An invader within an altered landscape: one catfish, two rivers and an inter-basin water transfer scheme
- Kadye, Wilbert T, Booth, Anthony J
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123776 , vital:35494 , https://doi.10.1002/rra.2599
- Description: African sharptooth catfish Clarias gariepinus has become established as a non-native invasive species in Eastern Cape, South Africa, where it was translocated primarily through an inter-basin water transfer scheme into the Great Fish and Sundays rivers. This study examined the patterns in catfish distribution and abundance, and compared trophic niches in relation to the ichthyofauna of the two rivers. Correspondence analysis revealed upstream to downstream gradients associated with the spatial distribution in species richness for most species within the mainstream and mainstream to tributary gradients that were associated mostly with the spatial distribution of native minnows in both rivers. Catfish was predicted to occur widely within the mainstream habitats and to decrease progressively from mainstreams to tributaries. Based on classification and regression trees, the physico-chemical environment was found to be a good proxy for predicting the occurrence and abundance of catfish. Although non-significant relationships were observed between catfish and other native fish species abundances, the study suggests potential impact due to predation and interference in habitats where the invader co-occurs with other fishes. Comparisons of trophic niches indicated higher trophic diversity for the mainstream ichthyofauna than the tributary communities in both rivers, suggesting an upstream to downstream continuum in community structure and resource availability. Catfish within the invaded mainstream had comparable trophic niches and similar dispersion patterns among individuals for both rivers, but indicated differences in shapes of scatter. This suggests that the catfish exhibited a differential response, probably in relation to resource availability, that may be indicative of its dietary plasticity. The study suggests the proliferation of catfish and its probable impact within the mainstream flow-altered habitats where invasion resistance was possibly reduced. Comparisons of trophic niches provided information on its probable impact at different scales and the potential risk of invasion of tributaries inhabited by native minnow species.
- Full Text:
- Date Issued: 2013
- Authors: Kadye, Wilbert T , Booth, Anthony J
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123776 , vital:35494 , https://doi.10.1002/rra.2599
- Description: African sharptooth catfish Clarias gariepinus has become established as a non-native invasive species in Eastern Cape, South Africa, where it was translocated primarily through an inter-basin water transfer scheme into the Great Fish and Sundays rivers. This study examined the patterns in catfish distribution and abundance, and compared trophic niches in relation to the ichthyofauna of the two rivers. Correspondence analysis revealed upstream to downstream gradients associated with the spatial distribution in species richness for most species within the mainstream and mainstream to tributary gradients that were associated mostly with the spatial distribution of native minnows in both rivers. Catfish was predicted to occur widely within the mainstream habitats and to decrease progressively from mainstreams to tributaries. Based on classification and regression trees, the physico-chemical environment was found to be a good proxy for predicting the occurrence and abundance of catfish. Although non-significant relationships were observed between catfish and other native fish species abundances, the study suggests potential impact due to predation and interference in habitats where the invader co-occurs with other fishes. Comparisons of trophic niches indicated higher trophic diversity for the mainstream ichthyofauna than the tributary communities in both rivers, suggesting an upstream to downstream continuum in community structure and resource availability. Catfish within the invaded mainstream had comparable trophic niches and similar dispersion patterns among individuals for both rivers, but indicated differences in shapes of scatter. This suggests that the catfish exhibited a differential response, probably in relation to resource availability, that may be indicative of its dietary plasticity. The study suggests the proliferation of catfish and its probable impact within the mainstream flow-altered habitats where invasion resistance was possibly reduced. Comparisons of trophic niches provided information on its probable impact at different scales and the potential risk of invasion of tributaries inhabited by native minnow species.
