Nicky Green CEnv MCIEEM

Intro to invasive crayfish

Crayfish impacts

The Barle Project

Est. 650 species globally

540 million years

Occur naturally on all continents except Africa

Highest diversity = North America, 405 species

Five species native to Europe

Tasmanian Giant 7kg Eastern Swamp 2cm

Rob McCormack; CC-BY 4.0

Several species introduced all over the world

Mainly for food, also bait, aquarium trade

Most invasives from North America

In Europe 5 native, 16 non-native species

Worse invaders: signal and red swamp crayfish

IMPACTS: ◦ Carry crayfish plague

◦ Out-compete native species

◦ Degrade river habitats & ecosystems

Introduced to Britain in the 1970’s

Highly invasive, have spread throughout UK

Virile Crayfish Red Swamp Crayfish

Peay et al. 2009, KMAE

Predation of fish at high density signal crayfish, c.20-30 m-2

Based on the River Barle in Exmoor National Park

Signal crayfish have colonised 15km of the SSSI

Major risk to the SSSI, salmonids and the river’s Water Framework Directive status

The project is subject to PhD research by N. Green supported by Bournemouth

University, EA and CEFAS.

◦ Trapping – standard traps select dominant males

◦ Electrofishing – only suitable for small watercourses, possible fish damage, doesn’t catch all animals

◦ Dewatering – only suitable for small watercourses

◦ Biocides – too much risk to ecosystem

◦ Barriers – effective in certain localities

◦ Research always ongoing,

e.g. GM, poison

Conventional baited trapping tends to catch large adults. Large males control breeding behaviour so their sterilisation and return maintains dominance whilst preventing successful mating.

Lab studies indicate manual sterilisation of males may be effective at eradication (CEFAS & Newcastle University)

Initial results in France highly

successful, never been trialled

in rivers in the UK

Combined with intensive

trapping using two methods

1.5km trial stretch near Withypool

Intensive trapping using two types of trap over three years – weekly in 2015

Large male crayfish are neutered manually and returned, whilst all other animals are humanely despatched.

Success will be measured by monitoring invertebrates, fish, young-of-year and berried female crayfish between 2015 and 2018.

Baited traps Artificial refugia

3275 crayfish captured

2848 humanely killed

427 large males sterilised – 13% of total

Baited traps less efficient but good in autumn

Weather – flow levels are a major constraint

Baseline data on invertebrates, fish & juvenile crayfish collected

Data analysis will inform future works

Volunteers are key….

Partnership project

Financial and in kind support from ENPA, EA, NE and RETA

No funding for PhD research!

• Report sightings to EA • Practice biosecurity –

check, clean dry! • Fund my PhD!