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Recovery of substrates and macro-benthos after fishing trials with a new Portuguese clam dredge

Published online by Cambridge University Press:  12 August 2003

M.B. Gaspar
Affiliation:
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Avenida 5 de Outubro s/n, P-8700-305 Olhão, Portugal
M.N. Santos
Affiliation:
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Avenida 5 de Outubro s/n, P-8700-305 Olhão, Portugal
F. Leitão
Affiliation:
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Avenida 5 de Outubro s/n, P-8700-305 Olhão, Portugal
L. Chícharo
Affiliation:
Universidade do Algarve (UAlg), Faculdade de Ciências do Mar e do Ambiente (FCMA), Campus de Gambelas, P-8000-117 Faro, Portugal
A. Chícharo
Affiliation:
Universidade do Algarve (UAlg), Faculdade de Ciências do Mar e do Ambiente (FCMA), Campus de Gambelas, P-8000-117 Faro, Portugal
C.C. Monteiro
Affiliation:
Instituto de Investigação das Pescas e do Mar (IPIMAR), Centro Regional de Investigação Pesqueira do Sul (CRIPSul), Avenida 5 de Outubro s/n, P-8700-305 Olhão, Portugal

Abstract

The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing SCUBA diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuroids reached densities eight times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately after escaping from the dredge.

Type
Research Article
Copyright
2003 Marine Biological Association of the United Kingdom

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