Biological responses to a resumption in river flow in a freshwater-deprived, permanently open Southern African estuary
- Vorwerk, Paul D, Froneman, P William, Paterson, Angus W, Strydom, Nadine A, Whitfield, Alan K
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, Alan K
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
- Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
- Full Text:
- Date Issued: 2008
- Authors: Vorwerk, Paul D , Froneman, P William , Paterson, Angus W , Strydom, Nadine A , Whitfield, Alan K
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6886 , http://hdl.handle.net/10962/d1011645
- Description: The Kariega Estuary is a freshwater-deprived system due to numerous impoundments in the catchment. This system has had little or no horizontal salinity gradient over the last 15 years, with hypersaline conditions sometimes predominating in the upper reaches. Following high rainfall events in the catchment during the spring of 2006, including a flood event (approximate 1:10 year) in August 2006, a series of riverine pulses entered the estuary and a horizontal salinity gradient was established. This study examined the influence of this freshwater pulse on four components of the biota within the estuary, namely the zooplankton, and larval, littoral and demersal fishes. The study demonstrated that in three of these components elevated densities were recorded following the riverine input, with only the littoral fishes retaining an almost constant density. In addition, changes in the relative contributions of the estuarine utilisation classes for all three fish groups examined indicated that freshwater input into these systems positively influences the abundances. This has significant implications for water managers as it demonstrates the importance of an Ecological Reserve (defined as ‘the water required to protect the aquatic ecosystems of the water resource’) for this system.
- Full Text:
- Date Issued: 2008
A survey of selected Eastern Cape estuaries with particular reference to the ichthyofauna
- Vorwerk, Paul D, Whitfield, Alan K, Cowley, Paul D, Paterson, Angus W
- Authors: Vorwerk, Paul D , Whitfield, Alan K , Cowley, Paul D , Paterson, Angus W
- Date: 2001
- Language: English
- Type: Text
- Identifier: vital:15032 , http://hdl.handle.net/10962/d1019908 , ISSN 0073-4381 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 72
- Description: The physical environment and ichthyofauna of 10 estuaries, the East Kleinemonde, Klein Palmiet, Great Fish, Mtati, Mpekweni, Mgwalana, Bira, Gqutywa, Ngculura and Keiskamma, was sampled over a four year period. The ichthyofauna of each estuary was sampled once during winter and once during summer in that period, with the physical environment being sampled on two occasions per season. This investigation provides baseline ichthyofaunal and physical information for these estuaries, the majority of which have never been studied before. The fish data presented for these systems includes species composition, relative abundance, richness and diversity, longitudinal distributions and length frequency data. Descriptions of the physical environment within each estuary are also presented. The permanently open estuaries had a greater proportion of marine and freshwater species relative to the temporarily open/closed systems which were dominated by marine species dependent on estuaries and estuarine resident species. The permanently open estuaries had a higher Margalef's species richness index relative to the temporarily open/closed systems but the Shannon-Wiener species diversity index did not follow any discernible trend. There were minor longitudinal distribution trends when analysing the community as a whole, with patterns for individual species being more pronounced. The length frequency histograms for estuarine resident species differed between estuary types, while those for the marine migrant species were similar in the different estuary types.\ , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 2001
- Authors: Vorwerk, Paul D , Whitfield, Alan K , Cowley, Paul D , Paterson, Angus W
- Date: 2001
- Language: English
- Type: Text
- Identifier: vital:15032 , http://hdl.handle.net/10962/d1019908 , ISSN 0073-4381 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 72
- Description: The physical environment and ichthyofauna of 10 estuaries, the East Kleinemonde, Klein Palmiet, Great Fish, Mtati, Mpekweni, Mgwalana, Bira, Gqutywa, Ngculura and Keiskamma, was sampled over a four year period. The ichthyofauna of each estuary was sampled once during winter and once during summer in that period, with the physical environment being sampled on two occasions per season. This investigation provides baseline ichthyofaunal and physical information for these estuaries, the majority of which have never been studied before. The fish data presented for these systems includes species composition, relative abundance, richness and diversity, longitudinal distributions and length frequency data. Descriptions of the physical environment within each estuary are also presented. The permanently open estuaries had a greater proportion of marine and freshwater species relative to the temporarily open/closed systems which were dominated by marine species dependent on estuaries and estuarine resident species. The permanently open estuaries had a higher Margalef's species richness index relative to the temporarily open/closed systems but the Shannon-Wiener species diversity index did not follow any discernible trend. There were minor longitudinal distribution trends when analysing the community as a whole, with patterns for individual species being more pronounced. The length frequency histograms for estuarine resident species differed between estuary types, while those for the marine migrant species were similar in the different estuary types.\ , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 2001
- «
- ‹
- 1
- ›
- »