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Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects
Bibliography: leaves 36-43.
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| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2014
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| _version_ | 1867613271693983744 |
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| access_status_str | Open Access |
| author | Mafwila, Samuel Kakambi. |
| author2 | Govender, Anesh |
| author_browse | Govender, Anesh Mafwila, Samuel Kakambi. |
| author_facet | Govender, Anesh Mafwila, Samuel Kakambi. |
| author_sort | Mafwila, Samuel Kakambi. |
| collection | Thesis |
| description | Bibliography: leaves 36-43. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/6972 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:33:28.738Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| 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:11427/6972 Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects Mafwila, Samuel Kakambi. Govender, Anesh Griffiths, M H Applied Marine Science Bibliography: leaves 36-43. The dusky kob Argyrosomus japonicus is an important commercial and recreational linefish species in South Africa. It has a wide distribution range from Cape Agulhas to the Mozambique border. Juveniles A. japonicus <1070 mm) occur inshore and in estuaries where surf-zone and estuarine anglers target them. Adult A. japonicus (> 1070 mm) are caught beyond the surf zone by line fishermen. In this study, 380 juvenile dusky kob were caught by hook and line from the Breede River, Fish River, and Keiskamma River estuaries. Age of juvenile A. japonicus in these three South African estuaries was estimated by counting growth rings in sectioned sagittal otoliths read under a dissecting microscope using reflected light. The reproducibility of otoliths readings was described by the average percentage error (APE) index and was found to be 0.44% (Breede), 2.78% (Fish), 0.25% (Keiskamma) for an experienced reader and 0.5% (Breede), 4.37% (Fish), 0.53% (Keiskamma) for an inexperienced reader. Comparisons of A. japonicus otoliths by an experienced and an inexperienced reader indicated a reasonable between-reader consistency, however, the otoliths from the Fish River estuary were more difficult to read than from the other two estuaries. The Schnute growth model was used to determine which sub-model would best describe the growth of juvenile A. japonicus. Linear regression lines were fitted to the age-at-length growth curves of juvenile A. japonicus for each estuary to determine whether there were significant differences in growth rate. It was found that growth was the highest in the Breede River estuary (113.7 mm/yr), followed by the Keiskamma River estuary (92.1 mm/yr) and the Fish River estuary (83.9 mm/yr). Variable growth rates of juvenile A. japonicus in the three estuaries may be related to food availability and prey item types and to a lesser extent to water temperature in the estuaries. The comparisons of estuarine diets of A. japonicus indicate that juvenile dusky kob in different estuaries have different dominant prey species. There were one or two taxa dominant in each estuary with Galeichthys feliceps (61.9%), and the mysids (71.8%) being the most important prey items in the Breede River and the Great Fish River estuaries respectively, while teleost Pomadasys commersonnii (73.8%) were the most important prey species in the Keiskamma River estuary. 2014-09-08T09:57:03Z 2014-09-08T09:57:03Z 2003 Master Thesis Masters MSc http://hdl.handle.net/11427/6972 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Applied Marine Science Mafwila, Samuel Kakambi. Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| thesis_degree_str | Master's |
| title | Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| title_full | Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| title_fullStr | Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| title_full_unstemmed | Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| title_short | Comparative age and growth of juvenile dusky kob (Argyrosomus japonicus) in three South African estuaries, with notes on diet and temperature effects |
| title_sort | comparative age and growth of juvenile dusky kob argyrosomus japonicus in three south african estuaries with notes on diet and temperature effects |
| topic | Applied Marine Science |
| url | http://hdl.handle.net/11427/6972 |
| work_keys_str_mv | AT mafwilasamuelkakambi comparativeageandgrowthofjuvenileduskykobargyrosomusjaponicusinthreesouthafricanestuarieswithnotesondietandtemperatureeffects |