80
100
Males26 61 46 40 42 39 28 38 38 27 20 15 8 6 1 22
L50
L50
Fig. 3.4 Percentage contributions of immature (i.e. stages I/II) and
maturing/mature (i.e. III-VII and III-VI for females and males,
respectively, black bars) gonadal development stages in sequential 5 mm
OCL intervals of female and male Cherax cainii in the Hutt River prior
to and during the breeding season, i.e. May to December. The logistic
curves (including 95% confidence limits) were fitted to the percentage of
contributions of C. cainii with maturing/mature gonads. N.B. The
number of C. cainii in each length interval is provided at the top of each
column.
Septembern = 127
Octobern = 141
Novembern = 118
Januaryn = 54
Februaryn = 74
Marchn = 108
Apriln = 98
Mayn = 107
Julyn = 128
Junen = 108
Augustn = 128
Decembern = 84
0
20
0
20
0 10 20 30 40 50 60 70 80 90
0
20
0
250
200
20
0
25
0
20
0
20
0
20
0
20
0
20
Num
ber o
f C. c
aini
i
Orbital carapace length (mm)
Fig. 3.5 Orbital carapace length-frequency histograms in each month for
Cherax cainii in the Hutt River. Normal distributions have
been fitted to the one or two size cohorts present in each month
that were subsequently used in creating the seasonal von
Bertalanffy growth curve. N.B. n = sample size, and the
vertical dashed line is the minimum legal OCL for the
recreational fishery in this system.
Months
S O N D J F M A M J J A S O N D J F M A M J J A S O N D
Orb
ital c
arap
ace
leng
th (m
m)
0
10
20
30
40
50
60
70
Age (months)
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Fig. 3.6 Modified seasonal von Bertalanffy growth curves of Cherax cainii
in the Hutt River. N.B. Curves were fitted to the monthly mean
OCL of the 0+, 1+ or 2+ cohorts.
Relative age (t years)
0 1 2 3 4
ln (F
/dt)
0
2
4
6
8
Ln(F/dt) = -0.4141(t) + 6.857 r 2 = 0.63
Ln(F/dt) = -1.7904(t) + 9.308 r 2 = 0.88
Fig. 3.7 Length-converted catch curve of Cherax cainii in the Hutt River. N.B.
Slope of the regression line through closed circles represents the
instantaneous natural mortality rate (Zu) and the slope of the regression
line through triangles represents the instantaneous rate of total mortality
(Ze). Data points with open circles were excluded as they represent
mean ages that were not fully recruited (ascending data points) or those
with small sample sizes (<10 individuals). Vertical dotted line is
approximate age at minimum legal size in the Hutt River.
Table 3.1 Parameters for the seasonal von Bertalanffy growth curves and estimates of mortality
of Cherax cainii in the Hutt River, where: OCL∞ is the asymptotic orbital carapace
length, K is the curvature parameter, t0 is the theoretical age at which the estimated
OCL is zero, C determines the relative amplitude of the seasonal oscillation (where 0 ≤
C ≤ 1), ts determines the phase of seasonal oscillation relative to t0, r2 is the coefficient
of determination, Ze is the instantaneous rate of total mortality determined by a length
converted catch curve of C. cainii > legal size, Zu is the instantaneous rate of natural
mortality determined by a length converted catch curve of C. cainii < legal size, M is
the instantaneous rate of natural mortality determined using the equation of Pauly
(1980), F1 and F2 are instantaneous rates of fishing mortality determined using Zu and
M, respectively, and E1 and E2 are exploitation rates determined using F1 and F2,
respectively
Parameter Value
OCL∞ (mm) 101.9
K 0.42
t0 (month) 1.54
C 0.37
ts 3.85
r2 0.99
Ze (1year-1) 1.79
Zu (1year-1) 0.41
M (1year-1) 0.60
F1 (1year-1) 1.38
F2 (1year-1) 1.19
E1 0.77
E2 0.66
Table 4.1 Macroscopic and histological descriptions of the oocytes of the different stages of
ovarian development for female Cherax quinquecarinatus in Bull Creek
Ovarian stage Macroscopic description Maximum oocyte
diameter (µm)
Histological description
I/II
Immature/ recovering
Ovaries very thin, string-like some very pale orange oocytes discernable in an otherwise creamy ovarian matrix.
600 Oogonia, chromatin nucleolar and perinucleolar oocytes dominate. Post-spent ovaries also contain atretic oocytes and post-ovulatory follicles.
III
Developing (yolk vesicle)
Ovaries slightly thickened with bright orange oocytes easily discernable.
1100 Perinucleolar oocytes dominate ovary that have undergone primary vitellogenesis. Oogonia oocytes still present.
IV
Developed (late yolk vesicle)
Ovaries thickened with an obvious increase in oocyte size which are grey-green.
1800 Oocytes have a distinct cytoplasmic yolk vesicle region and yolk granules present indicating secondary vitellogenesis. Perinucleolar oocytes present.
V
Mature or gravid (yolk vesicle)
Ovaries slightly swollen with oocytes becoming dark grey.
2200 Yolk granules dominate the cytoplasm indicating further vitellogenesis. Ovarian epithelium with follicle cells surrounds oocytes.
VI
Ripe/spawning
Ovaries very swollen containing very dark grey oocytes.
