Search

Irrigation ponds are increasingly abundant globally, particularly in water-stressed countries with limited natural surface waters, yet knowledge of their ecology is limited. Here, we assessed zoopl...

Habitat complexity plays an important role in structuring species diversity, behaviour and distribution. Furthermore, habitat complexity can mediate the strength of predator-prey interactions through the provision of prey refugia or through enhancing ambush predation. In this study, we use functional responses (FRs) to compare the effect of habitat complexity on resource utilisation between Largemouth Bass Micropterus salmoides and Florida Bass Micropterus floridanus predating upon Mozambique Tilapia Oreochromis mossambicus fry. Treatments for this study were zero and high habitat complexities, with the latter being artificially constructed using plastic strips. Both predator species exhibited a Type II FR in both habitat complexities, with Florida Bass exhibiting significantly higher FR magnitudes, compared with Largemouth Bass under both habitat complexities. Both species experienced dampening of FR magnitudes under high habitat complexity. Florida Bass had persistently lower handling parameters than Largemouth Bass regardless of habitat complexity. While higher habitat complexity may offer prey refugia from Florida Bass, changes in complexity had a negligible effect upon Largemouth Bass predatory efficiency. Measures to enhance natural complexity through system restoration may be a useful conservation measure for endemic fish in rivers invaded by Florida Bass, however, the same mitigation measures may not be as effective for Largemouth Bass.

We review the possible impacts of non-native biota on the indigenous fishes of South African estuaries, including macrophytes, algae, pathogens, invertebrates, and fishes. Freshwater macrophytes are one of the primary non-native groups in the oligohaline reaches of some predominantly open estuaries, lake and river mouth type estuaries, as well as the entire area of certain low salinity, temporarily closed estuaries. Anoxia and hypoxia in the water column below Salvinia molesta and Pontederia crassipes floating mats have caused fish kills in certain temporarily closed estuaries. Mass mortalities of fish in estuaries have arisen from harmful algal blooms (HABs) and a catchment-derived pathogenic water mould, Aphanomyces invadans. Non-native invertebrate species in local estuaries are derived from freshwater, estuarine and marine sources. The freshwater gastropod Tarebia granifera has invaded many subtropical estuaries and may be negatively impacting their food webs, with estuarine zoobenthivorous fishes not appearing to consume this mollusc. The marine polychaete Ficopomatus enigmaticus has invaded many South African estuaries and, in some of them, changed the zoobenthic food web by encrusting on hard surfaces and filtering particulate matter from the water column. This species also does not appear to be eaten by zoobenthivorous fishes within these systems. No non-native marine or estuarine fish species have been recorded in South African estuaries but non-native freshwater fish species now occur in 25% of estuaries in the region. Degraded estuaries in particular are more vulnerable to colonisation by non-native and translocated fish species than unimpacted systems. During the 1990s, a fish survey of 191 estuaries revealed that only 0.04% of the catch comprised non-native or translocated species but this percentage has increased in many estuaries in recent decades. Non-native and translocated freshwater fish species have successfully colonised the oligohaline and mesohaline reaches of many systems and there may be an impact due to predation on the eggs and larvae of resident estuarine taxa and the recruitment success of catadromous and some estuarine-associated fish species. However, most non-native fishes have a limited tolerance for the salinity regimes found in the lower and middle reaches of many South African estuaries, with an even larger threat to the indigenous estuarine ichthyofauna coming from non-native plant, invertebrate and pathogen invaders. Based on this review, and other similar global studies, there is a developing paradigm that non-native invasions by fishes and other organisms into South African and global estuaries are driven primarily from freshwater taxa and not estuarine or marine species.

