27
Overview
Scotland’s crayfish crisis: some background
Tackling the crisis
Biodiversity and environmental change
Scotland’s crayfish crisis: some background
American signal crayfish(Pacifastacus leniusculus)
Scotland’s crayfish crisis: some background
American signal crayfish(Pacifastacus leniusculus)
Large, freshwater, decapod crustacean
Native to western North America
Imported to Britain in 1970s for aquaculture
First recorded in Scotland in Galloway, 1995
Scotland’s crayfish crisis: some background
Non-native invasive species cited as one of the top 5 drivers of ecosystem change
Serious threat to biodiversity listed under ‘Species Action Framework’ in 2007
Scotland’s crayfish crisis: some background
Where is it?
How can we get rid of it?
What is it doing?
Tackling the crisis
Where is it? 1. Distribution
How can we get rid of it? 2. Control
What is it doing? 3. Impact
Tackling the crisis
3 broad aims of PhD
Where is it? 1. Distribution
How can we get rid of it? 2. Control
What is it doing? 3. Impact
Tackling the crisis
3 broad aims of PhD
1. Distribution
Fine-scale distribution of signal crayfish largely unknown
For effective control/containment, we must know where it is!
First aim: develop a protocol for detecting crayfish
applied across Scotland
1. Distribution
Compared the crayfish detection ability of four active sampling techniques
30 riffles on upper River Clyde
1. Hand searching 2. Electrofishing
(1, 2, 3 runs)3. Kick sampling 4. Surber sampling
1. Distribution
Results: combination of kick sampling and 3 runs of electrofishing best chance of detecting signal crayfish (Gladman et al., accepted)
Location River Catchment Fishery Trust Undertaking the Survey
Upper Clyde Clyde Clyde River Foundation
River North Esk (ponds); Lugar Burn/main stem North Esk Esks DSFBs
Pow Burn South Esk Esks DSFBs
Rankeillour Burn (Fife) Eden Forth Fisheries Trust
River Teith (pond and ditches) Forth Forth Fisheries Trust
River Tyne (stillwater fishery, East Lothian) East Lothian Tyne Forth Fisheries Trust
Tiel Burn (Fife) Tiel Forth Fisheries Trust
Murray Burn Water of Leith Forth Fisheries Trust
Kirkcudbrightshire Dee Galloway Fisheries Trust
Skyre Burn Fleet Galloway Fisheries Trust
River Nairn Nairn Ness and Beauly Fisheries Trust
Dighty Water (Dundee) Dighty Tay DSFB
River Earn Earn Tay DSFB
River Ardle (pond and small stream) Ericht Tay DSFB
Shee Water (pond and small stream) Ericht Tay DSFB
Rivers Ettrick and Till Tweed Tweed Foundation
Kirkbank (Teviot Water) Tweed Tweed Foundation
• Protocol
1. Distribution
Sinclair, CA (2009). Fine scale mapping of signal crayfish distribution in Scotland, Scottish Natural Heritage Commissioned Report, Project 26686.
1. Distribution
. . . So where is it?
2. Control
Physical
Chemical
Biological
Case study: Loch Ken’s crayfish crisis
2. ControlCrayfish crisis 'looming' on loch
Loch Ken’s crayfish crisis
Summer 2009: Marine Scotland funded an intensive 4-month trapping programme:
Assess the scale of the infestation
Assess the feasibility of control
Opportunity for research:
Effect of intensive trapping on the population
Two mark-and-recapture projects: one before and one after the trapping programme
2. Control Loch Ken’s crayfish crisis
Crayfish sampled at 3 sites (transects of 15 creels, 400 m apart) during two sessions: before (May/June) and after (September) the trapping programme
2. Control Loch Ken’s crayfish crisis
2. Control Loch Ken’s crayfish crisis
Total catch
3879 crayfish before trapping programme
3205 crayfish after trapping programme
. . . very little effect?!
2. Control Loch Ken’s crayfish crisis
Numbers of males and females caught during the two mark and recapture sessions before (May/June) the
removal programme and after (September) the removal programme
Denotes within‐sex pairwise
comparison with statistically significant difference p<0.01
2. Control
Site 1 Site 2 Site 3
Before After Before After Before After
1 M :0.42 F
1 M :1.04 F
1 M :0.37 F
1 M : 1.54 F
1 M :0.40 F
1 M :0.85 F
. . . Sex is important!
Loch Ken’s crayfish crisis
2. Control
. . . Sex is important!
Due to:
Bias of trapping towards large males
Changes in reproductive state of females: berried females in May are trap shy; egg release in summer
Numbers of males and females caught during the two mark and recapture sessions before (May/June) the
removal programme and after (September) the removal programme
Denotes within‐sex pairwise
comparison with statistically significant difference p<0.01
Loch Ken’s crayfish crisis
2. Control
Density estimates
Population estimates from mark and recapture data were used to make estimates of density (based on a trapping radius of 100 m2, Accosta & Perry, 2000)
Range 1.06 – 9.05 crayfish per m-2
Very high densities compared with other lakes:
Lake Billy Chinook: 0.24 c.p.m-2 and 1.13 c.p.m-2
Lake Donner: 0-1.15 c.p.m-2
Lake Tahoe: 0.53-8.38 c.p.m-2
Loch Ken’s crayfish crisis
2. Control
Other observations
Mean size of crayfish reduced
Significant for males
Movements
At least 800m in two weeks; 3 km in 6 months
Loch Ken’s crayfish crisis
2. Control
Summary
Trapping significantly reduced males; effect on females complicated by trap bias/reproductive status sex ratio skewed towards females
Mean size of crayfish reduced
Crayfish capable of significant movements
High densities mean loss to biodiversity likely to be significant
Loch Ken’s crayfish crisis
Biodiversity and environmental change
Alien species are a major threat to biodiversity
Very difficult (impossible?) to reverse changes
Prevention is preferable!
Research is important in helping us understand ecological problems . . . and deal with them!
