Freshwater crayfish invasions in South Africa: past,present and potential future

Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion. As is the case elsewhere, South Africans have shown a keen interest in both farming and keeping freshwater crayfish as pets, which has resulted in Cherax cainii, Cherax destructor, Cherax quadricarinatus and Procambarus clarkii being introduced to the country. There is evidence of successful establishment in the wild for C. quadricarinatus and P. clarkii in different parts of the country. Species distribution models suggest that the eastern part of the country and parts of the Eastern and Western Cape are at higher risk of invasion. At present, illegal translocations represent the most likely pathway of crayfish spread in South Africa. A continued risk of invasion by freshwater crayfish species in South Africa is highlighted, which reinforces the need for more research, as well as for strong mitigation measures, such as stronger policing of existing regulations, management or eradication where feasible and public education.     

Metal Sources for Freshwater Invertebrates: Pertinence for Risk Assessment

Ecological risk assessments are likely to be more effective if they are built upon knowledge of from where and in what manner animals take up contaminants. We discuss the relative importance of various metal sources for aquatic invertebrates. First, we address the question do sediment-dwelling animals take up their metals from the overlying water compartment or the sediment compartment or both (both compartments include water and particles). We find that the overlying water column is more important as a metal source for insects, whereas the sediment compartment is more important for oligochaete worms. We explain this tendency by the behaviors of the animals involved. Second, we ask the question do animals take up their metals from food or water within a given compartment. Through case studies on three widespread freshwater invertebrates, we conclude that for some predatory insects food is their major source of several metals, whereas for the crustacean Hyalella both food and water appear to be important depending on the metal involved and the experimental protocol used to study the question. We conclude that ignoring food as a metal source could severely underestimate metal exposures for some animals. We suggest that integrating these complexities into laboratory tests and risk assessment protocols will improve their meaningfulness and thus their ability to protect aquatic ecosystems.     

Guides to the Freshwater Invertebrates of Southern Africa. Volume 9: Diptera

February 2003, Water Research Commission, Pretoria, South Africa. Ring-bound, soft cover, 200 pages. WRC Report No. TT 201/02; ISBN 978-1-86845-900-1; price R100.00 (South Africa), US$50.00 (international). Obtainable from the Water Research Commission, Private Bag X03, Gezina, Pretoria 0031, South Africa, or orders@wrc.org.za     

Freshwater fishes of northern South America: a need for field guides

The efficient collection of fishes from structurally complex environments (e.g., coral reefs, kelp forests) is difficult because conventional collecting methods generally cannot be used and many of the fishes are mobile and active. We describe the design, operation, and application of a diver-propelled net for efficiently collecting many species of benthic fish that reside on coral reefs and on kelp-forested rocky reefs. The overall size of the net and mesh size of the netting can be adjusted according to the size and behavior of targeted species to minimize drag and damage to specimens. Altering these dimensions combined with proper use of the net can result in a high rate of capture success. This revised version was published online in July 2006 with corrections to the Cover Date.     

Duinefontein 2: an Acheulean site in the Western Cape Province of South Africa.

Excavations at Duinefontein (DFT) 2 near Cape Town, South Africa have recovered numerous stone artefacts and animal bones on an ancient surface sealed within iron-stained eolian sands. U-series analysis of an overlying calcrete places the sands before 150 ka ago, while the large mammal taxa imply an age between 400 and 200 ka ago. The artefacts include a classic Acheulean handaxe and probable biface shaping flakes that support this age estimate. The principal mammalian species are long-horned buffalo, black wildebeest, greater kudu, Cape zebra, and grysbok/steenbok, which imply a grass-and-bush mosaic instead of the historic small-leafed shrubland.Hippopotamus and reedbuck indicate that water stood nearby, probably in dune swales. The large mammal bones are mostly vertebrae and other axial elements, often in near-anatomical order. Both proximal and distal appendicular elements are rare. Bones with carnivore damage are common, but ones with stone tool marks are scarce. The sum suggests a water-edge attritional death site where people played a minimal role and carcasses were disarticulated mainly by carnivore feeding and by trampling. Stone tool marks tend to be equally rare at other Acheulean attritional death sites, and the implication may be that Acheulean people rarely obtained large mammals, whether by hunting or scavenging. Human scavengers at DFT2 would not have encountered a disproportionate number of distal (versus proximal) limb elements, and it follows that the tendency for distal elements to dominate many archeological assemblages need not reflect scavenging versus hunting. Even if DFT2 was not itself a locus of intense human activity, it provides a useful baseline for evaluating bone damage, skeletal part representation, and other variables at sites where people were deeply involved.     

