Season and environment modulate aquatic invertebrates’ responses to trout and indigenous fishes in three South African mountain streams
- Bellingan, Terence A, Hugo, Sanet, Villet, Martin H, Weyl, Olaf L F
- Authors: Bellingan, Terence A , Hugo, Sanet , Villet, Martin H , Weyl, Olaf L F
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441487 , vital:73893 , https://doi.org/10.3389/fenvs.2022.1004939
- Description: Introduced organisms are seen as one of the greatest threats to resource sustainability worldwide, and aquatic macroinvertebrates are regarded as good indicators of the health of water resources. To explore these two perspectives, the responses of macroinvertebrate faunas to native and introduced fishes in three headwater tributaries of the Keiskamma River system, South Africa, were examined by comparing potential indicator communities in reaches considered to be fishless, reaches invaded by introduced salmonid species, and reaches containing native fishes. Patterns in the macroinvertebrate faunal assemblage data were driven strongly by season and flow rate, and less strongly by the presence of insectivorous fishes and biotope availability, a finding in parallel with several similar studies from the region. This affirms that aquatic macroinvertebrate faunas are responsive indicators of both environmental and biotic factors and leaves room for further studies to resolve the effects of non-native fish in the Keiskamma River system and other similar systems from South Africa.
- Full Text:
- Date Issued: 2022
- Authors: Bellingan, Terence A , Hugo, Sanet , Villet, Martin H , Weyl, Olaf L F
- Date: 2022
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441487 , vital:73893 , https://doi.org/10.3389/fenvs.2022.1004939
- Description: Introduced organisms are seen as one of the greatest threats to resource sustainability worldwide, and aquatic macroinvertebrates are regarded as good indicators of the health of water resources. To explore these two perspectives, the responses of macroinvertebrate faunas to native and introduced fishes in three headwater tributaries of the Keiskamma River system, South Africa, were examined by comparing potential indicator communities in reaches considered to be fishless, reaches invaded by introduced salmonid species, and reaches containing native fishes. Patterns in the macroinvertebrate faunal assemblage data were driven strongly by season and flow rate, and less strongly by the presence of insectivorous fishes and biotope availability, a finding in parallel with several similar studies from the region. This affirms that aquatic macroinvertebrate faunas are responsive indicators of both environmental and biotic factors and leaves room for further studies to resolve the effects of non-native fish in the Keiskamma River system and other similar systems from South Africa.
- Full Text:
- Date Issued: 2022
Prey and predator density‐dependent interactions under different water volumes
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Sentis, Arnaud, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Sentis, Arnaud , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466957 , vital:76802 , https://doi.org/10.1002/ece3.7503
- Description: Predation is a critical ecological process that directly and indirectly mediates population stabilities, as well as ecosystem structure and function. The strength of interactions between predators and prey may be mediated by multiple density dependences concerning numbers of predators and prey. In temporary wetland ecosystems in particular, fluctuating water volumes may alter predation rates through differing search space and prey encounter rates. Using a functional response approach, we examined the influence of predator and prey densities on interaction strengths of the temporary pond specialist copepod Lovenula raynerae preying on cladoceran prey, Daphnia pulex, under contrasting water volumes. Further, using a population dynamic modeling approach, we quantified multiple predator effects across differences in prey density and water volume. Predators exhibited type II functional responses under both water volumes, with significant antagonistic multiple predator effects (i.e., antagonisms) exhibited overall. The strengths of antagonistic interactions were, however, enhanced under reduced water volumes and at intermediate prey densities. These findings indicate important biotic and abiotic contexts that mediate predator–prey dynamics, whereby multiple predator effects are contingent on both prey density and search area characteristics. In particular, reduced search areas (i.e., water volumes) under intermediate prey densities could enhance antagonisms by heightening predator–predator interference effects.
- Full Text:
- Date Issued: 2021
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Sentis, Arnaud , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2021
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466957 , vital:76802 , https://doi.org/10.1002/ece3.7503
- Description: Predation is a critical ecological process that directly and indirectly mediates population stabilities, as well as ecosystem structure and function. The strength of interactions between predators and prey may be mediated by multiple density dependences concerning numbers of predators and prey. In temporary wetland ecosystems in particular, fluctuating water volumes may alter predation rates through differing search space and prey encounter rates. Using a functional response approach, we examined the influence of predator and prey densities on interaction strengths of the temporary pond specialist copepod Lovenula raynerae preying on cladoceran prey, Daphnia pulex, under contrasting water volumes. Further, using a population dynamic modeling approach, we quantified multiple predator effects across differences in prey density and water volume. Predators exhibited type II functional responses under both water volumes, with significant antagonistic multiple predator effects (i.e., antagonisms) exhibited overall. The strengths of antagonistic interactions were, however, enhanced under reduced water volumes and at intermediate prey densities. These findings indicate important biotic and abiotic contexts that mediate predator–prey dynamics, whereby multiple predator effects are contingent on both prey density and search area characteristics. In particular, reduced search areas (i.e., water volumes) under intermediate prey densities could enhance antagonisms by heightening predator–predator interference effects.
