An estimation of the standing stock and population structure of Upogebia africana (Crustacea: Thalassinidae) in the Knysna Estuary
- Hodgson, Alan N, Allanson, Brian R, Cretchley, Robyn
- Authors: Hodgson, Alan N , Allanson, Brian R , Cretchley, Robyn
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6923 , http://hdl.handle.net/10962/d1011907
- Description: Within the Knysna Estuary Upogebia africana has an extensive distribution from north of Leisure Isle to the Red Bridge, occupying 62% of the available intertidal zone. Six sites were surveyed within the above distributional range. U. africana was found from the high-water level (Spartina zone) to the shallow subtidal zone (to about 1.5 m depth). The density, biomass and population structure of the mud prawns were found to be highly variable within the estuary. Only small animals (carapace length –× = 10.9 mm) were found in the upper estuary at the Red Bridge. Although large animals were present, the Invertebrate Reserve had a low density and biomass of U. africana (– × = 11.7 m–2; 3.9 g.m–2 dry weight). By contrast a relatively inaccessible centre mud bank (Oyster Bank) in the middle reaches of the estuary had much larger populations (–× = 176.5 m–2; 65.3 g.m–2 dry weight). This site is, therefore, a natural mud prawn reserve. Within the intertidal zone, mud prawn density (74–76 m–2) and biomass (26–27 g.m–2 dry weight) was usually greatest in the Spartina and lower Zostera zones. Sex ratios throughout the estuary did not deviate significantly from 1:1.
- Full Text:
- Authors: Hodgson, Alan N , Allanson, Brian R , Cretchley, Robyn
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6923 , http://hdl.handle.net/10962/d1011907
- Description: Within the Knysna Estuary Upogebia africana has an extensive distribution from north of Leisure Isle to the Red Bridge, occupying 62% of the available intertidal zone. Six sites were surveyed within the above distributional range. U. africana was found from the high-water level (Spartina zone) to the shallow subtidal zone (to about 1.5 m depth). The density, biomass and population structure of the mud prawns were found to be highly variable within the estuary. Only small animals (carapace length –× = 10.9 mm) were found in the upper estuary at the Red Bridge. Although large animals were present, the Invertebrate Reserve had a low density and biomass of U. africana (– × = 11.7 m–2; 3.9 g.m–2 dry weight). By contrast a relatively inaccessible centre mud bank (Oyster Bank) in the middle reaches of the estuary had much larger populations (–× = 176.5 m–2; 65.3 g.m–2 dry weight). This site is, therefore, a natural mud prawn reserve. Within the intertidal zone, mud prawn density (74–76 m–2) and biomass (26–27 g.m–2 dry weight) was usually greatest in the Spartina and lower Zostera zones. Sex ratios throughout the estuary did not deviate significantly from 1:1.
- Full Text:
Incorporating the spatial component of fisheries data into stock assessment models
- Authors: Booth, Anthony J
- Date: 2000
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124800 , vital:35698 , https://doi.10.1006/jmsc.2000.0816
- Description: Fisheries-dependent and independent data have a strong spatial component. These data are also multi-dimensional, making them difficult to visualize and analyze, prompting the use of spatial analysis to facilitate an understanding of their relationships. One aspect of fisheries data that is often ignored is the distribution and abundance of a particular resource and the fishing patterns of its harvesting fisheries. In order to improve management advice, stock assessors need to incorporate the spatial component of these data into an existing assessment framework. This paper presents a three-dimensional visualization of the age-structure and fishery dependent and independent data associated with the sparid fish Pterogymnus laniarius on the Agulhas Bank, South Africa. A spatially-referenced spawner biomass per-recruit model is developed to illustrate the applicability of incorporating spatially referenced information in providing management advice. The model provided evidence that, even on a spatial scale, fishing mortality is significantly correlated to fishing effort. Areas of high levels of spawner biomass are noted, all of which corresponded to those geographic areas with a combination of low fishing effort and high adult biomass.
- Full Text:
- Authors: Booth, Anthony J
- Date: 2000
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124800 , vital:35698 , https://doi.10.1006/jmsc.2000.0816
- Description: Fisheries-dependent and independent data have a strong spatial component. These data are also multi-dimensional, making them difficult to visualize and analyze, prompting the use of spatial analysis to facilitate an understanding of their relationships. One aspect of fisheries data that is often ignored is the distribution and abundance of a particular resource and the fishing patterns of its harvesting fisheries. In order to improve management advice, stock assessors need to incorporate the spatial component of these data into an existing assessment framework. This paper presents a three-dimensional visualization of the age-structure and fishery dependent and independent data associated with the sparid fish Pterogymnus laniarius on the Agulhas Bank, South Africa. A spatially-referenced spawner biomass per-recruit model is developed to illustrate the applicability of incorporating spatially referenced information in providing management advice. The model provided evidence that, even on a spatial scale, fishing mortality is significantly correlated to fishing effort. Areas of high levels of spawner biomass are noted, all of which corresponded to those geographic areas with a combination of low fishing effort and high adult biomass.
