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A new artificial reef design for octopus (Octopus vulgaris cuvier, 1797) in the Aegean sea and preliminary results

Keywords: Polvo , Octopus vulgaris , Octo-recifes artificiais , Mar Egeu , Gest o da pesca , MPA: área de Prote o Marinha , NTZ: área de Restri o da Pesca , Octopus , Octopus vulgaris , Artificial Octo-reefs , Aegean Sea , Fisheries management , MPA: Marine protected area , NTZ: No Take ZoneZone

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This study was carried out in the Gulf of 0zmir in the Aegean Sea between June 2006 and November 2008. The purpose was the creation of a new concept of the artificial reef for Octopus vulgaris, with a view to establishing new artificial reef sites to be used in the fisheries management of this species (MPA, NTZ or fishing areas). First, the main characteristics of natural octopus nests were recorded (entrance width, length, etc.) by divers. These characteristics were used in the construction of new octahedral artificial reef blocks. The blocks were made of reinforced concrete, in a shape like that of an inverted pyramid, with an upper surface of 100x100x25 cm3 and a lower one of 60x60 cm2. Four cylindrical holes each with two ellipsoidal openings were placed in one face and in the lateral edge of the octo-block, to serve as the entrances to the artificial nest. Each nest has a volume of 5000 cm3. Eighty octo-blocks were deployed as artificial reefs at 10 m from each other at 15 different depths at two sites by divers with the help of the winch of the R/V EGESUF. These artificial octo-reefs were censused by direct observation. Twenty-eight octopuses were sampled at the end of 25 dives. Minimum mantle length of the octopuses was 75 mm and the maximum 249 mm, with an average of 152.71 mm. The average total length was calculated to be 918.57 mm. The weight of the specimens was between 244 g and 7140 g with an average of 2335.43 g. The results showed that both sites were inhabited by octopuses coming from the artificial reefs, which used them as nests. These nests seem to have constituted special places for fisheries management and will permit the assessment of reserve areas or marine protection areas (MPA), thus opening up a new perspective for Turkish fisheries. Este estudo foi realizado no golfo de 0zmir, no Mar Egeu, entre junho de 2006 e novembro de 2008. O objetivo foi uma nova concep o de recife artificial para Octopus vulgaris, visando o estabelecimento de novos locais a serem utilizados na gest o da pesca dessa espécie (MPA, NTZ ou zonas de pesca). Primeiramente foram consideradas as principais características dos ninhos naturais do polvo (largura da entrada, comprimento, etc.). A seguir essas características foram utilizadas na constru o de novos blocos octaédricos de recifes artificiais. Os blocos foram feitos de concreto armado, assemelhando-se a uma piramide invertida, nas dimens es de 100x100x25 cm3 na face superior e 60x60 cm2 na face inferior. Quatro furos cilíndricos, com duas aberturas elipsoidais, foram dispostos em uma só face e na borda

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