An experimental study of gill net and trammel net 'ghost fishing' in the Algarve (southern Portugal)

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 158:257-265 (1997) - doi:10.3354/meps158257 An experimental study of gill net and trammel net 'ghost fishing' off the Algarve (southern Portugal) K. Erzini1,*, C. C. Monteiro2, J. Ribeiro1, M. N. Santos2, M. Gaspar2, P. Monteiro1, T. C. Borges1 1Unidade de Ciências e Tecnologias dos Recursos Aquáticos (UCTRA), Universidade do Algarve, P-8000 Faro, Portugal 2IPIMAR CIM-Sul, P-8700 Olhão, Portugal *E-mail: kerzini@ualg.pt Four 100 m lengths of both monofilament gill nets and trammel nets were deployed at depths between 15 and 18 m off the coast of the Algarve (south of Portugal) between April 1995 and June 1996. The nets were set on a natural rocky bottom with one end cut loose to simulate lost nets. Changes in net structure (net height, effective fishing area, movement, colonisation, wear and tear) and their catches (species, sizes, numbers, and biomass) were monitored by divers. Similar patterns were observed in all the nets, with a sharp decrease in net height and effective fishing area, and an increase in visibility within the first few weeks. Net movement was negligible except in the case of interference from other fishing gears. Catch rates were initially comparable to normally fished gill nets and trammel nets in this area, but decreased steadily over time. No sea birds, reptiles or mammals were caught in any of the 8 nets. Catches were dominated by fish (89% by number, at least 27 species), in particular by sea breams (Sparidae) and wrasses (Labridae). Under the conditions experienced throughout the study the fishing lifetime of a 'lost' net is between 15 and 20 wk. Based on an exponential model, we estimated that 100 m lengths of gill net and trammel net will catch 314 and 221 fish respectively over a 17 wk period. However, we consider this to be an underestimate due to high rates of predation and scavenging by octopuses, cuttlefish, moray eels, conger eels, and other fish such as the wrasse Coris julis. When the nets were surveyed in the following spring, 8 to 11 mo after being deployed, they were found to be completely destroyed or heavily colonised by algae and had become incorporated into the reef. Lost gear · Ghost fishing · Gill net · Trammel net · Catches · Incidental mortality Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 158. Publication date: November 17, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.