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The stomach contents of tigerfish Hydrocynus vittatus, caught in an angling competition on Lake Kariba, were examined to determine the extent to which they feed on the invasive crayfish Cherax quadricarinatus. The stomach contents of 281 tigerfish caught during three tournaments (2013, 2014 and 2015) were examined and grouped into six main categories. The proportion of empty stomachs ranged from 4.6 to 13.9% in males and from 11.9 to 29.1% in females. The main food items according to the frequency of occurrence were fish (Limnothrissa miodon (69.0 ± 13.0%) fish remains (bones and scales; 33.0 ± 22.0%), Cichlidae (26.8 ± 2.10%) and Mormyridae (0.5 ± 0.9%) and invertebrates, such as crayfish (24.9 ± 4.6%) and insects (5.2 ± 2.1%). This tournament has been useful in confirming changes in tigerfish diet following the introduction and establishment of non-native species, such as Limnothrissa miodon and, more recently, the crayfish, C. quadricarinatus. [ABSTRACT FROM AUTHOR]

Two new and one known species of Annulotrema Paperna & Thurston, 1969 are reported from the gills of the tigerfish Hydrocynus vittatus Castelnau, 1861, collected in Lake Kariba, Zimbabwe. The new species, Annulotrema pseudonili n. sp. and A. bracteatum n. sp., are described and distinguished mainly on the basis of features of the male copulatory organ (MCO). Annulotrema pseudonili n. sp. most closely resembles A. nili Paperna, 1973, but differs from it by possessing a more delicate MCO with a thin-walled base without a fibrous distal part. Annulotrema bracteatum n. sp. is most similar to Annulotrema ruahae Paperna, 1973, from which it differs by having an MCO composed of a longer copulatory tube and a leaf-shaped accessory piece enveloping the distal part of the tube. The presence of Annulotrema pikoides Guégan, Lambert & Birgi, 1988 on H. vittatus in Zimbabwe represents a new locality record for this parasite. [ABSTRACT FROM AUTHOR]

A pilot investigation was conducted in 2014 in the Sanyati Basin of Lake Kariba to ascertain whether long-term DDT spraying in the Kariba catchment had a negative effect on fish health. The aim was to assess the health of tigerfish,Hydrocynus vittatus,by means of histological analysis and to analyse water, sediment and tissue samples for bioaccumulated levels of chlorinated pesticides, including DDT. Eighteen tigerfish were collected by seine netting along the north-eastern shoreline of the Sanyati Basin in April 2014 and samples of their gill, liver, kidney, muscle and brain tissue were processed for histology and assessed using light microscopy. No detectable levels of DDT and/or its metabolites were found in the water or sediment samples and only a low concentration ofp,p′-DDE in fish tissues. No major histological alterations were observed in the fish tissues. Consequently, there seems to be no risk of DDT exposure following the consumption of tigerfish from the Sanyati Basin of Lake Kariba. These results were unexpected, given the historical use of DDT within the current study area. It is recommended that these findings be compared with those from other regions of Lake Kariba. [ABSTRACT FROM PUBLISHER]