Bivalve dredge fisheries play an important role in the social-economical context of the Algarve coast (southern Portugal), mainly due to the size of the fishing fleet and the number of fishermen involved in this activity. Among several bivalve species caught, the striped venus (Chamelea gallina) constitutes a very important fishing resource because of its high economic-value. Recently, intensive fishing coupled with recruitment failure resulted in large inter-annual fluctuations in stock abundance, threatening the biological and economic sustainability of this fishery. In this context, the implementation of management strategies, such as stock-enhancement programmes based on hatchery production of juveniles, could promote the rebuilding of bivalve beds.
The present study describes the biology (growth and reproductive cycle) and distribution of C. gallina. This species shows a high growth rate and short lifespan, a prolonged spawning period (between April and August), matures within its second year of life and occurs preferentially on sandy bottoms between 5 and 11m depth. Overall, this information was to establish the time of the year used to collect the wild broodstock and to assess the potential of C. gallina for hatchery production. Several spawning techniques were tested (thermal stimulation, scarification, and ?ow through). Growth and survival of larvae and juveniles were compared using different nutritional regimes (larvae: Isochrysis aff. galbana (T-iso), Chaetoceros calcitrans (C. cal) and unfed; juveniles: (1:1) T-iso + C. cal, T-iso and C. cal) and rearing temperatures (larvae: 20 and 23°C). Among the different methods used to obtain gametes, C. gallina only spawned in the ?ow through system. The highest larval survival and growth rates were obtained from larvae fed T-iso. First C. gallina pediveliger larvae were found at day 8. The presence of metamorphosed larvae, found even in the unfed treatment, is an advantage for aquaculture production. After metamorphosis, there was no mortality of C. gallina juveniles reared without substrate regardless the diet provided. Juveniles fed the binary diet (T-iso + C. cal) and the monodiet T-iso showed a relatively higher growth in shell length and weight than when fed with C. cal. (Fig. 1).
Based on these results, a production protocol was designed for C. gallina, which allowed the production of millions of juveniles that were seeded in the first restocking assay with this species, in an area off Portimão.