Below is some additional and more descriptive information about the Percebes harvest and also a couple of links where you can find out more. This description and information was given to us by Tom Marting.
Percebes are gooseneck barnacles that grow only on rocks with heavy surf. There are only a few regions that they can be cultivated, including the Rias Altas region of Galicia.
Watching fisherman gather percebes is like watching a high-wire act at the circus. A fisherman gets close to a rockface in a little rowboat as the surf comes in and out. He ties a rope to his ankle and holds a knife in his teeth. He times his jump into the water with the surf and swims over to the rock where the Percebes are growing. He quickly chisels off a handful and stuffs them in a net bag around his waist. He then rushes back to his rowboat and tries to clear the rock before the next wave comes in. Every time he goes out to gather the Percebes, he faces the very likely possibility that he or his boat will be smashed against the rock with the next wave.
Links to pages on Percebes
Click on any of the three links below to find out more about Percebes and see pictures of them being harvested.