2500 Cytoplasm of oocytes dominated by yolk vesicles. Perinucleolar oocytes still present.
VII
Spent
Ovaries thickened compared to virgins, orange oocytes of mixed sizes discernable in a predominantly creamy ovarian matrix.
1600 Post-ovulatory follicles present along with large un-extruded ova and perinucleolar oocytes.
Table 4.2 Parameters for the seasonal von Bertalanffy growth curves and mortality of
female and male of Cherax quinquecarinatus in Bull Creek where; OCL∞ is the
asymptotic orbital carapace length, K is the curvature parameter, t0 is the
theoretical age at which the estimated OCL is zero, C determines the relative
amplitude of the seasonal oscillation (where 0 ≤ C ≤ 1), ts determines the phase
of seasonal oscillation relative to t0, r2 is the coefficient of determination, Z is
the instantaneous total mortality rate (1year-1), M is the instantaneous natural
mortality rate (1year-1), F is the instantaneous rate of fishing mortality (1year-1)
and E is the exploitation rate
Growth parameter Females Males
OCL∞ (mm) 59.6 (71.2 mm CL) 73.8 (87.0 mm CL)
K 0.29 0.25
t0 (month) 0.18 0.44
C 1 0.71
ts 8.64 5.83
r2 0.99 0.99
Z (1year-1) 2.34 1.95
M (1year-1) 0.55 0.48
F (1year-1) 1.78 1.47
E 0.76 0.75
Wat
er te
mpe
ratu
re (o C
)
Month
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
15
20
25
Fig. 4.1 The mean water temperature (± 1 s.e.) in Bull Creek during the
sampling period.
Stage IV
Stage VII
Fig. 4.2 Microscopic characteristics of the ovarian developmental
stages IV and VII of Cherax quinquecarinatus in Bull Creek.
Pn = perinucleolar oocyte; N = nucleus; NI = nucleoli; YG =
yolk granule; YV = yolk vesicle; POF = post-ovulatory follicle;
FC = Follicle cell; OD = Ovarian duct; OE = Ovarian
epithelium; OL = Ovarian lumen; and RO = resorbing oocyte.
Pn
RO
POF
N
NI
Pn
YG
YV
OL
OE
OD
N
Pn
500 µm
1000 µm
Stage IIIn = 8 (116)
0
50
0
50
0
50
0
50
0 500 1000 1500 2000 2500
0
50
Stage VIn = 7 (57)
Stage VIIn = 2 (16)
Stage IVn = 26 (250)
Stage Vn = 30 (303)
Freq
uenc
y (%
)
Oocyte diameter (μm)
Fig. 4.3 Size-frequency distribution of oocytes in mature ovarian stages
(III-VII) of female Cherax quinquecarinatus in Bull Creek.
Month
0.0
0.1
0.2
0.3
0.4
Males
Month
Gon
ados
omat
ic in
dex
0
1
2
3
5 126
1015
2
4 2 12
41
17
6
23
27
1610
182634
31
19
11
15
10
Females
Gon
ados
omat
ic in
dex
May Jun Jul Aug OctSep Nov Dec Jan Feb Mar Apr
May Jun Jul Aug OctSep Nov Dec Jan Feb Mar Apr
10
14
14
11
13
3317
16
17
1222
9
14
19 10
1
18
714
4
5 1011
16
Fig. 4.4 Mean gonadosomatic indices (± 1 s.e.) for female and male Cherax
quinquecarinatus in Bull Creek with immature (i.e. gonad stages I/II,
continuous line) and mature/maturing (i.e. gonad stages III-VI, dashed
line).
N
Females Males
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Freq
uenc
y (%
)0
100
0
100
0
100
0
100
0
100
0
100
0
100
Junen = 28
Julyn = 32
Augustn = 36
Mayn = 32
Septembern = 21
Octobern = 20
Novembern = 38
Decembern = 28
0
100
Junen = 34
Julyn = 31
Augustn = 14
Mayn = 52
Septembern = 26
Octobern = 28
Novembern = 61
Gonad stageI II III IV V VI VII
0
100
I II III IV V
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Januaryn = 22
Februaryn = 13
Marchn = 24
Apriln = 27
Januaryn = 20
Februaryn = 23
Marchn = 24
Apriln = 41
Decembern = 26
Fig. 4.5 Monthly frequency of different gonad developmental stages of female and
male Cherax quinquecarinatus in Bull Creek.
Orbital carapace length (mm)
8 12 16 20 24 28 32 36 40 44 48
Per
cent
age
(%)
0
20
40
60
80
100
L50
Females2 95 816 12 14 36 31 40 28 19 8 6 2
Orbital carapace length (mm)
8 12 16 20 24 28 32 36 40 44 48
Per
cent
age
(%)
0
20
40
60
80
100
Males
1 31 114 6 15 2211 28 27 19 7 2 3 122 1115 1
L50
Fig. 4.6 Percentage contributions of immature (i.e. stages I/II, grey bars) and
maturing/mature (i.e. stages III-VII for females and III-VI for males,
black bars) gonadal development stages in sequential 2 mm OCL intervals
of female and male Cherax quinquecarinatus immediately prior to and
during the breeding season in Bull Creek, i.e. June to February. The
logistic curves (including 95% confidence limits) were fitted to the
percentage of contributions of C. quinquecarinatus with maturing/mature
gonads. N.B. The number of C. quinquecarinatus in each length interval
is given at the top of each column.
