Sri Lanka Journal of Aquatic Sciences最新文献

{"title":"Livelihood status of the fishing community of Mahakanadarawa reservoir in Anuradhapura, Sri Lanka","authors":"C. K. Illangasingha, I. U. Wickramaratne, R. M. S. M. Rathnayaka, W. M. S. U. D. Dassanayake, M. G. K. N. Gamage","doi":"10.4038/sljas.v29i1.7614","DOIUrl":"https://doi.org/10.4038/sljas.v29i1.7614","url":null,"abstract":"Mahakanadarawa reservoir located in Anuradhapura is one of the major, perennial reservoirs in Sri Lanka, extending over 1,457 ha. It provides livelihood opportunities through fisheries, irrigation for agriculture, and fostering economic growth in the surrounding region. Yet the fisheries-based livelihoods of the Mahakanadarawa reservoir have not been fully assessed. Hence, this study investigated the fishery and fisher profile of the reservoir. Primary data were collected from  eight landing sites. A pre-tested questionnaire was used to interview 72 fishermen using a mixed method. Main variables including social, human, physical, natural, and financial capitals, fishery profile, fish and fisheries-based post-harvesting techniques, market chain analysis, and fisheries management practices, catch per unit effort for the gillnet fishery were calculated. Secondary data including stocking fish fingerlings and species-wise harvesting data for the past 10 years were collected from the district aquaculture extension office (Anuradhapura) of the NAQDA. A secondary study on the length-weight relationship of Oreochromis niloticus along with its condition factor value was performed. It was revealed that O. niloticus had negative allometric fish growth (b = 2.6667) with a condition factor value of 1.9092. The female fish had a higher mean total length compared to the male fish. In the fishing community, 95.83% of males and 4.17% of females were engaged in fishery activities. Mainly gill nets and non-mechanized fiberglass canoes were used for fishing. The average CPUE was 0.000339 kgm-2day-1. A strong positive (r =0.841) correlation was reported for fish stocking and fish production. Fish smoking and sun drying were the common fish processing techniques. The fish supply chain targeted the regional market. A cooperative level co-management system was identified among the reservoir fishing community. The current study discloses the livelihood capitals of the fishing community along with the existing supply chain which can be utilized for the sustainable management strategy of the Mahakanadarawa reservoir in the long run.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"15 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140240317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Are the stream macrobenthos impacted by the wastewater from rubber factories?","authors":"K. G. A. Dilhara, W. U. Chandrasekara","doi":"10.4038/sljas.v29i1.7612","DOIUrl":"https://doi.org/10.4038/sljas.v29i1.7612","url":null,"abstract":"We assessed how the wastewater generated from raw rubber factories affected the water quality parameters and how such changes influenced the stream macrobenthic assemblages in some streams in the wet zone of Sri Lanka. For this assessment, water quality parameters viz. DO, COD, BOD5, conductivity, TDS, T, pH, and OMC in the sediment were measured, and the macrobenthic fauna were sampled during the dry season at six sampling sites established based on judgemental sampling technique viz. rubber factory wastewater effluent canal (site A), point of wastewater discharge in the stream (site B),  50 m upstream site from site B (site C), 50 m downstream site from site B (site D), 100 m downstream site from site B (site E), and 150 m downstream site from site B (site F) following standard field sampling techniques. Secondary research data (dry season) from two other streams subjected to rubber factory wastewater effluents, namely Rakwatte Ela (2001) and Gurugoda Oya (2011), were also used for this assessment. Results revealed that the COD, BOD5, OMC, conductivity, and TDS levels were elevated, and the DO level was reduced significantly in the highly polluted A and B sites in all three streams. Parallel to them, the macrobenthic diversity decreased significantly (p<0.5; ANOVA) at these two sites. However, the complete opposite was observed at the furthermost downstream site F, where the water quality parameters and the microbenthic composition became almost the same as that in the upstream control site C. It is evident that the changes made to the stream water quality and the macrobenthic assemblages by the rubber factory wastewater are never permanent and disappear within a relatively short stretch of 150 m along the streams, most probably due to the dilution of wastewater along the stream. The pollution-tolerant tubificids and chironomids were bioindicator candidates to detect such changes where they became highly abundant at the highly polluted wastewater effluent canal (i.e., Site A) and point of wastewater discharge in the stream (i.e. Site B), but their abundance gradually decreased along the downstream sites probably due to wastewater dilution by the fresh water supply from the stream.