Marron, freshwater crayfish Cherax tenuimanus - Department of ...

Marron, freshwater crayfish Cherax tenuimanus 

1 Taxonomy 

Species: Cherax tenuimanus (Smith 1912) 

Family: 

Order: 

Class: 

Parastacidae 

Decapoda 

Crustacea 

Figure 1. 

Image of Cherax tenuimanus (Source: OpenCage, Wikimedia Commons). 

The marron crayfish Cherax tenuimanus is a robust freshwater species with a distinct prominence 

running back from the postorbital spine. In addition, the rostrum is characterised by lateral 

serrations present both sides, that ends in a sharp spine (Picker & Griffiths 2011). There has been 

some debate recently about the existence of two distinct species of marron crayfish. Genetic studies 

(involving allozyme data) have demonstrated that one of these forms (the hairy marron) is restricted 

to the Margaret River system while the other form (smooth marron) is the one that has been widely 

distributed as an aquaculture species (Austin & Ryan 2002). The authors proposed naming these two 

genetically distinct forms Cherax tenuimanus and Cherax cainii, respectively (Austin & Ryan 2002). 

However, these names are currently under review. 

Page | 1

2 Natural distribution and habitat 

The hairy marron C. tenuimanus is native to south-western Australia (Figure 2). This species is 

considered Critically Endangered on the International Union for Conservation of Nature (IUCN) Red 

List in its native range (Austin & Bunn 2010) and found only in the upper Margaret River in the 

south-west of Western Australia (Cubitt 1985). It is thought that C. tenuimanus occupies an area of 

approximately 10 km². However, the smooth marron C. cainii (the sub-species farmed globally) has a 

wider natural distribution and also appears to be moving into hairy marron territory (whereas 

previously the two sub-species were geographically distinct). Hybridisation between the two is 

causing the gradual displacement of the hairy marron (TSSC 2005). For the purposes of this study, 

we shall consider both C. tenuimanus and C. cainii as C. tenuimanus. 

Figure 2. 

Native (green) and introduced (red) ranges of C. tenuimanus globally (Source: M. Picker & C. Griffiths) 

C. tenuimanus prefer the sandy bottoms of rivers or dams, where they can find shelter from 

predators and access to accumulated organic matter, but can survive in a variety of habitats (TSSC 

2005). 

3 Biology 

3.1 Diet and mode of feeding 

Cherax tenuimanus is an omnivore and scavenger, feeding on dead plants and other forms of organic 

detritus (Read 1985). However, it will also consume living aquatic plants (Coetzee 1985). 

Page | 2

3.2 Growth 

The marron can grow to a maximum of approximately 40 cm and weigh 2.5 kg (Picker & Griffiths 

2011). Under culture conditions it can attain 2 to 3 tons/ha/annum (Read 1985) but in natural 

conditions in Australia they are known to attain densities of 400-600 kg/ha/annum (de Moor & 

Bruton 1988). Cherax tenuimanus is commercially viable when it reaches a weight of 75-125 g (De 

Moor 2002). Growth of C. tenuimanus occurs between 11 and 30°C with 24°C representing optimal 

growth temperatures (Morrissy 1990). The life history characteristics (e.g. body size, life span, time 

to sexual maturity and reproductive frequency) of C. tenuimanus could classify it as a k-selected 

species (de Moor 2002). Sexual maturity is reached at approximately three years (Picker & Griffiths 

2011). 

3.3 Reproduction 

Records indicate that C. tenuimanus breed in spring during their second year of life (Safriel & Bruton 

1984, de Moor & Bruton 1988). The number of eggs produced per individual ranges from 90 to 900 

and is dependent on the size of the female (Coetzee 1985). Eggs are carried by the female beneath 

its tail (pleopods) for a period of twelve to sixteen weeks, whereafter they hatch and undergo two 

development stages (de Moor & Bruton 1988). After this period, free swimming larvae resembling 

the adults are released (de Moor & Bruton 1988). The entire life cycle is completed within 

freshwater (Cubitt 1985). 

3.4 Environmental tolerance ranges 

Cherax tenuimanus is a temperate water species (Read 1985) but will tolerate temperatures as high 

as 30°C and as low as 8°C, with adults being more resilient to low temperature (Cubitt 1985). It has 

the ability to tolerate salinities of up to 18‰ but cannot survive very low oxygen concentrations or 

high nutrient conditions (Cubitt 1985). Preferred pH seems to be acidic as they have been cultured at 

levels of between 5 and 6.5 (Safriel & Bruton 1984). C. tenuimanus require good quality water, with 

minimal environmental disturbance (TSSC 2005). Similar to other crayfish species, it can survive out 

of water for several days (Ackefors & Lindqvist 1994). 

4 History of domestication 

Cherax tenuimanus were grown in farm dams in the 1960s in Australia before more serious efforts 

were made to improve their growth and survival. This accumulation of practical knowledge 

represented the beginning of the industry. In 1976 legislation was passed to allow the farming of 

marron under strict conditions. This lead to a slow growth of the industry until December 1995 when 

the industry was producing approximately 18 tons of marketable product per annum from a total of 

31 licensed growers. Since the mid to late 1990s, changes made to the legislation have made 

commercial farming more attractive. The total production of marron in Western Australia for 

1999/2000 was above 42 tons from approx 250 licenses (ACWA 2012). 

Page | 3

5 Introduction and spread (South Africa) 

C. tenuimanus was first introduced into the then Natal province of South Africa in 1976 by a private 

fish farmer (Borquin et al. 1984). In 1982, the first successfully recorded farm was established in 

George (de Moor & Bruton 1988). They were also kept at Pirie hatchery in King Williamstown, where 

they managed to escape into the Buffalo River. However, this population did not become established 

(Picker & Griffiths 2011). There are anecdotal reports of it being found in small streams at Nieu- 

Bethesda near Graaff Reinet during the mid 1990s (R. Scott, pers. comm.), and at Madam Dam, near 

Stutterheim (de Moor & Bruton 1988), but it is unclear whether these were viably reproducing 

populations. It is currently likely to be localised and restricted to a relatively small area in the Eastern 

Cape (Figure 3). 

Figure 3. 

Introduced range (red) of C. tenuimanus within South Africa (Source: M. Picker & C. Griffiths) 

6 Introduction and spread (International) 

Cherax tenuimanus have been experimentally introduced to Louisiana, USA for aquaculture 

purposes in the 1970s (Shireman 1973) and into Mauritius in 1990 (FAO 2012). The Food and 

Agricultural Organization of the United Nations (FAO) claim that the only country of introduction is 

Mauritius (FAO 2012), however it is unlikely to have established there. Picker & Griffiths (2011) 

indicate that it is only known from South Africa and Australia (Figure 2). 

7 Compatibility with local environmental conditions 

Compatibility of this species to local environmental conditions was evaluated by comparing the 

ambient annual temperature ranges of the 31 terrestrial ecoregions of South Africa (Kleynhans et al. 

