Spatial and Temporal Variations of Cockle (Cerastoderma spp.) Populations in Two Portuguese Estuarine Systems With Low Directed Fishing Pressure

Cockles are amongst the most exploited bivalve species in Portugal, playing an important ecological and socioeconomic role coastal ecosystems. Two sympatric of cockles, Cerastoderma edule ( Linnaeus, 1758 ) glaucum Bruguière, 1789–1792 may co-occur estuaries lagoons mixed populations along European Atlantic coast, namely France United Kingdom. The increasing importance shellfish harvesting Portugal requires a good knowledge cockle stocks temporal variability stock levels to better inform sustainable management practices. Therefore, this study aimed at assessing spatial variations two Portuguese estuarine systems where low levels. Sampling was carried out using clam dredge, covering entire potential area occurrence cockles Tagus Sado around same time year each three sampling years (2015, 2018, 2019). abundance, distribution population structure were examined system. Moreover, several water sediment parameters measured understand influence environmental conditions on abundance cockles. results obtained showed that occur mostly intermediate areas both more abundant estuary. Depth, average grain size Ruditapes philippinarum factors explained probability occurrence. analysis indicated natural mortality is constraining communities given adult individuals with marketable estuaries. This highlights need for appropriate measures ensure sustainability these have significant local populations.