The use of artificial habitats as tool for management and conservation of lentic freshwater ecosystems has been most studied in North America, with dominance of Centrarchidae fish. Contrary to north temperate ecosystems, Cichlidae species appear to be prevalent on artificial habitats in Neotropical reservoirs. Currently, due to the rapid expansion of non-native fish introductions globally, these two fish families are increasingly expected to coexist in the same environments. This study aimed to test experimentally the use of artificial habitats by fish in two Neotropical reservoirs between: (i) kind of habitats, (ii) Cichlidae and Centrarchidae, (iii) native and non-native species, and (iv) size classes. The results showed a higher number of individuals and species in pipes and rocks habitats. The dominance of Cichlidae over Centrarchidae in pipes, rocks and control habitats suggests a kind of partitioning between these groups. Native Cichlidae (

Data on ecological impacts of freshwater crayfish invasions in Africa are scarce but invasion history suggests the likelihood of negative implications for biodiversity. To evaluate the potential for ecological impacts we describe the consumer‐resource dynamics of two established crayfish species (Cherax quadricarinatus and Procambarus clarkii) in comparison with the native trophic analogue, the freshwater crab Potamonautes perlatus preying upon Clarias gariepinus fry using comparative functional responses (FRs) and FR ratio (FRR). Experiments were conducted under dark and light conditions as well as low (19°C) and high (28°C) temperature treatments. All three species exhibited potentially population destabilising Type II (hyperbolic) FRs towards prey, which was significantly higher in the dark than in the light. At low temperatures, P. perlatus exhibited the highest maximum feeding estimate although the FR curve was not significantly different from C. quadricarinatus at the highest prey densities. Both crayfish species had higher attack rates at both temperatures and consumed significantly more prey at the high temperature than P. perlatus. The FRR of both crayfish species at the high temperature treatment was higher than that of P. perlatus due to high attack rate and low handling parameters. At 19°C, P. perlatus had a higher or negligible relative FR magnitude compared to P. clarkii and C. quadricarinatus respectively, which suggests some degree of biotic resistance at this temperature; however, this resistance is decreased at 28°C. Cherax quadricarinatus consistently had disruptive FR parameters across both temperatures. Findings from this study represent an important step towards understanding the impacts of crayfish in Africa for public authorities and environmental managers. The two invasive crayfish species have the potential to exert greater per capita impacts on benthic prey communities in invaded systems as shown by their high FRs and FRRs. Furthermore, C. quadricarinatus is an emerging invader globally and our results provide evidence of potential for negative ecological impact regardless of thermal conditions. African countries and their respective environmental managers should therefore maximise efforts to prevent the introduction and spread of these invaders to conserve native biodiversity.

The global invasive anguillid gill parasite Pseudodactylogyrus anguillae (Yin and Sproston, 1948) has only recently been documented from eels in South Africa. As there is no known eel trade in South Africa, the source of introduction of this parasite has been debated, and its status as an alien parasite was rendered uncertain. We report on the first infection of Pseudodactylogyrus anguillae from the giant mottled eel Anguilla marmorata from the Phongolo River (South Africa) using classic morphological and molecular methodologies and clarify the introduction status category of this parasite as alien and invasive.

Labeo umbratus (Smith, 1841) is a widespread species with populations distributed across isolated southern African river systems. Given that cryptic lineages have been detected in freshwater fishes...

The River Goby, Glossogobius callidus, is native to freshwater and estuarine habitats in South Africa. Individuals (21.1 - 144.4 mm Total Length (LT )) were sampled from impoundments in the Sunday's River, Eastern Cape from February 2014 to March 2015. The largest female was 137.2 mm LT and the largest male was 144.4 mm LT . Length-at-50% maturity was 75.2 ± 2.1 mm LT for males and 76.2 ± 2.0 mm LT for females. Absolute fecundity was 1028.2 ± 131.7 oocytes/fish, and relative fecundity was 50.1 ± 18.1 oocytes/gram. The spawning season extended from October to December. Fish were aged using sectioned sagittal otoliths. Growth zone periodicity was validated by edge analysis. Longevity was 7+ years for females and 6+ years for males. Length-at-age was similar for the two sexes and was best described using the von Bertalanffy growth model as Lt = 74.7 (1 - e-1.0(t + 0.1) ) mm LT for the entire population. Using population age structure, mortality rate was estimated at 1.3 yr-1 . This article is protected by copyright. All rights reserved.

