Volume 03 No. 01 January 1991

The Role of Tilapia Species (Family Cichlidae) in the Fishery of Three Upland, Deep Reservoirs of Sri Lanka

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The Role of Tilapia Species (Family Cichlidae) in the Fishery of Three Upland, Deep Reservoirs of Sri Lanka De Silva, K.H.G.M.; De Silva, P.K. The fish catches of three upland reservoirs, namely, Kotmale, Victoria and Randenigala reservoirs, were studied for periods of 8, 18 and 9 months, respectively. Tilapia species formed 60-70 % of the catch of all three Reservoirs. Three species of tilapia, namely, Oreochromis mossambicus, O. niloticus and Tilapia rendalli were present in Victoria and Randenigala reservoirs but the last species was not caught in Kotmale reservoir. The three species formed, respectively, 50.8 %. 49.2 % and 0 % of the tilapia catch of Kotmale reservoir, 71.5% 26.6% and 1.9% of that of Victoria reservoir and 96.2%, 2.6% and 1.2% of that of Randenigala; reservoir. The relative abundance of the three species in the three reservoirs is discussed in relation to that of the three species in other reservoirs in Sri Lanka.

The Declining Pole and Line Fishery in Sri Lanka

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The Declining Pole and Line Fishery in Sri Lanka Amarasiri, C. Pole and line fishing, which is specifically aimed at skipjack tuna has been practised in Sri Lanka for about 70 years. Originally, this method was popular amongst fishermen in the southern coast, and was later expanded to the eastern coast by migrant fishermen from the southern coast. In early 1960's the pole and linecatcn contributed over 40% to the total tuna production in Sri Lanka. However, over the last 2-3 decades, the pole and line fishery has fallen to a relatively low level of significance. in early 1960's, the fishing effort by pole and line was about 21% of the total fishing effort on tunas in the southern coast. It is now reduced to about 7 %. The catch rates also show a decline by about 50%from 1960's to 1980's. The total production of pole and line fishery during early 1960's was 1200-2400 tonnes per annum, equivalent to 60% of the tunaproduction. The present production of 1057MT is equivalent to about 7%of the tuna production in tne region. The decline is due to variousfactors such as limited supply of live bail, introduction ofdrift gillnets, scarcity of surface tuna schools etc.

The Burying Ability of O Group Dover Sole

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The Burying Ability of O Group Dover Sole Jinadasa, J.; Baynes, S.M.; Howell, B.R. The particle size of a substrate determines the ability of 0 group Dover sole Solea solea (L.) to bury for concealment. The larger thefish, however, the larger the particle size in which they are able to bury. When presented with a choice ofa range of particle sizes, 95-120mmfish are more likely to befound in sediment of 1-2mm grain size, than in anything finer. Fish of 18-40mm were never found in sediment of a particle size larger than 0.35 - 0.50mm.

Preliminary Observations on the Anopheline Mosquitoes of Gomadiyagala A Village in the North Western Province of Sri Lanka

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Preliminary Observations on the Anopheline Mosquitoes of Gomadiyagala A Village in the North Western Province of Sri Lanka Wickramasinghe, M.B.; De Silva, B.G.D.N.K.; Perera, O.P.; Ratnayake, W.E. Investigations on anopheline mosquitoes were carried out in Gomadiyagala during January-December 1989, primarily to gather base-line data in relation toa collaborative study between the Entomology Division, Anti-Malaria Campaign and the Department of Zoology, University of Sri Jayewardenepura on the potential for a genetic approach for malaria control in Sri Lanka. Eight anopheline species were recordedfrom adult catches and lavae sampled. An. subpictus An. culicifacies and An. varuna were the most predominant species. The only stream with two tributaries in the study area was the permanent and very productive anopheline breeding habitat. Larval and adult anopheline densities were related to the rainfall received. The larval densities recorded in drought periods were observed to be significantly higher than those recorded in rainy periods (t=4.087, p