Ecological characterization of dredged and non-dredged bivalve fishing areas off south Portugal

  • Published source details Chícharo L., Chícharo A., Gaspar M., Alves F. & Regala J. (2002) Ecological characterization of dredged and non-dredged bivalve fishing areas off south Portugal. Journal of the Marine Biological Association of the United Kingdom, 82, 41-50.


This study is summarised as evidence for the following.

Action Category

Cease or prohibit dredging

Action Link
Subtidal Benthic Invertebrate Conservation
  1. Cease or prohibit dredging

    A replicated, site comparison study in 1999 of six sandy seabed sites off the Algarve coast, North Atlantic Ocean, southwestern Portugal (Chícharo et al. 2002) found that sites closed to dredging had different invertebrate community composition, higher macro-invertebrate (>1 mm) diversity, but lower meio-invertebrate (150 µm–1mm) diversity after four years, than sites where dredging continued. Communities in the closed and fished areas were 88% dissimilar (data presented as statistical model result). Macro-invertebrate diversity was higher, but meio-invertebrate diversity was lower, inside the closed area compared to the fished areas (reported as diversity indices). Macro-invertebrate abundance averaged 12 individuals/m2 in the closed area, and 4 individuals/m2 in the fished area. Macro-invertebrate biomass averaged 0.61 g/m2 in the closed area, and 0.65 g/m2 in the fished area. Meio-invertebrate abundance averaged 49 individuals/m2 in the closed area, and 42 individuals/m2 in the fished area. Meio-invertebrate biomass averaged 5 g/m2 in the closed area, and 0.1 g/m2 in the fished area. Abundance and biomass data were not statistically tested. In 1995, an area was closed to dredge fishing (whether other fishing activities continued is unclear). Invertebrates were surveyed at three 50 x 50 m sites in the closed area and three in a nearby area where dredging continued (7–9 m depth) using quadrats and cores. Macro- and meio-invertebrates were identified, counted, and dry-weighed. 

    (Summarised by: Anaëlle Lemasson)

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