Browsing by Author "Barekye, A."

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    Comparison of damage levels caused by Radopholus similis and Helicotylenchus multicinctus on bananas in Uganda
    (Annals of Applied Biology, 2000) Barekye, A.; Kashaija, N.; Tushemereirwe, W. K.; Adipala, E.
    Field surveys were done in 1997 and 1998 in Masaka district, Uganda, an area which is experiencing a decline in banana production, to assess level of damage caused by nematodes Radopholus similis and Helicotylenchus multicinctus at farm level. Ten farms within a radius of 2 km were selected and nematode damage assessed. The major nematodes encountered were Pratylenchus goodeyi, R. similis and H. multicinctus. P. goodeyi and H. multicinctus were more abundant than R. similis but R. similis had a stronger and significant correlation with root damage. A subsequent pot trial examined pathogenicities of R. similis and H. multicinctus in pure and mixed cultures on tissue cultured-banana plantlets. R. similis alone and in mixed population reduced root fresh weight significantly, and the percentage of root necrosis ranged between 22.8-41.6% and 18.3-45.5% for March 1998 and March 1999 trials, respectively. The difference in damage caused by R. similis alone and in mixed population was not statistically significant, and was higher than the damage caused by H. multicinctus alone. There were no significant differences in pathogenicity among the R. similis isolates from different parts of Uganda.
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    Growth performance of Monosex Nile Tilapia (Oreochromis niloticus) juveniles at different stocking densities in cages at Lake Bunyonyi in South Western Highland Agro-Ecological Zones (SWHAEZs)
    (International Journal of Fishery and Aquatic Studies, 2016) Kwikiriza, Gerald; Barekye, A.; Muhereze, R.; Makuma, K. A.; Tibihika, P. D.
    Stocking density is among the critical factors affecting fish growth. Although cage culture is gravely being promoted by the government, information regarding the impact of stocking density on fish growth performance of juveniles in cages in Uganda is limited. This study examined the growth performance of Monosex Nile tilapia (Oreochromis niloticus) juveniles at various stocking densities in cages. The fish of mean wet weight and total length of 1.1±0.1g and 1.3±0.1cm respectively were transferred from nursing ponds in aerated containers to experimental cages at three stocking densities (1000, 1250 and 1500 juveniles/m3). The fish were fed on 45% crude protein formulated diet and total length and wet weight were determined weekly for eight weeks. During each sampling event, water quality parameters (temperature, dissolved oxygen and pH) were measured at the surface and 1.5-2.0 meter depth, before, within and after cages to assess the effect of cages on the water quality in and around the farming area. Results indicate that juveniles stocked at 1000/m3 were significantly heavier and larger than those in higher stocking densities which, in turn were not different from each other. Better performance of fish at lower stocking density could be attributed to availability of space which reduces crowd-related stress, less competition for food and less loss of energy due to the antagonistic behavioral interactions, among others. Likewise, the survival rate was higher (74.0%) at 1000/m3 stocking density than 69.8% at 1250/m3 and 63.1% at 1500/m3 because of reduced mortalities at lower densities. Further, the cage system appeared not to affect water quality parameters measured probably because of low production level and the high circulating nature of water around the farming area. The study demonstrates that increasing stocking density of Nile tilapia juveniles in cages reduces growth and survival rate, hence, growth and survival of O. niloticus juveniles in cages are density-dependent. Thus, culture of Monosex tilapia juveniles at a density of 1000 fish/m3 cages can be considered ideal for augmented production of the fish under South Western Highland Agro-Ecological Zone’s context. However further studies at increased feeding rates are recommended for improved survival and growth rates and thinning of juveniles to avoid wastage of resources.