The influence of dredge design on the catch of Callista chione (Linnaeus, 1758)

Published source details Gaspar M.B., Dias M.D., Campos A., Monteiro C.C., Santos M.N., Chícharo A. & Chícharo L. (2001) The influence of dredge design on the catch of Callista chione (Linnaeus, 1758). Hydrobiologia, 153-167.
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This study is summarised as evidence for the following.

	Action	Category
	Modify the design of dredges Action Link

Modify the design of dredges

A controlled study in 1999 in one sandy area in the North Atlantic Ocean, off the southwest coast of Portugal (Gaspar et al. 2001) found that a modified bivalve dredge caught less unwanted invertebrate catch, but damaged or killed similar proportions of unwanted invertebrates, compared to a traditional unmodified dredge. The proportion of unwanted individuals/tow was lower for the modified dredge (30–35%), compared to the traditional dredge (42–62%). This pattern was also true when looking at the proportion by weight (modified: 24–26%; traditional: 25–47%). However, the modified dredge did not have statistically lower proportion of damaged invertebrates overall (6–9%) compared to traditional dredges (7–14%), or lower proportion of dead invertebrates (modified: 6–8%; traditional: 6.5–11%), but this effect varied with species (see paper for details). The modified dredge had a metallic grid for retaining bivalves, compared to the traditional dredge which had a net bag. All species other than the commercially targeted smooth clam Callista chione were considered to be unwanted catch. In March, 12 tows/design were investigated at 8–10 m depth. A net bag was fitted to the end of each dredge to retain the caught organisms that would otherwise escape through the dredge mesh. For each dredge design, invertebrates were identified, counted, and given a score of 1–4 according to the amount of damage (1 = perfect condition, 4 = dead).

(Summarised by: Anaëlle Lemasson & Laura Pettit)