Experimental harvesting of juvenile common octopus Octopus vulgaris, for commercial ongrowing in the Azores

• Autor(a) principal: Pham, Christopher K.
• Data de Publicação: 2010
• Outros Autores: Isidro, Eduardo
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.3/668
• topic: Aquaculture; Catch; Rocky-sediment; Soft-sediment; Traps; Tubes

Octopus aquaculture is currently restricted to ongrowing of sub-adult to commercial size because culture of paralarvae remains a bottleneck. In most countries, commercial ongrowing rely upon existing pot fisheries for octopuses for obtaining their specimens. In the Azores, such fishery does not exist and effective methods of harvest are required if farming is to be implemented. In this study, we investigated the potential of obtaining subadult octopuses on the coast of Faial Island, Azores. Two sets of traps (n=30) consisting of 3 PVC tubes within cement blocks were set-up on two different substrates; soft sediment (Pedro Miguel) and rocky-sand (Pasteleiro) at depth varying between 10 and 30 metres. From June to August 2006, 11 hauls per site were performed. A total of 191 octopuses (from 1.1 to 989 g; average = 135.3 g) were captured. Catches in the soft sediment site were significantly higher than in the other location (CPUE: mean ± SD: 0.33 ± 0.17 vs. 0.15 ± 0.17 octopus trap-1 hour-1*100). The catch was initially dominated by octopus of 300-400 g but as fishing continued, this size classes disappeared and was replaced by smaller individuals. As a result, half of the catch at both sites (51.8%) was composed of specimens with a weight equal or inferior to 50 grams. The occurrence of summer recruitment event combined with a natural displacement of larger individuals into deeper waters is most probably responsible for this pattern. Our results showed that in shallow water and during this period of the year, individuals inferior to 50 grams are far more abundant than larger octopuses and should be the target size class for ongrowing activities.