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In the present study, the phylogeography of the only southern African freshwater crab listed as Vulnerable (VU) on the International Union for Conservation of Nature (IUCN) Red List, Potamonautes lividus, was investigated by surveying several localities in the Eastern Cape and KwaZulu‐Natal provinces in South Africa. Both nuclear and mitochondrial DNA (nDNA and mtDNA) markers were used and, as it was hypothesized that marked genetic differentiation should be present, niche modelling was undertaken to explore the distribution of the species along the east coast of South Africa. In addition, shortfalls in the present approach to IUCN Red Listing, as illustrated by this Vulnerable species of crab, are discussed.Results from the mtDNA revealed the presence of two haploclades, confined to specimens from the two provinces, respectively, and the general absence of maternal dispersal, a fact that was further validated by the fixation index (FST) data and high ΦST values. Within the Eastern Cape haploclade, low‐frequency maternal dispersal occurred, corroborated by the low value of FST. In contrast, no haplotypes were shared in the KwaZulu‐Natal haploclade, as corroborated by the marked differences in FST.The microsatellite data demonstrated the presence of higher frequency, possibly paternally biased, dispersal of specimens between the Eastern Cape and KwaZulu‐Natal provinces. The results suggest the presence of two distinct management units within P. lividus. An estimate of divergence time suggests a late Pleistocene cladogenesis between the Eastern Cape and KwaZulu‐Natal haploclades.Considering the presence of P. lividus in several newly formed nature conservation areas in both provinces, and its potential presence in the intermediary area, based on maximum entropy (Maxent) niche modelling, our data suggest that the species status in the IUCN Red List should be downgraded to Least Concern.A comparison of all the Endangered, Vulnerable, and Critically Endangered IUCN Red Listed freshwater crabs for the entire Afrotropical region reveals the lack of recent sampling in the three biodiversity hot spots in West, Central, and East Africa, with mountainous areas containing a disproportionate number of species but with most species being devoid of phylogeographical study. [ABSTRACT FROM AUTHOR]

Abstract Marine fishes in the intermittently open East Kleinemonde Estuary, South Africa, were sampled using seine nets over a twenty year period between 1994 and 2014. This dataset was analysed after 11 years (1994–2005), and represented one of the few medium-term studies of fish communities in an intermittently open estuary. A further nine years of sampling (2006–2014) allowed us to revisit the fish community and to gauge if 20 years of data provides more insight into long-term trends in the fish community. The overall species abundance follows a cyclical pattern with two to three years of low abundance and two to three years of high abundance. This pattern broke down in the last five years of the study, with a decline in species richness and consistently low catches of almost all marine species recorded. This may have been as a result of a reduction in the area of submerged macrophytes in the estuary, as well as an increase in the frequency of mouth opening and subsequent decrease in available water area. Graphical abstract Image 1 Highlights • Fish species abundance shows cyclical pattern. • Consistently low catches of all species recorded in last five years of the study. • Low catches may be attributed to habitat loss and a decrease in available water area. • Study shows value of long-term monitoring. [ABSTRACT FROM AUTHOR]

The distribution of Cape clawless otters, Aonyx capensis, in South Africa and their habitat requirements in freshwater and marine systems has been well established. There is, however, a lack of information on how otters are adapting to urban development and the transformation of critical freshwater habitat., Within the Western Cape, the Cape Peninsula exhibits substantial variation in levels of human impact over a small geographic range, offering an excellent opportunity to explore the hypothesis that otters are adversely affected by habitat transformation., A single season occupancy model was used based on otter sign to determine the probability of otter occupancy across a gradient of habitat transformation at both landscape and local scales., The probability of otters occupying river habitat in the Cape Peninsula was low ( P = 0.29) but increased with proximity to marine protected areas (MPAs) that included estuaries and wetland habitat. Otter presence was not influenced by proximity to urban areas at the landscape scale, but declined in canalized sections of river that were heavily degraded by human activity., Despite being heavily transformed, lowland aquatic ecosystems may still provide critical resources in the form of fresh water and breeding sites, and together with food within the marine habitat may be sustaining the peninsula's otter population., In order for otters to persist on the peninsula, conservation authorities must maintain wetland, estuarine and river habitat in close proximity to MPAs. Further research is needed to determine the long-term impacts on otters persisting in degraded ecosystems., Annual single season occupancy surveys provide a rapid, cost-effective method for monitoring changes in otter occupancy which should be incorporated into current monitoring efforts to provide much needed long-term monitoring of a top predator in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

The grey mullet usually occur in large numbers and biomass in the estuaries of all three South African biogeographic regions, thus making it an ideal family to use in terms of possibly acting as an environmental indicator of global warming. In this analysis the relative estuarine abundance of the dominant three groups of mugilids, namely tropical, warm-water and cool-water endemics, were related to sea surface coastal temperatures. The study suggests a strong link between temperature and the distribution and abundance of the three mullet groups within estuaries and indicates the potential of this family to act as an indicator for future climate change within these systems and adjacent coastal waters. [ABSTRACT FROM AUTHOR]