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"10 38","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140237228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evolution of trends in Sri Lankan mangrove research and future prospects","authors":"M. Amarasinghe","doi":"10.4038/sljas.v29i1.7611","DOIUrl":"https://doi.org/10.4038/sljas.v29i1.7611","url":null,"abstract":"The trend of sporadic surveys and qualitative descriptions of Sri Lankan mangrove flora in the first half of the 20th century has gradually changed to include quantitative studies on floristics, nevertheless, studies on quantification of fauna associated closely with mangrove ecosystems are scarce. Microbial diversity, especially in soil, and its ‘contribution to the detritus cycle are the least studied. The tendency to engage in short-term research at convenient sites affects the quality and relevance of research output with some redundancy, resulting in a marginal contribution to the knowledge base on mangrove ecology. Studying mangrove ecosystem functions/ services demands long-term collection of data that would have made them less attractive research ventures.  Research on trophic relationships, detritus and nutrient cycling, habitat and pollination functions too have had the same fate. The Indian Ocean tsunami in 2004 triggered a considerable interest in the coastal protection function of mangroves, as it was evident that mangroves and other coastal vegetation provided superior resistance to tsunami waves than hard engineering coastal protective structures. This has led to an unprecedented trend of mangrove afforestation for coastal defense, more than to research on planting techniques and maintenance to enhance the survival and growth of seedlings. This is still an under-researched aspect. Escalating recognition of blue carbon as a climate-smart solution and the development of market mechanisms for blue carbon trading have induced a considerable research interest in quantifying the mangrove blue carbon stocks, especially in the soil. Research on atmospheric carbon removal capacity/rates of mangrove plants/forests through photosynthesis however, lags behind for the reason that it requires data collection for a longer period that demands greater financial and labour investment. The urgency created by the current climate change crisis for effective solutions to reduce atmospheric greenhouse gases may provide a conducive environment for mangrove research.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"106 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140238036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Some warning signs detected in coastal pelagic fisheries of the west coast of Sri Lanka: Declining trend of Amblygaster sirm suggesting the need for immediate management initiatives","authors":"K. Bandaranayake, S. S. Gunasekara, S. Haputhantri, R. P. P. K. Jayasinghe","doi":"10.4038/sljas.v29i1.7613","DOIUrl":"https://doi.org/10.4038/sljas.v29i1.7613","url":null,"abstract":"Coastal fisheries, mainly characterized by small pelagic species, are significant on the west coast of Sri Lanka in terms of livelihood and food security. However, currently, the fishery has faced numerous challenges, particularly with the stock depletion allied with poor management practices. The present study was carried out using the time series data of 2001–2020 on the west coast of Sri Lanka representing four fisheries districts - Kalutara, Colombo, Negombo, and  Chilaw - to explore the present status and the tendency of the fishery towards management considerations. The analysis was based on the outboard engine fiber-reinforced plastic boats (OFRP) with small meshed gillnets, which are the main boat gear combination that exists in the fishery. The recent five-year landings within the study period indicated that the highest average catch rates resulted in the onset of the southwest monsoon and extended until the end of the northeast monsoon. The catch rates of fishery exhibited greater inter-annual fluctuations during a two-decade period, with an average of 66.7 ± 17.3 kg per trip from 2011 to 2020. Over the past two decades, the Mean Trophic Level (MTL) of the coastal fish landings ranged from 3.13 to 3.62 and showed a declining trend with the forecast of 3.38 for 2022-2026. Moreover, the catch rates and the relative contribution of Amblygaster sirm, one of the main target species in the country, showed a declining trend over the past two decades while indicating the need for immediate management initiatives.