A development and management framework for a new Octopus vulgaris fishery in South Africa
- Authors: Oosthuizen, Ané
- Date: 2004
- Subjects: Common octopus -- South Africa Octopus fisheries -- South Africa Octopus fisheries -- South Africa -- Economic aspects Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5255 , http://hdl.handle.net/10962/d1005098
- Description: A new policy incorporating an operational protocol was developed for the establishment of new fisheries in South Africa. The common octopus, Octopus vulgaris was used as a candidate species for the project. The operational protocol consisted of a three-phased development framework, namely information gathering (Phase 0), an experimental fishery (Phase 1) and the final implementation of a commercial fishery (Phase 2). The present study focussed on phase 0 of this theoretical framework and protocol and was implemented by using a proposed octopus pot fishery in South Africa as a case study. Phase 0 included a desktop study, information gathering in the field, an economic feasibility study and the formulation of a Fishery Management Plan and experimental design for the fishery. Information gaps identified during the desktop study were addressed during field investigations into the population structure and biology of O. vulgaris along the southeast coast. Immature females were found to use the intertidal area to feed and grow before migrating to the subtidal area to mature and spawn. Mean size differed substantially between intertidal and subtidal areas, with larger octopus found subtidally. Age and growth trials using tetracycline as a marker showed that O. vulgaris deposit daily growth lines in their beaks. A genetic study showed that there is most likely only one panmitic population along the coast. The economic feasibility study indicated that a longline pot fishery could be feasible provided a 30% catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used in this fishery. The Fishery Management Plan proposed in this study includes management measures such as effort limitation of licences and gear, size restrictions, vessel monitoring systems, and observer programmes. Based on the population dynamics and biology of O. vulgaris it is suggested that a precautionary approach to developing fisheries for this species in both the inter- and subtidal areas along the South African coast.
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- Date Issued: 2004
Economic feasibility of an experimental octopus fishery in South Africa
- Authors: Oosthuizen, Ané
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6760 , http://hdl.handle.net/10962/d1007773
- Description: Octopus vulgaris was identified as a new marine resource to be commercially exploited through an experimental fishery. A recent policy on developing fisheries in South Africa emphasizes the importance of investigating the economic feasibility of a fishery as part of its management framework. The study reported here generated baseline information necessary in the design of the experimental fishery, giving guidelines as to which vessels, fishing gear and markets would be most feasible. The proposed fishery, gear and vessel type, fishing techniques and expected catch rates are described, the results of market research are outlined, and the cost of fishing is estimated. The potential business should consist of small and medium-sized vessels deploying unbaited pots attached to long lines. The longline pot fishery could be economically feasible, provided a 30 percent catch in 6600 pots/month is attained. Only existing, debt-free vessels should be used. The minimum catch per unit effort (CPUE) for various fishing operation scenarios was calculated to determine economic feasibility. This is an estimated minimum CPUE, based on assumptions that cannot be confirmed until the fishery starts. Furthermore, this economic analysis also needs to be assessed by stakeholders with experience of fishery operations , Rhodes Centenary issue of: South African Journal of Science.
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- Date Issued: 2004
Genetic analysis of the Octopus vulgaris population on the coast of South Africa
- Authors: Oosthuizen, Ané , Jiwaji, Meesbah , Shaw, Paul W
- Date: 2004
- Language: English
- Type: Article
- Identifier: vital:6761 , http://hdl.handle.net/10962/d1007922
- Description: This study on Octopus vulgaris focused on the COIII gene region of mitochondrial DNA. Sequences from 21 samples from the Eastern Cape, and 14 samples from the Western Cape, were compared to determine whether different populations exist along the South African coast. A 380-bp segment of the COIII region of mtDNA was amplified using the polymerase chain reaction with specific designed primers. Phylogenetic inference was made using maximum parsimony (MP), maximum likelihood (ML), and distance based methods. All sequences conformed to a single haplotype. Lack of variation within and between east and west coast samples precluded further population genetic analysis. The sequence obtained in this study was also compared with other sequences lodged in the Genbank database. Phylogenetically, the South African O. vulgaris is closely related to O. vulgaris from Senegal (0.67% divergence) and the Mediterranean (1.51% divergence). Within the Mediterranean group, O. vulgaris from South Africa displayed less sequence divergence from Senegalese and Mediterranean individuals than O. vulgaris from Venezuela (3.85%) and Taiwan (3.87%). These data do not, therefore, refute the hypothesis of a single O. vulgaris genetic population around the coast.
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- Date Issued: 2004