Month
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Dry
hep
atop
ancr
eas
inde
x (%
)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
39
19
2813
23
24
55
22
25
46
18
25
30
19
36
23
18
23
2131
22
13
23 21
Fig. 4.7 Dry hepatosomatic index of female (dashed line) and male (continuous
line) Cherax quinquecarinatus in Bull Creek. N.B. Sample sizes are
provided.
Month
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Hep
atop
ancr
eas
moi
stur
e (%
)
40
50
60
70
80
3719
28 1323
2458
22
2525
30 46 18
19
36 2318
23
21
31
22
13
2321
Fig. 4.8 Hepatopancreas moisture content (%) of female (dashed line) and male
(continuous line) Cherax quinquecarinatus in Bull Creek. N.B.
Sample sizes are provided.
Orbital carapace length (mm)
Females Males
0
40
0
40
0 10 20 30 40 50
0
40
0
60
0
40
0
40
0
40
Num
ber o
f C. q
uinq
ueca
rinat
us
0
40
0
40
0 10 20 30 40 50
0
40
0
40
0
40
0
40
0
40Septembern = 88
Octobern = 62
Novembern = 73
Mayn = 113
Julyn = 117
Junen = 157
Augustn = 76
Decembern = 49
Septembern = 123
Octobern = 117
Novembern = 95
Mayn = 145
Julyn = 131
Junen = 175
Augustn = 101
Decembern = 69
0
40
0
40
0
400
400
40
0
400
400
400
40
0
40
Januaryn = 41
Februaryn = 78
Marchn = 63
Apriln = 99
Januaryn = 93
Februaryn = 148
Marchn = 96
Apriln = 124
Fig. 4.9 Orbital carapace length-frequency histograms in each month for female and
male Cherax quinquecarinatus in Bull Creek. Normal distributions have
been fitted to the 0+ size cohort in each month. N.B. n = sample size.
Months
S O N D J F M A M J J A S O N
Orb
ital c
arap
ace
leng
th (m
m)
0
10
20MalesFemale
Age (months)0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Fig. 4.10 Modified seasonal von Bertalanffy growth curves of Cherax
quinquecarinatus in Bull Creek. Curves are fitted to the monthly
length-frequency data for female and male C. quinquecarinatus.
Ln(F/dt) = -2.3381(t) + 11.839
Relative age (t years)
0 1 2 3 4 5
ln (F
/dt)
0
1
2
3
4
5
6
7
8
Ln(F/dt) = -1.95(t) + 10.93
Relative age (t years)
0 1 2 3 4 5
ln (F
/dt)
0
2
4
6
8
Females
Males
Fig. 4.11 Length-converted catch curve of female and male Cherax
quinquecarinatus in Bull Creek. N.B. Slope of the regression
line represents instantaneous mortality rate (Z) and data points
with open circles were excluded as they represent either mean
ages that were not fully recruited (ascending data points) or
those with small sample sizes (< 10 individuals).
Table 5.1 Macroscopic and histological descriptions of the ovarian development stages of Cherax destructor in the Hutt River
Ovarian stage Mean GSI
(± 1 s.e.) Macroscopic description Maximum oocyte
diameter (µm) Histological description
I/II
Virgin/Maturing virgin
0.35 ±0.06 Thin strand like (stage I) or slightly thickened creamy yellow (stage II) ovaries.
600 Ovarian matrix dominated by oogonia, chromatin nucleolar and perinucleolar oocytes. Post-ovulatory follicles in recently spent ovaries.
III
Developing
0.70 ±0.04 Thickened and bright orange oocytes visible in the ovarian matrix.
800 Perinucleolar oocytes that have increased in size reflecting primary vitellogenesis having occurred present. Ovarian epithelium that consists of flattened follicle cells is visible surrounding developing oocytes. Oogonia also present.
IV
Developed
1.43 ±0.08 Thick with light-green oocytes dominating ovarian matrix and occasional orange oocytes also visible.
1100 Perinucleolar oocytes and oogonia continue to be present, however, ovarian matrix dominated by oocytes undergoing secondary vitellogenesis with yolk globules clearly visible in cytoplasm.
V
Mature
2.65 ±0.13 Swollen and large dark-green oocytes clearly dominate matrix.
1600 Larger oocytes with yolk granules and vesicles dominating the ovarian matrix surrounded by ovarian epithelium. Perinucleolar oocytes continue to be present.
VI
Ripe
3.71 ±0.22 Very swollen with very large, dark grey-green oocytes dominating the ovarian matrix.
1900 Oocytes continue to increase in size with cytoplasm completely consisting of yolk vesicle and large yolk granules. Perinucleolar oocytes continue to be present.
VII
Spent
0.96 Predominantly creamy-yellow matrix with orange and green oocytes present throughout.
1200 Perinucleolar oocytes continue to be present along with post-ovulatory follicles and large, apparently unspent ova.
Table 5.2 Macroscopic descriptions of the different stages of testicular development for male
Cherax destructor in the Hutt River
Testicular stage Mean GSI
(± 1 s.e.)
