Crayfish campaign with Hugh Fearnley Whittingstall and the River Cottage team In May 2008 ARK and the River Cottage team ran an experimental crayfish trapping exercise to assess the impact of intensive trapping on American Signal Crayfish in the River Kennet. The project was broadcast in Episode 2 of the River Cottage Springseries on Channel 4 (Wednesday 4 June, 2008; repeated Saturday 7 June, 7pm). We set 20 traps in a 40m stretch of river and checked and emptied them every day. The traps were sized to catch both adult and young crayfish. Over 13 days we caught around 140 crayfish (or several thousand if you count the tiny babies that the females were carrying). We had expected to see a decline in size and number caught over time, suggesting that we were making an impact on the population. In fact we found the catch was fairly consistent from day to day and the size of the crayfish varied in randomly. This suggests that taking out 140 crayfish from a short stretch of stream has no significant impact on the population, and in order to 'fish out' a stretch, one would have to set hundreds of traps (and eat lots of crayfish). American signal crayfish are an 'alien species' introduced accidentally when they escaped from fish farms in the late 1970s and early 1980s. They quickly wiped out the native crayfish, both by out-competing them, and because they carry a virus deadly to the native population. Crayfish eat almost anything, including caddisfly larvae, trout eggs and each other. They burrow into soft river banks, causing bank erosion. The next phase of the Crayfish Campaign is to set sampling traps in the upper Kennet to assess crayfish distribution. Initial findings suggest that the population declines steeply above Marlborough. Once we have established a suitable location we intend to run a large, community project, with lots of local volunteers, to 'fish out' a section of river and monitor the impact of intensive trapping on invertebrates and weed growth. We'll celebrate with a giant crayfish cook up! If you'd like to be involved please email us. Please note: it is illegal to trap crayfish without a licence, it is also illegal to replace a crayfish (even baby ones) once caught. It is illegal to put a caught crayfish in another waterbody (your own pond included!). You must get permission from the riparian owner before setting any trap on the River Kennet. | 