Different techniques have been employed for fish surveys in freshwater impoundments, however, despite the increasing applicability of underwater video systems for fish sampling in different aquatic ecosystems, such technology has not been tested in reservoirs. This study compares estimates of fish species richness, community composition, and size structure derived from visual census (VC) and underwater video (UWV) in two Neotropical reservoirs. The total number of species recorded by both sampling methods was similar, even though UWV recorded higher mean number of species than VC, in both reservoirs. In general, VC was more efficient in recording cryptic and resident species, while UWV, was better for highly mobile species. Considering size classes, VC was more efficient than UWV in detecting smaller individuals (i.e., 31–79 mm total length). Although observational sampling methods depend on water transparency, UWV can be considered a complementary and promising technique for fish surveys in shallow areas of clear reservoirs.

1. Land use intensification and climate change are two prominent drivers of variation in biological communities. However, we know very little about how these two potential environmental stressors interact. Here, we use a stable isotope approach to quantify how animal communities respond to urban and agriculture land use, and to latitudinal variation in climate (rainfall and temperature), in 29 streams across South Africa. 2. Community structure was shaped by both land use and climatic factors. The taxonomic diversity of invertebrates was best explained by an independent negative effect of urbanisation, while abundance declined in summer. However, we could not use our variables to predict fish diversity (suggesting that other factors may be more important). 3. Both trophic functional diversity (quantifed using isotopic richness ) and food chain length declined with increasing temperature. Functional redundancy (quantifed using isotopic uniqueness ) in the invertebrate community was high in wet areas, and a synergistic interaction with urbanisation caused the lowest values in dry urban regions. There was an additive effect of agriculture and rainfall on abundance‐weighted vertebrate functional diversity (quantified using isotopic dispersion ), with the former causing a decline in dispersion, with this partially compensated for by high rainfall. 4. In most cases, we found that a single dominant driver (either climate or land use) explained variation between streams. We only found two incidences of combined effects improving the model, one of which was amplified (i.e., the drivers combined to cause an effect larger than the sum of their independent effects), indicating that management should first focus on mitigating the dominant stressor in stream ecosystems for successful restoration efforts. 5. Overall, our study indicates subtle food web responses to multiple drivers of change, only identified by using functional isotope metrics – these are a useful tool for a whole‐systems biology understanding of global change.

Habitat degradation is one of the greatest threats to endemic freshwater fish in the Cape Fold Ecoregion. One habitat restoration strategy is the replication of critical habitat using artificial ma...

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. Copepods exhibited destabilising Type II functional responses in all treatments, with female copepods significantly more voracious than males under multiple predator groups. Lovenula raynerae exhibited significantly negative MPEs overall which resulted in prey risk reductions. However, whilst not statistically clear, the magnitude of antagonistic interactions subtly differed among predator-predator compositions and prey densities, with female-female antagonisms generally prevalent at low prey densities, and male-male negative interactions greater under high prey densities. Mixed-sex copepod group predation was predicted by both additive and substitutive models, and additive models generated significantly higher consumption estimates than substitutive equivalents given that their predictions were based on the absence of antagonistic non-trophic interactions. We propose the importance of internal population sex demographics as a further context-dependency which influences the nature of MPEs, with demographic implications requiring investigation across other taxonomic and trophic groups.

Our ability to predict invasions has been hindered by the seemingly idiosyncratic context-dependency of individual invasions. However, we argue that robust and useful generalisations in invasion science can be made by considering “invasion syndromes” which we define as “a combination of pathways, alien species traits, and characteristics of the recipient ecosystem which collectively result in predictable dynamics and impacts, and that can be managed effectively using specific policy and management actions”. We describe this approach and outline examples that highlight its utility, including: cacti with clonal fragmentation in arid ecosystems; small aquatic organisms introduced through ballast water in harbours; large ranid frogs with frequent secondary transfers; piscivorous freshwater fishes in connected aquatic ecosystems; plant invasions in high-elevation areas; tall-statured grasses; and tree-feeding insects in forests with suitable hosts. We propose a systematic method for identifying and delimiting invasion syndromes. We argue that invasion syndromes can account for the context-dependency of biological invasions while incorporating insights from comparative studies. Adopting this approach will help to structure thinking, identify transferrable risk assessment and management lessons, and highlight similarities among events that were previously considered disparate invasion phenomena.