2005) (Figure 4, Table 1) to the known environmental tolerance ranges for C. tenuimanus (Cubitt 

1985). 

Page | 4

Figure 4. Map of South African Ecoregions (Kleynhans et al. 2005). 

Page | 5

Table 1. 

Altitude and ambient temperature (annual average range and maximum and minimum temperatures 

reported) in the 31 ecoregions of South Africa. This information was collated from Kleynhans et al. 

2005 and assessed to determine compatibility with C. tenuimanus culture. 

Ecoregion 

Altitude (m a.m.s.l) 

Temperature 

range (°C) 

Mean annual 

temp (°C) 

C. tenuimanus 

climatic suitability 

1. Limpopo Plain 

300-1100 (1100-1300 

limited) 

2 to 32 18 to >22 Y 

2. Soutpansberg 300-1700 4 to 32 16 to >22 Y 

3. Lowveld 0-700; 700-1300 limited 4 to 32 16 to >22 Y 

4. North Eastern 

300-1300 (1300-1500 

Highlands 

limited) 

2 to 32 16 to 22 Y 

5. Northern Plateau 

900-1500 (1500-1700 

limited) 

2 to 30 16 to 20 Y 

6. Waterberg 

700 –900 (limited), 900- 

1700 

2 to 32 14 to 22 Y 

7. Western Bankenveld 900-1700 0 to 32 14 to 22 Y 

8. Bushveld Basin 

700-1700 (1700-1900 very 

limited) 

0 to 32 14 to 22 Y 

9. Eastern Bankenveld 500-2300 0 to 30 10 to 22 Y 

10. Northern Escarpment 500-900 (limited) 900- 

Mountains 

2300 

0 to 30 10 to 22 Y 

11. Highveld 

1100-2100, 2100-2300 

(very limited) 

-2 to 32 12 to 20 Y 

12. Lebombo Uplands 0-500 6 to 32 18 to >22 Y 

13. Natal Coastal Plain 0-300 8 to 32 20 to >22 Y 

14. North Eastern Uplands 0-100 (limited), 100-1500 0 to 30 14 to >22 Y 

15. Eastern Escarpment 1100-3100; 3100-3500 

Mountains 

limited 

32 10 to 20 Y 

24. South Western 

Coastal Belt 

0-300; 300-900 limited 4 to 32 10 to 20 Y 

25. Western Coastal Belt 0-700, 700-1100 (limited) 2 to >32 16 to 20 Y 

26. Nama Karoo 

300-1700, 1700-1900 

(limited) 

0 to >32 12 to 20 Y 

27. Namaqua Highlands 

100-1300; 1300-1500 

limited 

2 to 32 12 to 20 Y 

28. Orange River Gorge 0-1100 2 to >32 16 to 22 Y 

29. Southern Kalahari 

500-1700; 1700-1900 

limited 

-2 to >32 14 to 22 Y 

30. Ghaap Plateau 900-1700 0 to 32 16 to 20 Y 

31. Eastern Coastal Belt 0-500, 500-900 (limited) 4 to 28 16 to 20 Y 

Page | 6

From this, it is clear that culture of C. tenuimanus is possible in all but one (the Eastern Escarpment 

Mountains) of the ecoregions in this country (although some may only be feasible on a seasonal 

basis, when the water temperature is above 8°C). Equally, it should be noted that this species is 

potentially able to establish naturalised populations in thirty of these regions. Indeed, C. tenuimanus 

has reportedly already been introduced and/or is currently established in at least two of these 

regions (Picker & Griffiths 2011). Established populations have been recorded in the following 

regions: 

 

 

16. South Eastern Uplands 

31. Eastern Coastal Belt 

7.1 Culture techniques 

C. tenuimanus are typically cultured in earthen ponds. The water in the ponds can be oxygenated 

through the use of paddlewheel aerators. The ponds require a partial water change every few weeks 

to allow a removal of sediment and ensure high water quality. Protection from predators (for 

example, heron, otters or frogs) is essential, and in South Africa, takes the form of pond netting, 

corrugated iron fencing and electric fence around the entire facility. In addition, C. tenuimanus have 

cannibalistic tendencies, so juveniles must be separated from adult populations as soon as possible 

(V. Bursey, pers. comm.). 

Due to their desiccation tolerance, certain precautions are necessary to reduce the biosecurity risk 

(i.e. risk of escapement and/or transfer of pathogens and diseases to native species). One marron 

farm in the Eastern Cape, directs all effluent water into a drainage pond containing predatory fish 

such as the largemouth bass (V. Bursey, pers. comm.). Biosecurity risks can be further mitigated 

through a range of control measures listed in Section 11. 

8 Research requirements 

Before introducing non-native species, indigenous crustaceans should be considered for aquaculture 

wherever possible. However, in order to do so, further research is necessary with regards to the 

ecology, genetics, physiology and environmental requirements (Mikkola 1996). As there are no true 

freshwater crayfish native to Africa, other macrocrustaceans, such as crab, should also be 

considered for farming. 

Currently geographic data on C. tenuimanus in South Africa refers only to the distribution of the 

species and there is no information on abundance at these locations. These data are crucial in 

determining the true current and future impacts. In addition, research into the impacts of habitat 

degradation and climate change on C. tenuimanus survival are necessary to determine future 

cumulative impacts. 

Page | 7

Production (tonnes) 

9 Benefit assessment 

The Food and Agriculture Organisation of the United Nations (FAO) does not publish global annual 

statistics on the international production and value of C. tenuimanus. In 2008, there were two small 

marron farms in South Africa (Britz et al. 2009). The total 2010 production from these farms was 

listed as was 0.8 tonnes (DAFF 2012a). The growth of marron production in South Africa over the last 

five years has increased overall (DAFF 2012a) (Figure 5). However, marron farming in South Africa 

was valued at less than ZAR 0.1 million in 2008 (Britz et al. 2009). 

0.9 

0.8 

0.7 

0.6 

0.5 

0.4 

0.3 

0.2 

0.1 

0 

2006 2007 2008 2009 2010 

Figure 5. 

South African marron production (tonnes) 2006-2010 (Source: DAFF 2012a). 

The South African marron farms employed four full time (and no part time) staff in 2008. These 

figures are conservative as they include only those involved in primary production and not those 

who work in the secondary services (such as feed manufacturers or those employed in fish 

processing plants) (Britz et al. 2009). 

There are very few crayfish aquaculture projects that can be regarded as ‘successful’ (Mikkola 1996). 

This, and the recent abandonment of a C. quadricarinatus farm in Swaziland, previously touted as 

being extremely successful (Copeland 1999), raises serious doubts about the actual benefit of 

culturing freshwater crayfish species in Africa. On the other hand, there are farms which, despite the 

high set up costs and development setbacks, have persevered and are now making a profit (Burgess 

2007). 

