Shell strength and fishing damage to the smooth clam (Callista chione): simulating impacts caused by bivalve dredging.

Vasconcelos, P., Morgado-André, A., Morgado-André, C., and Gaspar, M. B. 2011. Shell strength and fishing damage to the smooth clam (Callista chione): simulating impacts caused by bivalve dredging. – ICES Journal of Marine Science, 68: 32–42. The smooth clam Callista chione is exploited by a fleet of dredgers along the southwestern coast of Portugal and suffers from a high incidence of shell damage. The force required to break C. chione shells in relation to fishing impacts and dredge damage is quantified. Fishing trials and shell-strength measurements (compression and compaction experiments) were performed to determine whether shell damage was attributable to the direct impact of the dredge teeth or to sediment compaction. A three-dimensional model of C. chione was subjected to simulated force by the finite element method. Analyses of damage areas and breakage patterns revealed two groups of samples, one containing the samples from compression experiments and another with the samples from dredging and compaction experiments, suggesting that most shell damage was attributable to compaction within the sediment. Information is provided to help improve the design of bivalve dredges, by increasing both length and angle of the dredge teeth, which would reduce the compaction force and distribute it differentially within the sediment, forcing upward movement of the bivalves. [ABSTRACT FROM PUBLISHER]