- Full Text:
- Date Issued: 2021
Alternative prey impedes the efficacy of a natural enemy of mosquitoes
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Coughlan, Neil E, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Coughlan, Neil E , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467148 , vital:76831 , https://doi.org/10.1016/j.biocontrol.2019.104146
- Description: Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Coughlan, Neil E , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467148 , vital:76831 , https://doi.org/10.1016/j.biocontrol.2019.104146
- Description: Adaptive foraging behaviour in the presence of multiple prey types may mediate stability to predator-prey relationships. For biological control agents, the presence of alternative prey may thus reduce ecological impacts towards target organisms, presenting a key challenge to the derivation of agent efficacies. Quantifications of non-target effects are especially important for generalist biocontrol agents in their regulation of pests, vectors and invasive species. We examined the predatory impact of the notonectid Anisops debilis towards larvae of the vector mosquito complex Culex pipiens in the presence of varying densities of alternative daphniid prey. Experimentally, we quantified functional responses of A. debilis towards target mosquito prey under different background daphniid compositions, and also tested for prey switching propensities by the notonectid predator.
- Full Text:
- Date Issued: 2020
Benthic diatom-based indices and isotopic biomonitoring of nitrogen pollution in a warm temperate Austral river system
- Dalu, Tatenda, Cuthbert, Ross N, Taylor, Jonathan C, Magoro, Mandla L, Weyl, Olaf L F, Froneman, P William, Wasserman, Ryan J
- Authors: Dalu, Tatenda , Cuthbert, Ross N , Taylor, Jonathan C , Magoro, Mandla L , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466917 , vital:76798 , https://doi.org/10.1016/j.scitotenv.2020.142452
- Description: Rivers are impacted by pollutants from anthropogenic activities such as urbanisation and agricultural practices. Whilst point source pollution has been widely studied and in some cases remediated, non-point pollutant sources remain pervasive, particularly in developing countries that lack economic and human specialist capacity. Monitoring of pollution levels in many regions is additionally challenged by a lack of robust indicators for nitrogen inputs, however, diatom community indices and analysis of variation in microphytobenthos (MBP) stable isotope analysis variations have potential. The present study investigates variations and utilities in benthic diatom indices and MPB δ15N along different river sections (n = 31) of an austral river between two seasons (wet and dry), testing for relationships with key environmental variables (physical, water and sediment), in the context of N monitoring. One hundred and eighteen diatom taxa belonging to 36 genera were identified, with physical (water flow), water (nitrate, P and total dissolved solids) and sediment (B, Ca, Cr, Na, N, P, SOM, Pb and Zn) variables correlating to one or more of the 12 diatom indices presented. In particular, Biological Diatom Index, Biological Index of Water Quality, Central Economic Community, Index of Artois-Picardie Diatom (IDAP) and Sládeček's Index were strongly explained by sediment variables, whilst Descy's Pollution Index and Schiefele and Schreiner's Index were explained by water and physical variables.
- Full Text:
- Date Issued: 2020
- Authors: Dalu, Tatenda , Cuthbert, Ross N , Taylor, Jonathan C , Magoro, Mandla L , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466917 , vital:76798 , https://doi.org/10.1016/j.scitotenv.2020.142452
- Description: Rivers are impacted by pollutants from anthropogenic activities such as urbanisation and agricultural practices. Whilst point source pollution has been widely studied and in some cases remediated, non-point pollutant sources remain pervasive, particularly in developing countries that lack economic and human specialist capacity. Monitoring of pollution levels in many regions is additionally challenged by a lack of robust indicators for nitrogen inputs, however, diatom community indices and analysis of variation in microphytobenthos (MBP) stable isotope analysis variations have potential. The present study investigates variations and utilities in benthic diatom indices and MPB δ15N along different river sections (n = 31) of an austral river between two seasons (wet and dry), testing for relationships with key environmental variables (physical, water and sediment), in the context of N monitoring. One hundred and eighteen diatom taxa belonging to 36 genera were identified, with physical (water flow), water (nitrate, P and total dissolved solids) and sediment (B, Ca, Cr, Na, N, P, SOM, Pb and Zn) variables correlating to one or more of the 12 diatom indices presented. In particular, Biological Diatom Index, Biological Index of Water Quality, Central Economic Community, Index of Artois-Picardie Diatom (IDAP) and Sládeček's Index were strongly explained by sediment variables, whilst Descy's Pollution Index and Schiefele and Schreiner's Index were explained by water and physical variables.
- Full Text:
- Date Issued: 2020
Examining intraspecific multiple predator effects across shifting predator sex ratios:
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150119 , vital:38941 , https://doi.org/10.1016/j.baae.2020.03.002
- Description: Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/150119 , vital:38941 , https://doi.org/10.1016/j.baae.2020.03.002
- Description: Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions.
- Full Text:
- Date Issued: 2020
Influence of intra-and interspecific variation in predator–prey body size ratios on trophic interaction strengths:
- Cuthbert, Ross N, Wasserman, Ryan J, Dalu, Tatenda, Kaiser, Horst, Weyl, Olaf L F, Dick, Jaimie T A, Sentis, Arnaud, McCoy, Michael W, Alexander, Mhairi E
- Authors: Cuthbert, Ross N , Wasserman, Ryan J , Dalu, Tatenda , Kaiser, Horst , Weyl, Olaf L F , Dick, Jaimie T A , Sentis, Arnaud , McCoy, Michael W , Alexander, Mhairi E
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149358 , vital:38839 , https://0-doi.org.wam.seals.ac.za/10.1002/ece3.6332
- Description: Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking. We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Wasserman, Ryan J , Dalu, Tatenda , Kaiser, Horst , Weyl, Olaf L F , Dick, Jaimie T A , Sentis, Arnaud , McCoy, Michael W , Alexander, Mhairi E
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149358 , vital:38839 , https://0-doi.org.wam.seals.ac.za/10.1002/ece3.6332
- Description: Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking. We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.