Schoonbee (1993) also regards the aquaculture potential of C. tenuimanus as being less favorable 

than that of the C. destructor-complex and C. quadricarinatus. At least two aquaculture operations 

based on C. tenuimanus, at Pirie Hatchery near King Williams Town, Eastern Cape, and at Amanzi 

farm in the Wilderness area, have been discontinued (de Moor & Bruton 1988). De Moor (2002) 

concluded that due to the negative impact of introduced parasites that came with C. tenuimanus, 

and its disappointing results in terms of aquaculture, the environmental damage is likely to outweigh 

economic benefits. 

Currently, export of marron to the European Union is under contention, due to the absence of a 

‘residue monitoring plan’. In addition, China will not allow exports until certain food safety 

requirements are met. Export permits are not being issued within South Africa until the relevant 

Page | 8

legislation is in place (D. Allan, Kei Chamber of Business, pers. comm.). The facilitation of exportation 

will allow the benefits of marron culture to the South African economy to be fully realised. 

10 Risk assessment 

10.1 Likelihood of this species becoming established in South Africa 

If introduced for aquaculture purposes, escapes are likely (unless cultured in a closed system), so 

such actions should be considered an intentional introduction into the wild which defies the 

precautionary principle (Mikkola 1996). C. tenuimanus has already escaped from aquaculture 

facilities in the Eastern Cape (de Moor & Bruton 1988). Populations, however, failed to establish in 

the Buffalo River (de Moor & Bruton 1988). Nevertheless, there are areas of the country that have 

water bodies with parameters within the tolerance thresholds of C. tenuimanus. Coetzee (1985) 

concluded that the species would be able to survive in the Western Cape should it escape. It is 

probable that viable populations of C. tenuimanus could establish themselves if released into the 

upper and mid reaches of many perennial rivers where temperatures are moderate and dissolved 

oxygen levels sufficient. However, it is unlikely that they would become a significant invasive threat 

in all rivers as they are susceptible to predation from otters, water mongoose and cormorants 

(Coetzee 1985, de Moor & Bruton 1988). 

The invasive potential of C. tenuimanus in the thirty-one ecoregions of South Africa has been 

assessed in accordance with the European Non-Native Species Risk Analysis Scheme (ENSARS) (Copp 

et al. 2008) developed by CEFAS (UK Centre for Environment, Fisheries & Aquaculture Science). 

ENSARS provides a structured framework (Crown Copyright 2007-2008) for evaluating the risks of 

escape, introduction to and establishment in open waters, of any non-native aquatic organism being 

used (or associated with those used) in aquaculture. For each species, 49 questions are answered, 

providing a confidence level and justification (with source listed) for each answer. The questions and 

results of the assessment on C. tenuimanus can be found in Appendix 1. 

The outcome of the scoring was that C. tenuimanus should be further evaluated before additional 

introductions are undertaken within South Africa. See Section 12 for tailored recommendations. 

10.2 Potential ecological impacts 

Escapees from aquaculture facilities are inevitable and occur worldwide, unless appropriate 

mitigatory methods are applied. Due to their ability to survive out of water and travel across land, C. 

tenuimanus have the potential to seriously threaten native biodiversity. 

The presence of alien crayfish can lead to dramatic alterations to the benthos which could 

potentially indirectly affect fish recruitment and growth (Charlebois & Lamberti 1996). De Moor 

(2002) conducted an in depth analysis and review of the potential impacts freshwater crayfish may 

have in South Africa. Of the four alien species known to occur in South Africa, C. tenuimanus was 

deemed to have the least impact (de Moor 2002). Potential impacts caused by C. tenuimanus are 

likely to be the destruction of living aquatic macrophytes, resulting in wide ranging ecosystem 

Page | 9

consequences; possible destruction of adjacent terrestrial vegetation in the riparian zone, a small 

but possible disturbance to breeding of bottom-spawning fish, introduction of associated 

undesirable parasites, and lastly far-ranging but slight impacts on benthic macroinvertebrate 

communities the degree to which would be dependent on the population size of C. tenuimanus. It is 

not likely to hybridize with any indigenous species as there are no native freshwater African crayfish 

species (de Moor 2002). 

The existing broodstock of C. tenuimanus in South Africa has been used for several years and as a 

result, the industry requires new blood lines to prevent inbreeding and associated genetic issues (D. 

Impson, Cape Nature, pers. comm.). If new stock is imported from Australia, there are risks of 

disease or parasite introduction which must be considered. 

A significant impact which must be considered is the threat of introduction of undesirable parasites 

with C. tenuimanus. The ‘crayfish plague’ fungus, Aphanomuyces astaci can affect all species in the 

Parasticidae family (as well as other freshwater crayfish families (de Moor 2002). Also, C. tenuimanus 

is host to a microsporidian parasite, Thelohania sp., commonly known as ‘porcelain disease’ 

(Morrissy et al. 1990, Langdon 1991) which affects striated muscle fibres in the tail. There is no 

treatment for this disease and the only means of prevention is by ensuring that stocks are disease 

free. The disease is, however, extremely difficult to detect during the early stages of infection, so the 

prevention of its importation is likely to be difficult (Langdon 1991). However, this disease has not 

been reported in South Africa to date (DAFF 2012b) and is unlikely to affect any indigenous 

freshwater species. 

There are various worms which are hosted by crayfish without causing the host any harm, but have 

the potential to infect other species. For example, temnocephalan worms (which are non-native to 

Africa) can infect other decapods species and can predate on freshwater invertebrates. 

Temnocephala chaeropsis was introduced with C. tenuimanus in the southern Cape and affected the 

marketability of infected individuals, in some cases causing mortalities (Mitchell & Kok 1988). The 

worms also have the potential to infect a species of indigenous freshwater crab, Potomonautes 

warreni (Avenant-Oldewage 1993). In addition, T. chaeropsis could affect other indigenous 

decapods, either by killing or by lowering its fitness to a level which would allow C. tenuimanus a 

competitive advantage (De Moor 2002). 

10.3 Potential socio-economic impacts 

Currently there are no commercial freshwater fisheries in South Africa, and subsistence reliance on 

freshwater crustaceans is extremely low (B. Clark Anchor Environmental, pers. comm.), so neither of 

these fisheries should suffer significant impacts as a result of further introductions of C. tenuimanus. 

It is also unlikely that recreational fisheries will be negatively affected. 

Page | 10

10.4 Risk summary 

There is reasonable likelihood that: 

 

 

 

 

 

There will be escapees from any established culture facility unless best management 

practises are followed; 

Unless barriers are provided, C. tenuimanus could colonise and establish in any previously 

un-invaded streams across some areas of the country, especially the Highveld, and in the 

southern and south-western Cape (de Moor 2002); 

In these areas, introduced crayfish will predate on or compete with indigenous species and 

will pose a risk (albeit small) to the continued survival of native species especially those that 

are already rare or range restricted; 

No hybridisation will occur with indigenous species; and 

Diseases or parasites could be transferred to populations of indigenous and non-native 

crustaceans unless appropriate best management practises are adopted, and all individuals 

are certified disease free by suitably qualified veterinarians prior to introduction. 