The availability of appropriate refugia may ameliorate some impacts of habitat degradation and can aid in the conservation of target species. In addition to natural refugia, the provision of artificial refugia may be viable, particularly in degraded habitats. We examined the conservation potential of natural and artificial refugia for the endangered Eastern Cape redfin, Pseudobarbus afer. We show that deeper water is preferred so is likely to constitute a natural refuge. However, this preference is overridden by the provision of artificial refugia (a plastic pipe). We highlight that the most important habitat factor in the conservation of P. afer is availability of suitable natural refugia through avoidance of habitat destruction. However, when redfin habitat is already compromised, appropriate artificial refugia may supplement the protection provided by natural refugia and may provide benefits to the whole aquatic community.

Freshwater biodiversity is declining at an unprecedented rate. Freshwater conservationists and environmental managers have enough evidence to demonstrate that action must not be delayed but have insufficient evidence to identify those actions that will be most effective in reversing the current trend.\ud Here, the focus is on identifying essential research topics that, if addressed, will contribute directly to restoring freshwater biodiversity through supporting ‘bending the curve’ actions (i.e. those actions leading to the recovery of freshwater biodiversity, not simply deceleration of the current downward trend).\ud The global freshwater research and management community was asked to identify unanswered research questions that could address knowledge gaps and barriers associated with ‘bending the curve’ actions. The resulting list was refined into six themes and 25 questions.\ud Although context-dependent and potentially limited in global reach, six overarching themes were identified: (i) learning from successes and failures; (ii) improving current practices; (iii) balancing resource needs; (iv) rethinking built environments; (v) reforming policy and investments; and (vi) enabling transformative change.\ud Bold, efficient, science-based actions are necessary to reverse biodiversity loss. We believe that conservation actions will be most effective when supported by sound evidence, and that research and action must complement one another. These questions are intended to guide global freshwater researchers and conservation practitioners, identify key projects and signal research needs to funders and governments. Our questions can act as springboards for multidisciplinary and multisectoral collaborations that will improve the management and restoration of freshwater biodiversity.

Many conservation efforts for freshwater fishes have been undertaken; however, continuing the monitoring of both the distribution and the abundance of species to determine the effectiveness of these actions can be difficult. As species increase in rarity, they are more difficult to detect in the field, making inferences on occupancy less reliable. Conventional sampling methods, such as electrofishing and seining, require the physical handling of rare fishes, which may cause stress and mortality and, consequently, compromise conservation goals and limit monitoring programmes. Non‐invasive surveillance methods, including underwater video, are playing an increasingly important role. In this study, occupancy models were used to estimate the detection probability of underwater cameras as an alternative to the conventional sampling methods for rare stream fishes. Redside dace (Clinostomus elongatus), a small minnow listed as Endangered, was used as a model organism for rarity. A total of 69 historical redside dace sites were sampled using three sampling methods to determine the effect of gear type on detecting and identifying the habitat preferences of this rare minnow. On average, using multiple underwater cameras is as effective at detecting a rare minnow as conventional sampling methods (backpack electrofisher and seine) and causes no harm. The detection probability of both underwater cameras and backpack electrofishing were adversely affected by turbidity, whereas seining was positively affected by stream velocity. The probability of occupancy of redside dace is driven by open channels and sediment size, and this provides a strong basis for informing stream restoration projects. The use of multiple underwater cameras over conventional sampling methods is recommended when sampling for rare and endangered minnows in systems with low turbidity.

