Studies on the fish ponds at Pitipana, Negombo 1: seasonal and diurnal variation of some hydrobiological factors

The present paper is a part of a detailed investigation on the biology of grey mullet, Mugli cephalus L., and the feasibility of its culture in the brackish waters of Sri Lanka. The authors present the results of investigation on the water quality of five experimental ponds at the Pitipana Brackishwater Fisheries Station, Negombo, carried out over a period of one year, December 1976 to November 1977, together with studies on the primary productivity are presented

Fish fauna of a coastal lagoon in Sri Lanka: distribution and seasonal variation

In this paper results of investigations carried out over the period of September 1977 to August 1978 are presented. These data were collected in the course of a detailed investigation into the biology and the eco-physiology of the young grey mullet and the grey mullet fishery of the Negombo Lagoon. In this paper the distribution and seasonal variation of fin fish species within the Negombo Lagoon are presented

Occurrence of toxigenic cyanobacterial blooms in freshwaters of Sri Lanka.

A previous pioneering study of freshwater bodies in Sri Lanka revealed the presence of toxic cyanobacteria in three out of four water bodies tested. It was therefore important to perform a more detailed investigation into the presence of cyanobacteria and their toxins throughout Sri Lanka. The country has a long history of well-planned water management with the agricultural economy and drinking water supply still dependent on thousands of man-made tanks. Seventeen reservoirs from different user categories and different climatic zones were selected to study variations in phytoplankton communities with relation to major nutrients, with particular emphasis on cyanobacteria. The study was carried out during a two-year period and heavy growths or blooms of cyanobacteria observed during the study period were tested for microcystins. The results clearly categorised the 17 reservoirs into four groups parallel to the classification based on the user categories of water bodies. Biomass of total phytoplankton, the abundance of cyanobacteria, the dominance of Microcystis spp. and concentration of nitrate (N) and total phosphorous (P) were the lowest in drinking water bodies and the highest in aesthetic water bodies. Irrigation water bodies showed the second lowest values for phytoplankton biomass, and concentration of N and P, while hydropower reservoirs showed the second highest values for the same parameters. The fraction of cyanobacteria in irrigation waters was higher than that in hydropower reservoirs, but surprisingly the dominance of Microcystis spp. was reversed. Possible reasons for these variations are discussed. More than half of the bloom material tested contained microcystins up to 81 μg l−1. Our findings indicate the potential for high-risk situations due to toxigenic cyanobacterial blooms in susceptible freshwaters of Sri Lanka

The tadpole of Ramanella palmata (Anura: Microhylidae), a frog endemic to Sri Lanka

Of the 107 species of amphibians known from Sri Lanka (Megaskumbura et al. 2009), the family Microhylidae is represented by 10 species (Pethiyagoda et al. 2006). The genus Ramanella Rao and Ramanna, 1925 is represented by four species in Sri Lanka (Pethyagoda et al. 2006). Except for R. variegata (Stoliczka, 1872), which is also found in neighboring India, the other three species are endemic to Sri Lanka. Larval stages and the breeding ethology of R. obscura (Guenther, 1864) and R. nagaoi Manamendraarachchi and Pethiyagoda, 2001 are well known (Morgan-Davis 1953; Meegaskumbura 2001; Manamendraarachchi & Pethyagoda 2001). Kirtisinghe (1958) briefly outlined the general morphology of the R. palmata tadpoles. Here we re-describe tadpoles of R. palmata highlighting some important characters that were initially not described by Kirtisinghe (1958), provide standard morphometric measurements of the tadpoles and also a photograph.K. D. B. Ukuwela, E. I. L. Silva, N. P. Athukoral

Environmental flow in Sri Lanka: ancient anicuts versus modern dams

Environmental flow describes the stream flow (quantity and regime) required to sustain upstream and downstream habitats, riparian vegetation, human livelihoods and wildlife. When natural rivers or tributaries are held back by weirs, anicuts, barrages or dams, for a variety of purposes such as diversion for irrigation, hydropower generation or flood control often the downstream flow requirement is ignored or neglected. Although there is no universally accepted definition, convention or law on environmental flow, it has been now recognized that environmental flow is essential for sustainability of riparian ecosystem and their services, which are essential for our own existence, livelihoods and many more. This paper looks at physical structures constructed across rivers and tributaries in Sri Lanka since ancient times to date (including mini-hydro power stations) with a view to understand whether simple ancient wisdoms are more appropriate than modern structures for nature conservation. There are tangible evidence to defend that the ancient anicuts known as “amuna” surged sufficient water in tributaries and rivers, to sustain the environment than modern engineering works which has created dead river beds immediately downstream in many streams and rivers

Structure of microcrustacean zooplankton communities in five tropical Asian water bodies.

Carl Moons and colleagues provide a checklist and background explanation for critically appraising and extracting data from systematic reviews of prognostic and diagnostic prediction modelling studies. Please see later in the article for the Editors' Summary