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Providing evidence to improve practice

Individual study: A fish-passable barrier to stop the invasion of non-indigenous crayfish

Published source details

Frings R.M., Vaeßen S.C.K., Groß H., Schüttrumpf H. & Hollert H. (2012) A fish-passable barrier to stop the invasion of non-indigenous crayfish. Biological Conservation, 159, 521-529



Create barriers

A replicated, controlled study in artificial flumes in Aachen University, Germany (Frings et al. 2012) found that signal crayfish Pacifastus leniusculus could not move upstream across barriers with slopes greater than 35° if the water flow rate was at least 0.5 m/s. In still water crayfish could pass any barrier. Faster flow rates reduced the angle of barrier needed to stop crayfish. Crayfish were able to cross rough barriers at steeper angles and faster water flow rates than smooth barriers. At a flow rate of 0.45 m/s a smooth barrier with an approximately 5° slope prevented crayfish crossing, but a 45° slope was required if the barrier was rough. Thirty two experiments were carried out with varying flow rates (0.04 – 0.77 m/s), barrier slopes (0-48°) and barrier roughness (either smooth or covered with sandpaper). Barriers consisted of PVC plates 1.5 cm thick and 35 cm long with at least 10 cm water depth above the barrier. In each experiment eight crayfish were placed downstream of a barrier with dogfood bait above it.  (Nynke Wemer)