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Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii
Summary in English.
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2016
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| _version_ | 1867613269258141696 |
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| access_status_str | Open Access |
| author | Roel, Beatriz Adelaida |
| author2 | Field, John G |
| author_browse | Field, John G Roel, Beatriz Adelaida |
| author_facet | Field, John G Roel, Beatriz Adelaida |
| author_sort | Roel, Beatriz Adelaida |
| collection | Thesis |
| description | Summary in English. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/19576 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:26.520Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/19576 Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii Roel, Beatriz Adelaida Field, John G Butterworth, Doug S Cochrane, K L Marine Science Marine Biology Summary in English. Bibliography: p. [199]-210. The primary aim of the study was to assess the status and productivity of chokka squid. Main hypotheses examined are the following: that the sharp decline in the trawl fishery catch per unit effort (CPUE) data in the early 1980s, reflects a real decline in the trawlers catch rate; that the decline in the trawl CPUE index is caused by the jig fishery removing the biomass that otherwise would be available to the trawl fishery; that the jig fishery "disturbs" the spawning process and causes a decline in subsequent recruitment. Catch and effort data from the two fisheries, as well as biomass estimates from spring and autumn research surveys, were used. The two main fisheries and the catch and effort data are described. General Linear Modelling (GLM) was performed on the CPUE data from the trawl fishery in order to obtain annual indices of abundance. Further, results from a GLM analysis on two years of monthly jig CPUE data are presented. The dynamics of the stock biomass on the spawning grounds were modelled in order to assess the effects of current levels of effort and the existing closed season on the resource. The dynamics of the stock and the fishery were captured by a simple biomass-based model. Two dynamic methods were used to estimate model parameters: 1. a process-error estimator; 2. an observation-error estimator. All model parameter were estimated by maximum likelihood, and the corresponding confidence intervals were estimated by bootstrapping. 2016-05-11T08:06:45Z 2016-05-11T08:06:45Z 1998 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/19576 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Marine Science Marine Biology Roel, Beatriz Adelaida Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| thesis_degree_str | Doctoral |
| title | Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| title_full | Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| title_fullStr | Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| title_full_unstemmed | Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| title_short | Stock assessment of the Chokka Squid : Loligo vulgaris reynaudii |
| title_sort | stock assessment of the chokka squid loligo vulgaris reynaudii |
| topic | Marine Science Marine Biology |
| url | http://hdl.handle.net/11427/19576 |
| work_keys_str_mv | AT roelbeatrizadelaida stockassessmentofthechokkasquidloligovulgarisreynaudii |