Quantitative Risk Assessment for African Horse Sickness in Live Horses Exported from South Africa

African horse sickness (AHS) is a severe, often fatal, arbovirus infection of horses, transmitted by Culicoides spp. midges. AHS occurs in most of sub-Saharan Africa and is a significant impediment to export of live horses from infected countries, such as South Africa. A stochastic risk model was developed to estimate the probability of exporting an undetected AHS-infected horse through a vector protected pre-export quarantine facility, in accordance with OIE recommendations for trade from an infected country. The model also allows for additional risk management measures, including multiple PCR tests prior to and during pre-export quarantine and optionally during post-arrival quarantine, as well as for comparison of risk associated with exports from a demonstrated low-risk area for AHS and an area where AHS is endemic. If 1 million horses were exported from the low-risk area with no post-arrival quarantine we estimate the median number of infected horses to be 5.4 (95% prediction interval 0.5 to 41). This equates to an annual probability of 0.0016 (95% PI: 0.00015 to 0.012) assuming 300 horses exported per year. An additional PCR test while in vector-protected post-arrival quarantine reduced these probabilities by approximately 12-fold. Probabilities for horses exported from an area where AHS is endemic were approximately 15 to 17 times higher than for horses exported from the low-risk area under comparable scenarios. The probability of undetected AHS infection in horses exported from an infected country can be minimised by appropriate risk management measures. The final choice of risk management measures depends on the level of risk acceptable to the importing country.     

Guides to the Freshwater Invertebrates of Southern Africa. Volume 6: Arachnida and Mollusca

June 2002, Water Research Commission, Pretoria, South Africa

Ring-bound, soft cover, 141 pages

WRC Report No. TT 182/02; ISBN 978–1-86845875–2; price R100.00 (South Africa), US$50.00 (International)

Obtainable from the Water Research Commission, Private Bag X03, Gezina, Pretoria 0031, South Africa. or orders@wrc.org.za     

The development of a Biotic Pollution Index for the River Nile in Egypt

This article describes the development of a Nile Biotic Pollution Index (NBPI) for the River Nile in Egypt. Chemical data were collected from 30 locations along the Nile from Aswan to Cairo and 21 sites within the river delta, incorporating a range of conditions from unpolluted to grossly polluted. Seven chemical variables were used to calculate a Nile Chemical Pollution Index (NCPI) for each site. Biological data were collected primarily using Artificial Substrate Samplers (ASS). The UK developed, Biological Monitoring Working Party (BMWP) biotic index and the BMWP-ASPT were applied to the data. A Nile Biotic Pollution Index (NBPI) and the NBPI-ASPT were obtained by incorporating more of the Nile taxa. There were highly significant regressions (P < 0.001) for both the UK and the Nile Pollution Index scores with the NCPI for the whole river. The modification of the UK indices improved the Nile Indices increasing the number of taxa recorded from 29 to 43 and the total number of recorded taxon occurrences from 377 to 490. The Nile Indices provided better discrimination at both ends of the pollution spectrum. The NBPI-ASPT was best for the river as a whole, and particularly for the river from Aswan to Cairo. The NBPI was much better in the delta than from Aswan to Cairo. These differences in performance were attributed to the fact that the NBPI-ASPT excludes information on taxon diversity. In clean waters there was a wide range of NBPI score suggesting that the biodiversity of taxa is dependent on other aspects of habitat quality. Conversely in the polluted delta the high score of an individual taxon is critical for the NBPI-ASPT as it may have a distorting effect. As the NBPI-ASPT was the most consistent biotic index it is recommended as the regular biological assessment and regulatory tool for Egypt to meet the requirements of the Convention for Biodiversity. Handling editor: R. Norris     