In this study, population genetic and demographic parameters were inferred using sequence data from 151 individuals of Anguilla mossambica originating from continental south and south-east Africa and Madagascar. The analyses were based on a 532 bp segment of the mitochondrial cytochrome b gene. The absence of genetic structuring was observed thereby supporting the hypothesis of panmixia for the endemic A. mossambica. The overall nucleotide diversity π = 0.002 and the haplotype diversity reached h = 0.691. Significant negative values from several tests of neutrality and mismatch analysis pointed to fluctuating historical population sizes. Bayesian averaging resulted in higher support for population growth models vs. a constant population-size model. Population decline and subsequent growth most likely predated the last glacial and were probably related to extended periods of extreme drought followed by wetter and more stable hydroclimate between 150 and 75,000 years before present (kBP). According to this scenario the female effective population size has increased since 110 kBP by c. two orders of magnitude to a recent level of about 650,000 (219,317-2,292,000).

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.

We examined innate responses to conspecific and heterospecific alarm cues in a small cyprinid minnow, the Eastern Cape redfin Pseudobarbus afer. We found that redfins respond to conspecific skin extract, which contains alarm chemicals, and showed that their preferred response is to hide in refugia. Redfins also respond to skin extract from an allopatric, distantly related minnow species, the chubbyhead barb Enteromius anoplus indicating that neither sympatry nor close phylogenetic relationships are necessary for recognition of heterospecific alarm cues. Although both conspecific and heterospecific alarm cues induced similar responses, the response to heterospecific cues was less intense. This may be explained by a trade-off between selection to maximise threat recognition and selection to avoid the costs of responding to irrelevant cues, or by differences in chemical structures of alarm cues between species. These findings have implications for the conservation of this Endangered fish species and for freshwater fishes throughout Africa.

Largemouth Bass (Micropterus salmoides) have been introduced on a global scale for sport fishing but represent a conservation concern given their documented negative impacts on native faunal diversity and abundance. Recent research using molecular data to characterize invasive Largemouth Bass populations elsewhere has demonstrated that populations are typically characterized by limited genetic diversity, or represent a combination of Largemouth Bass and Florida Bass (Micropterus floridanus). To test whether these traits were consistent with invasive populations in Brazil, we generated mitochondrial sequence data from four established populations of Largemouth Bass collected in southern Brazil as well as a local aquaculture facility to confirm species identity and quantify levels of genetic diversity. We identified the exclusive presence of Largemouth Bass in the region and observed limited levels of haplotype (haplotype diversity = 0.0684, SE = 0.038) and nucleotide diversity (0.0003, SE = 0.0002) which suggested the presence of a founder effect associated with introduction. Each of the four populations were dominated by a single haplotype that was identical to one recovered from a nearby aquaculture facility, which identified this facility as a potential introduction source.

Predation shapes community structures via direct and indirect mechanisms and it is an ecological imperative that predatory impacts are predicted. In this study, we used comparative functional responses (FRs) to compare resource utilisation (i.e. per capita effects) between young-of-year Largemouth Bass and Florida Bass across different temperatures treatments (18, 24 and 30 °C). Culex mosquito larvae were used as prey during the experiments. Across all temperature treatments, Type II FRs were observed, which could cause population-destabilising pressures towards native prey communities due to high predation rates at low prey densities. Attack rates did not differ significantly between the fish species at either temperature. Handling times of Largemouth Bass increased significantly with temperature, whilst the converse was true for Florida Bass. Largemouth Bass were found to have higher maximum feeding rates at the low temperature (18 °C), driven by significantly shorter handling times compared to Florida Bass. At the intermediate temperature (24 °C), handling times and thus maximum feeding rates did not differ significantly between the two species. At high temperature (30 °C) Florida Bass exhibited a significantly higher maximum feeding rate and shorter handling time than Largemouth Bass. These results suggest that temperature drives differential ecological impacts, with Florida Bass exerting higher impact than Largemouth Bass on prey at high temperatures and Largemouth Bass having higher impacts than Florida Bass at lower temperatures.

