 Subjects -> WATER RESOURCES (Total: 160 journals)
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- Potential solutions to environmental conflict on exploitation of fish
stocks in palk strait among fishermen of India and Sri Lanka
Abstract: Illegal catching of fish stocks beyond the borders of India and Sri Lanka by violating the International Maritime Boundary Line (IMBL) by the fishing communities of both countries has become a major international direct environmental conflict between both nations. Overexploitation of natural resources is a keystone environmental problem. It has been reported that Indian fishermen are stealing fish catch worth many millions of US dollars annually from Sri Lankan coastal waters. The bilateral agreements of 1974 and 1976 are frequently violated. The heavy use of trawlers that are not permitted to fish on coastal seas and the use of internationally banned bottom sea nets by Indian poachers are major threats to the coastal resources of north Sri Lanka. Trawlers catch fish flocks unselectively; the catch may include several non-targeted species and juvenile stages of fish, which is leading to species extinction. Arresting and imprisoning of fishermen by coastal guards of both countries (and collecting penalties) continue, and this is an unsustainable way of handling the issue. Sri Lanka has banned bottom trawling since the 6th of July 2017, which is a sustainable solution and beseeched possible greener solutions such as creating awareness, sensitizing fishermen, and promoting the use of GPS navigation, and also provoked conventional solutions such as monitoring or patrolling, which often lead to imprisonment and penalties for trespassing and seizing of fishing trawlers. Restorative solutions such as coral restoration, mangrove restoration, implantation of artificial reefs, and establishing mutually beneficial ‘no catch zone’ along the IMBL and marine reserves (or marine protected areas) by both nations may facilitate preventing the deterioration of fish stocks and ensuring their revival in the region. Above all, if this illegal catching continues, the availability of fish stocks in the Palk Strait region in the next ten years will be in question. Published on 2023-03-15 00:00:00
- Population dynamics of two squid species, Uroteuthis duvaucelii
(D'Orbigny, 1835) and U. singhalensis (Ortmann, 1891) (Family:
Loliginidae) in the Trincomalee bay, Sri Lanka
Abstract: In the Trincomalee bay of Sri Lanka, two species of squids, Uroteuthis duvaucelii and U. singhalensis, support profitable small-scale fisheries. The present study is an attempt to assess the fisheries of these two squid species using length-based stock assessment methodologies. Length frequency data collected from the landings of two species, collected during the fishing season from May to October 2003 were analyzed using FiSAT II software package. The asymptotic length (mantle length) and growth constant of U. duvaucelii were 31.8 cm and 0.90 yr-1 respectively and of U. singhalensis were 31.2 cm and 0.72 yr-1 respectively. Using the mortality coefficient estimates based on these growth parameters, exploitation rates (E) of U. duvaucelii and U. singhalensis during the study period were found to be 0.55 and 0.44 respectively. Optimal fishing strategies determined by relative yield-per-recruit (Y’/R) analyses of two squad species indicated that the sizes of first capture (Lc) and E were at sub-optimal levels. As both squid species are exploited by the same fishing gear, optimal E values predicted by Y’/R analyses cannot be achieved. This analysis indicates that levels of exploitation during the study period having Lc of 15.8 cm for U. duvaucelii at E = 0.55 and 14.3 cm at E = 0.44 for U. singhalensis be maintained. It is therefore concluded that fishing effort and the sizes of the first capture of the two squid species in the Trincomalee bay do not require adjustments through fishery regulations for the sustainability of their fisheries. Published on 2023-03-15 00:00:00
- Validating the fishing locations reported in the logbooks using the
positional data of vessel monitoring systems in the multi-day fishery of
Sri Lanka
