Action: Use ‘mussel socks’ to prevent birds from attacking shellfish
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A randomised, replicated controlled experiment in Canada found that fewer medium-sized mussels were taken from mussel socks with a protective ‘sleeve’, compared to un-sleeved socks. There were no differences for small or large mussels.
‘Mussel socks’ are protective netting materials designed to reduce predation by birds on shellfish. The socks are made from polypropylene material with a biodegradable layer sown around it. The second layer (which has smaller mesh openings) prevents mussels from migrating towards the outside of the sock in order to filter feed and so reduces the threat from predation. The mussels are buffered between these layers over winter until the following spring when the protective layer decomposes and allows mussel growth to continue unhindered.
Supporting evidence from individual studies
A randomised, replicated controlled experiment in October 2002 in three bays on Prince Edward Island, Canada (Dionne et al. 2006), found that mussel socks with a ‘sleeve’ of a biodegradable cotton-polyester mesh lost fewer medium-sized (20 mm) mussels to greater scaup Aythya marila predation than un-sleeved socks. Losses were similar for small (14 mm) and large (26 mm) mussels, but more small mussels migrated through sleeved socks (thus more vulnerable to predation).