11 Control and prevention options 

There are a number of control options for limiting the introduction and spread of alien freshwater 

invertebrate species in South Africa. The focus needs to be on preventing their spread or deliberate 

introduction to new areas or river systems, as well as seeking to eradicate these animals from 

systems where their impact on biodiversity is considered to be unacceptably high. 

Controlling the spread of invasive species through prevention is thought to be the most costeffective 

means (Leung et al. 2002). The Department of Environmental Affairs & Development 

Planning Generic Environmental Best Management Practice Guideline for Aquaculture Development 

and Operation in the Western Cape (Hinrichsen 2007) should be used as a guide for construction of 

facilities and management thereof. These measures can serve to reduce biosecurity risks and key 

points from these guidelines are summarised below. 

It is recommended that all new aquaculture facilities should be built above the 1 in 50 year flood 

line, with infrastructure built to resist the impacts of floods (Hinrichsen 2007). The Freshwater 

Crayfish policy for the Western Cape Province specifies that facilities must be sited away from 

natural waters courses (D. Impson, Cape Nature, pers. comm.). 

The creation of physical barriers around the facility can also be effective in preventing spread of 

invasive species. Dams have been successful in controlling invasive freshwater crayfish spread 

elsewhere in the world, so may also be a practical consideration for potential marron farms in South 

Africa. Three meter high walls were effective in preventing Procambarus clarkii escaping from a 

mountain stream in Spain therefore protecting a population of the endangered Austropotamobius 

pallipes (Dana et al. 2011). Secure fencing around an aquaculture facility in combination with 

restricted access will assist in preventing any person intentionally removing live individuals 

(Hinrichsen 2007). In addition, facilities must be supervised continuously (i.e. full time) by a person 

deemed responsible by the authorities (D. Impson, Cape Nature ,pers. comm.). 

Page | 11

In order to decrease the risk of escapes, pond culture systems should be designed with stable walls 

(free from tree roots or burrowing animals) at a suitable gradient. In the Western Cape, permits will 

only be issued if facilities are completely enclosed in ‘’smooth, vertical barriers of at least 0.5m high’’ 

(D. Impson, Cape Nature, pers. comm.). Water levels should be monitored to determine flood 

threats and also be built with a capacity for overflow, with an option to be drained completely 

(Hinrichsen 2007). Stocking drainage ponds with predatory fish (preferably indigenous species) will 

help minimise the risk of escapees entering river systems (V. Bursey, pers. comm.). It is 

recommended that all outlet and inlet pipes (as well as overflow pipes) should have mesh screens 

which will prevent the escape of juveniles and adults from the ponds (Hinrichsen 2007, D. Impson, 

Cape Nature, pers. comm.). 

The creation of marron farmers associations in most producing countries has been encouraged and 

facilitated (FAO 2012). These associations should encourage their members to adhere to the rules of 

the FAO Code of Conduct for Responsible Fisheries and the FAO Technical Guidelines for Responsible 

Fisheries (Aquaculture Development). Given that commercial farmers require a licence and must 

comply with regulations, they are unlikely to intentionally encourage the spread of C. tenuimanus. 

There are a number of control options for limiting the introduction and spread of alien freshwater 

species in South Africa. There may be a few potentially small populations of C. tenuimanus in the 

Eastern Cape. The focus thus needs to be on determining if these actually exist or not, determining 

what impacts they have had if they do indeed exist, and preventing any further spread. In addition, 

the deliberate introduction of this species to new areas or river systems should be strictly 

prohibited, and remaining populations should be eradicated. Species can be trapped but complete 

elimination is considered to be practically impossible (Picker & Griffiths 2011). Assisting and 

enhancing high predation rates by indigenous species (e.g. platana frogs, catfish, otters) may be a 

possible way to moderate and keep C. tenuimanus at low population levels (de Moor 2002). Priority 

should be given at the earliest possible stage to contain and eradicate this species (de Moor 2002). 

Costs of control or eradication and prevention measures should ideally be incurred by the party 

responsible for the introduction. However, in practice, this is extremely difficult to determine as well 

as enforce (de Moor 2002). Even if there is such an escape proof system there is always the chance 

of theft as happened to the Australian freshwater crayfishes which were stolen from a supposedly 

escape-proof facility in Bloemfontein (Cambray 2003). 

12 Recommendations regarding suitability for use in aquaculture in South Africa 

In South Africa, National Freshwater Ecosystem Priority Areas (NFEPA) guidelines provide strategic 

spatial priorities for conserving South Africa’s freshwater ecosystems and supporting sustainable use 

of water resources. The NFEPA guidelines were designed to assist those involved in the conservation 

and management of FEPAs, to preserve these important areas in the high quality condition they 

currently exist. FEPAs are river or wetland areas which are in a largely unmodified/natural condition. 

These can include free-flowing rivers (free from dam structures), habitats which support threatened 

species and their migration corridors, areas which are relied upon as a water source for catchments, 

or simply provide a representative selection of wetland types. Rivers and their associated subquaternary 

catchments which were determined important areas in protecting viable populations of 

threatened and near-threatened fish are broadly termed Fish Sanctuaries. 

Page | 12

Figure 6 displays the location of FEPAs and their associated sub-quaternary catchments (blue 

shading). Fish sanctuaries which are deemed to be of high ecological condition were also assigned 

FEPA status and accordingly, for the purpose of this study, we have grouped together Fish and River 

FEPAs. Fish sanctuaries that are not in as good condition but nonetheless recognised as vital to the 

protection of threatened fish species, were classified as Fish Support Areas (green shading). Fish 

migration corridors represent areas for potential migration between essential habitats (yellow 

shading). Upstream Management Areas require protection to prevent degradation of downstream 

areas (brown shading). Phase 2 FEPA sub- quaternary catchments (pink shading) include riverine 

areas that are in a poorer ecological condition but nonetheless still considered important for 

conservation of freshwater aquatic resources provided they can be rehabilitated. Rehabilitation of 

these areas is expected to be undertaken when all other FEPAS are considered well managed. 

Collectively, these areas all represent important habitats and sites for the conservation of freshwater 

biodiversity in South Africa and should be protected from development and other adverse impacts. 

In spite of their value in conservation planning and management, FEPAs are considered to be of 

lesser value in guiding decision making regarding allocation of aquaculture permits for alien species 

such as C. tenuimanus. This is because FEPAs tend to cover restricted conservation worthy aquatic 

ecosystems within river basins or sub-quaternary catchments that are by nature, linked to the rest of 

the catchment by existing river channels. C. tenuimanus, being mostly highly mobile, can very easily 

invade an area designated as a FEPA from virtually any other portion of the catchment except where 

a barrier (such as a dam wall or waterfall) prevents this from happening. In addition, FEPA maps do 

not offer a species-specific approach i.e. the FEPAs recommend that no species be farmed in these 

areas. However, not all species will impact on threatened native species in an equal manner. 