- Full Text:
- Date Issued: 2020
Inter-population similarities and differences in predation efficiency of a mosquito natural enemy
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466928 , vital:76799 , https://doi.org/10.1093/jme/tjaa093
- Description: Predation is a critical factor that mediates population stability, community structure, and ecosystem function. Predatory natural enemies can contribute to the regulation of disease vector groups such as mosquitoes, particularly where they naturally co-occur across landscapes. However, we must understand inter-population variation in predatory efficiency if we are to enhance vector control. The present study thus employs a functional response (FR; resource use under different densities) approach to quantify and compare predatory interaction strengths among six populations of a predatory temporary pond specialist copepod, Lovenula raynerae, from the Eastern Cape of South Africa preying on second instar Culex pipiens complex mosquito larvae.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466928 , vital:76799 , https://doi.org/10.1093/jme/tjaa093
- Description: Predation is a critical factor that mediates population stability, community structure, and ecosystem function. Predatory natural enemies can contribute to the regulation of disease vector groups such as mosquitoes, particularly where they naturally co-occur across landscapes. However, we must understand inter-population variation in predatory efficiency if we are to enhance vector control. The present study thus employs a functional response (FR; resource use under different densities) approach to quantify and compare predatory interaction strengths among six populations of a predatory temporary pond specialist copepod, Lovenula raynerae, from the Eastern Cape of South Africa preying on second instar Culex pipiens complex mosquito larvae.
- Full Text:
- Date Issued: 2020
Lack of prey switching and strong preference for mosquito prey by a temporary pond specialist predator
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466946 , vital:76801 , https://doi.org/10.1111/een.12801
- Description: The strengths of trophic interactions within ecosystems can be mediated by complex mechanisms that require elucidation if researchers are to understand and predict population‐ and community‐level stabilities. Where multiple prey types co‐occur, prey switching (i.e. frequency‐dependent predation) by predators may facilitate low‐density prey refuge effects which promote coexistence. On the other hand, lack of switching and strong preferences by predators can strongly suppress prey populations, which is especially important considering vector species such as mosquitoes.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466946 , vital:76801 , https://doi.org/10.1111/een.12801
- Description: The strengths of trophic interactions within ecosystems can be mediated by complex mechanisms that require elucidation if researchers are to understand and predict population‐ and community‐level stabilities. Where multiple prey types co‐occur, prey switching (i.e. frequency‐dependent predation) by predators may facilitate low‐density prey refuge effects which promote coexistence. On the other hand, lack of switching and strong preferences by predators can strongly suppress prey populations, which is especially important considering vector species such as mosquitoes.
- Full Text:
- Date Issued: 2020
Sex demographics alter the effect of habitat structure on predation by a temporary pond specialist
- Cuthbert, Ross N, Sithagu, Rotondwa, Weyl, Olaf L F, Froneman, P William, Wasserman, Ryan J, Dick, Jaimie T A, Callaghan, Amanda, Foord, Stefan, Dalu, Tatenda
- Authors: Cuthbert, Ross N , Sithagu, Rotondwa , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Foord, Stefan , Dalu, Tatenda
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466968 , vital:76803 , https://doi.org/10.1016/j.limno.2020.125747
- Description: Habitat structure can profoundly influence interaction strengths between predators and prey. Spatio-temporal habitat structure in temporary wetland ecosystems is particularly variable because of fluctuations in water levels and vegetation colonisation dynamics. Demographic characteristics within animal populations may also alter the influence of habitat structure on biotic interactions, but have remained untested. Here, we investigate the influence of vegetation habitat structure on the consumption of larval mosquito prey by the calanoid copepod Lovenula raynerae, a temporary pond specialist. Increased habitat complexity reduced predation, and gravid female copepods were generally more voracious than male copepods in simplified habitats. However, sexes were more similar as habitat complexity increased. Type II functional responses were exhibited by the copepods irrespective of habitat complexity and sex, owing to consistent high prey acquisition at low prey densities. Attack rates by copepods were relatively unaffected by the complexity gradient, whilst handling times lengthened under more complex environments in gravid female copepods. We demonstrate emergent effects of habitat complexity across species demographics, with predation by males more robust to differences in habitat complexity than females. For ecosystems such as temporary ponds where sex-skewed predator ratios develop, our laboratory findings suggest habitat complexity and sex demographics mediate prey risk.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Sithagu, Rotondwa , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Foord, Stefan , Dalu, Tatenda
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466968 , vital:76803 , https://doi.org/10.1016/j.limno.2020.125747
- Description: Habitat structure can profoundly influence interaction strengths between predators and prey. Spatio-temporal habitat structure in temporary wetland ecosystems is particularly variable because of fluctuations in water levels and vegetation colonisation dynamics. Demographic characteristics within animal populations may also alter the influence of habitat structure on biotic interactions, but have remained untested. Here, we investigate the influence of vegetation habitat structure on the consumption of larval mosquito prey by the calanoid copepod Lovenula raynerae, a temporary pond specialist. Increased habitat complexity reduced predation, and gravid female copepods were generally more voracious than male copepods in simplified habitats. However, sexes were more similar as habitat complexity increased. Type II functional responses were exhibited by the copepods irrespective of habitat complexity and sex, owing to consistent high prey acquisition at low prey densities. Attack rates by copepods were relatively unaffected by the complexity gradient, whilst handling times lengthened under more complex environments in gravid female copepods. We demonstrate emergent effects of habitat complexity across species demographics, with predation by males more robust to differences in habitat complexity than females. For ecosystems such as temporary ponds where sex-skewed predator ratios develop, our laboratory findings suggest habitat complexity and sex demographics mediate prey risk.
