Season and environment modulate aquatic invertebrates’ responses to trout and indigenous fishes in three South African mountain streams
- 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
Examining intraspecific multiple predator effects across shifting predator sex ratios:
- 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:
- 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
Playing with food: Detection of prey injury cues stimulates increased functional foraging traits in Xenopus laevis
- Authors: South, Josie , Botha, Taryn L , Wolmarans, Nico J , Wepener, Victor , Weyl, Olaf L F
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443386 , vital:74114 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: Animal behavioural traits determine trophic interaction strength, which in turn structures ecological communities. Behavioural responses to prey cues can inform upon how prey are perceived and detected and therefore determine whether certain stimuli can increase or dampen predatory efficiency and therefore community structuring. We examined the functional foraging traits of an amphibian predator Xenopus laevis on mosquito larvae (Culex sp.), with regard to responses towards different prey cues. We assessed a suite of foraging behaviours exhibited when supplied with three abundances of live prey (2, 4 and 20); non-injury prey cues; prey injury kairomones from mechanically damaged prey in order to determine the importance of cues in stimulating foraging. High abundance of live prey caused frogs to visit the top of the arena significantly more than in the other treatments. This suggests that hydromechanical and visual cues alert X. laevis to prey items in different spatial zones, which results in foraging where the prey have aggregated, while the non-injury prey cue resulted in a decrease in foraging behaviours. The injury kairomone cue elicited a significantly farther distance travelled, and similar responses in terms of velocity of movement and duration of time spent moving when supplied with 20 live prey items. Previous work on X. laevis predation has focused on prey detection via lateral line sensitivity, however, the strength of response elicited by the prey injury kairomone treatment indicates that there are also complex olfactory pathways involved in detecting prey items. This is possibly related to abiotic context (i.e. turbid ponds) and high predator density in the wild.
- Full Text:
- Date Issued: 2020
Using action cameras to estimate the abundance and habitat use of threatened fish in clear headwater streams:
- 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
An evaluation of the current extent and potential spread of Black Bass invasions in South Africa
- 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
Food web structure and trophic dynamics of a fish community in an ephemeral floodplain lake
- 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
Rapid recovery of macroinvertebrates in a South African stream treated with rotenone:
- 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
- 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
- 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
- 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
Estimating δ15N fractionation and adjusting the lipid correction equation using Southern African freshwater fishes
- Authors: Taylor, Geraldine C , Hill, Jaclyn M , Jackson, Michelle C , Peel, Richard A , Weyl, Olaf L F
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69124 , vital:29392 , https://0-doi.org.wam.seals.ac.za/10.1371/journal.pone.0178047
- Description: Stable isotope analysis is an important tool for characterising food web structure; however, interpretation of isotope data can often be flawed. For instance, lipid normalisation and trophic fractionation values are often assumed to be constant, but can vary considerably between ecosystems, species and tissues. Here, previously determined lipid normalisation equations and trophic fractionation values were re-evaluated using freshwater fish species from three rivers in the Upper Zambezian floodplain ecoregion in southern Africa. The parameters commonly used in lipid normalisation equations were not correct for the 18 model species (new D and I parameters were estimated as D = 4.46‰ [95% CI: 2.62, 4.85] and constant I = 0 [95% CI: 0, 0.17]). We suggest that future isotopic analyses on freshwater fishes use our new values if the species under consideration do not have a high lipid content in their white muscle tissue. Nitrogen fractionation values varied between species and river basin; however, the average value closely matched that calculated in previous studies on other species (δ15N fractionation factor of 3.37 ± 1.30 ‰). Here we have highlighted the need to treat stable isotope data correctly in food web studies to avoid misinterpretation of the data.
- Full Text:
- Date Issued: 2017
The abundance of an invasive freshwater snail Tarebia granifera (Lamarck, 1822) in the Nseleni River, South Africa
- Authors: Jones, Roy W , Hill, Jaclyn M , Coetzee, Julie A , Hill, Martin P , Avery, T S , Weyl, Olaf L F
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69077 , vital:29382 , https://doi.org/10.2989/16085914.2017.1298984
- Description: The invasive freshwater snail Tarebia granifera (Lamarck, 1822) was first reported in South Africa in 1999 and it has become widespread across the country, with some evidence to suggest that it reduces benthic macroinvertebrate biodiversity. The current study aimed to identify the primary abiotic drivers behind abundance patterns of T. granifera, by comparing the current abundance of the snail in three different regions, and at three depths, of the highly modified Nseleni River in KwaZulu-Natal, South Africa. Tarebia granifera was well established throughout the Nseleni River system, with an overall preference for shallow waters and seasonal temporal patterns of abundance. Although it is uncertain what the ecological impacts of the snail in this system are, its high abundances suggest that it should be controlled where possible and prevented from invading other systems in the region.
