Species identification, distribution and abundance of Gerreidae (Teleostei) Bleeker,1859 in the estuaries of Natal

Comparison of published meristic and taxonomic data with measurements taken from specimens collected from Natal estuaries have provided information for an identification key to the Gerres of southern Africa. Body markings were different on each species of fry (< 40 mm S.L.) as well as immatures and adults (> 40 mm S.L.). A comparison of otoliths from the different species showed that they can be used to Identify specimens from a standard length of 20 mm. Turbidity may be a factor limiting the distribution of the genus in estuaries. The known distribution of Gerres species in the estuaries of southern Africa is given. The species of Gerres which is dominant in a particular locality depends on the salinity

Inter-basin water transfer effects on the invertebrates of the Mvuzane River: A test of the SASS rapid biomonitoring protocol to assess the impact of flow modification

Effects of the transfer of water from the Thukela to the Mvuzane River were investigated using the SASS rapid bioassessment technique and more quantitative methods of guild composition and community analyses. Although the transfer was relatively small (< 1 m3/s) it completely dominated natural flows in the recipient system. SASS monitoring was found to be useful as a rapid, field-based assessment of water quality and can be used to act as a ‘red flag’ to problems in the future. However, it was not sensitive to changes in the community structure at different sites and was inefficient as a tool to investigate the wider ecological impacts of the transfer scheme, most notably those associated with flow modification. Changes in the invertebrate fauna were most easily explained in terms of the effect of increased flow velocities and volumes on taxa that were classified as ‘swimmers’ and ‘skaters’. Impacts via disruption to trophic pathways cannot be discounted and will most certainly occur with prolonged water transfer

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Diet of Gerres fry in the Kosi system

No Abstrac

A preliminary investigation of the effects of an Inter Basin Transfer on the ichthyofauna of a small river in northern KwaZulu-Natal, South Africa

A study was carried out to provide baseline data so that future impacts of an Inter Basin Transfer on the fish fauna of the Mvuzana River could be assessed. Seven species of fish were recorded, and all were present under natural and regulated flow conditions. Although there were no significant differences in community structure between natural and regulated flow conditions, species distribution was more and the CPUE values lower under regulated conditions downstream from the transfer point.Key words: freshwater, Mvuzana River, impacts, fish

Article Mouthpart structure and function and the feeding mechanisms of Gerres (Teleostei)

Members of the genus Gerres feed almost exclusively on benthic invertebrates and have evolved efficient protrusible jaw mechanisms and modes of feeding. The methods employed in prey capture and feeding by five species that occur in the estuaries of Natal were studied using slow-motion cine photography and results were supplemented by field observations. All species use visual cues to detect and capture prey on or just below the surface of the substrate.The protrusible jaw mechanism is the most important feature in prey capture. Bones and muscles involved in jaw movement were studied by dissecting preserved specimens and cleaning jaws and skulls of muscle. The whole mechanism of protrusion of the mouthparts was found to be controlled by two sets of muscles acting on a modified maxilla which together with the cross-palatine ligament forms a groove along which the ascending process of the maxilla can slide when the mouthparts are protruded. The setting up of a suction pressure within the mouth further aids the uptake of items from the substrate. However, whether or not suction pressure is applied depends on the prey type

Salinity ranges of some southern African fish species occurring in estuaries

The recorded salinity ranges of 96 fish species occurring in southern African estuaries are documented. Factors influencing the tolerance of fishes to low and high salinity regimes are discussed, with most species tolerant of low rather than high salinity conditions. This is important since most systems are subject to periodic freshwater flooding, especially during summer. The penetration of freshwater teleosts and elasmobranchs into estuaries is examined and the occurrence of marine fishes in rivers documented. Mortalities arising from salinity extremes in southern African estuaries are discussed, with temperature a key factor initiating such fish kills. Only eight fish species have been recorded spawning in estuaries although the fry of many species are attracted to estuarine waters. It is concluded that a small percentage of southern African fishes have succeeded in utilizing estuaries and this may be attributed to the paucity of strong osmoregulators