Macroscopic description
I
Virgin
0.17 ±0.01 Very thin testes, strand-like transparent vas-deferens.
II
Maturing virgin
0.27 ±0.02 Slightly thickened testes and vas deferens.
III
Mature
0.35 ±0.02 Thickened testes, opaque vas deferens.
IV
Gravid
0.41 ±0.03 Swollen testes, milky opaque vas deferens.
V
Spawning
0.44 ±0.03 Swollen, milky vas deferens with distal region being less opaque than proximal and mid regions.
VI
Spent
0.53 ±0.03 Well developed testes and relatively flattened, clear distal region of the vas deferens.
Table 5.3 Comparison of life-history parameters for: Cherax destructor in the Hutt River (the
current study), Cherax cainii in Lake Navarino (Chapter 2) and the Hutt River
(Chapter 3), and Cherax quinquecarinatus in Bulls Creek (Chapter 4). N.B.
Breeding period refers the period from initial spawning through the release of
juveniles from pleopods of females. Spawning rate of mature females is based on
the maximum percentage of mature females that possessed stage VII (i.e.
ovigerous), stage V (mature) or VI (gravid) ovaries in any month during the
breeding period. OCL∞ is the asymptotic orbital carapace length, K is the curvature
parameter. The range of a number of the parameters from the two populations of
C. cainii studied are displayed
Parameter Cherax destructor Cherax cainii Cherax cainii Cherax quinquecarinatus
Habitat range Perennial/ephemeral Perennial Perennial Perennial/ephemeral
Habitat of population
studied
Perennial river Perennial reservoir Perennial river Perennial stream
Breeding period July-January August-December July-November August-February
Potential for multiple
spawning?
Yes No No Yes
Spawning rate of
mature females (%)
29 96 10 43
Ovarian fecundity mean 210 443 82
Length at first maturity
(L50, mm OCL)
Females = 21.6 Males = 26.5
Females = 32.1 Males = 28.6
Females = 70.4 Males = 39.6
Females = 18.8 Males = 24.5
OCL∞ (mm) 51.25 101.9 Females = 59.6 Males = 73.8
K 0.78 0.42 Females = 0.29 Males = 0.25
Age at L50 (months) Females = 9 Males = 11
Females = 36 Males = 16
Females = 19 Males = 19
Life span (years) 3.86 7.16 Females = 10.55
Males = 11.97
Size at age 12 months
(mm OCL)
29.0 27.9 Females = 14.7 Males = 14.1
0 200 km
Hutt RiverBowes River
Chapman RiverGreenough River
Irwin RiverArrowsmith River
Hill River
Harvey RiverVasse River
Kalgan River
Fitzgerald RiverPhillips River
Duggan DamBottle Creek Reservoir Bromus Dam
Canegrass Swamp
Niagra Dam
Malcolm Dam
PERTHPERTHPERTHPERTHPERTHPERTHPERTHPERTHPERTH
Murray River
Canning River
Lake Shaster
GeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldton
EsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperance
AlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyGairdner River
Dog Hole Swamp(Prickle Park)
Avon River
Warren River
Pilbara Drainage Division
Southwest Coast Drainage Division
Zone of uncoordinated
drainage
Albany Hwy
Blackwood River
Yerina Springs
Gunyulgup Brook
0 200 km
Hutt RiverBowes River
Chapman RiverGreenough River
Irwin RiverArrowsmith River
Hill River
Harvey RiverVasse River
Kalgan River
Fitzgerald RiverPhillips River
Duggan DamBottle Creek Reservoir Bromus Dam
Canegrass Swamp
Niagra Dam
Malcolm Dam
PERTHPERTHPERTHPERTHPERTHPERTHPERTHPERTHPERTH
Murray River
Canning River
Lake Shaster
GeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldtonGeraldton
EsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperanceEsperance
AlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyAlbanyGairdner River
Dog Hole Swamp(Prickle Park)
Avon River
Warren River
Pilbara Drainage Division
Southwest Coast Drainage Division
Zone of uncoordinated
drainage
Albany Hwy
Blackwood River
Yerina Springs
Gunyulgup Brook
Fig. 5.1 The location of the Hutt River study site and the waterbodies within Western
Australia where Cherax destructor was captured (black dots correspond to capture
sites).
Orbital carapace length (mm)
6 10 14 18 22 26 30 34 38 42
Perc
enta
ge (%
)
0
20
40
60
80
100
Females3 4 13 14 20 20 35 31 38 41 24 11 12 2 32
Orbital carapace length (mm)
6 10 14 18 22 26 30 34 38 42
Perc
enta
ge (%
)
0
20
40
60
80
100
Males2 3 13 22 20 29 26 34 38 31 31 15 12 12 113 4 2 1
L50
L50
Fig. 5.2 Percentage contributions of immature (i.e. stages I/II, grey bars) and
maturing/mature (i.e. stages III-VII and III-VI for females and males,
respectively, black bars) in gonadal development in sequential 2 mm
OCL intervals of female and male Cherax destructor during the
breeding season in the Hutt River, i.e. May to January. N.B. The
logistic curves (including 95% confidence limits) were fitted to the
percentage contributions of C. destructor with maturing/mature gonads.
The number of C. destructor in each length interval is given at the top
of each column.