Abstract: Habitat variability is one of the factors influencing species richness within estuarine systems, and a loss of habitat can result in a restructuring of the estuarine ichthyofaunal assemblage, particularly if these conditions persist over long time periods. The potential effects of the loss of extensive submerged macrophyte beds (Ruppia cirrhosa and Potamogeton pectinatus) on an estuarine fish assemblage were investigated through an analysis of a long-term seine net catch dataset from the temporarily open/closed East Kleinemonde Estuary, South Africa. Catch data for a 12-year period, encompassing six years of macrophyte presence and six years of macrophyte senescence, indicated that the loss of this habitat did not influence species richness but changes in the relative abundance of certain species were evident. A shift in dominance from vegetation-associated species to those associated with sandy environments (e.g. members of the family Mugilidae) was observed. However, species wholly dependent on macrophytes such as the critically endangered estuarine pipefish Syngnathus watermeyeri were only recorded during years when macrophyte beds were present, while vegetation-associated species such as the sparid Rhabdosargus holubi persisted at lower levels of relative abundance. The reduced abundance of all vegetation-associated fish species during years of macrophyte senescence was probably reflective of declining food resources resulting from the loss of macrophyte beds and/or increased vulnerability to predation. Submerged beds of aquatic plants are therefore important habitats within temporarily open/closed estuaries, South Africa’s dominant estuary type. [Copyright &y& Elsevier]

The effects of timing, frequency and duration of mouth opening and marine overwash events on fish assemblages in two, adjacent temporarily open/closed estuaries were investigated. Sampling was conducted biannually over two years during summer and winter, using selective sampling gear to target estuarine-associated marine species. During this period the East Kleinemonde Estuary opened more frequently than the West Kleinemonde Estuary and it also experienced a greater number of bar overwash events when larval recruitment can occur. The timing of mouth opening and the frequency of marine overwash events did not influence species richness of marine-spawning species but had a pronounced effect on abundances (catch-per-unit-effort) of species. The species composition of both estuaries was similar, but the catch-per-unit-effort in the East Kleinemonde Estuary was more than three times greater than that of the West Kleinemonde Estuary. The East Kleinemonde also supported a greater proportion of immature individuals ofRhabdosargus holubi and Monodactylusfalciformis, and the length frequency distributions of both these species differed significantly between the two estuaries. The larger fish sizes in the West Kleinemonde Estuary were attributed to the prolonged mouth closure that resulted in the trapping of larger juveniles and mature fish within the estuary. [ABSTRACT FROM AUTHOR]

The coexistence of trees and grasses in savanna ecosystems is a contentious phenomenon. Fire and herbivory disturbances are often cited as major structuring forces that create a sustainable tree- grass relationship. However, periodic flooding of savanna patches may also enable coexistence. The aim of this study was to investigate the effects of flooddisturbance on the recruitment patterns of Acacia karroo trees in a semi-arid savanna system in South Africa. We analysed the spatial coincidence of A. karroo seedlings with tussocks of the tall spiny grass Stipagrostis namaquensis in the riverbed and related herbivory intensity to spatial position. The data showed that A. karroo seedlings were significantly positively associated with S. namaquensis (Chi-square test, χ12 = 45:20, n = 118, P < 0.001); A. karroo seedlings growing inside of tussocks experienced less browsing pressure than those growing in the floodplain (Kruskal-Wallis test, H = 11.90, n = 118, P < 0.01); and recruitment success of A. karroo trees was spatially discrete (K-S test, D = 0.78, n = 196, P < 0.01). We suggest that floods create an enemyfree zone, which S. namaquensis colonises and then facilitates successful A. karroo establishment. High levels of A. karroo recruitment in the riverbed may replenish the woodlands fringing the river, which appear to be sink areas for A. karroo seedlings. Thus, the interaction between disturbances at different spatial and temporal scales (flooding versus herbivory) seems to maintain the inherently unstable coexistence of tree and grass species in this ecosystem. These findings also suggested that flood disturbances alter the tree-grass relationship. [ABSTRACT FROM AUTHOR]

Estuarine-dependent marine fish species rely on shallow, sheltered and food rich habitats for protection from predators, growth and ultimately recruitment to adult populations. Hence, habitats within estuaries function as critical nursery areas for a variety of fish species. Results from stomach content analysis and dietary diatom composition of a ubiquitous estuarine-dependent species Rhabdosargus holubi (Steindachner, 1881) in the main vegetated and un-vegetated habitats in the Bushmans Estuary, South Africa, were interpreted along with published information on habitat complexity, relative abundance and behaviour of this species. Although the complexity of seagrass, together with the higher abundance and behaviour of R. holubi in seagrass suggests that this is the main nursery habitat (in terms of both feeding and protection from predation), the dominance of red filamentous algae and the presence of some invertebrates mainly in the diet of fish from un-vegetated habitats indicates that this species is using a mosaic of habitats, including un-vegetated areas, for foraging. Based on the above findings, and results from other studies, it is concluded that juvenile R. holubi in permanently open estuaries makes use of a range of habitats according to macrophyte shelter from predators, the availability of preferred food resources and physical drivers such as water depth and tidal phase. This study demonstrated that a multi-method approach, as opposed to a single method approach (diet alone) is useful to assess the nursery value of juvenile fish habitats. Image 1 [ABSTRACT FROM AUTHOR]

