Monitoring of the Reserve Effect

When a Marine Protected Area (MPA) is well protected, monitored and managed, the fish found there grow and multiply. Therefore larger, more numerous and more diverse fish are found inside the MPA than outside. This is called “Reserve Effect”.

Monitoring of the reserve effect, carried out by Thalassa Marine Research & Environmental Awareness, began in 2016 in the Larvotto Marine Protected Area and in unprotected areas located either to the East (Roquebrune-Cap-Martin, Menton) or to the West (Beaulieu-sur-Mer, Saint-Jean-Cap-Ferrat). Two annual campaigns are organized, one in June before the summer season and a second in September after the summer season. The counts are carried out in two habitats, the Posidonia meadow (Posidonia oceanica) and in a superficial artificial rocky environment (dykes), between 8-12 m and 3-5 m, respectively. Counts are carried out by underwater visual censuses along 25 x 5 m transects. This technique consists of listing fish species, evaluating their abundance and size (total length) in order to determine biomass (weight) from the number of individuals (density). Since 2021, monitoring of the reserve effect has also been implemented in the Spélugues Marine Protected Area.

Dr. Alexis PEY from THALASSA Marine Research carrying out a visual census of fish on the Posidonia meadow and rocky environment.

The results obtained since the implementation of monitoring leave no doubt as to the presence of larger and more numerous fish in Monaco's MPAs than outside, proving the effectiveness of management measures and the proper functioning of these MPAs.