Abstract: As part of monitoring, control and surveillance of marine fisheries, a logbook monitoring and vessel monitoring system (VMS) were introduced for multi-day fishing. The present study investigates the possibility of using VMS data to validate logbook records of fishing locations of multi-day fishing vessels. The data from 1,424 multiday vessels were fitted with VMS, which was operated from May 2017 to April 2018. During the period, there were 17,626 fishing trips and 66,717 fishing occasions. In the VMS tracks where the locations were flooded, drift gillnet-operated vessels were seen as a condensed zig-zag pattern, while longline fishing vessels as curve-shaped tracks, and ring net fishing vessels as condensed locations had irregular-shaped clumps. The differences in coordinates of fishing locations in the logbook records matched with the tracks predicted by VMS in multi-day boats of three gear types indicating that almost all fishing operations were within ±10º of both latitudes and longitudes and further around 70% of fishing locations had less than 1 arcminute of a difference. Therefore, VMS track data can be used to verify and validate logbook records of fishing locations in multi-day vessels. Published on 2023-03-15 00:00:00
- Spatial and temporal variation of physicochemical parameters of coastal
waters in the southwestern region of Sri Lanka
Abstract: Physicochemical parameters of coastal water in the southwestern area of Sri Lanka were studied from January to November 2016. Surface water samples from 15 selected locations were analysed according to standard methods. The ranges of the values recorded were; water temperature (WT) 26.5-33.9 ºC, pH 7.1-8.4, dissolved oxygen (DO) 4.4-7.4 mg L-1, salinity 14-38 ppt, electrical conductivity (EC) 27.1-53.8 mS cm-1, total suspended solids (TSS) 50.2-403.4 mg L-1, turbidity 1.2-64.9 NTU, nitrate nitrogen (NO3--N) 0.00-0.57mg L-1, nitrite nitrogen (NO2--N) 0.00-0.035mg L-1, ammoniacal nitrogen (NH4+-N) 0.00-1.72mg L-1, dissolved inorganic phosphorous (DIP) 0.00-0.65 mg L-1, biochemical oxygen demand (BOD) 0.1-11.6 mg L-1 and chemical oxygen demand (COD) 40-768 mg L-1. Results of Two-way ANOVA showed that there was a seasonal variability in parameters such as water temperature (p<0.001), dissolved oxygen (p<0.001), BOD (p<0.001), COD (p<0.001), nitrite nitrogen (p<0.001), nitrate nitrogen (p<0.001), dissolved inorganic phosphorous (p<0.001), turbidity (p<0.001), TSS (p<0.001) and Chlorophyll a (p<0.001). Spatial variation was identified in parameters, pH (p<0.001), turbidity (p<0.001), dissolved oxygen (p=0.004) and nitrite nitrogen (p<0.001) whereas the interaction between time and location was significant in pH (p=0.005) and turbidity (p=0.007). However, EC, salinity and ammoniacal nitrogen were not significant by either of the factors of consideration. In conclusion, the physicochemical characteristics of water are highly variable over time and location due to both natural and human factors. Water quality near fish processing areas such as fishery harbours and fish markets relatively deteriorated in terms of pH, DO, turbidity and nitrite nitrogen compared to recreational beaches. It is recommended to regulate any discharges of sewage and industrial wastewater directly into the sea. A long-term coastal water quality monitoring programme is vitally important to comprehensively characterise the coastal segments for a long-term strategic plan for sustainable development. Published on 2023-03-15 00:00:00
- Water quality, microcystin-LR, and Cylindrospermopsin contamination status
of spring and dug well water in CKDu high, low, and non-prevalent areas of
Sri Lanka
Abstract: Cyanotoxins, Microcystin LR (MC-LR) and Cylindrospermopsin (CYN) are hepato and nephro toxins and considered as one of the hypotheses for Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka. Recent studies have revealed that significant number of dug wells in the North Central and Uva provinces where CKDu is prevalent are contaminated with cyanotoxins MC-LR and CYN. In the present study, cyanotoxin; MC-LR, CYN, and potential toxin-producing cyanobacteria were studied in 330 dug wells and 9 spring water samples collected from CKDu high prevalent areas in several Divisional Secretariats (DS) and Grama Niladhari (GN) divisions of Anuradhapura (Padaviya DS, Medawachchiya DS, Kebithigollewa DS), Polonnaruwa (Medirigiriya DS), Badulla (Girandurukotte GN) and Ampara (Dehiaththakandiya DS) districts, low prevalent areas in Anuradhapura district (Galnewa DS, Rajanganaya DS), non-prevalent areas in Angunakolapelessa DS of the Hambanthota district. General water quality parameters: temperature, pH, conductivity, Dissolved Oxygen (DO), Nitrate (N-NO3-), Nitrite (N-NO2-), Ammonia (N-NH3), Total Phosphorus (TP), and Total Hardness (TH) were determined using standard spectrophotometric and titrimetric methods. BACON test kits were used following manufactures instructions to quantify the CYN, and MC-LR concentrations by using the ELISA plate reader. Cyanobacteria density and species composition were determined under light microscopy following the standard algae and cyanobacteria keys. With the exception of Electrical Conductivity, all of the water quality parameters tested remained within the SLSI drinking water quality standard range. Microcystis spp. cell densities ranged from 14±3 to 1590±256 cells mL-1, where MC-LR concentration ranging from 0.04±0.01 to 3.89±0.02 µg L-1. At different CYN concentrations (0.04±0.01 to 3.59±0.05 µg L-1), Cylindrospermopsis spp. cell densities varied from 15 ±4 to 615±112 cells mL-1. Well water collected from Hambanthota district and spring water was collected Kebithigollewa DS, in Anuradhapura did not record cyanotoxins and cyanobacteria. The factor analysis classified well waters into three clusters of high, low, and non-prevalence areas with presence and absence of cyanobacteria and cyanotoxins. In contrast, springs were classified to a separate cluster. High concentrations of MC-LR and CYN were found in wells where CKDu high prevalent 85% of Padaviya DS and 80% of Medirigiriya DS, respectively. High Nitrate-N (3.01±0.56 mg L-1) and Nitrite-N (0.69±0.09 mg L-1) concentrations were recorded in well water collected from high CKDu prevalence areas. Thus, the results of the present study showed a relationship between cyanobacteria, cyanotoxins and CKDu records in the study area. Accordingly, further comprehensive studies are needed to be carried out to confirm the relationship between cyanotoxins and CKDu in Sri Lanka as cyanotoxin were listed in the WHO report as one of the possible reasons for CKDu. Published on 2022-10-05 00:00:00
- A field guide to the fishes in freshwaters of Sri Lanka
Abstract: No abstract available Published on 2022-10-05 00:00:00
- Microcystin-LR contamination in Nile tilapia (Oreochromis niloticus) in
some water bodies in Sri Lanka
Abstract: Microcystin-LR (MC-LR) is a cyanotoxin produced by certain cyanobacteria species. It is toxic to humans and animals. Several studies have demonstrated that cyanotoxins accumulate throughout the food chain, eventually reaching high levels in freshwater fish. The Nile tilapia (Oreochromis niloticus) is the most popular freshwater fish in Sri Lanka and in most Asian countries. The current study sought to determine MC-LR concentration in Nile tilapia collected from thirteen freshwater reservoirs; Nallachchiya, Galkulama, Anakattiya, Padaviya, Nachchaduwa and Kalawewa in Anuradhapura District, Parakrama Samudraya, Halmilla, Kaudulla and Ambagaswewa in Polonnaruwa District, Muwapatigewela in Ampara District, and Ulhitiya and Rathkinda in Badulla District. The fish and water samples were collected, transported, and analyzed following standard procedures, and MC-LR was determined using a BEACON ELISA kit. To determine the MC-LR and Tolerable Daily Intake (TDI) levels in fish, samples of the fish skin, flesh, and head were collected and analyzed according to World Health Organization (WHO) guidelines. A comparison was made between the MC-LR levels of fish in different reservoirs and the WHO TDI standards (0.04 μgkg-1day-1). From the Padaviya, the highest mean concentrations of MC-LR were found in fish skin (3004.25 ± 30 μg kg-1), following head (836.25±18 μg kg-1) and flesh (41.67±8 μg kg-1). The average daily intake of MC-LR in the skin and head of all samples exceeded the WHO's TDI (0.04 μg kg-1 day-1). According to the findings of this study, consumption of fish heads and skin increases the risk of MC-LR accumulation in the human body by a significant amount. Published on 2022-10-05 00:00:00
- Physico-chemical properties of chitosan extracted from Whiteleg shrimp
(Litopenaeus vannamei) processing shell waste in Sri Lanka
