Rebuilding viable spawner patches of the overfished Spisula solida (Mollusca: Bivalvia): a preliminary contribution to fishery sustainability

Joaquim, S., Gaspar, M. B., Matias, D., Ben-Hamadou, R., and Arnold, W. S. 2008. Rebuilding viable spawner patches of the overfished Spisula solida (Mollusca: Bivalvia): a preliminary contribution to fishery sustainability. – ICES Journal of Marine Science, 65: 60–64. Populations of commercially important bivalves along the coast of Portugal are depleted as a consequence of natural and anthropogenic causes. A pilot experiment was designed to determine the feasibility of transplanting individuals from natural clam beds to a closed fishing area in an effort to rebuild relatively high-density patches of Spisula solida. For this purpose, clams were equally partitioned into two groups (undersize and legal clams) and transplanted at a density of 40 clams m−2 into two areas 50 m2. Transplanted and control clams were sampled to estimate survival, condition index, biochemical composition, and reproductive condition. Generally, the physiological condition of clams was not affected by the method of transplanting. One year after transplanting, survival was 45%. The increase in local abundance of mature clams should facilitate successful fertilization and increase the residual reproductive value of each clam relative to its pre-transplant value. Transplanting undersize clams may be more advantageous because they are more likely to spawn at least once before harvest. The experiments demonstrate that spawner transplants may strengthen S. solida populations and can be used in stock-enhancement programmes which, in conjunction with effective management measures, can contribute to the sustainability of the S. solida fishery.