Assessment of veld conditions with multivariate techniques in mixed bushveld,South Africa

The species composition of the herbaceous layer was surveyed in eight plant communities with a small-quadrat method. Ordination techniques were applied to these data to identify relative homogenous grazing areas, assess the veld condition of each unit and to identify indicator species, based on a grazing gradient. Five relative homogenous grazing areas were identified and should be treated as such for management purposes. The veld in the Nylsvlei Nature Reserve was generally in a good condition due to the low stocking densities of game (≈0.29 animals ha^?1) which have been maintained for many years. Nine indicator species, i.e. Cynodon dactylon, Digitaria eriantha, Ischaemum afrum, Leersia hexandra, Oryza longistaminata, Setaria sphacelata, Sporobolus ioclados, Sporobolus pyramidalis, and forbs, were identified which may be used for future monitoring of veld condition in the different vegetation units.     

Species-specific impact of introduced largemouth bass Micropterus salmoides in the Groot Marico Freshwater Ecosystem Priority Area,South Africa

Largemouth bass Micropterus salmoides are among the world's 100 worst invaders and negatively affect aquatic biodiversity in many regions worldwide. In South Africa there is a paucity of empirical studies describing their impacts. The impact of M. salmoides on the fish community in the Groot Marico River catchment, an otherwise near-pristine river ecosystem and a freshwater ecosystem priority area, was assessed from surveys conducted in 2012. Fish presence and abundance were enumerated using multiple survey techniques, and their association with key habitat variables and the presence or absence of M. salmoides were assessed. A total of 14 native fish species were recorded, besides introduced M. salmoides, which occupied the majority of the mainstem and several tributaries downstream of barriers to upstream movement. Canonical correspondence analysis showed that only one native species, the Marico barb Barbus motebensis, had a negative spatial association with M. salmoides. Assessment of relative distributions showed this species to be excluded from M. salmoides-invaded river reaches, whereas the other native species were not visibly affected by the invader. This species-specificity of the impact of M. salmoides indicates that their impacts in South African streams may be dependent on predator-naiveté of prey.     

The Planktonic Index of Biotic Integrity (P-IBI): An approach for assessing lake ecosystem health

Using historical (1970) and more recent (1996) Lake Erie plankton and trophic status data, we developed a Planktonic Index of Biotic Integrity (P-IBI) to measure changes in lake ecosystem health. We used discriminant analysis to determine phytoplankton and zooplankton community characteristics (metrics) that distinguished among levels of impairment. Traditional measures of lake trophic status classes (i.e., oligotrophic, mesotrophic, eutrophic), such as chlorophyll a and total phosphorus concentrations, were used to classify sites on a gradient of impairment. We then judged the ability of plankton metrics to distinguish among trophic status classes. Because of the temporal variability found in plankton communities, we conducted analyses on a monthly basis (May–September). For June, July and August we found five unique metrics that could distinguish among trophic status classes. The P-IBI showed an increase in water quality in Lake Erie between 1970 (<3 = eutrophic) and the mid-1990s (1996 and 1997) (3–4 = mesotrophic) (which reflected mean (±standard error) total phosphorus concentrations (μg/L) 1970 > 1996; western basin (41.53 ± 2.68 > 29.75 ± 1.39), eastern basin (14.84 ± 0.82 > 7.74 ± 0.28) and mean (±standard error) chlorophyll a concentrations (μg/L) uncorrected for pheophytin 1970 > 1996; western basin (12.58 ± 1.82 > 5.40 ± 0.22), central basin (5.90 ± 0.36 > 3.17 ± 0.54), and eastern basin (5.17 ± 0.38 > 1.67 ± 0.18)), with declining water quality in the late 1990s (1998 and 1999) (3) and 2002 (<3). We recommend that the techniques used in creating the P-IBI be investigated for determining ecosystem health of other lakes.     

