Marine fishes where males defend nests and provide parental care often migrate from deeper to littoral waters to breed. In this study we describe seasonal patterns of shelter occupation in estuarine shallow waters and assess social aggregation in the Lusitanian toadfish (Halobatrachus didactylus, Batrachoididae), a vocal species with male parental care. Occupation of intertidal shelters was restricted to the breeding season but adult fish remained in the subtidal during the non-reproductive season, since they produced sounds throughout the year. Intertidal shelters were aggregated with up to five shelters found per 2 m segment of an 80 m transect. This aggregation probably resulted from social attraction since many segments were found unoccupied. Moreover, shelters contained on average two fish (maximum of nine). Based on size, shelters with multiple fish seemed to contain females, or possibly sneakers, but also more than one type I male, showing high social tolerance for conspecifics.