Rocky beaches provide for very rich ecosystems as they combine a series of factors favourable to the development of a great diversity of living beings. In addition to serving as feeding grounds during the high tide period, they are also used as recruitment and growth grounds for juveniles of many commercially valuable fish species (such as the sea bream, the mullet or the sea bass), being extremely important 'maternity' areas to ensure the renewal and maintenance of fish stocks.
LIFE IN THE EBB AND FLOW OF TIDES
• Limpets - Their soft body is covered by a cone-shaped shell that resists the impact of waves. It clings strongly to the rocks and digs a small cavity, to which it fits perfectly, withstanding periods of exposure to the air. When submerged, the limpet moves slowly, scraping the surface of the rocks to feed on the algae that cover them and leaving their characteristic 'zig-zag' marks.
• Sea urchins shape the rocks, forming rounded cavities where they live, thus withstanding the agitation of the water.
• Mussels attach themselves firmly to the rocks using the byssus. When the tide goes out, they close their shells tightly and only open them again when they are completely submerged, filtering the food suspended in the water.
• Beadlet anemones - during low tide, they retract their tentacles into their bodies, which close completely to avoid dehydration. When the tide rises, they open again, letting out their tentacles, covered with stinging cells, which help them capture their food.
• Blennies and gobies - their small size allows them to take shelter in cavities and crevices. They have mechanisms to resist being transported by the action of waves, such as fused ventral fins, which function as suction cups, or wide and well-developed pectoral fins, which allow them to move on a substrate.