- Full Text:
- Date Issued: 2020
Using action cameras to estimate the abundance and habitat use of threatened fish in clear headwater streams:
- Hannweg, B, Marr, S M, Bloy, Lesley E, Weyl, Olaf L F
- Authors: Hannweg, B , Marr, S M , Bloy, Lesley E , Weyl, Olaf L F
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148911 , vital:38785 , DOI: 10.2989/16085914.2019.1701404
- Description: Snorkel and electrofishing surveys are the traditional baseline methods for fish surveys in clear headwater streams. However, action cameras provide a non-harmful alternative to monitor freshwater fish populations to develop informed conservation management initiatives. In this paper, estimates from photographs and videos from action cameras are compared with snorkel survey estimates of the density of a threatened endemic minnow species in a headwater stream, Eastern Cape, South Africa. Photograph-based relative abundances of fish summed over five microhabitats in each pool returned equivalent results to snorkel surveys, whereas the equivalent video-based abundance estimates were approximately 50% greater than the snorkel estimates. Therefore, photograph-derived estimates could be used as an alternative to snorkel surveys for fish population monitoring and habitat use studies in clear headwater streams.
- Full Text:
- Date Issued: 2020
- Authors: Hannweg, B , Marr, S M , Bloy, Lesley E , Weyl, Olaf L F
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148911 , vital:38785 , DOI: 10.2989/16085914.2019.1701404
- Description: Snorkel and electrofishing surveys are the traditional baseline methods for fish surveys in clear headwater streams. However, action cameras provide a non-harmful alternative to monitor freshwater fish populations to develop informed conservation management initiatives. In this paper, estimates from photographs and videos from action cameras are compared with snorkel survey estimates of the density of a threatened endemic minnow species in a headwater stream, Eastern Cape, South Africa. Photograph-based relative abundances of fish summed over five microhabitats in each pool returned equivalent results to snorkel surveys, whereas the equivalent video-based abundance estimates were approximately 50% greater than the snorkel estimates. Therefore, photograph-derived estimates could be used as an alternative to snorkel surveys for fish population monitoring and habitat use studies in clear headwater streams.
- Full Text:
- Date Issued: 2020
Water volume differentially modifies copepod predatory strengths on two prey types
- Cuthbert, Ross N, Sithagu, Rotondwa, Weyl, Olaf L F, Froneman, P William, Wasserman, Ryan J, Dick, Jaimie T A, Callaghan, Amanda, Foord, Stefan, Dalu, Tatenda
- Authors: Cuthbert, Ross N , Sithagu, Rotondwa , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Foord, Stefan , Dalu, Tatenda
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466979 , vital:76804 , https://doi.org/10.1016/j.limno.2020.125747
- Description: Predatory interaction strengths are highly context-dependent, and in temporary aquatic ecosystems, may be affected by water volume changes. We examine the influence of water volume on Lovenula raynerae (Copepoda) functional responses towards two temporary pond prey types. Daphnia prey risk was not affected by increasing water volume, whereas for Culex prey risk was reduced. Accordingly, water volume changes through the hydroperiod may have species-specific effects on prey, with implications for population persistence under environmental change.
- Full Text:
- Date Issued: 2020
- Authors: Cuthbert, Ross N , Sithagu, Rotondwa , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Foord, Stefan , Dalu, Tatenda
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/466979 , vital:76804 , https://doi.org/10.1016/j.limno.2020.125747
- Description: Predatory interaction strengths are highly context-dependent, and in temporary aquatic ecosystems, may be affected by water volume changes. We examine the influence of water volume on Lovenula raynerae (Copepoda) functional responses towards two temporary pond prey types. Daphnia prey risk was not affected by increasing water volume, whereas for Culex prey risk was reduced. Accordingly, water volume changes through the hydroperiod may have species-specific effects on prey, with implications for population persistence under environmental change.
- Full Text:
- Date Issued: 2020
Additive multiple predator effects of two specialist paradiaptomid copepods towards larval mosquitoes
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Weyl, Olaf L F, Froneman, P William, Callaghan, Amanda, Dick, Jaimie T A
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467137 , vital:76828 , https://doi.org/10.1016/j.limno.2019.125727
- Description: Interactions between multiple predators can profoundly affect prey risk, with implications for prey population stability and ecosystem functioning. In austral temporary wetlands, arid-area adapted specialist copepods are key predators for much of the hydroperiod. Limited autoecological information relating to species interactions negates understandings of trophic dynamics in these systems. In the present study, we examined multiple predator effects of two key predatory paradiaptomid copepods which often coexist in austral temporary wetlands, Lovenula raynerae Suárez-Morales, Wasserman and Dalu 2015 and Paradiaptomus lamellatus Sars, 1985. Predation rates towards larval mosquito prey across different water depths were quantified.