Fig. 5.3 Microscopic appearance of the different ovarian developmental stage
of Cherax destructor from the Hutt River, Western Australia. CN =
chromatin nucleolar; N = nucleus; NI = nucleoli; YG = yolk granule;
YV = yolk vesicle; POF = post-ovulatory follicle; FC = follicle cell;
OE = ovarian epithelium; OL = ovarian lumen; og = Oogonia; PN =
perinucleolar oocyte.
Stage VII: Spent
POF
Og
Stage III: Developing
Og
PN OE
200 μm
YGNI
Stage IV: Developed
YV
200 μm 200 μm
Stage V: Mature / gravid
Stage VI: Ripe / spawning
YV
YG
OE
FC
YV
YGPN 200 μm
200 μm
OE
PN
Stage I: Virgin (immature)
Og
100 μm
CN
NI
PN
Stage II: Virgin (maturing)
OL
100 μm
Og
YG
10 μm
Stage VI: Magnified oogonia
0
50
0
50
0
50
0
50
0
50
0
50
0
50
0
50
0
50
0
50
0
50
Gonad stage
I II III IV V VI VII0
50
Junen = 61
Julyn = 7
Augustn = 24
Januaryn = 14
Februaryn = 22
Marchn = 13
Apriln = 36
Mayn = 23
Septembern = 23
Octobern = 43
Novembern = 32
Decembern = 34
Freq
uenc
y (%
)0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
0
100
Gonad stage
0
100
Junen = 45
Julyn = 13
Augustn = 27
Januaryn = 14
Februaryn = 23
Marchn = 11
Apriln = 19
Mayn = 24
Septembern = 35
Octobern = 73
Novembern = 31
Decembern = 31
I II III IV V VI
Females Males
Fig. 5.4 Monthly frequency of different gonad developmental stages of female and male
Cherax destructor in the Hutt River.
Females
Males
Month
J F M A M J J A S O N D
Gon
ados
omat
ic in
dex
0
1
2
3
4 ImmatureMature
0.5
Month
J F M A M J J A S O N D
Gon
ados
omat
ic in
dex
0
1
97
151018 10
34
2
12 4 10 156
1621
5
1251
19
5
26
33
19
13 3722149
22
14
12
9
16
3825
1
2 8
52
115
4
35
21
156
Fig. 5.5 Mean gonadosomatic indices (+ or - 1 s.e.) for female and male Cherax
destructor in the Hutt River with immature gonad stages (i.e. stages I/II)
and mature/maturing gonad stages (i.e. stages III-VII and III-VI for
females and males, respectively).
Septembern = 60
Octobern = 139
Novembern = 182
Januaryn = 50
Februaryn = 52
Marchn = 72
Apriln = 70
Mayn =171
Julyn = 98
Junen = 117
Augustn = 51
Decembern = 119
0
30
0
30
0 10 20 30 40
0
30
0
300
300
30
0
30
0
30
0
30
0
30
0
30
0
30
Num
ber o
f C. d
estru
ctor
Orbital carapace length (mm)
Fig. 5.6 Orbital carapace length-frequency histograms in each month for
Cherax destructor in the Hutt River. Normal distributions have
been fitted to the one or two size cohorts present in each month
used to fit the von Bertalanffy growth curve. N.B. n = sample
size.
Months
D J F M A M J J A S O N D
Orb
ital c
arap
ace
leng
th (m
m)
0
5
10
15
20
25
30
Age (months)
0 1 2 3 4 5 6 7 8 9 10 11 12
Fig. 5.7 Modified seasonal von Bertalanffy growth curves of Cherax destructor
in the Hutt River. Curves are fitted to the monthly mean orbital carapace
lengths at age of the 0+ and 1+ cohorts.
Ln(F/dt) = -2.91(t) + 9.78 r2 = 0.93
Relative age (t years)
0 1 2
ln (F
/dt)
2
3
4
5
6
7
8
Fig. 5.8 Length-converted catch curve of Cherax destructor in the Hutt River.
N.B. Slope of the regression line represents the instantaneous mortality
rate (Z) and data points with open circles were excluded as they represent
mean ages that were not fully recruited (ascending data points) or those
with small sample sizes (less than 10 individuals).
-30 -28 -26 -24 -222
4
6
8
10
12
14
16
18
Winter
d13C
-30 -28 -26 -24 -22
d15
N
2
4
6
8
10
12
14
16
18
G. holbrooki juvenile P. olorum
G. holbrooki adult
C. cainii juvenile
C. cainii adultPlotiopsis sp.C. destructor
adult
Juncas sp.
FPOM
CPOMMelaleuca sp.
Casuarina sp.*
Summer
d13C
d15
N
G. holbrooki adultG. holbrooki
juvenile
C. cainii juvenile
C. cainiiadult
C. destructor adult
Plotiopsis sp.algae
Melaleuca sp.FPOM
Juncas sp.
CPOMCasuarina sp.
C. destructorjuvenile
P. olorum
algae*
B,CC,BC
C,B
C,C
C,BCA,A
ABC,BC
Fig 6.1 The mean (± 1 s.e.) δ13C and δ15N signatures of Cherax cainii, Cherax destructor
and their potential food sources in the Hutt River during summer and winter. N.B
* denotes that the δ13C and/or δ15N signature of the items was duplicated from the
other season. Crayfish groups with different subscripts indicate significant
differences (α = 0.05) for δ13C (given first) and δ15N signatures (given second).