For this reason a complimentary mapping process (termed the NEM:BA AIS fish maps, Swartz 2012) 

was initiated specifically to support the process of identifying locations for the farming of alien 

invasive freshwater fish species. These maps are based on the same sub-quaternary layers as utilised 

in the FEPA process, and are thus compatible with the NFEPA maps. Biodiversity protection was 

maximised wherever possible in both sets of maps, however, no consideration was given to climatic 

suitability for the non-indigenous species of concern. The NEM:BA maps were created using known 

distribution records and expert opinion. These maps were then developed in consultation with 

anglers and aquaculturists to take into account socio-economic impacts of the zonation process (O. 

Weyl, SAIAB, pers. comm.). 

A NEM:BA AIS fish map has been prepared for C. tenuimanus on the premise that C. tenuimanus is a 

NEM:BA List 3: Category 2 species i.e. one to be managed by area. Category 2 species generally have 

high economic value for aquaculture and angling, but have a high potential negative impact on the 

environment where they occur outside their native range. In the case of C. tenuimanus, it is classed 

as a species with no risk of hybridisation or genetic contamination. 

These maps have not been implemented by government as part of the legislative regime as yet, 

owing to the fact that NEM:BA currently does not allow for the approach of regulating these species 

as envisaged by the maps. As a result, they have not been included in this Biodiversity Risk and 

Benefit Assessment profile. 

Page | 13

Figure 6. South Africa’s Ecoregions with FEPAs, Fish Support areas, Fish Corridors, Upstream Management Areas and Phase 2 FEPAs. Source: Kleynhans et al. 2005 and Nel 2011. 

Page | 14

It is recommended that conservation authorities responsible for evaluating aquaculture permit 

applications should make use of all of the available resources including the FEPA maps and 

ecoregions maps as well as the NEM:BA AIS fish maps when these are released, to inform their 

decision making processes. However, this remains a complex procedure, despite the availability of 

these visual tools, therefore further consultation with experts may be necessary. 

At present, in the absence of the NEM:BA AIS maps, recommendations for culture activities have 

been based on the FEPA maps (Figure 6) and environmental tolerance ranges of the species (Table 

1). In the first instance, it is recommended that no permits for culture activities be issued in areas 

designated as FEPAs (Table 2). All aquaculture facilities in Phase 2 FEPAs, should have high 

biosecurity measures in place, in order to protect non-fish species which are threatened and may 

not be directly protected in the FEPAs or Fish Support Areas. In the case of marron, this involves 

either closed Recirculating Aquaculture Systems (RAS) or a facility that is constructed at a distance of 

greater than 1000 m from a watercourse. 

Table 2. 

Recommendations for C, tenuimanus culture in South Africa. Red shading indicates ‘No culture”, orange 

shading indicates “high biosecurity” (closed RAS or facilities >1000 m from watercourse), blue shading 

indicates “medium biosecurity” (partial RAS or pond >500 m from watercourse) and green shading indicates 

low biosecurity requirements (pond >100 m from a watercourse). White blocks represent “Nonapplicability”, 

i.e. in this case, there is no native distribution of C. tenuimanus in South Africa. ‘1’ has been 

categorised as high biosecurity to include the protection of non-fish threatened species (which are not 

directly recognised in the fish sanctuary format of FEPAs). 

FEPA map category 

Native 

distribution 

Existing 

introduced 

population 

Species not 

present 

(climatically 

suitable) 

Species not 

present 

(climatically 

unsuitable) 

FEPA (Fish and River FEPAs) 

Fish Support Area 

Fish Corridor 

Upstream management Area 

Phase 2 FEPAs 1 1 1 

All other areas 

In Fish Support Areas, where the species is currently not present, (whether the climate is suitable for 

culture or not), culture of C. tenuimanus can be undertaken only following construction of the high 

biosecurity facilities. In Fish Support Areas, where the species is currently found, culture should only 

be permitted with medium biosecurity measures in place (i.e. partial RAS or in a facility that has 

been constructed at a distance of greater than 500 m from a watercourse). 

Culture activities in Fish Corridors and Upstream Management Areas should be restricted to high 

biosecurity facilities in water catchments which are suitable for culture but the species is currently 

not present. If the species is already established in these areas, culture facilities must be of a 

medium biosecurity status. Where marron is not present and the area is climatically unsuitable, low 

biosecurity measures can be employed (where the pond is sited at a distance of greater than 100 m 

from a watercourse). 

Page | 15

In all other freshwater areas, low biosecurity culture facilities can be installed. It should be noted 

that all these recommended levels of biosecurity should be implemented in conjunction with the 

other preventative measures discussed in Section 11. 

The construction of closed and partial recirculating facilities which treat water and/or recyclewater 

should be encouraged wherever possible, to prevent the discharge of organisms and waste products 

into the surrounding environment. 

De Moor (2002) warns against the further import of live C. tenuimanus. He concludes that due to the 

high risk posed by parasites of C. tenuimanus infecting indigenous species, and the damages already 

caused by this, combined with the disappointing results that have been achieved so far in terms of 

aquaculture, it is clear the environmental damage has already outweighed the economic benefits 

from imports, and that there is no point in allowing the importation of species unlikely to be of 

commercial value. 

An assessment of the invasive potential of C. tenuimanus undertaken in accordance with the 

European Non-Native Species Risk Analysis Scheme (ENSARS) suggests that C. tenuimanus should be 

evaluated in more detail before further introduced to this country. Assessments conducted on the 

potential impacts of this species on local fauna in areas where it has already been introduced 

indicate that these impacts are potentially severe, especially the threat posed by diseases and 

parasites. Scientific monitoring should be undertaken at the current aquaculture facilities to assess 

the impacts of individual farms (and the techniques utilised in each facility). 

13 References 

Ackefors, H. &. Lindqvist, O.V. 1994. Cultivation of freshwater crayfishes in Europe. In: Huner, J.V. 

(Ed.) Freshwater crayfish aquaculture in North America, Europe, and Australia. Food 

Products Press, New York, USA. Pp.157-216. 

ACWA. 2012. Aquaculture Council of Western Australia. 

http://www.aquaculturecouncilwa.com/marron/guide-to-marron-farming Accessed: 10 

September 2012. 

Austin, C.M. & Ryan, S.G. 2002. Allozyme evidence for a new species of freshwater crayfish of the 

genus Cherax Erichson (Decapoda: Parastacidae) from the south-west of Western Australia. 

Invertebrate Systematics 16: 357-367. 

Austin, C.M. & Bunn, J. 2010. Cherax tenuimanus. In: IUCN 2012. IUCN Red List of Threatened 

Species. Version 2012.1. . Downloaded on 22 August 2012. 