- Full Text:
- Date Issued: 2019
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Weyl, Olaf L F , Froneman, P William , Callaghan, Amanda , Dick, Jaimie T A
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467137 , vital:76828 , https://doi.org/10.1016/j.limno.2019.125727
- Description: Interactions between multiple predators can profoundly affect prey risk, with implications for prey population stability and ecosystem functioning. In austral temporary wetlands, arid-area adapted specialist copepods are key predators for much of the hydroperiod. Limited autoecological information relating to species interactions negates understandings of trophic dynamics in these systems. In the present study, we examined multiple predator effects of two key predatory paradiaptomid copepods which often coexist in austral temporary wetlands, Lovenula raynerae Suárez-Morales, Wasserman and Dalu 2015 and Paradiaptomus lamellatus Sars, 1985. Predation rates towards larval mosquito prey across different water depths were quantified.
- Full Text:
- Date Issued: 2019
An evaluation of the current extent and potential spread of Black Bass invasions in South Africa
- Khosa, Dumisani, Marr, Sean M, Wasserman, Ryan J, Zengeya, Tsungai A, Weyl, Olaf L F
- Authors: Khosa, Dumisani , Marr, Sean M , Wasserman, Ryan J , Zengeya, Tsungai A , Weyl, Olaf L F
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103867 , vital:32317 , https://doi.org/10.1007/s10530-019-01930-0
- Description: Black Bass, a collective name for members of the centrarchid genus Micropterus, are native to North America, but have been introduced globally to enhance recreational angling. This study assessed the distribution of Micropterus salmoides, M. dolomieu and M. punctulatus in South Africa using both formal (survey-based) and informal (tournament data and social media) information sources. Analysis of the distribution data showed habitat bias between the data sources. Survey data from formal information sources were dominated by locality records in riverine environments while those derived from informal information sources focused more on lacustrine habitats. Presence data were used to develop niche models to identify suitable areas for their establishment. The predicted distribution range of M. salmoides revealed a broad suitability over most of South Africa, however, the Cape Fold Ecoregion and all coastal regions were most suitable for the establishment for both M. dolomieu and M. punctulatus. Flow accumulation and precipitation of coldest quarter were the most important environmental variables associated with the presence of all Black Bass species in South Africa. In addition, anthropogenic disturbance such as agricultural activities were associated with the presence of both Smallmouth Bass and Spotted Bass. An extensive area-based invasion debt was observed for all Micropterus spp. The potential for further spread of Black Bass in South Africa is of ecological concern because of their impact on native biota.
- Full Text:
- Date Issued: 2019
- Authors: Khosa, Dumisani , Marr, Sean M , Wasserman, Ryan J , Zengeya, Tsungai A , Weyl, Olaf L F
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/103867 , vital:32317 , https://doi.org/10.1007/s10530-019-01930-0
- Description: Black Bass, a collective name for members of the centrarchid genus Micropterus, are native to North America, but have been introduced globally to enhance recreational angling. This study assessed the distribution of Micropterus salmoides, M. dolomieu and M. punctulatus in South Africa using both formal (survey-based) and informal (tournament data and social media) information sources. Analysis of the distribution data showed habitat bias between the data sources. Survey data from formal information sources were dominated by locality records in riverine environments while those derived from informal information sources focused more on lacustrine habitats. Presence data were used to develop niche models to identify suitable areas for their establishment. The predicted distribution range of M. salmoides revealed a broad suitability over most of South Africa, however, the Cape Fold Ecoregion and all coastal regions were most suitable for the establishment for both M. dolomieu and M. punctulatus. Flow accumulation and precipitation of coldest quarter were the most important environmental variables associated with the presence of all Black Bass species in South Africa. In addition, anthropogenic disturbance such as agricultural activities were associated with the presence of both Smallmouth Bass and Spotted Bass. An extensive area-based invasion debt was observed for all Micropterus spp. The potential for further spread of Black Bass in South Africa is of ecological concern because of their impact on native biota.
- Full Text:
- Date Issued: 2019
Combined impacts of warming and salinisation on trophic interactions and mortality of a specialist ephemeral wetland predator
- Cuthbert, Ross N, Weyl, Olaf L F, Wasserman, Ryan J, Dick, Jaimie T A, Froneman, P William, Callaghan, Amanda, Dalu, Tatenda
- Authors: Cuthbert, Ross N , Weyl, Olaf L F , Wasserman, Ryan J , Dick, Jaimie T A , Froneman, P William , Callaghan, Amanda , Dalu, Tatenda
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467160 , vital:76832 , https://doi.org/10.1111/fwb.13353
- Description: Wetlands are of enormous importance for biodiversity globally but are under increasing risk from multiple stressors driven by ongoing anthro-pogenic environmental change. As the trophic structure and dynamics of ephemeral wetlands are poorly understood, it is difficult to predict how these biodiverse ecosystems will be impacted by global change. In particular, warming and salinisation are projected to have profound im-pacts on these wetlands in future. The present study examined the combined effects of warming and salinisation on species interaction strengths and mortality rates for two ephemeral wetland species. Using an ephemeral pond specialist copepod, Lovenula raynerae Suárez‐Morales, Wasserman, and Dalu, (2015) as a model predator species, we applied a functional response approach to derive warming and salinisa-tion effects on trophic interactions with a prey species. Furthermore, the effects of a salinisation gradient on mortality rates of adult copepods were quantified.
