Pinna nobilis, commonly known as the fan mussel, is an endemic and endangered species of the Mediterranean Sea. Using specimens collected monthly from March 2008 to February 2009, this study examines the gonadal development and biochemical composition in the adductor muscle of the fan mussel in relation to environmental parameters, such as chlorophyll-a, seawater temperature, salinity, particulate organic and particulate inorganic matter at Karantina Island, Aegean Sea, Turkey. We observed gonadal development primarily in the spring months and at the beginning of the summer. The spawning period was observed from May to September (primarily in July, with 88.8%). Monthly variation of the gonadosomatic index (GSI) was inversely correlated with protein of adductor muscle and positively correlated with glycogen of adductor muscle, meat yield, and the adductor muscle index (p <= 0.05). Our findings suggest that protein in the adductor muscle was used as an energy reserve for gametogenesis. No correlation was found between reproduction and environmental parameters, with the exception of salinity (p>0.05).