- Full Text: false
- Date Issued: 2017
Emergent effects of structural complexity and temperature on predator–prey interactions
- Authors: Wasserman, Ryan J , Alexander, Mhairi E , Weyl, Olaf L F , Barrios‐O'Neill, Daniel , Froneman, P William , Dalu, Tatenda
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69190 , vital:29444 , https://doi.org/10.1002/ecs2.1239
- Description: Ephemeral aquatic environments are important habitats for a variety of species. They are highly variable with regards to vegetation structure and physico‐chemical features that potentially mediate outcomes of biotic interactions. Multiple environmental variables and their emergent impacts on the relationship between prey consumption rate by a predator and prey density (functional response), however, are rarely assessed. Here, we investigated the combined effects of temperature and habitat complexity on the functional response of the freshwater predatory notonectid Enithares sobria on the cladoceran prey organism Daphnia longispina. A Type II functional response was observed for E. sobria predating on D. longispina and while temperature and habitat complexity had no effect on the response type, these environmental variables interacted with consequences for the magnitude of the functional responses. Overall, structural complexity favored the predator as greater consumption was observed in the most complex habitat treatment. Temperature effects were also evident although these effects were not unidirectional with regard to treatment factor gradients as predators were the most successful at intermediary temperatures. Furthermore, there was a complex interplay between habitat complexity and temperature, with attack rates being greatest at low and high complexities within intermediate temperatures, while at zero complexity attack rates were greatest at the lowest temperature. The effect of habitat on handling times was only evident in the low temperature treatments which decreased steadily with each increase in complexity. Through the application of functional responses the synergistic effects of multiple environmental drivers on predator–prey interaction outcomes have been highlighted, adding insight into how interactions among species may be affected by natural or artificially induced environmental variability.
- Full Text:
- Date Issued: 2016
Monitoring of invertebrate and fish recovery following river rehabilitation using rotenone in the Rondegat River
- Authors: Weyl, Olaf L F , Barrow, S , Bellingan, Terence A , Dalu, Tatenda , Ellender, Bruce R , Esler, K , Impson, D , Gouws, Jeanne , Jordaan, M , Villet, Martin H , Wasserman, Ryan J , Woodford, Darragh J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/442411 , vital:73982 , https://www.wrc.org.za/wp-content/uploads/mdocs/2261.pdf
- Description: Fish invasions have been cited as a primary threat to imperilled South African fishes and other aquatic fauna. As a result, the management and control of alien invasive species is a legislated priority in South Africa. From a river rehabilitation perspective, eradicating alien fish allows for the rehabilitation of several kilometres of river, with very significant benefits for the endangered fish species present and for the associated aquatic biota. In South Africa, the piscicide rotenone is one of the preferred methods for achieving eradication.
- Full Text:
- Date Issued: 2016
Trophic interactions in an austral temperate ephemeral pond inferred using stable isotope analysis
- Authors: Dalu, Tatenda , Weyl, Olaf L F , Froneman, P William , Wasserman, Ryan J
- Date: 2016
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68022 , vital:29185 , https://doi.org/10.1007/s10750-015-2533-5
- Description: Publisher version , Ephemeral ponds are vulnerable aquatic habitats which are difficult to protect given their dynamic nature and sensitivity to degradation during dry periods. Little information is available on these habitats in austral regions, with almost no information on food-web structure and complexity. The study aimed to assess trophic interactions among dominant organisms in an ephemeral pond food web, and investigate the importance of autochthonous and allochthonous carbon, using 13C and 15N isotopes. Results of the investigation suggest that the food web comprised four trophic levels, with the top predators being Notonectids (Notonecta sp.) and diving beetles (Cybister tripunctatus (Olivier)). Intermediary trophic levels comprised zooplankton (daphniids and copepodids), macroinvertebrates (e.g. micronectids and molluscs) and tadpoles. Generalist feeders dominated the higher trophic levels (>3) with specialists comprising the lower trophic levels (≤3). The consumers preferred autochthonous fine particulate organic matter, epiphyton and submerged macrophyte organic matter sources over allochthonous sources. Autochthonous organic matter was transferred to the food web via zooplankton and select macroinvertebrates including Micronecta sp. and Physa sp. The food-web structure within the pond appeared to reflect the secondary stage of trophic structural complexity in the evolution of ephemeral ponds over the course of their hydro-period.