- Full Text:
- Date Issued: 2019
- Authors: Cuthbert, Ross N , Weyl, Olaf L F , Wasserman, Ryan J , Dick, Jaimie T A , Froneman, P William , Callaghan, Amanda , Dalu, Tatenda
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467160 , vital:76832 , https://doi.org/10.1111/fwb.13353
- Description: Wetlands are of enormous importance for biodiversity globally but are under increasing risk from multiple stressors driven by ongoing anthro-pogenic environmental change. As the trophic structure and dynamics of ephemeral wetlands are poorly understood, it is difficult to predict how these biodiverse ecosystems will be impacted by global change. In particular, warming and salinisation are projected to have profound im-pacts on these wetlands in future. The present study examined the combined effects of warming and salinisation on species interaction strengths and mortality rates for two ephemeral wetland species. Using an ephemeral pond specialist copepod, Lovenula raynerae Suárez‐Morales, Wasserman, and Dalu, (2015) as a model predator species, we applied a functional response approach to derive warming and salinisa-tion effects on trophic interactions with a prey species. Furthermore, the effects of a salinisation gradient on mortality rates of adult copepods were quantified.
- Full Text:
- Date Issued: 2019
Food web structure and trophic dynamics of a fish community in an ephemeral floodplain lake
- Peel, Richard A, Hill, Jaclyn M, Taylor, Geraldine C, Weyl, Olaf L F
- Authors: Peel, Richard A , Hill, Jaclyn M , Taylor, Geraldine C , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444690 , vital:74260 , https://doi.org/10.3389/fenvs.2019.00192
- Description: In Africa, wetlands, such as shallow, ephemeral lakes provide ecosystem services, such as water purification, food supply, and flood control but are subject to dynamic flooding/drying cycles which vary in duration from years to decades. The stochastic nature of drying events subjects ephemeral lake fauna to persistent disturbance regimes, therefore understanding how biota respond to flooding and drying events is essential for their conservation and management. Primary production sources supporting consumer biomass in the shallow ephemeral Lake Liambezi (upper Zambezi Ecoregion), were investigated using stable isotope analysis, mixing models and stomach content analysis to investigate the following hypotheses: (1) algal primary production supports a higher consumer biomass than aquatic macrophytes; (2) the lake food chain is short, because the majority of fish fauna are detritivorous/herbivorous cichlids that are consumed by top predators; (3) fish community trophic structure will be similar between years; and (4) with short food chains and stochastic resource availability, there will be substantial competition for food among fish species.
- Full Text:
- Date Issued: 2019
- Authors: Peel, Richard A , Hill, Jaclyn M , Taylor, Geraldine C , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444690 , vital:74260 , https://doi.org/10.3389/fenvs.2019.00192
- Description: In Africa, wetlands, such as shallow, ephemeral lakes provide ecosystem services, such as water purification, food supply, and flood control but are subject to dynamic flooding/drying cycles which vary in duration from years to decades. The stochastic nature of drying events subjects ephemeral lake fauna to persistent disturbance regimes, therefore understanding how biota respond to flooding and drying events is essential for their conservation and management. Primary production sources supporting consumer biomass in the shallow ephemeral Lake Liambezi (upper Zambezi Ecoregion), were investigated using stable isotope analysis, mixing models and stomach content analysis to investigate the following hypotheses: (1) algal primary production supports a higher consumer biomass than aquatic macrophytes; (2) the lake food chain is short, because the majority of fish fauna are detritivorous/herbivorous cichlids that are consumed by top predators; (3) fish community trophic structure will be similar between years; and (4) with short food chains and stochastic resource availability, there will be substantial competition for food among fish species.
- Full Text:
- Date Issued: 2019
Quantifying reproductive state and predator effects on copepod motility in ephemeral ecosystems
- Cuthbert, Ross N, Dalu, Tatenda, Wasserman, Ryan J, Dick, Jaimie T A, Callaghan, Amanda, Froneman, P William, Weyl, Olaf L F
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Froneman, P William , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467171 , vital:76836 , https://doi.org/10.1016/j.jaridenv.2019.05.010
- Description: Ephemeral wetlands in arid environments are unique ecosystems with atypical trophic structuring, often dominated by invertebrate predation. Copepod behavioural traits and vulnerabilities to predation can vary substantially according to reproductive status. Gravid female copepods may be more vulnerable to predation due to reduced escape speeds or higher visibility to predators. Here, we quantify how reproductive status modulates horizontal motility rates of the predatory ephemeral pond specialist copepod Lovenula raynerae, and the responsiveness of the copepod to predator cues of the notonectid Anisops debilis. Males exhibited significantly higher motility rates than gravid female copepods, however chemical predator cues did not significantly influence activity rates in either sex. The lack of responsiveness to predator cues by specialist copepods in ephemeral wetlands may result from a lack of predation pressure in these systems, or due to time stress to reproduce during short hydroperiods. In turn, this could increase predation risk to copepods from externally-recruited top predators in ephemeral wetlands, and potentially contribute to the development of skewed sex ratios in favour of females.