Abstract: The present study investigated the potential of whiteleg shrimp shell waste to use as a source of chitosan which has a limited focus on previous Sri Lankan studies. Comparatively higher amount of chitosan yield (33.53%) was obtained in the study with 91.78 ± 0.66 (%) of dry matter content, 8.22 ± 0.66 (%) of moisture content, 1.08 ± 0.24 (%) of ash content, 80.43% of the degree of deacetylation, 435.87 ± 1.03 cP dynamic viscosity and a good thermal stability up to 312 °C. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the structure of chitin and chitosan by the presence of their characteristic IR bands and X-ray diffraction analysis further verified the crystalline structure of the extracted chitin and chitosan. Scanning electron microscopic (SEM) images of the extracted chitosan recognized the layers of flakes with porous and fibril structures. According to the energy-dispersive X-ray spectroscopy image, carbon, oxygen and nitrogen were observed as the major elements in the extracted chitosan and no calcium peaks were detected confirming effective demineralization in the extraction process. Further, DPPH (2,2-diphenyl-1-picryl hydrazy) assay revealed that the chitosan solution with the concentration of 10 mg/mL was having 66.45% of free radical scavenging activity. Thus, the present study reveals that the chitosan with high quantity and quality can be extracted from whiteleg shrimp (Litopenaeus vannamei) processing shell waste in Sri Lanka suggesting a solution to the waste accumulation in processing factories while proposing an alternative income generation strategy from waste. Published on 2022-10-05 00:00:00
- Spatial distribution and dynamics of selected mangrove forests on the east
and west coasts of Sri Lanka
Abstract: The climate and edaphic characteristics primarily determine the spatial distribution and dynamics of mangrove forests. The present study was initiated to determine how species composition and structural characteristics vary along with climate and substrate salinity of six mangrove forests located on the west coast, i.e., Negombo estuary, Chilaw lagoon, and Malwathu oya estuary, and east coast, i.e., Batticaloa lagoon, Uppar lagoon, and Urani lagoon. The structural parameters in terms of tree height, basal area, biomass, and density were obtained to determine the vegetation structure of mangrove forests. The current study found that although the structure of mangrove communities of the two coasts does not differ significantly (P<0.05), plant diversity in mangrove areas on the west coast is significantly higher than that of the east coast mangroves. In contrast, the biomass accumulation in west coast mangroves is relatively lower than that of east coast. Tree height was found to influence the productivity in terms of biomass increment of mangrove forests under investigation. As such, our study suggests that regional variations in salinity, temperature, and rainfall primarily serve as drivers of variation in mangrove species composition and vegetation structure of mangrove forests along the coasts of Sri Lanka. Published on 2022-10-05 00:00:00
- Knowledge and prospects of Sri Lankan aquatic science research: A
bibliometric analyses
Abstract: The present study summarizes the research productivity and international collaboration in aquatic studies conducted by Sri Lankan scholars during 2000-2019. The study was based on the SCOPUS® database. R programming language, package bibliometrix and Vosviewer software were employed in the analysis. Results of the present study indicate that increasing growth trend in the annual number of publications. A significant correlation (p<0.05) between the number of articles and per capita GDP (Gross Domestic Production) was also observed. Senior authors dominated in terms of the article count, citation count, h index, and other author productivity indices. Journal of the National Science Foundation of Sri Lanka had the highest article count (n=33). Aquatic studies in Sri Lanka were more locally funded. Sri Lanka had strong research collaborations with Japan, South Korea and Australia. During 2000-2019, the transition of aquatic studies from lacustrine field studies to molecular lab-based studies were observed. The findings of the present study may provide a comprehensive understanding on the current context and future directions of aquatic studies in Sri Lanka. Published on 2022-03-21 00:00:00
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