Avenant-Oldewage, A. 1993. Occurrence of Temnocephala chaeropsis on Cherax tenuimanus 

imported into South Africa, and notes on its infestation of an indigenous crab. South African 

Journal of Science 89: 427–428. 

Borquin, O., Pike, T., Johnson, D., Rowe-Rowe, D. & Appleton, C.C. 1984. Alien animal species. 

Internal report to the Natal Parks, Game and Fish Preservation Board, Pietermartizburg. Pp. 

36. 

Britz, P.J., Lee, B. & Botes, L. 2009. AISA 2009 Aquaculture Benchmarking Survey: Primary Production 

and Markets. AISA report produced by Enviro-Fish Africa (Pty) Ltd. 117 pp. 

Page | 16

Burgess, M. 2007. Pioneers of SA marron production. Farmer's Weekly Magazine. Mon 30 April 2007. 

http://www.farmersweekly.co.za/article.aspxid=520&h=Pioneers-of-SA-marron-production 

Cambray, J.A. 2003. Impact on indigenous species biodiversity caused by the globalization of alien 

recreational freshwater fisheries. Hydrobiologia 500: 217–230. 

Coetzee, D.J. 1985. Verslag oor die kunsmatige aanhouding van die marron, Cherax tenuimanus, by 

die Jonkershoek-Natuurbewaringstasie, Stellenbosch. Internal Report to the Director of the 

Cape Department of Nature and Environmental Conservation. 

Charlebois, P.M. & Lamberti G.A. 1996. Invading crayfish in a Michigan stream: direct and indirect 

effects on periphyton and macroinvertebrates. Journal of the North American Benthological 

Society 15: 551-563. 

Copeland, J. 1999. Rich pickings from crayfish. Farmer’s Weekly, 8 October 1999: 89–91. 

Copp, G.H., Britton, J.R., Cowx, I.G., Jeney, G., Joly, J-P., Gherardi, F., Gollasch, S., Gozlan, R.E., Jones, 

G., MacLeod, A., Midtlyng, P.J., Miossec, L., Nunn, A.D., Occhipinti-Ambrogi, A., Oidtmann, 

B., Olenin, S., Peeler, E., Russell, I.C., Savini, D., Tricarico, E. & Thrush, M. 2008. Risk 

assessment protocols and decision making tools for use of alien species in aquaculture and 

stock enhancement. EU Co-ordination Action Project: IMPASSE Environmental impacts of 

alien species in aquaculture, Deliverable report 3.2. 

Cubitt, G.H. 1985. Candidate species in aquaculture: freshwater crayfish. In: Hecht, T., Bruton, M.N. 

& Safriel, O. (Eds.). Aquaculture South Africa. Occasional Report Series No. 1. Foundation for 

Research and Development, CSIR. Pp. 30-32. 

DAFF 2012a. Department of Agriculture, Forestry and Fisheries. South Africa’s Auaculture Annual 

Report 2011. 

DAFF 2012b. Department of Agriculture, Forestry and Fisheries. Animal Disease Status of South 

Africa (24 February 2012). 

Dana, E.D., Garcia-de-Lomasa, J., Gonzaleza, R. & Ortega, F. 2011. Effectiveness of dam construction 

to contain the invasive crayfish Procambarus clarkii in a Mediterranean mountain stream. 

Ecological Engineering 37: 1607–1613. 

de Moor, I.J. 2002. Potential impacts of alien freshwater crayfish in South Africa. African Journal of 

Aquatic Science 27: 125-139. 

de Moor, I.J. & Bruton, M.N. 1988. Atlas of alien and translocated indigenous aquatic animals in 

southern Africa. South African National Scientific Programmes Report No. 144. CSIR. 

Driver, A., Nel, J.L., Snaddon, K., Murray, K., Roux, D., Hill, L., Swartz, E.R., Manuel, J. & Funke, N. 

2011. Implementation Manual for Freshwater Ecosystem Priority Areas. WRC Report No. 

1801/1/11. ISBN 978-1-4312-0147-1. Pretoria. 

FAO. 2012. http://www.fao.org/fishery/introsp/294/en Accessed: 10 September 2012. 

Hinrichsen, E. 2007. Generic Environmental Best Practice Guideline for Aquaculture Development 

and Operation in the Western Cape: Edition 1. Division of Aquaculture, Stellenbosch 

University Report. Republic of South Africa, Provincial Government of the Western Cape, 

Department of Environmental Affairs & Development Planning, Cape Town. 

Kleynhans, C.J., Thirion, C. & Moolman, J. 2005. A Level I River Ecoregion classification System for 

South Africa, Lesotho and Swaziland. Report No. N/0000/00/REQ0104. Resource Quality 

Services, Department of Water Affairs and Forestry, Pretoria, South Africa. 

Langdon, J.S. 1991. Microsporidiosis due to a plesstophorid in marron, Cherax tenuimanus (Smith), 

(Decapoda: Parastacidae). Journal of Fish Diseases 14: 33–44. 

Leung, B., Lodge, D.M., Finnoff, D., Shogren, J.F., Lewis, M.A. & Lamberti, G. 2002. An ounce of 

Page | 17

prevention or a pound of cure: bioeconomic risk analysis of invasive species. Proceedings of 

the Royal Society of London B 269: 2407-2413. 

Mikkola, H. 1996. Alien freshwater crustacean and indigenous mollusc species with aquaculture 

potential in eastern and southern Africa. Southern African Journal of Aquatic Sciences 22: 

90-99. 

Mitchell, S.A. & Kok, D.C. 1988. Alien symbionts introduced with imported marron from Australia 

may pose a threat to aquaculture. South African Journal of Science 84: 877–878. 

Morrissy, N.M. 1990. Optimum and favourable temperatures for growth of Cherax tenuimanus 

(Smith 1912) (Decapoda: Parastacidae). Australian Journal of Marine and Freshwater 

Research 41: 735–746. 

Picker, M.D. & Griffiths, C.L. 2011. Alien and Invasive Animals – A South African Perspective. 

Randomhouse/Struik Cape Town. 240pp 

Read, G.H.L. 1985. A possible aquacultural crustacean with temperate growth requirements. In: 

Aquaculture South Africa. Proceedings of a joint symposium by the CSIR and the South 

African Agricultural Union. Occasional report no. 1 30-32. 

Safriel, O. & Bruton, M.N. 1984. A cooperative aquaculture research programme for South Africa. 

South African National Scientific Programmes Report 89. CSIR, Pretori pp. 79. 

Schoonbee, H.J. 1993. Report to the Chief Directorate: Nature and Environmental Conservation of 

the Transvaal on the Australian freshwater crayfish Cherax albidus (yabbiee) and C. 

quadricarinatus (red claw). Unpublished report, Zoology Department, Rand Afrikaans 

University, South Africa, 64pp. 

