From sea to land: study of the invertebrate animals of «Casa das Bicas» (Loulé, southern Portugal)

• Six centuries of marine and terrestrial invertebrate use in inland Algarve. • Oyster specialisation marks dietary change from the 14th century onwards. • Terrestrial gastropods show evidence of consumption, particularly in Medieval Islamic times. • Preservation indices used to assess recovery bias and depositional variation. • Stable clam harvesting contrasts with variable cockle procurement patterns. «Casa das Bicas», located in the historic centre of Loulé (Algarve, southern Portugal), presents a diachronic sequence of occupations spanning from the 12th to the 19th centuries, offering valuable evidence of invertebrate exploitation practices. The site comprises successive phases, including the Islamic ḥammām (12th–13th centuries), the Christian medieval period, post-medieval use as communal waste disposal areas, the construction and occupation of the Barreto Stately Home (15th–17th centuries), and subsequent occupation episodes following the building’s abandonment. More than 16,700 invertebrate remains (NISP) representing over 4,100 individuals (MNI) were examined, comprising bivalves, gastropods, crustaceans, cephalopods, scaphopods, and anthozoans. The assemblage reveals sustained exploitation of marine resources from the nearby Ria Formosa lagoon and adjacent coastal environments, with oysters ( Ostrea edulis ), clams ( Ruditapes decussatus ), and cockles ( Cerastoderma edule ) dominating throughout the phases. Terrestrial gastropods also show evidence of consumption, especially during the earliest phase. Significant dietary shifts are evident from the 14th century onwards, with marked specialisation towards oyster consumption in Late Medieval and Modern contexts. Taphonomic analyses, including preservation indices and shell alteration patterns, clarify depositional processes and identify methodological biases affecting assemblage composition. Biometric data suggest stable harvesting practices for R. decussatus , whilst C. edule exhibits temporal variation indicative of changing procurement strategies or environmental conditions. Comparative analysis with other Algarve sites demonstrates consistent local shellfish collection patterns strongly influenced by proximity to harvesting areas. This study advances the understanding of invertebrate exploitation, dietary practices, and resource management in the historic Algarve region of southern Portugal.