Spatial distribution of characteristic population parameters (density, biomass and mean size) of Chamelea gallina were analyzed from systematic survey data applying a geostatistical approach in the Gulf of Cádiz (SW Spain). The influence of static (depth and distance to inland outflows), dynamic (sediment and water column features) environmental variables on density, biomass and mean size was also investigated. The global estimations of kriged density mean was 8.30 ind m−2, biomass mean was 23.78 g m−2, and mean size was 18.71 mm, with the species heterogeneously distributed along the whole sandy subtidal strip of the coast of Huelva. The resulting kriged map shows the location and extension of the patches (5 NM range) in the study area; where the highest density and biomass hot-spots were observed near the river mouths, except for the Guadiana River. This species was present from 3 to 16 m, but preferred the depth window between 6-8 m, having a density and biomass peak at approximately 7 m depth. A negative and significant correlation was found between density/biomass and the coefficient of variation of mean size suggesting a density-dependent process. The most influential factors on density and biomass were depth, sediment characteristics (grain size and percentage of organic content), distance from river mouths and waste water treatment plants, and sea bottom temperature. This study, in addition to reporting on the current status of these natural beds and the influence of dynamic and static environmental variables on their distribution, proposes an additional approach to estimating several biological parameters in C. gallina that could be valuable for the spatial management of this commercial resource and highlight the role of marine protected areas.

The present study was supported by the project FEMP_AND_05 (“Programa plurianual en el ámbito de la recopilación de datos de la comunidad autónoma de Andalucía: Seguimiento análisis de la pesquería de chirla en el Golfo de Cádiz”) cofinanced by the European Maritime and Fisheries Fund (FEMP); and the project VENUS (“Estudio integral de los bancos naturales de moluscos bivalvos en el Golfo de Cádiz para su gestión sostenible la conservación de sus hábitats asociados”) (0139_VENUS_5_E; INTERREG-POCTEP), cofinanced by the European Regional Development Fund (FEDER, Interreg V-A España-Portugal (POCTEP) 2014–2020 program).

Peer reviewed