Shireman, J.V. 1973. Experimental introduction of the Australian crayfish (Cherax tenuimanus) into 

Louisiana. The Progressive Fish-Culturist 35: 107-109. 

Swartz, E. 2012. Summary of the mapping process for alien invasive fishes for NEM:BA (list 3 

category 2: species managed by area). Prepared for the South African National Biodiversity 

Institute. 

TSSC 2005. Advice to the Minister for the Environment and Heritage from the Threatened Species 

Scientific Committee (the Committee) on Amendments to the list of Threatened Species 

under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) – 

Cherax tenuimanus. 

Page | 18

Appendix 1. Risk scoring methodology for C. tenuimanus for South Africa (all ecoregions) with guidance supplied by the FI-ISK 

toolkit (Copp et al. 2008). 

Risk query: 

Question Biogeography/historical Reply Comments & References Certainty 

1 

Is the species adapted for aquacultural or ornamental purposes Guidance: This taxon must have been grown 

deliberately and subjected to substantial human selection for at least 20 generations, or is known to be easily reared in 

captivity (e.g. aquaculture or aquaria). 

Y 

ACWA 2012; Picker & Griffiths 

2011 4 

2 

Has the species become naturalised where introduced Guidance: The taxon must be known to have successfully 

established self-sustaining populations in at least one habitat other than its usual habitat (eg. Lotic vs lentic) and 

persisted for at least 50 years (response modifies the effect of Q1). Y Picker & Griffiths 2011 3 

3 

Does the species have invasive races/varieties/sub-species Guidance: This question emphasizes the invasiveness of 

domesticated, in particular ornamental, species (modifies the effect of Q1). Y TSSC 2005 4 

4 

Is species reproductive tolerance suited to climates in the risk assessment area (1-low, 2-intermediate, 3-high) ) 

Guidance: Climate matching is based on an approved system such as GARP or Climatch. If not available, then assign the 

maximum score (2). 2 Cubitt 1985 4 

5 

What is the quality of the climate match data (1-low; 2-intermediate; 3-high) ) Guidance: The quality is an estimate 

of how complete are the data used to generate the climate analysis. If not available, then the minimum score (0) 

should be assigned. 2 Kleynhans et al. 2005 4 

6 

Does the species have broad climate suitability (environmental versatility) Guidance: Output from climate matching 

can help answer this, combined with the known versatility of the taxon as regards climate region distribution. 

Otherwise the response should be based on natural occurrence in 3 or more distinct climate categories, as defined by 

Koppen or Walter (or based on knowledge of existing presence in areas of similar climate). N Cubitt 1985 3 

7 

Is the species native to, or naturalised in, regions with equable climates to the risk assessment area Guidance: 

Output from climate matching help answer this, but in absence of this, the known climate distribution (e.g. a tropical, 

semi-tropical, south temperate, north temperate) of the taxons native range and the ‘risk are’ (,e, country/region/area 

for which the FISK is being run) can be used as a surrogate means of estimating. Y Picker & Griffiths 2011 3 

8 

Does the species have a history of introductions outside its natural range Guidance: Should be relatively well 

documented, with evidence of translocation and introduction. N de Moor & Bruton 1985 3 

9 

Has the species naturalised (established viable populations) beyond its native range Guidance: If the native range is 

not well defined (i.e. uncertainty about it exists), or the current distribution of the organism is poorly documented, 

then the answer is “Don’t know”. Y de Moor & Bruton 1985 4 

10 

In the species' naturalised range, are there impacts to wild stocks of angling or commercial species Guidance: 

Where possible, this should be assessed using documented evidence of real impacts (i.e. decline of native species, 

disease introduction or transmission), not just circumstantial or opinion-based judgments. N No record of this 3 

11 

In the species' naturalised range, are there impacts to aquacultural, aquarium or ornamental species Guidance: 

Aquaculture incurs a cost from control of the species or productivity losses. This carries more weight than Q10. If the N de Moor 2002 3 

Page | 19

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

types of species is uncertain, then the yes response should be placed here for more major species, particularly if the 

distribution is widespread. 

In the species' naturalised range, are there impacts to estuaries, coastal waters or amenity values Guidance: 

documented evidence that the species has altered the structure or function of natural ecosystems. PLEASE NOTE THAT 

THIS IS AN ERROR WITH THE FIISK TOOLKIT AND THE CREATORS WILL BE ALERTED. FOR THE PURPOSES OF THIS STUDY, 

THE QUESTION SHOULD BE “In the species' naturalised range, are there impacts to rivers, lakes or amenity values” N No record of this 3 

Does the species have invasive congeners Guidance: One or more species within the genus are known to be serious 

pests. N GISD 2012 4 

Is the species poisonous, or poses other risks to human health Guidance: Applicable if the taxon’s presence is 

known, for any reason, to cause discomfort or pain to animals. In the case of mollusks, which can become poisonous 

to humans by accumulating algae toxins, restrict this question to animals other than humans. N No record of this 4 

Does the species out-compete with native species Guidance: known to suppress the growth of native species, or 

displace from the microhabitat, of native species. Y de Moor 2002 3 

Is the species parasitic of other species or may it act a major predator on a native species that was previously 

subject to low predation Guidance: Needs at least some documentation of being a parasite of other species N No reference 3 

Is the species unpalatable to, or lacking, natural predators Guidance: this should be considered with respect to 

where the taxon is likely to be present and with respect to the likely level of ambient natural or human predation, if 

any. N No reference 4 

Is the species likely to exert a notable increased predation on any native species Guidance: There should be 

evidence that the species is known to reduce the abundance of native species. Y de Moor 2002 3 

Does the species host, and/or is it a vector, for recognised pests and pathogens, especially non-native Guidance: 

The main concerns are non-native pathogens and parasites, with the host being the original introduction vector of the 

Mitchell & Kock 1988; Avenantdisease 

or as a host of the disease brought in by another taxon. 

Y Oldewage 1993 4 

For crustaceans, does the species achieve an ultimately large body size (e.g > 10 cm body length) or for mussels, 

does the species form extensive colonies/cluster/aggregations (e.g. >1m^3) ) Guidance: Although small-bodied 

invertebrates may be abandoned, large-bodied invertebrates are the major concern, as they soon outgrow their 

aquarium. Y Picker & Griffiths 2011 4 

Does the species tolerate a wide range of salinity regimes Guidance: There should be evidence that the species 

tolerates a wide range of salinities, from freshwater to highly saline. N Cubitt 1985 4 

Is the species desiccation tolerant at some stage of its life cycle Guidance: Should be able to withstand being out of 

water for extended periods (e.g. minimum of one or more hours). Y Ackefors & Lindqvist 1994 4 

Is the species flexible/versatile in terms of habitat use Guidance: Species that are known to persist in a wide variety 

of habitats, including areas of standing and flowing waters (over a wide range of Velocities: 0 to 0.7 m per sec). Y TSSC 2005 3 

Does feeding, settlement or other behaviours of the species reduce habitat quality for native species Guidance: 

There should be evidence that the foraging results in an increase in suspended solids, reducing water clarity water 

chemistry etc. Y de Moor 2002 3 

Does the species require minimum population size to maintain a viable population Guidance: If evidence of a 

population crash or extirpation due to low numbers (e.g. overexploitation, pollution, etc.), then response should be 

‘yes’. 

