Hatchery cultivation of the common cockle (Cerastoderma edule L.): from conditioning to grow-out

This study describes for the first time the cultivation of Cerastoderma edule on a commercial scale. A protocol to grow F-2 generation cockles was developed, which led to fine-tuning experiments for broodstock conditioning and spat growth. Broodstock animals were conditioned with diets of Isochrysis galbana (T-Iso) or Tetraselmis suecica, whereas a third group was not fed. The best diet, T. suecica, induced 12 females out of 100 animals to spawn a total of 3380000 eggs. The non-fed group did not spawn. Cockle spat (4.9 +/- 1.0mm) grew best when given a mixed diet of C. muelleri, T-Iso and Sceletonema costatum, or a mixture of P. tricornutum and S. costatum at a concentration of 240cells l(-1)day(-1), resulting in a tripling of their wet weight after 14days. The impact of density, burrowing substrate and food availability on cockle spat growth (41days old, 5.6 +/- 1.2mm) was studied for 11weeks. Best results were obtained by culturing spat at ad libitum food conditions at 500 indm(-2), resulting in an average growth rate of 168mday(-1), an average final size of 19.0 +/- 1.9mm and a total final biomass of 1040gm(-2).