| Southern California rocky shores are heavily visited by humans who frequent the rocky intertidal zone for aesthetic pleasure, tidepooling, fishing, and collecting. At sites used by recreational fishers, the effects of foot traffic combined with the collection of mussels for bait may reduce mussel cover and create mussel-free gaps. To test this hypothesis, mussel cover and gap frequency in mussel beds were determined at sites receiving various levels of fisher use (low, moderate, and high use). Results indicated a trend of decreasing mussel cover with increasing fisher activity. In addition, the effects of trampling and bait removal on mussel populations were experimentally tested. Twenty-four 0.5 m x 0.7 m plots were randomly established in a mussel bed and subjected to monthly combinations of trampling (0, 150, or 300 steps) and simulated bait removal (0 or 2 removed mussels). Even during a period of high natural disturbance associated with the 1997–98 ENSO, plots receiving treatments experienced significantly greater reductions in mussel cover, mass, and density than controls. These results indicate that visitor foot traffic and bait removal by fishers can significantly reduce mussel abundance and impact southern California mussel beds. |