- Full Text: false
- Date Issued: 2016
Validation of the periodicity of growth zone formation in the otoliths of four fish species from the Upper Zambezi ecoregion, southern Africa
- Authors: Taylor, Geraldine C , Peel, Richard A , Weyl, Olaf L F , Hay, Clinton J
- Date: 2016
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/443414 , vital:74116 , https://hdl.handle.net/10520/EJC196537
- Description: In the Upper Zambezi and Okavango ecoregions, Brycinus lateralis, Hepsetus cuvieri, Schilbe intermedius and Serranochromis macrocephalus are important in subsistence fisheries, while S. intermedius and S. macrocephalus are often caught in commercial catches. Despite their importance, there is little information on their age and growth and age validation. Growth zone deposition rate in otoliths of B. lateralis, H. cuvieri, S. intermedius and S. macrocephalus was validated as annual using edge analysis in this study. Annual deposition of growth zones was corroborated by a fluorochrome marking experiment. Both methods demonstrated that one growth zone was deposited annually. Edge analysis demonstrated that the highest proportion of opaque zones was detected between August and December, most likely as a result of slow growth during lower temperature water during the preceding winter. With growth zone deposition validated as annual, future research should focus on determining the growth, maturity and mortality rates of these species, parameters which are important for their management.
- Full Text:
- Date Issued: 2016
An Assessment of the Effect of Rotenone on Selected Non-Target Aquatic Fauna
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Jordaan, Martine , Froneman, P William , Weyl, Olaf L F
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124240 , vital:35579 , https://doi.org/10.1371/journal.pone.0142140.g001
- Description: Rotenone, a naturally occurring ketone, is widely employed for the management of invasive fish species. The use of rotenone poses serious challenges to conservation practitioners due to its impacts on non-target organisms including amphibians and macroinvertebrates. Using laboratory studies, we investigated the effects of different rotenone concentrations (0, 12.5, 25, 37.5, 50, 100 μg L-1) on selected invertebrate groups; Aeshnidae, Belostomatids, Decapods, Ephemeroptera, Pulmonata and zooplankton over a period of 18 hours. Based on field observations and body size, we hypothesized that Ephemeropterans and zooplank- ton would be more susceptible to rote none than Decapods, Belostomatids and snails. Experimental results supported this hypothesis and mortality and behaviour effects varied considerably between taxa, ranging from no effect (crab Potamonuates sidneyi) to 100% mortality (Daphnia pulex and Paradiaptomus lamellatus). Planktonic invertebrates were par- ticularly sensitive to rotenone even at very low concentrations. Future research should investigate the recovery time of invertebrate communities after the application of rotenone and conduct field assessments assessing the longer term effects of rotenone exposure on the population dynamics of those less sensitive organisms.
- Full Text:
- Date Issued: 2015
An assessment of the effect of rotenone on selected non-target aquatic fauna:
- Authors: Dalu, Tatenda , Wasserman, Ryan J , Jordaan, Martine , Froneman, P William , Weyl, Olaf L F
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143247 , vital:38214 , https://doi.org/10.1371/journal.pone.0142140
- Description: Rotenone, a naturally occurring ketone, is widely employed for the management of invasive fish species. The use of rotenone poses serious challenges to conservation practitioners due to its impacts on non-target organisms including amphibians and macroinvertebrates. Using laboratory studies, we investigated the effects of different rotenone concentrations (0, 12.5, 25, 37.5, 50, 100 μg L-1) on selected invertebrate groups; Aeshnidae, Belostomatids, Decapods, Ephemeroptera, Pulmonata and zooplankton over a period of 18 hours. Based on field observations and body size, we hypothesized that Ephemeropterans and zooplankton would be more susceptible to rotenone than Decapods, Belostomatids and snails.
- Full Text:
- Date Issued: 2015
Comparisons of isotopic niche widths of some invasive and indigenous fauna in a South African river
- Authors: Hill, Jaclyn M , Jones, Roy W , Hill, Martin P , Weyl, Olaf L F
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423711 , vital:72088 , xlink:href="https://doi.org/10.1111/fwb.12542"
- Description: Biological invasions threaten ecosystem integrity and bio-diversity, with numerous adverse implications for native flora and fauna. Established populations of two notorious freshwater invaders, the snail Tarebia granifera and the fish Pterygoplichthys disjunctivus, have been reported on three continents and are frequently predicted to be in di-rect competition with native species for dietary resources.
- Full Text:
- Date Issued: 2015