- Full Text:
- Date Issued: 2019
- Authors: Cuthbert, Ross N , Dalu, Tatenda , Wasserman, Ryan J , Dick, Jaimie T A , Callaghan, Amanda , Froneman, P William , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/467171 , vital:76836 , https://doi.org/10.1016/j.jaridenv.2019.05.010
- Description: Ephemeral wetlands in arid environments are unique ecosystems with atypical trophic structuring, often dominated by invertebrate predation. Copepod behavioural traits and vulnerabilities to predation can vary substantially according to reproductive status. Gravid female copepods may be more vulnerable to predation due to reduced escape speeds or higher visibility to predators. Here, we quantify how reproductive status modulates horizontal motility rates of the predatory ephemeral pond specialist copepod Lovenula raynerae, and the responsiveness of the copepod to predator cues of the notonectid Anisops debilis. Males exhibited significantly higher motility rates than gravid female copepods, however chemical predator cues did not significantly influence activity rates in either sex. The lack of responsiveness to predator cues by specialist copepods in ephemeral wetlands may result from a lack of predation pressure in these systems, or due to time stress to reproduce during short hydroperiods. In turn, this could increase predation risk to copepods from externally-recruited top predators in ephemeral wetlands, and potentially contribute to the development of skewed sex ratios in favour of females.
- Full Text:
- Date Issued: 2019
Rapid recovery of macroinvertebrates in a South African stream treated with rotenone:
- Bellingan, Terence A, Hugo, Sanet, Woodford, Darragh J, Gouws, Jeanne, Villet, Martin H, Weyl, Olaf L F
- Authors: Bellingan, Terence A , Hugo, Sanet , Woodford, Darragh J , Gouws, Jeanne , Villet, Martin H , Weyl, Olaf L F
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140751 , vital:37915 , DOI: 10.1007/s10750-019-3885-z
- Description: South Africa’s Cape Fold Ecoregion supports a unique freshwater fish assemblage with many endemics. To mitigate impacts of alien invasive fishes on this unique assemblage, nature conservation authority CapeNature used rotenone to remove smallmouth bass (Micropterus dolomieu) from the Rondegat River. We investigated whether the rotenone treatments had an adverse impact on the aquatic macroinvertebrate community over the long-term, the first study of its kind in Africa. We monitored macroinvertebrates within treated and untreated (control) sites on multiple sampling events for 2 years before and 2 years after two rotenone treatments. We analysed the difference in invertebrate abundance between treatment and control sites before and after treatment, using generalised linear mixed models with sampling event as a random factor to partition out natural fluctuations in abundances over time.
- Full Text:
- Date Issued: 2019
- Authors: Bellingan, Terence A , Hugo, Sanet , Woodford, Darragh J , Gouws, Jeanne , Villet, Martin H , Weyl, Olaf L F
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140751 , vital:37915 , DOI: 10.1007/s10750-019-3885-z
- Description: South Africa’s Cape Fold Ecoregion supports a unique freshwater fish assemblage with many endemics. To mitigate impacts of alien invasive fishes on this unique assemblage, nature conservation authority CapeNature used rotenone to remove smallmouth bass (Micropterus dolomieu) from the Rondegat River. We investigated whether the rotenone treatments had an adverse impact on the aquatic macroinvertebrate community over the long-term, the first study of its kind in Africa. We monitored macroinvertebrates within treated and untreated (control) sites on multiple sampling events for 2 years before and 2 years after two rotenone treatments. We analysed the difference in invertebrate abundance between treatment and control sites before and after treatment, using generalised linear mixed models with sampling event as a random factor to partition out natural fluctuations in abundances over time.
- Full Text:
- Date Issued: 2019
Species succession and the development of a lacustrine fish community in an ephemeral lake
- Peel, Richard A, Hill, Jaclyn M, Taylor, Geraldine C, Tweddle, Denis, Weyl, Olaf L F
- Authors: Peel, Richard A , Hill, Jaclyn M , Taylor, Geraldine C , Tweddle, Denis , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444704 , vital:74261 , https://doi.org/10.1111/jfb.14081
- Description: Here, we present a gillnet survey of Lake Liambezi a 370 km2 shallow ephemeral floodplain lake situated in north‐eastern Namibia, which is fed irregularly by the upper Zambezi and Kwando Rivers during years of high flooding. The lake dried up in 1985 and, with the exception of sporadic minor annual inundation events, remained dry until 2007. We describe the temporal succession of fish species over an 8 year period from initial inundation 2007 to maturation in 2014. The succession of the fish community did not follow the typical pattern of opportunistic strategists during colonisation, to periodic strategists that are eventually succeeded by equilibrium strategists. Instead, the evolution of the fish community was characterised by three distinct phases. The first phase involved the inundation and colonisation of the lake in 2007, followed by its decline until the floods that filled the lake in 2009. During this phase the lake was colonised by fishes from the adjacent upper Zambezi and Chobe River floodplains.
- Full Text:
- Date Issued: 2019
- Authors: Peel, Richard A , Hill, Jaclyn M , Taylor, Geraldine C , Tweddle, Denis , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444704 , vital:74261 , https://doi.org/10.1111/jfb.14081
- Description: Here, we present a gillnet survey of Lake Liambezi a 370 km2 shallow ephemeral floodplain lake situated in north‐eastern Namibia, which is fed irregularly by the upper Zambezi and Kwando Rivers during years of high flooding. The lake dried up in 1985 and, with the exception of sporadic minor annual inundation events, remained dry until 2007. We describe the temporal succession of fish species over an 8 year period from initial inundation 2007 to maturation in 2014. The succession of the fish community did not follow the typical pattern of opportunistic strategists during colonisation, to periodic strategists that are eventually succeeded by equilibrium strategists. Instead, the evolution of the fish community was characterised by three distinct phases. The first phase involved the inundation and colonisation of the lake in 2007, followed by its decline until the floods that filled the lake in 2009. During this phase the lake was colonised by fishes from the adjacent upper Zambezi and Chobe River floodplains.
