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Reducing discards in a demersal purse-seine fishery

Published online by Cambridge University Press:  29 April 2008

Jorge M.S. Gonçalves
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
Luis Bentes
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
Pedro Monteiro
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
Rui Coelho
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
Margarida Corado
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
Karim Erzini
Affiliation:
Centro de Ciências do Mar – CCMAR, Universidade do Algarve, FCMA Campus de Gambelas, 8005-139 Faro, Portugal
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Abstract

Fisheries bycatches and discards constitute a significant problem in many fisheries worldwide. Unlike the pelagic purse-seine, the demersal purse seine usually targets high commercial value demersal species such as sea breams (e.g., Diplodus spp., Pagellus spp., Sparus aurata) and the European sea bass (Dicentrarchus labrax), while discards consist mainly of pelagic species and juveniles of the above mentioned species. In order to evaluate the efficiency of a selectivity device in reducing bycatch and consequently of discards in a demersal purse seine fishery, experimental deployments were carried out. The bycatch reducing device (BRD) consisted in the use of a panel of diamond-shaped mesh netting of 70 mm stretched mesh in the posterior part of the purse seine. Data from 61 experimental fishing trials allowed the evaluation of discards, with Scomber japonicus, Boops boops, Sardina pilchardus, Diplodus bellottii and Belone belone being the main discarded species. The mean discard ratio per set was 0.49 (± 0.30 standard deviation). The causes for discarding were also identified, with low commercial value being the most important reason. The results of the trials with BRD, were promising, with an average of 49% (± 24%) of the fish escaping per set, especially from those species that are most discarded. Overall, the use of this method for reducing discards can be considered positive for the following reasons: there is no need for structural modification of the fishing gear, the BRD is easy to deploy, and it is efficient in terms of species, sizes and quantities of fish that manage to escape. It therefore has significant benefits for the demersal purse seine fishery and possibly for other “métiers” as well.

Type
Research Article
Copyright
© EDP Sciences, IFREMER, IRD, 2008

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