Browsing by Author "Chandrasekara, C.M.K.N.K"

Now showing 1 - 2 of 2

Habitat vise fish species richness in Negombo Lagoon
(Department of Geography, University of Kelaniya, Sri Lanka., 2020) Jayathilake, P.P.G; Chandrasekara, C.M.K.N.K
Lagoon environments are very rich ecosystems having greater species diversity in different types of habitats. The increase of anthropogenic activities in and surrounding areas exerted different types of threats to both biotic and abiotic factors in lagoonal environments. Fish species are one of the most impacted biotic components in these ecosystems. Negombo lagoon is located in an area where the anthropogenic activities are high. Thus the influence of human activities in the area is rapidly increasing and fish species receive great threats. Therefore, an attempt was made to study the richness and diversity of the fish species in the Negombo lagoon. A field survey was performed to collect primary data based on habitat heterogeneity. A total of twenty-three (23) samples were strategically selected; eleven (11) from natural habitats, eight (08) from artificial habitats and (04) from semi-natural habitats. Cast net with the mesh size of 1.25 inches was used to catch the fish for counting and observations were carried out three consecutive times in each sample. Margalef richness index and Shannon-Wiener diversity index were used to calculate the richness and diversity of fish species. SPSS and Arc GIS soft wares were interactively used for data analysis. A total of 16 fish species were enumerated belonging to 7 orders, 15 families and 16 genera. According to the findings, the highest species richness was found in semi-natural habitats, with 1.6423 Margalef richness index. While the second highest species richness was found in natural habitats with the value of 1.6029 Margalef index. The lowest richness value was reported in artificial habitats (1.5984). The highest diversity was recorded in semi-natural habitats with 1.2688 Shannon-Wiener index. While 1.0148 and 0.7511 diversity indexes were found in natural and artificial habitats respectively. The highest richness and diversity could be identified to inform the Semi-natural habitats.
Spatial distribution of Dragonfly Species of Henarathgoda Botanical Garden in Gampaha District
(Department of Geography, University of Kelaniya, Sri Lanka., 2020) Jayasekara, K.H.M; Chandrasekara, C.M.K.N.K
Dragonflies are common insects and are interesting species to study. The dragonflies’ populations are under threat due to increasing trends of anthropogenic activities. The consequence of deforestation, wetland reclamation, water pollution, urbanization and climate changes like global warming, rainfall patterns changes are highly impacted on the survival and the diversity of the dragonfly population. Therefore investigation of dragonfly species and their distribution patterns is important. This study was focused on identifying the different dragonfly species and the differences in their distribution in the Gampaha Henarathgoda Botanical Garden. Samples were located to represent the land use heterogeneity of the garden. The field survey was carried out to identify the dragonfly species using 23 samples. The observations were carried out during the southwest monsoon period in 2019. Observations were conducted during eight consecutive days for each sample. A total of 16 species of dragonflies and damselflies were identified from the area. Among them 14 from the Anisoptera suborder and 2 from the Zygoptera suborder. All the dragonflies have belonged to 3 families namely Libellulidae, Gomphidae and Coenagrionidae. The most common species are Brachythemis contaminate, Trithemis aurora, Neurothemis tullia tullia, and the least common species are Rhodothemis rufa, Brachydiplax sobina, Ictinogomphus rapax. Spatially the highest diversity of dragonfly species was identified in water areas and open lands. According to the IUCN categorization dragonflies in the botanical garden can be categorized into three groups namely Vulnerable, Near threatened, Least concern. Among them 2 species were belong to vulnerable, 3 species belong to near threatened and 11 species belong to least concern groups. The resent alterations of habitat in the garden and the surrounding area harms the population of dragonflies.