- Full Text:
- Date Issued: 2019
The diet and trophic ecology of non-native Micropterus salmoides in two South African impoundments
- Taylor, Geraldine C, Hill, Jaclyn M, Weyl, Olaf L F
- Authors: Taylor, Geraldine C , Hill, Jaclyn M , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444718 , vital:74262 , https://doi.org/10.2989/16085914.2019.1612318
- Description: Largemouth bass Micropterus salmoides is a highly successful predator that preys on fish and invertebrates. Highly popular with anglers, it is one of the most introduced and invasive fish globally, with strong potential to alter ecosystem structure and functioning. A better understanding of the trophic dynamics of M. salmoides populations is critical for effective management of its ecological impacts in their invasive range. This study investigated the diets and dietary ontogenetic shifts of M. salmoides in two South African dams along with its trophic positioning relative to other fish community members, through stomach content and stable isotope analyses. Micropterus salmoides was a top predator in both dams. In the Mankazana Dam, it depended predominately on insect prey, demonstrating a generalised feeding strategy, with shifts to include increasing proportions of fish prey with increasing size. Contrastingly, in the Wriggleswade Dam, M. salmoides displayed no ontogenetic shifts and preferred Gilchristella aestuaria, likely indicating a shift to a predominantly fish-based diet at smaller sizes, in the presence of small pelagic fish prey. Overall, M. salmoides diet was opportunistic, likely associated with prey morphology and behaviour (associated with refuge availability) and therefore directly linked to prey abundance and availability, which consequently dictated feeding strategy.
- Full Text:
- Date Issued: 2019
- Authors: Taylor, Geraldine C , Hill, Jaclyn M , Weyl, Olaf L F
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/444718 , vital:74262 , https://doi.org/10.2989/16085914.2019.1612318
- Description: Largemouth bass Micropterus salmoides is a highly successful predator that preys on fish and invertebrates. Highly popular with anglers, it is one of the most introduced and invasive fish globally, with strong potential to alter ecosystem structure and functioning. A better understanding of the trophic dynamics of M. salmoides populations is critical for effective management of its ecological impacts in their invasive range. This study investigated the diets and dietary ontogenetic shifts of M. salmoides in two South African dams along with its trophic positioning relative to other fish community members, through stomach content and stable isotope analyses. Micropterus salmoides was a top predator in both dams. In the Mankazana Dam, it depended predominately on insect prey, demonstrating a generalised feeding strategy, with shifts to include increasing proportions of fish prey with increasing size. Contrastingly, in the Wriggleswade Dam, M. salmoides displayed no ontogenetic shifts and preferred Gilchristella aestuaria, likely indicating a shift to a predominantly fish-based diet at smaller sizes, in the presence of small pelagic fish prey. Overall, M. salmoides diet was opportunistic, likely associated with prey morphology and behaviour (associated with refuge availability) and therefore directly linked to prey abundance and availability, which consequently dictated feeding strategy.
- Full Text:
- Date Issued: 2019
Comparing the fish assemblages and food web structures of large floodplain rivers
- Taylor, Geraldine C, Weyl, Olaf L F, Hill, Jaclyn M, Peel, Richard A, Hay, Clinton J
- Authors: Taylor, Geraldine C , Weyl, Olaf L F , Hill, Jaclyn M , Peel, Richard A , Hay, Clinton J
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68961 , vital:29343 , https://doi.org/10.1111/fwb.13032
- Description: The Upper Zambezi, Kavango and Kwando are large floodplain rivers with substantial biodiversity, providing water and ecosystem services to a large tract of southern Africa. These rivers differ in hydrological regime. The Upper Zambezi and Kavango rivers are in flood for 4 months (March, April, May, June) while, in the Kwando River, floods are later and last for 1–2 months in July and August. The Upper Zambezi River has the largest annual flood pulse, followed by the Kavango River, while the Kwando River experiences small and unreliable floods. During years of exceptional flooding of the Upper Zambezi and Kavango rivers, the rivers are interconnected at peak flows and therefore share a common ichthyofauna. This provided a natural experiment to investigate the responses of fish communities comprised of the same species to differing flood regimes by comparing the fish assemblages and food‐web structures between rivers.
- Full Text: false
- Date Issued: 2017
- Authors: Taylor, Geraldine C , Weyl, Olaf L F , Hill, Jaclyn M , Peel, Richard A , Hay, Clinton J
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68961 , vital:29343 , https://doi.org/10.1111/fwb.13032
- Description: The Upper Zambezi, Kavango and Kwando are large floodplain rivers with substantial biodiversity, providing water and ecosystem services to a large tract of southern Africa. These rivers differ in hydrological regime. The Upper Zambezi and Kavango rivers are in flood for 4 months (March, April, May, June) while, in the Kwando River, floods are later and last for 1–2 months in July and August. The Upper Zambezi River has the largest annual flood pulse, followed by the Kavango River, while the Kwando River experiences small and unreliable floods. During years of exceptional flooding of the Upper Zambezi and Kavango rivers, the rivers are interconnected at peak flows and therefore share a common ichthyofauna. This provided a natural experiment to investigate the responses of fish communities comprised of the same species to differing flood regimes by comparing the fish assemblages and food‐web structures between rivers.
- Full Text: false
- Date Issued: 2017