Browsing by Author "Jayamanne, S.C."

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Assemblages of macro-invertebrates in the Negombo estuarine ecosystem in relation to the locations of drainage outlets
(University of Kelaniya, 2006) Dahanayaka, D.D.G.L.; Jayamanne, S.C.; Wijeyaratne, M.J.S.
Benthic Invertebrates of a Tropical Estuary in the Western Coast of Sri Lanka
(2008) Dahanayaka, D.D.G.L.; Jayamanne, S.C.; Wijeyaratne, M.J.S.
Growth and survival of post-larvae of giant freshwater prawn (Macrobrachiumrosenbergii) reared using feeds formulated with different sources of protein.
(Sri Lanka Association for Fisheries and Aquatic Resources, 2013) Amaraweera, K.W.R.R.; Wijeyaratne, M.J.S.; Jayamanne, S.C.
Semi-intensive aquaculture of giant freshwater prawn, Macrobrachium rosenbergii (de Man) in Sri Lanka is limited mainly due to unavailabilty of suitable commercial feeds. At present, the widely used commecial feed is poultry feed starter-I, which is of low nutritive value. Present study was therefore carried out to develop a suitable feed using currently unutilized material as the protein source namely, cattle intestines disacrded from slaughter houses, mussel meat discarded after removing shells for lime and poultry industries, and trash fish discarded at landing sites. Post-larvae of M. rosenbergii having an initial weight of 44-78 mg were stocked in glass tanks measuring 60 cm x 30 cm x 30 cm at a stocking density of 50 individuals per tank and fed with formulated experimental feeds and the poultry feed starter-I as the control diet. Feeding experiments were carried out in triplicate in two culture cycles of 90 days each. Specific growth rates of post-larvae when fed with experimental feeds formulated with mussel, trash fish and cattle intestines as the protein source were 2.08, 2.07 and 2.03 in the first culture cycle and 2.25, 2.27 and 2.33 in the second culture cycle respectively. These were significantly higher than those observed when fed with the control diet which were 1.36 and 1.39 in the first and second culture cycles respectively (p < 0.05). Higher specific growth rates resulted in significantly higher weight gains in post-larvae fed with experimental feeds (458-898 mg) than in those fed with the control diet (217-318 mg) (p<0.05). Survival rates of post-larvae fed with experimental feeds (42-52%) were significantly higher than those of the post-larvae fed with the control diet (16-24%) whereas food conversion ratios of the former (2.47-3.22) were significantly lower than those of the latter (4.90-5.02) (p < 0.05). Present study indicates that lower amounts of feeds formulated using mussel meat, trash fish or cattle intestines as the protein source yield better growth and survival rates of M. rosenbergii post-larvae than the currently used poultry feed starter-I. Since discarded material are used as the protein source, the cost of feed will also be low resulting in high profits.
Macrobenthic Community Structure in Relation to Land Based Pollution - Case Study in a Tropical Estuary in the West Coast of Sri Lanka
(Ibaraki University, Hitachi, Japan, 2009) Wijeyaratne, M.J.S.; Dahanayaka, D.D.G.L.; Jayamanne, S.C.
Macrozoobenthic community structure in the channel segment, Negombo estuary, Western coast of Sri Lanka
(National Aquatic Resources Research and Development Agency, 2006) Dahanayaka, D.D.G.L.; Jayamanne, S.C.
Ctrannesl r:gmenot f the Negomboe stuary (7o6'- 7ol2'N, 79o49'- 79o53'E) is very importantf or the continuation of estuarine functrons through exchange of water between sea and the estuary, but are subjected to changes due to vario'rs anthropogenic activities such as planting mangroves, boat and fishing gear operations and discharge of industrial effluents. A survey was carried out in August 2005 to study the community structure of the macrozoobenthic coinmunity in the channel segment in relationt o the environmentalf actorsa nd antlrropogenica ctivities.E leven stations,a ccuratelyr ecorded using a hadd held GPS were sampledu sing a Petersong rab and macrobenthosw ere separatedb y wet sieving ancl identified up to the lowest possible level. At each sampling site, the depth and salinity were measured and the presence of sea grasses and mangroves was recorded. The anthropogenic activities that are carried out at each sampling site such as disposal of sewage and fishing were also noted. I'he diversity of macrobenthos was determined using Shannon-Wiener and Pielou's indices respectiveiy.T he similarities amongt he macrobenthicc ommunitiesa t different sites were determined using Bray-Curtis similaritv coefficient, ordinations of Non-parametric Multidimensional Scaling (MDS) and the BIO-ENV function was used to relate the multivariate community structure to environtnentavl ariablesa nd to determinet he most responsiblev ariablesf or the inter-sitev ariability of the benthic community using PRIMER-5 software package (Version 5.2.2). Thirty-two species of invertebratecso nsistingo f 3 specieso f polychaetesl,4 specieso f gastropods,'7s pecieso f bivalves and 8 specieso f crustaceansw ere recordedd uring the presents tudy.N eritids andH ydrobiirls were the mosi abrndant gastropods whiie Venerids wbre the most abundant bivalves. Salinity of water changed from 17 to 30g/kg and the water depth changedifrom 0.3 to 2.5 m. Highest diversity (2.031) was recorded in association of sea grasses and lowe$t (0) in highly pblluted site near Dutch canal. As indicated by Bray-Curtis similarity index and MDS ordination, two sample sites located at the mouth of the estuarya nd upper left region of Munnakkate clearly separatedfr om the other sites which rnay be explainedb y the presenceo f trvo specieso f biValvesi n theses ites. Resultso f the Spearmanra nk correlationc oefficients for permutationso f envirohmentalv ariableso f the BIO-ENV function indicate that the combination of abundanceo f sea grassesa nd mangr.ovesm ostly affect the abundanc"a :id diverslry, .rlm acrobenthosi n the channels egmento f the Negombo estuary
Polychaete Diversity in a tropical Estuarine Ecosystem
(Sri Lanka Foundation Institute, 2007) Dahanayaka, D.D.G.L.; Jayamanne, S.C.; Wijeyaratne, M.J.S.