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Size selectivity of the Spisula solida dredge in relation to tooth spacing and mesh size
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Advisor(s)
Abstract(s)
A study was undertaken on the northwestern coast of Portugal to evaluate the selectivity effect of both tooth spacing and
mesh size on the catch of the white clam (Spisula solida). Two typical clam dredges, equipped with different tooth spacing
and mesh size, were towed side by side. Three tooth spacing (20, 40 and 60 mm) and three mesh sizes (35, 40 and 50 mm) were investigated. The dredge selectivity experiments were performed by attaching a cover bag with a 20mm mesh to the gear. Individual hauls were analysed by the SELECT model. The Fryer’s mixed model of between-haul variation was also applied to data. The results showed that the space between teeth does not have an effect on selectivity. Tooth length was directly related to the dredge’s capture efficiency. The only factor that contributed to dredge size selection was mesh size. The 50% retention lengths estimated for mesh sizes 30, 40 and 50mm were 25.68, 26.35 and 31.94 mm, respectively. For all mesh sizes, very narrow selection ranges were observed. The most appropriate mesh size to be enforced within the Portuguese northwestern S. solida fishery should be 40 mm.
Description
Keywords
Spisula solida Size selectivity Dredge Efficiency Tooth spacing Mesh size
Citation
Gaspar, M. B.; Leitao, F.; Santos, M. N.; Sobral, M.; Chicharo, L. M. Z.; Chicharo, A.; Monteiro, C. C. Size selectivity of the Spisula solida dredge in relation to tooth spacing and mesh size, Fisheries Research, 60, 2-3, 561-568, 2003.
Publisher
Elsevier