Anthropogenic induced climate change is predicted to increase the thermal variability in coastal waters, which can have strong physiological effects on individuals and populations of marine ectotherms. The magnitude and direction of these thermal effects varies depending on species, life stage, biogeography, habitat and season. This study aimed to compare the thermal tolerance of a range of juvenile fish and adult macro-invertebrates from intertidal and estuarine habitats in a warm-temperate, thermally variable region on the south-east coast of South Africa. Seasonal variability in thermal tolerance was compared between species, taxonomic groups, biogeographical distribution and habitat affinity and related to existing and projected water temperature data to gauge the local vulnerability of each species. Critical thermal maximum (CT max), critical thermal minimum (CT min), thermal breadths and scopes, and the thermal safety margins of each species were quantified. The greatest differences in thermal tolerance patterns were based on taxonomy, with macro-invertebrates having broader thermal tolerance compared to fish, with the exception of the Cape sea urchin, in both summer and winter. Relatively narrow lower breadths in tolerance and safety margin values for transient juvenile sub-tropical and temperate fish species from the intertidal rocky low-shore habitat were observed in both summer and winter. This indicates that these fish species and the Cape sea urchin may be more vulnerable to projected increases in cold temperature (upwelling in summer) than warm temperature variability in this warm-temperate region if they are unable to seek thermal habitat refuge. • Marine ectotherms physiology is a key research focus under climate change effects. • Dynamic method determined marine ectotherms upper and lower thermal limits. • Individual thermal limits differed based on taxonomy, biogeography and habitat. • Macro-invertebrates are more thermally tolerant than fish species in this region. • Tropical and temperate fish species may be susceptible to rising upwelling events. [ABSTRACT FROM AUTHOR]

Physiological rates and processes underpin the relationships between ectothermic organisms, such as fish, and their environment. The response and persistence of fish populations in an increasingly variable ocean is dependent on the distribution and diversity of physiological phenotypes. Growing evidence suggests that fisheries exploitation can selectively target certain physiological and behavioural phenotypes, which may shift exploited populations to altered physiological states. Here we test if commercial fisheries have the potential to do this in a "natural laboratory" along the South African coast. We compare metabolic traits of exploited and protected populations of the fish species, Chrysoblephus laticeps, which is a major component of the South African hook and line fishery. We find that high-performance aerobic scope phenotypes are reduced in the fished population. The most likely mechanism for this finding is a positive relationship between aerobic scope and capture vulnerability in passive-gear fisheries. Our results further highlight the selective nature of capture-fisheries and suggest that exploitation has the capacity to alter climate responses of fish populations on a physiological level. Our finding also implicates how Marine Protected Areas, through harbouring individuals with a greater diversity of physiological traits, may provide greater fish response diversity to environmental variability.

Background: The regression equations of Slaughter and Dezenberg, which are based on mixed ethnic samples, are currently recommended for predicting body fat from skinfold-thickness measures in prepubescent children of African ancestry. These equations contain methodologic problems that could make them inappropriate for African children., Objective: The objective was to apply the Slaughter and Dezenberg equations to predict body fat in African prepubertal children and to compare the results with body fat measured by dual-energy X-ray absorptiometry (DXA). If significantly different outcomes were observed, then the objective was to develop new prediction equations and validate them on African children., Design: The Slaughter and Dezenberg equations were applied to a cross-sectional sample of 214 prepubescent (Tanner stage 1) African children (118 boys). Body fat was determined by DXA, and subcutaneous fat at triceps, biceps, subscapular, suprailiac, thigh, and calf sites was measured with use of Holtain calipers. A randomly selected sample of 134 participants (78 boys) was used to generate new prediction equations that were validated on the remaining 80 participants (40 boys)., Results: The Slaughter and Dezenberg equations significantly underestimated (P < 0.001) body fat compared with DXA in both boys and girls. The best combination of skinfold thicknesses to predict body fat in African prepubertal boys, controlling for chronologic age, was triceps, biceps, subscapular, suprailiac, and thigh (SEE = 2.87), and for girls it was biceps, subscapular, suprailiac, thigh, and calf (SEE = 3.51)., Conclusion: The Slaughter and Dezenberg equations are unsuitable for predicting body fat in 9-y-old African prepubertal children. New equations that are based on skinfold-thickness combinations from African children provide more accurate estimates.