δ13C
δ13C
δ15N
δ15N
0
100000
200000
0
75000
150000
0
60000
120000
0
90000
180000
0
90000
180000
0
40000
80000
0
12500
25000
0.0 0.2 0.4 0.6 0.8 1.00
12500
25000
0
80000
1600000
150
300
0
300
600
0
200
400
0
350
700
0
300
600
0
100
200
0
150
300
0
50
100
0.0 0.2 0.4 0.6 0.8 1.00
50
100
C. cainiijuvenile
C. cainiiadult
Proportion
Num
ber o
f obs
erva
tions
0
25000
50000
0
8000
16000
0
12500
25000
0
3000
6000
0.0 0.2 0.4 0.6 0.8 1.00
3500
7000
0
20000
40000
0
15000
30000
0
40000
80000
0
25000
500000
70
140
0
90
180
0
150
300
0
125
250
0
50
100
0
70
140
0
25
50
0.0 0.2 0.4 0.6 0.8 1.00
25
50
0
120
240
C. destructorjuvenile
C. destructoradult Casuarina sp.
Juncas sp.
Melaleuca sp.
Algae
FPOM
CPOM
Plotiopsis sp.
G. holbrookiadult
G. holbrookijuvenile
Fig. 6.2 Distributions of feasible proportions of food sources (determined by IsoSource)
contributing to the assimilated diet of Cherax cainii and Cherax destructor in the
Hutt River in summer.
Num
ber o
f obs
erva
tions
Juncas sp.
Melaleuca sp.
FPOM
CPOM
Plotiopsis sp.
G. holbrookiadult
G. holbrookijuvenile
P. olorum
0
90
180
0
100
200
0
140
280
0
120
240
0
70
140
0
40
80
0.0 0.2 0.4 0.6 0.8 1.00
70
140
C. destructoradult
0
70
140
C. cainiijuvenile
C. cainiiadult
0
700
1400
0
700
1400
0
500
1000
0
125
250
0
80
160
0
450
900
Proportion
0.0 0.2 0.4 0.6 0.8 1.00
60
120
0
900
1800
0
225
450
0
250
500
0
225
450
0
200
400
0
50
100
0
25
50
0
150
300
0.0 0.2 0.4 0.6 0.8 1.00
20
40
Fig. 6.3 Distributions of feasible proportions of food sources (determined by IsoSource)
contributing to the assimilated diet of Cherax cainii and Cherax destructor in the
Hutt River in winter.
Sim
ilarit
y
Fig. 6.4 Classification of the assimilated diets of juvenile and adult Cherax cainii and Cherax destructor
during summer and winter in the Hutt River. N.B. The major groupings in the dietary data are
shown; m = marron, y = yabbie, a = adult, j = juvenile, s = summer, and w = winter.
yaW
yaW
yaW
yaW
yaW
yaW
yaW
yaW
maS yaS
maS
maS mjS yjS
yaS
yaS
yaS
maW m
jSm
jWm
aS yjS
yjS
mjW mjS
mjS
maW mjW
maW
maW
100
80
60
40
20
I IIa IIb IIc
maS mjS
yaS yjS
maW mjW
yaW
Stress: 0.04
Fig. 6.5 Multi-dimensional scaling of the assimilated diets of juvenile and adult Cherax cainii
and Cherax destructor during summer and winter in the Hutt River. N.B. m =
marron, y = yabbie, a = adult, j = juvenile, s = summer, and w = winter.
Table 6.1 Trophic levels of juvenile and adult Cherax cainii and Cherax destructor in the
Hutt River determined using a variation of the formula of Kline and Pauly (1998)
Season Consumer Mean δ15N of
consumer (δ15Nsc)
Mean δ15N of food web base
(δ15Nbase)
Trophic level of consumer
Summer C. cainii (juvenile) 13.81 7.75 4.03 C. cainii (adult) 12.82 7.75 3.53 C. destructor (juvenile) 13.45 7.75 3.85 C. destructor (adult) 13.58 7.75 3.92 Winter C. cainii (juvenile) 13.14 7.18 3.98 C. cainii (adult) 12.9 7.18 3.86 C. destructor (adult) 9.1 7.18 1.96
Table 6.2 ANOSIM pairwise comparisons of the assimilated diets (as determined by IsoSource) between juvenile and adult Cherax cainii and
Cherax destructor in summer and winter in the Hutt River. N.B. R-statistics are presented and the significance levels (%) are given in
parentheses: * (P < 5%), ** (P < 1%)
Summer Winter Group C. cainii
(juvenile) C. cainii (adult)
C. destructor (juvenile)
C. destructor (adult)
C. cainii (juvenile)
C. cainii (adult)
C. destructor (adult)
C. cainii (juvenile) - - - - - - - C. cainii (adult) 0.229 (14.3) - - - - - - C. destructor (juvenile) -0.065 (54.3) 0.056 (28.6) - - - - -
Summer
C. destructor (adult) 0.396 (8.6) 0.167 (17.1) 0.259 (17.1) - - - - C. cainii (juvenile) 0.074 (28.6) 0.63 (2.9)* 0.259 (10) 0.722 (2.9)* - - - C. cainii (adult) 0.51 (2.9)* 0.927 (2.9)* 0.778 (2.9)* 0.969 (2.9)* 0.056 (40) - -
Winter
C. destructor (adult) 1 (0.2)** 1 (0.2)** 1 (0.6)** 1 (0.2)** 0.984 (0.6)** 1 (0.2)** -
Plate 7.1 External appearance of Cherax destructor infected with
Thelohania sp. compared with that of an un-infected animal. N.B.
