CRAYFISH PLAGUE - UK: ENGLAND
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Date: Mon 8 Nov 2010
Source: BristolZooUK [accessed 8 Nov 2010, summarised, edited] <http://www.bristolzoo.org.uk/conservationists-highlight-worsening-plight-of-uk-crayfish?theme=orange>
Bristol conservationists are highlighting the worsening plight of native crayfish as the species is officially upgraded to "endangered".
White-clawed crayfish are the UK's only native freshwater crayfish, but their numbers have suffered extensive decline in recent years. Experts warn the species could become extinct from the UK within the next 30 years; it is currently a protected species.
Today, white-clawed crayfish have been upgraded from "vulnerable" to "endangered" on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, following a Sampled Red List Index (SRLI) assessment by the Zoological Society of London (ZSL). The ranking gives an indication of how likely a species is to become extinct.
Eve Leegwater, technical biodiversity officer at the Environment Agency,
said: "It is important to base conservation efforts on scientific research, and the IUCN Red List has become an increasingly important tool to guide government and scientific institutes towards the conservation and legislation of species and habitats at risk of extinction." She added: "The change in status of white-clawed crayfish will help stress the need for conservation strategies to be implemented to aid this valuable species."
Up to 70 per cent of white-clawed crayfish have been lost from the south west, and some parts of the UK have lost their entire populations. This is predominantly due to the crayfish plague, a fungus-like disease which is harmless to people and most animals but lethal to white-clawed crayfish.
The crayfish plague is spread by the invasive American signal crayfish, a non-native species which is taking over UK waterways and wiping out our smaller native species.
The South West Crayfish Project is currently running the largest strategic translocation in the UK to date, re-homing at-risk populations of white-clawed crayfish to new safe sites. In addition, a breeding programme for the crayfish is being developed at Bristol Zoo Gardens, the sister organisation to the Bristol Conservation and Science Foundation (BCSF).
Maddy Rees, UK conservation officer for the Bristol Conservation and Science Foundation, said: "The plague can be carried on anything that gets wet in infected water, so we are urging people to wash, dry and, if possible, disinfect footwear, fishing tackle, nets and other equipment that gets damp in our rivers and lakes. Never trap for any species of crayfish without a trapping licence, as it is illegal, and finally, never move wild fish between waterways; always use a reputable stockist."
The survival of white-clawed crayfish will be the focus of a conference held at Bristol Zoo Gardens later this year [2010]. The event, called "Species survival: Securing white-clawed crayfish in a changing environment" will take place on 16 and 17 Nov 2010. It will include a range of lectures from speakers from across Europe and presentations from experts in the field of UK crayfish conservation.
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[The aetiological agent of crayfish plague is _Aphanomyces astaci_, a member of a group of organisms commonly known as the water moulds. Although long regarded to be fungi, this group, the Oomycetida, are now considered protists and are classified with diatoms and brown algae in a group called the Stramenopiles or Chromista.
There is evidence that established older _A. astaci_ strains that have been present in Europe for many years are less aggressive than newer strains introduced with crayfish imports from North America since the 1960s. Some isolates from warmer waters in Spain have temperature/growth curves with higher optimum temperatures compared with those from northern Europe.
Although _A. astaci_ is not an obligate parasite and will grow well under laboratory conditions on artificial media, in the natural environment it does not survive well for long periods in the absence of a suitable host.
It has been shown that _A. astaci_ cysts survive for 2 weeks in distilled water, and that zoospores remained motile for up to 3 days. As _A. astaci_ can go through 3 cycles of zoospore emergence, the maximum life span outside of a host could be several weeks.
_A. astaci_, both in culture and in infected crayfish, is killed by a short exposure to temperatures of 60 C (140 F) or to temperatures of -20 C (-4 F) or less for 48 hours or more. Sodium hypochlorite and iodophores are effective for disinfection of contaminated equipment. Thorough drying of equipment (more than 24 hours) is also effective, as _Aphanomyces_ is not resistant to desiccation.
There is good field and experimental evidence that movements of fish from areas in which crayfish plague is active can transmit infection from one watershed to another. _A. astaci_ can also be spread by contaminated equipment (nets, boots, clothing, etc).
The information above is derived from chapter 2.3.7. "Crayfish Plague (_Aphanomyces astaci_)" in OIE's (World Organisation for Animal Health) Manual of Diagnostic Tests for Aquatic animals. The chapter includes additional comprehensive information on the agent factors, host factors, disease pattern, diagnosis, control and prevention, etc; see <http://oie.int/eng/normes/fmanual/2.2.01_CRAYFISH.pdf>. - Mod.AS
The HealthMap/ProMED-mail interactive map of the United Kingdom can be accessed at <http://healthmap.org/promed?v=54.5,-2,5>. - Mod.SH]
[see also:
2008
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Crayfish plague - UK: (England) 20080808.2444
2007
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Crayfish plague - UK (England) 20071023.3447]
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