- Full Text:
- Date Issued: 2013
A search for coherence: Social learning in natural resource management
- Cundill, Georgina, Rodela, Romina
- Authors: Cundill, Georgina , Rodela, Romina
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/436597 , vital:73285 , ISBN 978-1-919991-81-8 , https://transformativelearning.education/wp-content/uploads/2013/01/reviews-on-social-learning-literature.pdf
- Description: This paper presents the results of a review process that sought to disen-tangle the different ways in which social learning is conceptualised in nat-ural resource management. We begin with an historical review that seeks to reveal the roots of social learning theory in natural resource manage-ment. Based on this analysis, we develop typologies of statements about the processes that support social learning, and the outcomes of these processes. We then conduct a systematic review of the literature to as-sess the extent to which there is an emerging consensus around these typologies. We conclude that a key source of the confusion currently prevalent in the literature, stems from the fact that the same term is used to refer to quite different processes, which have different outcomes as their goal. To find our way out of the current confusion in the literature, researchers must be explicit about the definitions that they adopt for so-cial learning, and locate these definitions within the historical develop-ment of thinking around social learning in this field. Active debate about appropriate definitions for social learning, based on empirical studies and experience, should form the basis of this field of research in the coming years.
- Full Text:
- Date Issued: 2012
- Authors: Cundill, Georgina , Rodela, Romina
- Date: 2012
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/436597 , vital:73285 , ISBN 978-1-919991-81-8 , https://transformativelearning.education/wp-content/uploads/2013/01/reviews-on-social-learning-literature.pdf
- Description: This paper presents the results of a review process that sought to disen-tangle the different ways in which social learning is conceptualised in nat-ural resource management. We begin with an historical review that seeks to reveal the roots of social learning theory in natural resource manage-ment. Based on this analysis, we develop typologies of statements about the processes that support social learning, and the outcomes of these processes. We then conduct a systematic review of the literature to as-sess the extent to which there is an emerging consensus around these typologies. We conclude that a key source of the confusion currently prevalent in the literature, stems from the fact that the same term is used to refer to quite different processes, which have different outcomes as their goal. To find our way out of the current confusion in the literature, researchers must be explicit about the definitions that they adopt for so-cial learning, and locate these definitions within the historical develop-ment of thinking around social learning in this field. Active debate about appropriate definitions for social learning, based on empirical studies and experience, should form the basis of this field of research in the coming years.
- Full Text:
- Date Issued: 2012
Life history strategy and population characteristics of an unexploited riverine cyprinid, Labeo capensis, in the largest impoundment in the Orange River Basin
- Winker, A Henning, Weyl, Olaf L F, Booth, Anthony J, Ellender, Bruce R
- Authors: Winker, A Henning , Weyl, Olaf L F , Booth, Anthony J , Ellender, Bruce R
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124910 , vital:35709 , https://doi.10.3377/004.047.0124
- Description: Common carp (Cyprinus carpio) is one of the world’s most widely introduced and established freshwater fishes (Casal 2006). The species is considered to be one of the eight most invasive freshwater fishes (Lowe et al. 2000) and worldwide, it accounts for most of the records of successful establishments and adverse ecological effects (Casal 2006; Kulhanek et al. 2011). This invasive success suggests that feral C. carpio is equipped with a set of adaptable life history attributes that allow it to successfully colonise a wide range of habitats (Koehn 2004; Zambrano et al. 2006; Britton et al. 2007). Where feral C. carpio occurs in high densities, it is often perceived as an invasive pest species (Sivakumaran et al. 2003; Brown and Walker 2004; Koehn 2004) because it can have severe impacts on habitat heterogeneity and biodiversity by increasing water turbidity through its bottom feeding behaviour, increasing nutrient availability, decreasing benthic and macrophyte density and diversity, altering zooplankton assemblages and decreasing endemic fish abundance (Zambrano et al. 2001; Khan 2003; Kulhanek et al. 2011). Within south-east Australia, for example, C. carpio comprises the largest proportion of the ichthyobiomass in the continent’s largest river system – the Murray–Darling Basin (Gehrke et al. 1995). As a consequence, serious concerns about its threat to endemic freshwater species (Koehn 2004) have prompted several of the most recent investigations into its life history (e.g. Sivakumaran et al. 2003; Smith and Walker 2004; Brown et al. 2005). Other potential threats posed also include competition with indigenous species and the spread of diseases and parasites (Dudgeon et al. 2006). In South Africa, for example, Asian tapeworm Bothriocephalus acheilognathi is now widely distributed in seven river systems and has infected eight novel cyprinid hosts due to the translocation of infected by C. carpio from a centralized aquaculture facility (Stadtlander et al. 2011).
