Medes Islands

Protected by the Catalan government in 1983 and now the marine core of the Montgrí, Medes Islands and Baix Ter Natural Park (declared in 2010), the Medes archipelago is one of the longest-established fully protected marine reserves in the western Mediterranean. The strictly protected no-take core covers roughly 95 hectares of limestone seabed riddled with tunnels, archways, and caves, where decades of protection have rebuilt populations of large predatory fish — a 19-year scientific monitoring series (1992–2009) recorded total fish biomass inside the reserve reaching about 50 g/m², nearly 20 times the ~2.6 g/m² of nearby unprotected coast, with dusky groupers, brown meagre, zebra seabream and European seabass recovering toward carrying capacity. The most visible result for divers is the resident dusky groupers, which are large (specimens over 30 kg are reported) and unusually unafraid of divers. Sites are mostly shallow (typical maxima 18–30 m, with deeper drop-offs to 40–50 m at the southern islets), so the diving suits a broad range of experience, though the photogenic tunnels and deeper gorgonian walls reward intermediate skills. Honest caveats: this is not a tropical reef — visibility is variable, the summer thermocline drops sharply to cool water below ~20 m, the area is busy in July–August, and all diving is rationed under a per-buoy annual quota (about 450 divers/day overall) and carries a per-dive reserve fee (€5.30 in 2026).

• The Medes Islands have been a fully protected (no-take) marine reserve since 1983, making them one of the oldest marine reserves in the western Mediterranean; the reserve was later folded into the Montgrí, Medes Islands and Baix Ter Natural Park, declared by the Catalan Parliament in 2010. Decades of protection are the reason divers reliably encounter large, approachable dusky groupers (Epinephelus marginatus), some reported at over 30 kg.
• A 19-year scientific monitoring series (1992–2009) inside the ~95-hectare no-take core found total fish biomass climbing to roughly 50 g/m², compared with only about 2.6 g/m² in adjacent unprotected areas in 2009. The study cautioned that full recovery of large predatory fish took decades (13–31 years to exceed 95% of carrying capacity) and that spillover beyond the reserve boundary was very moderate.
• Diving is rationed under a permit-and-quota system, not open access: licensed centres book mooring slots at buoyed sites around the islands under an annual per-buoy limit, with roughly 450 divers per day permitted across about 10 dive zones. Open Water / 1-star divers may dive but must be accompanied by an experienced (3-star or instructor) guide at a maximum of four trainees to one guide.