Browsing by Author "Athula, J.A."

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Cattle and water buffalo densities wading into small village reservoirs of Sri Lanka impact on yields on the culture-based fisheries thereof
(Sri Lanka J. Aquat. Sci. 23(1) (2018): 67-75, 2018) Jayasinghe, A.D.; Athula, J.A.; De Silva, S.S.; Amarasinghe, U.S.
This study investigated whether allochthonous inputs generated by cattle and water buffaloes grazing in the catchment or wading in the water in small village reservoirs of Sri Lanka can make a significant effect on yields from culture-based fisheries of those reservoirs. The analysis is based on limnological data of 37 randomly selected reservoirs. As culture-based fish yield data were available over the 2002 - 2003 period only for 23 reservoirs, fish yield data from seven more reservoirs were gleaned for the present analysis. Cattle and water buffalo densities (BD) in 37 reservoirs where limnological data were available, were found to be significantly correlated to the biological productivity-related parameters such as chlorophyll-a content. Culture-based fish yield in the 30 reservoirs varied from 54.6 to 1800.8 kg ha-1 and BD associated with the reservoirs studied varied from 0.90 number ha-1 to 216.25 numbers ha-1. Fish yield (FY) was significantly correlated with BD the relationship being, FY = 4.758 BD + 242.740 (R2 = 0.345; p<0.001). The importance of taking into consideration factors such as grazing cattle and buffalo density in preparing management strategies for culture-based fisheries in small village reservoirs is discussed.
Culture-based fisheries in non-perennial reservoirs in Sri Lanka: production and relative performance of stocked species
(Fisheries Management and Ecology, 2005) Wijenayake, W.M.H.K.; Jayasinghe, U.A.D.; Amarasinghe, U.S.; Athula, J.A.; Pushpalatha, K.B.C.; de Silva, S.S.
In Sri Lanka, there is a great potential for the development of culture-based fisheries because of the availability of around 12 000 non-perennial reservoirs in the dry zone (<187 cm annual rainfall) of the island. These reservoirs fill during the north-east monsoonal period in October to December and almost completely dry up during August to October. As these non-perennial reservoirs are highly productive, hatchery-reared fish fingerlings can be stocked to develop culture-based fisheries during the water retention period of 7?9 months. The present study was conducted in 32 non-perennial reservoirs in five administrative districts in Sri Lanka. These reservoirs were stocked with fingerlings of Indian (catla Catla catla Hamilton and rohu Labeo rohita Hamilton) and Chinese (bighead carp Aristichthys nobilis Richardson) major carps, common carp Cyprinus carpio L., genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (L.) and post-larvae of giant freshwater prawn, Macrobrachium rosenbergii De Man, at three different species combinations and overall stocking densities (SD) ranging from 218 to 3902 fingerlings ha?1, during the 2002?2003 culture cycle. Of the 32 reservoirs stocked, reliable data on harvest were obtained from 25 reservoirs. Fish yield ranged from 53 to 1801 kg ha?1 and the yields of non-perennial reservoirs in southern region were significantly (P < 0.05) higher than those in the northern region. Naturally-recruited snakehead species contributed the catches in northern reservoirs. Fish yield was curvilinearly related to reservoir area (P < 0.05), and a negative second order relationship was evident between SD and yield (P < 0.05). Chlorophyll-a and fish yield exhibited a positive second order relationship (P < 0.01). Bighead carp yield impacted positively on the total yield (P < 0.05), whereas snakehead yield impact was negative. Bighead carp, common carp and rohu appear suitable for poly-culture in non-perennial reservoirs. GIFT strain O. niloticus had the lowest specific growth rate among stocked species and freshwater prawn had a low return.
Evaluation of the performance of selected exotic and indigenous fish species in culture-based fisheries of village reservois in Sri Lanka
(2010) Athula, J.A.
Strategies for management of culture-based fisheries in seasonal reservoirs of Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Athula, J.A.; Wijenayake, W.M.H.K.; Jayasinghe, U.A.D.
The seasonal reservoirs retain water for 6 to 9 months of the year and completely dry-up yearly or retain very little amount of water for a few months. The extent of seasonal reservoirs estimated to be around 40,000 ha and most of them are located in the dry zone of the country with <200 mm of annual rainfall. These reservoirs are highly productive. Stocking of hatchery-reared fingerlings of Chinese carps, Indian major carps and common carp in these reservoirs resulted in high yields with an average of 449.8 kg ha-1 (range: 53-1,801 kg ha-1). Nearly 60% of the Sri Lankan population mainly depends on fish to obtain the daily requirement of animal protein. According to investigations of the Medical Research Institute, Colombo, minimum fish consumption per day should be at least 60 g, in order to get the daily requirement of protein by fish consumption. As there is about more than 12,000 seasonal tanks scattered as cascade systems throughout the dry zone of the country, which can be utilized for development of culture-based fisheries, they could be used to supply the animal protein requirement of the rural communities. The culture-based fishery activities in seasonal reservoirs depend on both ecological characteristics of the reservoir and the socioeconomic status of village communities. Although the legal empowerment is not yet completed for the culture-based fisheries in seasonal reservoirs, introduction of a set of criteria for the selection of seasonal reservoirs for culture-based fisheries activities on the basis of physical, biological and socioeconomic features and the development of a best practice model for optimization of the yield are important