Spatial considerations for the Dakhla stock of Octopus vulgaris: indicators, patterns, and fisheries interactions
1 INRH, 2 rue Tiznit, 20200 Casablanca, Morocco
2 IRD, CRHMT, rue Jean Monnet, BP 171, 34203 Sète, France
Correspondence to A. Faraj: tel/fax: +212 22 484542; e-mail: faraj{at}inrh.org.ma or abdelmalekfaraj{at}yahoo.fr
Faraj, A., and Bez, N. 2007. Spatial considerations for the Dakhla stock of Octopus vulgaris: indicators, patterns, and fisheries interactions. – ICES Journal of Marine Science, 64: 1820–1828.The common octopus (Octopus vulgaris) is the target species of the cephalopod fishery that exploits two stocks, Dakhla and Cap Blanc, off southern Morocco (26°N 21°N), an area commonly referred to as the Saharan Bank. Octopus vulgaris is also one of the most abundant demersal species in this highly productive area, and plays a key role in the upwelling ecosystem. Spatial patterns of the main phases of the Octopus vulgaris life cycle of the Dakhla stock are described, using trawl surveys carried out twice a year from 1998 to 2003. Using geostatistics and spatial indicators, mature females and juveniles are analysed and mapped to characterize the main features of the spawning and recruitment phases. There are clear distinctions between the spatial patterns of the spawning and recruitment phases: juveniles are more coastal, less spatially dispersed, more anisotropically distributed, and more patchy. Our results suggest that the spatial pattern of the Octopus vulgaris Dakhla stock is different from that of the same species in other ecosystems such as the Mediterranean. GIS reveals that the spawning–stock biomass is globally more accessible to the industrial fleet than to the artisanal one, a finding contrary to contemporary thinking and with important resource management implications.
Keywords: accessibility indices, cephalopod fishery, Dakhla stock, geostatistics, GIS, Octopus vulgaris, recruitment, spatial indicators, spatial patterns, spawning
Received 7 April 2006; accepted 3 October 2007.
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