Predator‐induced changes in byssal attachment, aggregation and migration in the blue mussel,Mytilus edulis

Blue mussels, Mytilus edulis, were exposed to the water‐borne scent of predators, either to the starfish Asterias rubens, or the shore crab Carcinus maenas, in laboratory experiments. Predator‐exposed mussels developed a stronger byssal attachment compared to that of unexposed mussels, which was significant after about, 24 h, and twice as strong after four days. The byssal attachment response was variable. In the short term (<10h), predator scents could inhibit byssus production in those experimental batches where unexposed mussels had a high rate of byssus production. Predator‐exposed mussels also formed larger aggregates, migrated less, and sought structural refuges more often. Experiments showed that these traits gave significant protection against predation from both crabs and starfish.