The pale abdominal muscle tissue of the infected animal
(Photograph: Department of Fisheries, Government of Western
Australia).
Infected
Un-infected
Table 7.1 Spore dimensions and infection rates of Thelohania parastaci from Cherax destructor and the microsporidian from
Cherax cainii in the present study. N.B. Included are those recorded for microsporidian infections of freshwater crayfish
in previous studies
Study Microsporidian species Species infected / spore type n = number of spores measured
Tissue fixative Mean spore dimensions (μm ±1 s.e./s.d.) Length Width
Range in spore dimensions (μm) Length Width
Disease prevalence (% of population
infected)
This study Thelohania parastaci Cherax destructor (n = 107)
Live spores 3.98 (±0.005 s.e.) 2.78 (±0.005 s.e.) 2.42 – 4. 84 2.02 – 3.63 15.7
This study Vavraia parastacida / T. parastaci
Cherax cainii (n = 32)
Live spores 4.44 (±0.096 s.e.) 2.95 (±0.074 s.e.) 3.22 – 5.64 2.42 – 4.03 5.1
Moodie et al. (2003a)
T. parastaci C. destructor binucleate spores (n = 80)
Unfixed 3.9 2.0 3.2 - 4.9 1.5 - 2.7
Moodie et al. (2003b)
Thelohania montirivulorum C. destructor binucleate spores (n = 40)
Unfixed 5.9 2.6 4.9 - 7.2 2.0 - 3.1
Jones and Lawrence (2001)
Thelohania sp. Cherax albidus (i.e. C. destructor) (n = 100)
Live spores 3.8 (±0.4 s.d.) 2.3 (±0.2 s.d.) 30.1 (of aquaculture
farms tested)
Lom et al. (2001)
Thelohania contejeani Astacus fluviatilis binucleate spores
3.8 1.8
T. contejeani Astacus fluviatilis uninucleate spores
4.2 2.1
Jones (1980) T. contejeani Paranephrops zealandicus (n = 50)
Live spores (aged 15 months)
2.67 (±0.248 s.d.) 1.88 (±0.140 s.d.) 2.24 – 3.60 1.68 – 2.24
T. contejeani P. zealandicus (n = 50)
Bouin’s fixative 2.93 (±0.256 s.d.) 1.89 (±0.133 s.d.) 1.84 – 3.12 1.60 – 2.08
T. contejeani P. zealandicus (n = 50)
10 % buffered formalin
3.10 (±0.175 s.d.) 1.89 (±0.107 s.d.) 2.80 – 3.44 1.76 – 2.16
T. contejeani Paranephrops planifrons (n = 50)
Live spores 4.00 (±0.269 s.d.) 2.27 (±0.169 s.d.) 3.36 – 4.80 1.92 – 2.64 1.83
T. contejeani P. planifrons (n = 50)
10 % buffered formalin
3.82 (±0.293 s.d.) 2.48 (±0.280 s.d.) 3.20 – 4.48 2.00 – 3.60 1.83
Quilter (1976) T. contejeani P. zealandicus (n = 100)
Live spores 2.7 1.5 13 (of sites where disease was present)
Plate 7.2 Phase contrast images of mature microsporidian spores (Sp) from muscle tissue of
Cherax cainii (A, B) and Thelohania parastaci from Cherax destructor (C, D) in
the Hutt River. N.B. Polar vacuoles (PV), muscle fibres (MF) and bacterial rods
(BR) are shown, magnification = 1000x.
Sp
MF
PV
BR
Sp
PV
BR
B
PV
BR
Sp
MF
A
SpBR
PV
C D
Sp
5µm 5µm
5µm 5µm
Plate 7.3 Scanning electron microscope images of mature spores
(Sp) of Thelohania parastaci from Cherax destructor in
the Hutt River. N.B. Bacterial rods are shown (BR),
magnification = 3600x.