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SASBO Code of ethics
- SASBO
- Authors: SASBO
- Date: 2000
- Subjects: SASBO
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/160565 , vital:40475
- Description: Formed as a trade union in 1916, SASBO's primary objectives are to improve the conditions of service and protect the interests of its members, individually and collectively, in relation to their employers and otherwise, and generally to raise their status. Operating in the South African finance sector, SASBO identifies with the ethics and conventions of finance professionals and has always encouraged sound industrial relations with employers and/or their organisations, with the intention of regulating conflict as peacefully and constructively as possible by endeavouring to settle disputes by conciliatory methods. The union has always been, and continues to be, committed to fair and honest dealings, and integrity, in its interaction with all its stakeholders, this in the fundamental belief that SASBO's operation and business should be conducted honestly, fairly and within the parameters of labour and other laws.
- Full Text:
- Authors: SASBO
- Date: 2000
- Subjects: SASBO
- Language: English
- Type: text
- Identifier: http://hdl.handle.net/10962/160565 , vital:40475
- Description: Formed as a trade union in 1916, SASBO's primary objectives are to improve the conditions of service and protect the interests of its members, individually and collectively, in relation to their employers and otherwise, and generally to raise their status. Operating in the South African finance sector, SASBO identifies with the ethics and conventions of finance professionals and has always encouraged sound industrial relations with employers and/or their organisations, with the intention of regulating conflict as peacefully and constructively as possible by endeavouring to settle disputes by conciliatory methods. The union has always been, and continues to be, committed to fair and honest dealings, and integrity, in its interaction with all its stakeholders, this in the fundamental belief that SASBO's operation and business should be conducted honestly, fairly and within the parameters of labour and other laws.
- Full Text:
The development of a geomorphological classification system for the longitudinal zonation of South African rivers
- Rowntree, Kate M, Wadeson, Roy A, O'Keeffe, Jay H
- Authors: Rowntree, Kate M , Wadeson, Roy A , O'Keeffe, Jay H
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6722 , http://hdl.handle.net/10962/d1006799
- Description: The recognition of the Reserve by the new South African Water Law poses new challenges for river scientists. The ecological water requirement or environmental flow is recognised by that part of the Reserve known as the ecological Reserve. If the ecological Reserve is to be implemented, it must first be defined and quantified for all river systems subject to water related developments. Standard procedures are being developed through the Resource Directed Measures (RDM) of the Department of Water Affairs and Forestry while monitoring the health of South Africa's rivers is taking place through the National River Health Programme (NRHP). Cost effective methods of developing spatial frameworks for both the RDM and NRHP are required. Concepts of longitudinal river zonation were developed by river ecologists in the 1960s and 1970s to assist in the classification of ecologically uniform stretches of rivers. This paper reviews the different zonation concepts and presents a geomorphological classification of South African river zones that is being applied to the RDM and NRHP. The classification is tested on three rivers, the Sabie, Buffalo and Olifants.
- Full Text: false
- Authors: Rowntree, Kate M , Wadeson, Roy A , O'Keeffe, Jay H
- Date: 2000
- Language: English
- Type: Article
- Identifier: vital:6722 , http://hdl.handle.net/10962/d1006799
- Description: The recognition of the Reserve by the new South African Water Law poses new challenges for river scientists. The ecological water requirement or environmental flow is recognised by that part of the Reserve known as the ecological Reserve. If the ecological Reserve is to be implemented, it must first be defined and quantified for all river systems subject to water related developments. Standard procedures are being developed through the Resource Directed Measures (RDM) of the Department of Water Affairs and Forestry while monitoring the health of South Africa's rivers is taking place through the National River Health Programme (NRHP). Cost effective methods of developing spatial frameworks for both the RDM and NRHP are required. Concepts of longitudinal river zonation were developed by river ecologists in the 1960s and 1970s to assist in the classification of ecologically uniform stretches of rivers. This paper reviews the different zonation concepts and presents a geomorphological classification of South African river zones that is being applied to the RDM and NRHP. The classification is tested on three rivers, the Sabie, Buffalo and Olifants.
- Full Text: false
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