Assessment of Welfare Issues During Traditional Slaughter of Goats in Pretoria,South Africa

Goats are traditionally slaughtered to celebrate marriages and births, venerate ancestors, address personal problems, or perform a ritual during funerals. The objective of this study was to assess nonhuman animal welfare issues associated with the traditional slaughter of goats in and around Pretoria, South Africa. Participatory research methods were used to interview 105 respondents. Four of those interviewed were visited to observe the slaughter process. The most common method of transport was a vehicle (47%), followed by transport on foot (30%). The distance traveled (68%) was usually less than 10 km, and in all cases, it was less than 50 km. The most common (57%) method of restraining goats during transport was tying all 4 legs together. During slaughter, assistants held the head and legs of the goat (55%). Prior to slaughter, the majority of goats were tied under a tree (66%). In total, 97% of the goats were slaughtered within 24 hr, and no stunning was performed. In this study, animal welfare problems were widespread. Research should be undertaken to find practical ways to address animal welfare issues during traditional slaughter.     

The Freshwater Animal Diversity Assessment: an overview of the results

The geographic genetic structure of two common encrusting sponges, Hymeniacidon sinapium and Hymeniacidon flavia (family Halichondriidae), was investigated using two DNA markers, Internal Transcribed Spacers (ITS) of nuclear ribosomal DNA and NADH dehydrogenase subunit 5 (nad5) of mitochondrial DNA. In the ITS analyses, multiple sequence types were identified within each species. Geographic distribution patterns of sequence types showed higher diversity in the western than eastern areas in both species. However, intraspecific genetic diversity of the two species in Japan differed markedly. Hymeniacidon flavia had far more diverse sequence types, and several genetic differentiations between localities were detected. In contrast, H. sinapium had only four sequence types in Japan, and two Atlantic Hymeniacidon species had sequence types similar to this species. In comparison to ITS, nad5 showed very low genetic diversity in both species, with two haplotypes identified in each species. In H. flavia, frequency of haplotype changed gradually from north to south. In H. sinapium, one haplotype was predominant in most regions, and another haplotype was minor and distributed only in the Korean and Tsushima populations. Based on the unique distribution patterns of sequence types around Shikoku and Kyushu, geographical history and ocean currents were assumed to affect the generation of genetic structure. The geographic genetic structure of H. flavia suggests low dispersal ability of pelagic larvae, whereas higher larval dispersal ability and a far broader distribution range are suggested in H. sinapium. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: C. Sturmbauer     

The Freshwater Animal Diversity Assessment: an overview of the results

We present a summary of the results included in the different treatments in this volume. The diversity and distribution of vertebrates, insects, crustaceans, molluscs and a suite of minor phyla is compared and commented upon. Whereas the available data on vertebrates and some emblematic invertebrate groups such as Odonata (dragonflies and damselflies) allow for a credible assessment, data are deficient for many other groups. This is owing to knowledge gaps, both in geographical coverage of available data and/or lack of taxonomic information. These gaps need to be addressed urgently, either by liberating date from inaccessible repositories or by fostering taxonomic research. A similar effort is required to compile environmental and ecological information in order to enable cross-linking and analysis of these complementary data sets. Only in this way will it be possible to analyse information on freshwater biodiversity for sustainable management and conservation of the world’s freshwater resources. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

A host of hypercholesterolaemic homozygotes in South Africa.

From 1972 to 1979 34 patients with homozygous familial hypercholesterolaemia were seen in one clinic in Johannesburg. All were Afrikaners and most lived in Transvaal Province. Their epidemiological, genetic, clinical, and biochemical characteristics were studied. The course of the disease varied considerably among the 34 patients, with no fewer than six surviving into their fourth or fifth decades. In some patients arterial atheroma was severe while cutaneotendinous xanthomas were slight and vice versa. Coronary heart disease was common but peripheral and cerebral arterial disease was rare. Another prominent finding was high concentrations of low-density lipoprotein cholesterol coupled with low high-density lipoprotein cholesterol values. The prevalences of homozygotes and heterozygotes with familial hypercholesterolaemia in Transvaal Afrikaners, calculated from this group of patients, were 1 in 30,000 and 1 in 100 respectively. These figures are the highest ever reported and may help to explain why South African whites have the highest death rate from coronary heart disease in the Western world.