- Full Text:
- Date Issued: 2012
- Authors: Winker, A Henning , Weyl, Olaf L F , Booth, Anthony J , Ellender, Bruce R
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124910 , vital:35709 , https://doi.10.3377/004.047.0124
- Description: Common carp (Cyprinus carpio) is one of the world’s most widely introduced and established freshwater fishes (Casal 2006). The species is considered to be one of the eight most invasive freshwater fishes (Lowe et al. 2000) and worldwide, it accounts for most of the records of successful establishments and adverse ecological effects (Casal 2006; Kulhanek et al. 2011). This invasive success suggests that feral C. carpio is equipped with a set of adaptable life history attributes that allow it to successfully colonise a wide range of habitats (Koehn 2004; Zambrano et al. 2006; Britton et al. 2007). Where feral C. carpio occurs in high densities, it is often perceived as an invasive pest species (Sivakumaran et al. 2003; Brown and Walker 2004; Koehn 2004) because it can have severe impacts on habitat heterogeneity and biodiversity by increasing water turbidity through its bottom feeding behaviour, increasing nutrient availability, decreasing benthic and macrophyte density and diversity, altering zooplankton assemblages and decreasing endemic fish abundance (Zambrano et al. 2001; Khan 2003; Kulhanek et al. 2011). Within south-east Australia, for example, C. carpio comprises the largest proportion of the ichthyobiomass in the continent’s largest river system – the Murray–Darling Basin (Gehrke et al. 1995). As a consequence, serious concerns about its threat to endemic freshwater species (Koehn 2004) have prompted several of the most recent investigations into its life history (e.g. Sivakumaran et al. 2003; Smith and Walker 2004; Brown et al. 2005). Other potential threats posed also include competition with indigenous species and the spread of diseases and parasites (Dudgeon et al. 2006). In South Africa, for example, Asian tapeworm Bothriocephalus acheilognathi is now widely distributed in seven river systems and has infected eight novel cyprinid hosts due to the translocation of infected by C. carpio from a centralized aquaculture facility (Stadtlander et al. 2011).
- Full Text:
- Date Issued: 2012
The recognition of unenumerated rights in South Africa
- Krüger, Rósaan, Govindjee, Avinash
- Authors: Krüger, Rósaan , Govindjee, Avinash
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71093 , vital:29783 , https://hdl.handle.net/10520/EJC153177
- Description: In 1997 a South African man married a woman who, at the time of the conclusion of their marriage, was a national of a foreign country. The couple decided to set up home and start a family in South Africa. They were advised that the granting of a permanent residence permit to the wife would only be considered upon payment of a hefty application fee, and that she had to apply for the permit from outside South Africa. The couple was of the view that the high cost of the application coupled with their temporary separation at the time of the lodging of the application amounted to an unjustifiable limitation of their right to family life. One of the obstacles faced by the couple was the silence of the South Africa Constitution on the right to family life.
- Full Text: false
- Date Issued: 2012
- Authors: Krüger, Rósaan , Govindjee, Avinash
- Date: 2012
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/71093 , vital:29783 , https://hdl.handle.net/10520/EJC153177
- Description: In 1997 a South African man married a woman who, at the time of the conclusion of their marriage, was a national of a foreign country. The couple decided to set up home and start a family in South Africa. They were advised that the granting of a permanent residence permit to the wife would only be considered upon payment of a hefty application fee, and that she had to apply for the permit from outside South Africa. The couple was of the view that the high cost of the application coupled with their temporary separation at the time of the lodging of the application amounted to an unjustifiable limitation of their right to family life. One of the obstacles faced by the couple was the silence of the South Africa Constitution on the right to family life.
- Full Text: false
- Date Issued: 2012
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