A taphonomic study of seal remains from archaeological sites on the Western Cape coast

Bibliography: leaves 238-259.A method of interpreting the seal body part representation from archaeological sites is presented and applied to three Holocene archaeological assemblages from the west coast of South Africa. The approach that is developed integrates several different methods that have previously been applied to terrestrial species, but that, with few exceptions, have not be.en employed in the analysis of seal remains. Most of the existing taphonomic indices cannot be applied to seals because of their unique physiology. Appropriate field observations and laboratory measurements are used to construct taphonomic indices that can be widely applied to seal bone assemblages. These include: a hardness index that mediates bone destruction through mechanical attrition, a utility index that mediates differential transport of body elements, and two indices that mediate the impact of carnivore ravaging - the carcass consumption sequence, and the carnivore destructive template. A new approach that caters for the simultaneous application of several taphonomic indices to an assemblage, where previously they have been applied individually or in pairs, is developed. In addition to the taphonomic indices, a method of determining ontogenic age is presented, and the potential limits of seal storage are explored

Trophic ecology and persistence of invasive silver carp Hypophthalmichthys molitrix in an oligotrophic South African impoundment

The alien invasive silver carp Hypophthalmichthys molitrix established a self-sustaining feral population in an oligotrophic impoundment, Flag Boshielo Dam, in South Africa. The ability of this population to persist in a dam with low algal biomass (median annual suspended chlorophyll a = 0.08 µg l−1), and limited access to rivers considered large enough for successful spawning, has implications for their invasive potential in other systems. Stomach content and stable isotope analysis were used to assess the trophic ecology of H. molitrix, which was then compared with indigenous Mozambique tilapia Oreochromis mossambicus, on a seasonal basis during 2011. Hypophthalmichthys molitrix are generalist filter feeders, with a diet consisting primarily of sediment, vegetative detritus, dinoflagellates and diatoms. The dominance of sediments in their stomachs suggests occasional benthic scavenging. However, H. molitrix occupied a higher trophic level (TL = 2.8) than expected, suggesting that this population subsidised their diet with an unidentified dietary constituent, characterised by enriched nitrogen values. Although the stomach contents indicated dietary overlap between H. molitrix and O. mossambicus, stable isotopes revealed fine-scale resource partitioning, despite both species occupying the same trophic level. Nonetheless, the persistence of this feral H. molitrix population in an oligotrophic impoundment highlights their phenotypic plasticity.The Olifants River Forum, the DST-NRF Centre of Invasion Biology, University of Pretoria and the National Research Foundation (NRF).http://www.tandfonline.com/loi/taas202017-12-31hb2016Zoology and Entomolog

The origin and development of the Nyl River floodplain wetland, Limpopo Province, South Africa: trunk–tributary river interactions in a dryland setting

The Nyl River floodplain wetland, one of South Africa\u27s largest floodplain wetlands and a Ramsar site of international conservation importance, is located in an area of long-term and still active valley sediment accumulation. Creation of accommodation space for sedimentation has previously been attributed to tectonic controls, but new investigations reveal that a more likely cause is progradation of coarse-grained tributary fans across the narrow river valley downstream of the main area of floodplain wetland. Obstruction of trunk river flow and sediment transfer by these tributary fans has led to backponding and upstream gradient reduction and to accumulation of valley fills up to 35m thick. Chronological control for the timing and rate of sediment accumulation is limited, but we hypothesise that a semi-arid to arid climate, characterised by asynchronous trunk-tributary activity that results in marked discontinuities in downstream water and sediment transfer, is likely to have been a key control. These interpretations are supported by other studies of dryland rivers globally and the findings add to our growing understanding of the controls on the origin and development of southern African wetlands, particularly by demonstrating how the combination of a particular physiography and a dryland climate can impart some distinctive geomorphological characteristics. Copyright 2011 Copyright Society of South African Geographers