African tigerfish Hydrocynus vittatus (n = 35) were tagged with external radio-transmitters in the Kavango River, Namibia, to determine whether freshwater protected areas could be an effective tool for the management and conservation of this species. They were manually tracked in the core study area of 33 km every c. 12 days from July-October 2016 to May 2017 for between 123 to 246 days. In addition, 14 extended surveys were carried out for up to 680 km to determine the total area use of the tagged individuals. Tigerfish displayed at least two behavioural patterns either having high site fidelity with shorter movements or using larger areas with longer movements. Twenty-three (66%) of the tigerfish had high site fidelity using an area of less than 33 km of river, whereas 12 tigerfish (34%) undertook long distance movements of up to 397 km upstream and 116 km downstream from their tagging locations. During the long-distance movements tigerfish crossed the territorial boundaries of Angola, Namibia and Botswana. Of the 35 fish that were monitored, 14 (40%) spent more than 80% of the monitored time in the 33 km study area and 18 (51%) stayed within the study area for at least 50% of the monitored time. These findings suggest that freshwater protected areas may be a useful management tool and we predict that a protected river area of 2-5 km river length could protect 25.9-34.6% of the population for at least 75% of the time whereas protection of 10 km river length could protect at least 50% of tigerfish for at least 75% of the time.

Despite the high abundance of the gobiid fish Glossogobius callidus in many freshwater ecosystems in South Africa, very few studies have assessed the biology and ecology of the species. Here, we in...

The geographic occurrence of moggel Labeo umbratus × mud fish Labeo capensis hybrids and the threat of hybridisation to the genetic integrity of L. umbratus were investigated. Genetic evidence from mtDNA cytb and nDNA s7 intron sequence data indicated probable interspecific hybridisation in two impoundments, Hardap Dam (Orange River Basin, Namibia) and Darlington Dam (Sundays River Basin, Eastern Cape, South Africa). Some putative hybrids were morphologically identifiable on account of their meristic and morphometric intermediacy to the parent species. Human activities appear to drive the observed hybridisation, either through dam construction and direct stocking of L. umbratus or via translocation of Labeo capensis and the previously isolated Orange River lineage of L. umbratus into the southern-flowing systems by inter-basin water transfers. It is recommended that further translocation of fish from these areas should be avoided.

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,...

Inter‐specific interactions are key factors in the structuring and functioning of ecological communities. Therefore, it is necessary to assess species interactions, such as predator–prey dynamics and competitive exclusion, within the context of continuing global species introductions. The aim of the present study was to assess ecological impacts and competitive exclusion dynamics involving co‐occurring introduced and native fish species, using the multiple predator functional response (FR) approach. We use comparative FR analysis (resource uptake as a function of resource density) to assess inter‐specific interactions between the invasive western mosquitofish Gambusia affinis and the native freshwater river goby Glossogobius callidus towards chironomid larvae. The FR was derived for each fish species as individuals and when in heterospecific pairings. Data from single individuals were used to predict the expected FR of individuals when in heterospecific multiple predator combinations. Expected FRs were then compared to the observed FRs of each predator in combination trials, enumerated using prey items in their gut contents. Both fish species displayed Type II FRs, however, in single fish trials, invasive mosquitofish had significantly higher FRs (curve asymptotes; i.e. shorter handling times and higher maximum feeding rates) than native river gobies. Heterospecific mosquitofish‐river goby combinations revealed that the FR of the river goby was reduced (i.e. longer handling times and lower maximum feeding rates) by the presence of mosquitofish, whereas this combination greatly enhanced mosquitofish FR magnitudes (i.e. shorter handling times and higher maximum feeding rates). The heterospecific treatments resulted in neutral impacts on prey and there were clear inter‐species interference in favour of the non‐native mosquitofish. This study demonstrates how multiple predators can alter the shape of individual FRs, with neutral effects on prey but superior invader competitive ability. This has implications for predicting the naturalisation success of invasive predators, as predatory and competitive interactions with native predators and prey may facilitate rather than impede establishment.

Different values have resulted in conflicts between anglers and conservation lobbies in the management of trout in South Africa. Key to the conflict is the demarcation of boundaries to areas in whi...