Y 

Need certain number to 

prevent inbreeding 4 

Page | 20

26 

27 

28 

Does the species have a wide temperature tolerance range Guidance: There should be documented evidence of the 

taxon being able to survive in extreme low and/or high temperatures. N V. Bursey pers. comm. 4 

Is the species a voracious predator Guidance: Obligate piscivores are most likely to score here, but some facultative 

species may become voracious when confronted with naïve prey. N No record of this 3 

Is the species omnivorous Guidance:Evidence exists of foraging on a wide range of prey items, including incidental 

piscivory. Y Read 1985 4 

29 Is the species planktivorous or detrivorous Guidance: Should be an obligate planktivore to score here. Y Read 1985 4 

30 

Does it exhibit parental care and/or is it known to reduce age-at-maturity in response to environment Guidance: 

Needs at least some documentation of expressing parental care and/or variable age at maturity under different 

environmental conditions. Y de Moor & Bruton 1988 4 

31 Does the species produce viable gametes Guidance: If the taxon is a sub-species, then it must be indisputably sterile. Y No reference 4 

32 

Does the species hybridize naturally with native species Guidance: Documented evidence exists of interspecific 

hybrids occurring, without assistance under natural conditions. N No reference 4 

33 

Is the species hermaphroditic or gynogenetic (e.g. Melanoides tubercolata or the marble crayfish) Guidance: Needs 

at least some documentation of hermaphroditism or gynogenesis. N de Moor & Bruton 1988 4 

34 

Is the species dependent on the presence of another species or specific habitat features to complete life cycle 

Guidance: Some species may require specialist incubators (e.g. unionid mussels used by bitterling) or specific habitat 

features (e.g. fast flowing water, particular species of plant or types of substrata) in order to reproduce successfully. N No record of this 4 

35 

Is the species highly fecund, iteropatric or extended spawning season Guidance: Species is considered to have 

relatively high fecundity for its taxonomic Order. N Coetzee 1995 4 

36 

What is the species' known minimum generation time (in years) Guidance: Time from hatching to full maturity (i.e. 

active reproduction, not just presence of gonads). Please specify the number of years. 3 Picker & Griffiths 2011 4 

37 

Are life stages likely to be dispersed unintentionally Guidance: Unintentional dispersal resulting from human 

activity, including as ship ballast or hull foulant. PLEASE NOTE THAT THIS IS AN ERROR WITH THE FIISK TOOLKIT AND 

THE CREATORS WILL BE ALERTED. FOR THE PURPOSES OF THIS STUDY, THE GUIDANCE SHOULD BE Unintentional 

dispersal resulting from human activity. Y Mikkola 1996 3 

38 Are life stages likely to be dispersed intentionally by humans (and suitable habitats abundant nearby) N No record of this 3 

39 

40 

41 

Are life stages likely to be dispersed as a contaminant of commodities Guidance: Taxon is associated with organisms 

likely to be sold commercially. 

N 

Depends on management 

practices 3 

Does natural dispersal occur as a function of dispersal of eggs and/or the movement of the suitable substratum 

Guidance: there should be documented evidence that eggs are taken by water currents or displaced by other 

organisms either intentionally or not. N de Moor & Bruton 1988 4 

Does natural dispersal occur as a function of larval or juvenile dispersal (along linear and 'stepping stone' habitats) 

Guidance: There should be documented evidence that larvae enter, or are taken by, water currents, or can move 

between marine areas via connections. PLEASE NOTE THAT THIS IS AN ERROR WITH THE FIISK TOOLKIT AND THE 

CREATORS WILL BE ALERTED. FOR THE PURPOSES OF THIS STUDY, THE GUIDANCE SHOULD BE: There should be 

documented evidence that larvae enter, or are taken by, water currents, or can move between water bodies via 

connections Y de Moor & Bruton 1988 4 

42 Are adults of the species known to migrate (reproduction, feeding, etc.) Guidance: There should be documented Y Molony et al. 2003 4 

Page | 21

43 

44 

45 

46 

47 

48 

49 

evidence of migratory behavior, even at a small scale (tens or hundreds of meters). 

Are any life stages of the species known to be dispersed by other animals (externally) Guidance: For example, are 

they moved by birds accidentally when the water fowl move from one marine area to another For example, are they 

moved by birds accidentally when the water fowl move from one water body to another No record of this 2 

Is dispersal of the species density dependent Guidance: There should be documented evidence of the taxon 

spreading out or dispersing when its population density increases. N No record of this 3 

Is any life history stage likely to survive out of water transport Guidance: There should be documented evidence of 

the taxon being able to survive for an extended period (e.g. an hour or more) out of water. PLEASE NOTE THAT THIS IS 

SIMILAR TO QUESTION 22. THIS IS AN ERROR WITH THE FIISK TOOLKIT AND THE CREATORS WILL BE ALERTED. FOR THE 

PURPOSES OF THIS STUDY, THE ANSWER HAS BEEN REPEATED. Y Ackefors & Lindqvist 1994 4 

Does the species tolerate a wide range of water quality conditions, especially oxygen depletion & high 

temperature Guidance: This is to identify taxa that can persist in cases of low oxygen and elevated levels of naturally 

occurring chemicals (e.g. ammonia). N Cubitt 1985 4 

Is the species susceptible to chemical control agents Guidance: There should be documented evidence of 

susceptibility of the taxon to chemical control agents. No record of this 1 

Does the species tolerate or benefit from environmental disturbance Guidance: The growth and spread of some 

taxa may be enhanced by disruptions or unusual events (coastal turbidity due to river floods and/or spates), especially 

human impacts (coastal dredging, desiccation, trawl fishing, etc). PLEASE NOTE THAT THIS IS AN ERROR WITH THE FIISK 

TOOLKIT AND THE CREATORS WILL BE ALERTED. FOR THE PURPOSES OF THIS STUDY, THE GUIDANCE SHOULD BE: The 

growth and spread of some taxa may be enhanced by disruptions or unusual events (floods, spates, dessication), 

especially human impacts. N TSSC 2005 4 

Does the species have effective natural enemies present in the risk assessment area Guidance: A known effective 

natural enemy of the taxon may or may not be present in the Risk Assessment area. The answer is ‘Don’t know’ unless 

a specific enemy/enemies is known. Y Picker & Griffiths 2011 4 

Page | 22

Marron, freshwater crayfish Cherax tenuimanus - Department of ...

Create successful ePaper yourself

Delete template?

Save as template?