Invasive Alien Crayfish in the UK
Native Species Threatened With Extinction
White clawed crayfish are being threatened by introduced red signal crayfish. Local cooperation is working to turn the tide.
The problems caused by invasive alien species are now recognized around the world. But thirty years ago we were much less aware of how much effect they could have. In the 1970s the American red signal crayfish (Pacifastacus leniusculus) was introduced into England.
Loss of Biodiversity and Habitat Damage
Today in the Brecks, in eastern England, the Lark Angling and Preservation Society (LAPS) and the Brecks Countryside Project are working to protect not just the native white-clawed crayfish (Austropotamobius pallipes), but the overall biodiversity of local rivers. In addition to native crayfish being pushed out, invertebrates and vegetation are disappearing, as the omnivorous signal crayfish consumes everything in sight.
Signal crayfish also burrow deeply into riverbanks and flood control levees, causing the loss of a meter of riverbank a year in heavily infested areas, threatening homes and lives. The net result is habit degradation and loss.
Native White-clawed crayfish
The native white-clawed crayfish is smaller, less aggressive, produces fewer eggs and out-competed for habitat. The signal crayfish carries a fungus that is usually fatal to the natives. And, as often happens with introduced species, there are few natural predators to keep them under control.
Trapping Program
The Brecks/LAPS team has spent many hours improving on traps designed for a sustainable fishery (i.e. ones that trap the best animals for sending to market), to make them more effective in trapping other ages and sizes. Success is good with juveniles but they are still working on more effective traps for females carrying eggs and traps that can be incorporated into the riverbank, to prevent further erosion as they catch crayfish. Removing juveniles (crayfish can reproduce within the first year) and females reduces the breeding populationTraps are only used on rivers where there are no native crayfish left.
The next problem to be faced is dealing with the numbers of crayfish caught (over 600,000 in 2005).Luckily, the UK has discovered the culinary value of these invaders. But most of the crayfish eaten in the UK is imported from China and northern Europe. So Eat2Beat is in the works, creating a branded environmentally positive food Crayfish is low in fat and high in protein so it appeals to modern dietary preferences. And by educating people on the issues-saving local native species, low food miles and protecting the local environment- they are setting the stage for adding other alien species to the menu. Eat2Beat is being developed to actively increase local employment as well.
