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Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration
Closed seasons are generally implemented on the presumption that they increase reproductive output of fished populations. This is based on the assumption that the imposition of a closed season during the breeding season allows more individuals to reproduce, as they are not being harvested. I evaluat...
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2017
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| _version_ | 1867613398607331328 |
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| access_status_str | Open Access |
| author | Govender, Anesh ;Arendse, Clement |
| author2 | Branch, George M |
| author_browse | Branch, George M Govender, Anesh ;Arendse, Clement |
| author_facet | Branch, George M Govender, Anesh ;Arendse, Clement |
| author_sort | Govender, Anesh ;Arendse, Clement |
| collection | Thesis |
| description | Closed seasons are generally implemented on the presumption that they increase reproductive output of fished populations. This is based on the assumption that the imposition of a closed season during the breeding season allows more individuals to reproduce, as they are not being harvested. I evaluated the validity of imposing closed seasons during the breeding season by creating a simulation model using the limpet Cymbula granatina as a test case and then compared the fol lowing four scenarios: 1) an unharvested population; 2) no closed season imposed; 3) a closed season imposed during the breeding season; and 4) a closed season imposed outside the breeding season, to determine the effects of the latter three situations on the reproductive output and yield. It was determined that closed seasons do not significantly affect the reproductive output of the population and that the timing of closed seasons made no difference to the reproductive output of the population, as the output was the same for populations with closed seasons during the breeding season or outside the breeding season. Survivors, catch in numbers and yield in biomass were affected by the timing of closed seasons, with higher outputs for each obtained when the closed season was closer to the month when individuals become of harvestable size. It was thus concluded that the imposition of a closed season at any time of the year is an effective management measure if imposing the closed season can reduce annual fishing mortality, but the imposition of a closed season specifically during the breeding season with a view to increase reproductive output brings no benefits relative to closure at any other time of the year. Moreover, any closure will be ineffective if it does not also bring about a reduction of annual fishing mortality. The reasons for advocating closure of a fishery during the breeding season are thus based on false grounds in the case of the limpet C. granatina. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/26495 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:35:31.228Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| 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:11427/26495 Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration Govender, Anesh ;Arendse, Clement Branch, George M Zoology Marine Biology Closed seasons are generally implemented on the presumption that they increase reproductive output of fished populations. This is based on the assumption that the imposition of a closed season during the breeding season allows more individuals to reproduce, as they are not being harvested. I evaluated the validity of imposing closed seasons during the breeding season by creating a simulation model using the limpet Cymbula granatina as a test case and then compared the fol lowing four scenarios: 1) an unharvested population; 2) no closed season imposed; 3) a closed season imposed during the breeding season; and 4) a closed season imposed outside the breeding season, to determine the effects of the latter three situations on the reproductive output and yield. It was determined that closed seasons do not significantly affect the reproductive output of the population and that the timing of closed seasons made no difference to the reproductive output of the population, as the output was the same for populations with closed seasons during the breeding season or outside the breeding season. Survivors, catch in numbers and yield in biomass were affected by the timing of closed seasons, with higher outputs for each obtained when the closed season was closer to the month when individuals become of harvestable size. It was thus concluded that the imposition of a closed season at any time of the year is an effective management measure if imposing the closed season can reduce annual fishing mortality, but the imposition of a closed season specifically during the breeding season with a view to increase reproductive output brings no benefits relative to closure at any other time of the year. Moreover, any closure will be ineffective if it does not also bring about a reduction of annual fishing mortality. The reasons for advocating closure of a fishery during the breeding season are thus based on false grounds in the case of the limpet C. granatina. 2017-12-08T06:08:27Z 2017-12-08T06:08:27Z 2004 2017-02-06T12:33:10Z Bachelor Thesis Honours BSc (Hons) http://hdl.handle.net/11427/26495 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Zoology Marine Biology Govender, Anesh ;Arendse, Clement Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| thesis_degree_str | Bachelor's / Honours |
| title | Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| title_full | Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| title_fullStr | Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| title_full_unstemmed | Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| title_short | Does the implementation of a closed fishing season during the breeding season benefit a species? : a per-recruit-based approach using Cymbula granatina as an illustration |
| title_sort | does the implementation of a closed fishing season during the breeding season benefit a species a per recruit based approach using cymbula granatina as an illustration |
| topic | Zoology Marine Biology |
| url | http://hdl.handle.net/11427/26495 |
| work_keys_str_mv | AT govenderanesharendseclement doestheimplementationofaclosedfishingseasonduringthebreedingseasonbenefitaspeciesaperrecruitbasedapproachusingcymbulagranatinaasanillustration |