Action: Procambarus crayfish control: Create barriers
Key messagesRead our guidance on Key messages before continuing
- A before-and-after study conducted between 2007 and 2010 in Spain found that the use of concrete dams across a stream, specifically designed with features to prevent red swamp crayfish from crawling over them, were effective at containing spread of the population upstream.
Physical barriers have the potential to prevent the spread of invasive crayfish, especially upstream within rivers. A review reported that building physical barriers was an effective mechanism to halt, or at least delay, the natural movement of red swamp crayfish Procambarus clarkii (Stebbing et al. 2012). However, a before-and-after study (Hänfling et al. 2011) found that an erected barrier in the River Buaa at the border between Sweden and Norway did not prevent the migration of signal crayfish Pacifastacus leniusculus into the Norwegian part of the river.
Stebbing P.D., Longshaw M., Taylor N., Norman R., Lintott R., Pearce F. & Scott A. (2012) Review of methods for the control of invasive crayfish in Great Britain. CEFAS. Contract C5471 final report. pp 105.
Hänfling B., Edwards F. & Gherardi F. (2011) Invasive alien Crustacea: dispersal, establishment, impact and control. BioControl, 56, 573–595.
Supporting evidence from individual studies
A before-and-after study from 2007 to 2010 in a mountain stream in Italy (Dana et al. 2011) found that building a series of small dams stopped migration of the red swamp crayfish Procambarus clarkii. The invasive crayfish did not penetrate into previously uninhabited areas upstream beyond the lower dams. In addition, numbers dropped below detectable levels in previously occupied areas in the mid reaches between dams. Dams were 1.5–2 m high and 6 m wide and constructed from reinforced concrete. Several design features discouraged crayfish from climbing over including vertical walls, smooth mortar, vertical wing-walls 3.5 m along the banks, and a projecting rim (crayfish are unable to walk upside down on a smooth surface). A flat stony platform was built downstream of each dam to create a shallow area with no refuges, discouraging crayfish from lingering near the dam. Crayfish populations were monitored for 30 days between July and October each year.