THE USE OF HOLDING CAGES FOR THE SPAWNING OF CLARIAS-GARIEPINUS

Use is made of plastic covered wire mesh cages to minimise the stress and physical damage caused by the inherent aggression of Clarias gariepinus during the spawning phase. The cages enable a single person to perform the entire hormonal injecting programme with a minimum of stress in a relatively short period of time

THE INFLUENCE OF DIFFERENT DIETARY LIPIDS ON THE GROWTH AND BODY-COMPOSITION OF THE AFRICAN SHARPTOOTH CATFISH, CLARIAS-GARIEPINUS (BURCHELL)

The influence of various lipid sources on the muscle fatty acid composition of juvenile African sharptooth catfish Clarias gariepinus, was tested Juveniles were fed an artificial diet,for 60 days, containing no lipid (Al control), or the following lipids at 10% of the diet, sunflower oil (B, a high level of C18:1 omega 9 and C18:2 omega 6), cod liver oil (C, a high level of 20 and 22 C omega 3 fatty acids) and tallow (D, predominantly SFA and MUFA). The best growth was achieved by fish fed the sunflower diet. Muscle total lipid composition was strongly influenced by diet and contained the following SFA, MUFA and PUFA percentages, and a omega 3/omega 6 ratio of A, 36.33; 45.13; 15.70% & 0.52; B, 30.78; 34.54; 33.96% & 0.11; C, 33.51; 38.75; 24.59% & 1.87; D, 38.87; 46.03; 13.06% & 0.44, respectively

COMPARISON OF HUMIDITY CHAMBER, MARISOURCE HATCHING-TRAY AND ZUGER GLASS FUNNEL INCUBATION SYSTEMS FOR BREEDING OF CYPRINUS-CARPIO (L) AND CLARIAS-GARIEPINUS (BURCHELL)

Humidity chamber, MariSource hatching-tray and ''Zuger'' glass funnel incubation systems were compared for hatching successes of both Cyprinus carpio and Clarias gariepinus fertilised eggs. The humidity chamber incubation system proved superior for C. carpio, whilst the MariSource hatching-tray system was better for C gariepinus. Fungal infections greatly influenced hatching results

Making sense of residues on flaked stone artefacts: learning from blind tests

Residue analysis has become a frequently applied method for identifying prehistoric stone tool use. Residues adhering to the stone tool with varying frequencies are interpreted as being the result of an intentional contact with the worked material during use. Yet, other processes during the life cycle of a stone tool or after deposition may leave residues and these residues may potentially lead to misinterpretations. We present a blind test that was designed to examine this issue. Results confirm that production, retouch, prehension, hafting, various incidental contacts during use and deposition may lead to residue depositions that significantly affect the accurateness of identifications of tool-use. All currently applied residue approaches are concerned. We therefore argue for a closer interaction with independent wear studies and a step-wise procedure in which a low magnification of wear traces is used as a first step for selecting potentially used flakes in archaeological contexts. In addition, residue concentrations on a tool's edge should be sufficiently dense before linking them with use