Sp
BR
BR Sp
Sp
BR
A
C
B
5µm
5µm
5µm
Table 8.1 Summary of key biological parameters of the native congeners Cherax cainii, Cherax quinquecarinatus and the introduced congener Cherax destructor,
where; OCL∞ is the asymptotic OCL (mm), K is the curvature parameter, t0 is the theoretical age at which the estimated orbital carapace length is zero, C
determines the relative amplitude of the seasonal oscillation (where 0 ≤ C ≤ 1), ts determines the phase of seasonal oscillation relative to t0 (month), Z is the
instantaneous rate of total mortality (1year-1) determined by a length converted catch curve, M is the instantaneous rate of natural mortality (1year-1), F is the
instantaneous rate of fishing mortality (1year-1) and E is the exploitation rate. N.B. For C. cainii Ze is the instantaneous rate of total mortality (1year-1)
determined by a length converted catch curve (C. cainii > legal size), Zu is the instantaneous rate of natural mortality (1year-1) determined by a length
converted catch curve (C. cainii < legal size), F1 and F2 are instantaneous rates of fishing mortality (1year-1) determined using Zu and M, respectively, and E1
and E2 are exploitation rates determined using F1 and F2, respectively
Parameter Cherax cainii (Chapter 2)
C. cainii (Chapter 3)
Cherax quinquecarinatus (Chapter 4)
Cherax destructor (Chapter 5)
Population habitat Lentic, reservoir Lotic, river Lotic, stream Lotic, river
Habitat range of species Permanent lentic and lotic Permanent lentic and lotic Permanent and temporary, lentic and lotic Permanent and temporary, lentic and lotic
Breeding period August - December July - December August - February July - Multiple spawning? No No Yes Probably Spawning rate of mature females 96 10 43 29
Ovarian fecundity 443 - 82 210 Pleopodal fecundity 286 - 77 -
L50 (mm OCL) Females = 32.1 Males = 28.6
Females = 70.4 Males = 39.6
Females = 18.8 Males = 24.5
Females = 21.6 Males = 26.5
L95 (mm OCL) Females = 37.9 Males = 38.8
Females = 92.9 Males = 54.5
Females = 24.9 Males = 33.9
Females = 28.0 Males = 31.2
OCL∞
-
101.9
Females 59.6
Males 73.8
51.25
K - 0.42 0.29 0.25 0.78 t0 - 1.54 0.18 0.44 -1.54 C - 0.37 1 0.71 0.36 ts - 3.85 8.64 5.83 0 Z - 2.34 1.95 2.91 Ze - 1.79 - - - Zu - 0.41 - - - M - 0.60 0.55 0.48 1.09 F - 1.78 1.47 1.82 F1 - 1.38 - - - F2 - 1.19 - - - E - 0.76 0.75 0.62 E1 - 0.77 - - - E2 - 0.66 - - -
Table 8.2 Summary of the diets of the three large predatory teleosts in Lake Navarino (Waroona Dam) using the
frequency of occurrence and points methods (Ball 1950; Hynes 1961). The former method determines the percentage of
stomachs in which a food item was recorded and the latter the relative contribution of each food item to the total volume of
the contents of the stomachs. N.B. Data presented is pooled from multiple sampling occasions using a variety of methods
including; gill nets, seine nets, and back-pack electro-fishing.
Oncorhynchus mykiss
n = 30
Size range = 201-315 mm TL
Salmo trutta
n = 26
Size range = 32-375 mm TL
Perca fluviatilis
n = 63
Size range = 70-245 mm TL
Prey Type % Contribution % Occurrence % Contribution % Occurrence % Contribution % Occurrence
Cherax cainii 33.9 33.3 7.3 11.5 11.5 31.8
Cherax quinquecarinatus 3.2 3.9 3.19 9.5
Palaemonetes australis
(freshwater shrimp) 56.7 73.0
Perca fluviatilis 3.7 3.3
Oncorhynchus mykiss /
Salmo trutta 16.7 16.7
Native teleost 1.0 3.3 0.5 3.9
Copepoda 2.3 1.6
Ostracoda 0.2 3.6
Diptera (larvae) 1.4 3.3 2.4 3.6 0.1 1.6
Diptera (pupae) 12.43 42.31 1.44 11.11
Trichoptera 5.14 17.46
Coleoptera (larvae) 9.2 2.0 9.7 30.8 2.5 3.2
Coleoptera (adult) 18.5 46.2
Hemiptera 2.3 6.7 1.8 15.4 3.2 17.5
Odonata (larvae) 18.4 30.8 8.0 20.6
Arachnida 0.3 3.9
Hymenoptera 1.5 3.9
Terrestrial Insecta 7.6 26.7 16.2 34.6 0.9 6.4
Oligochaeta 0.8 3.9
Amphibia 3.3 3.9
Cigarette butt 13.1 23.3
Unidentified plant material 3.6 6.7
Unidentified organic 0.9 6.7 3.3 3.9 4.8 7.9
Other inorganic 6.6 16.7
Table 8.1 Summary of the diet of Oncorhynchus mykiss in Bancell
Brook (Fig. 1.1) using the frequency of occurrence and points methods
(Ball 1950; Hynes 1961). The former method determines the percentage
of stomachs in which a food item was recorded and the latter the relative
contribution of each food item to the total volume of the contents of the
stomachs. N.B. Data presented is pooled from three sampling occasions
(November, February and May) using a back-pack electro-fishing.
Oncorhynchus mykiss
n = 15
Size range = 115-230 mm TL
Prey Type % Contribution % Occurrence
Cherax cainii 6.9 13.3
Cherax quinquecarinatus 29.2 46.7
Amphipoda 0.4 0.1
Notonectidae 0.4 0.1
Corixidae 2.2 0.1
Coleoptera (adult) 6.5 46.7
Anisoptera (larvae) 21.7 66.7
Chironomidae (larvae) 2.2 26.7
Culicidae (pupae) 6.0 33.3
Other Dipteran (adult) 13.8 46.7
Arachnida 0.3 0.1
Diplopoda 1.7 0.1
Unidentified animal material 2.0 0.1
Unidentified plant material 6.8 26.7
