Recruitment, Spat Settlement and Growth of the Cultured Mediterranean Mussel Mytilus galloprovincialis in the Maliakos Gulf (Central Aegean Sea)

The present study explored the seasonal dynamics of spat settlement and growth of the Mediterranean mussel (Mytilus galloprovincialis) in the semi-enclosed and eutrophic Maliakos Gulf (Central Aegean, Greece), a coastal system within the Natura 2000 network (GR 2440002, Natura 2000). Spat collectors were deployed at three mussel farms representing different locations in the gulf (north, south, and inner west) and at multiple depths over a year. The results revealed a clear reproductive cycle, with spawning initiated in early January and spat settlement occurring from March to June. Settlement intensity was highest in shallower waters during the beginning of the season (March) and in the end (June), while depth had no significant effect mid-season. Mussel size and weight varied significantly with season and location, with the largest individuals observed during spring and early summer at the north and south sites. Environmental monitoring depicted strong nitrogen enrichment and phosphorus limitation, driven by inputs from the Spercheios River and surrounding agricultural activities. During winter, elevated chlorophyll-a concentrations likely supported early larval development, while nutrient imbalances threaten long-term ecosystem stability. These findings underscore the importance of area- and season-specific management of spat collectors and call for integrated monitoring and regulation of nutrient inputs to safeguard the ecological integrity of the gulf and ensure sustainable mussel farming.