Broodstock conditioning and gonadal development of the smooth clam Callista chione (Linnaeus, 1758) (Mollusca: Bivalvia) on the Catalan coast (NE Spain)

The smooth clam Callista chione (Linnaeus, 1758), is distributed on sandy bottoms throughout the Mediterranean Sea and European Atlantic coasts over 0-180 m depth range (SALAS, 2011). This species is of great commercial interest in Spain, and is intensively exploited along the Catalan coast (DOGC, 2008). Catches have dramatically decreased over the recent years, threatening the biological and economic sustainability of this fishery along the natural beds of the Catalan coast (DOGC, 2008). This decline in catches and the interest in diversifying aquaculture, have led to the development of a program of investigation into the management in hatchIn order to select the most suitable broodstock conditions for Callista chione, a conditioning experiment was performed and the gametogenic cycle of a natural population on the coast of Arenys de Mar (Catalonia, NE Spain) was studied. The influence of food availability and sand bed presence on energy balance and gonadal development was analyzed, also the proliferation of intracellular bacteria in gills was monitored. The gametogenic cycle started between August and September. In November, most of the gonads were ripe and spawning began in December. The higher abundance of spawning clams occurred between January and April (with sea surface temperature 13-15oC). Three experimental conditions were tested in September at a constant temperature of 14oC:T1 (0.10% of organic weight of microalgae as a proportion of the live weight of the clams per day and a sand bed); T2 (0.05% and a sand bed); T3 (0.10% without a sand bed). Gonadal maturity was a priority for this species and was reached at the end of all trials. Food availability and sand bed presence benefit survival and gonadal development. The best results were obtained in clams from trial T1. Nevertheless, broodstock conditions seemed to trigger the proliferation of intracellular bacteria in gills, and as the experiment advanced, prevalence and intensity of infection increased for all trials reaching values of 100% and between 9-40 intracellular bacteria/pair of gill plica, respectively.