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"16 13","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140239067","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oviposition-Site Selection and Egg-Hatching of &lt;em&gt;Aedes aegypti&lt;/em&gt; and &lt;em&gt;Aedes albopictus &lt;/em&gt;(Diptera: Culicidae) in Leaf Infusions of Three Invasive Plants Found in Sri Lanka","authors":"N. E. Chathurangi, R. A. K. M. Gunathilaka, G. A. S. M. Ganehiarachchi","doi":"10.4038/sljas.v28i2.7608","DOIUrl":"https://doi.org/10.4038/sljas.v28i2.7608","url":null,"abstract":"Aedes aegypti and Aedes albopictus (Diptera: Culicidae) are the main human arboviral vectors in Sri Lanka. The oviposition behaviour of Aedes mosquitoes determines their survival and population dispersion. Using varying concentrations of plant leaf infusions is a vital technique in determining mosquito oviposition behaviour. The objective of this study was to evaluate the oviposition behavior and egg-hatching rate of Ae. aegypti and Ae. albopictus to three leaf infusions of three invasive plants found in Sri Lanka. The oviposition media were prepared using guinea grass (Megathyrsus maximus), alligator weed (Alternanthera philoxeroides) and Austroeupatorium (Austroeupatorium inulifolium). Each oviposition medium was prepared in four different concentrations: 25%, 50%, 75%, and 100%. The ovitraps were placed in a rubber plantation in Rathnapura district, Palmadulla, Sri Lanka in order to determine the oviposition site selection towards those leaf infusions. Different plant infusions have a significant effect on the oviposition and egg hatch rate of Ae. aegypti and Ae. albopictus. Accordingly, the highest number of eggs has been laid in ovitraps with a 25% concentration of M. maximus infusion. The ovitrap positivity index values were highest in A. philoxeroides at 25%, 50% and 75% concentrations; M. maximus at 25%, 50% and 100% concentrations; and A. inulifolium at 25% and 75% concentrations. Despite the type of infusion and concentration, the egg-hatching rate was highest on the second day of rearing. Ae. aegypti and Ae. albopictus responded differently to different plant infusions based on the plant species and biomass employed. The study shows that organic matter infusions composed of guinea grass improve trap effectiveness and attract females more effectively than ovitraps using aerated tap water. The use of leaf infusions of guinea grass at 25% concentration as an attractant in combination with lethal substances to control container-breeding mosquito species is suggested as a strategy in integrated pest management.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135153935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Review on In-Situ Denitrification Technology for Consideration in Jaffna Peninsula Aquifer Remediation","authors":"Sivakumaran Sivaramanan, Mark Reinsel","doi":"10.4038/sljas.v28i2.7610","DOIUrl":"https://doi.org/10.4038/sljas.v28i2.7610","url":null,"abstract":"The groundwater nitrate levels in the Jaffna peninsula of Sri Lanka are well above the World Health Organization limit of 10 mg/L as N and recent studies point to the high use of chemical fertilizers and the close proximity of septic systems to drinking water wells as probable causes. Since aquifers in the peninsula are primarily porous, and shallow karstic Miocene limestone, they provide high levels of infiltration. If the current situation continues unabated, the public may suffer the harmful effects of nitrate toxicity. This paper discusses in-situ bioremediation processes, along with other possible mitigation measures, to remove nitrate and improve the quality of the drinking water. Five in-situ denitrification projects conducted in the Northern USA and Canada are presented, using carbon sources such as ethanol, methanol, and acetate. Treatment was achieved by a) injecting carbon and phosphorus or b) infiltrating treated water with excess carbon and phosphorus into groundwater. Nitrate-nitrogen concentrations as high as 60 mg/L have been reduced to below the limit of 10 mg/L with no ill effects. Pump-and-treat methods are conventional techniques and comparatively high-cost solutions. Furthermore, greener solutions such as controlling inorganic fertilizer addition and implementing long-term protective measures are inexpensive, but the minimal threat continues to exist. In addition, sustainable solutions such as banning agrochemicals, switching to organic farming, and establishing groundwater source protection zones have no negative impacts on the environment, but they are highly expensive to implement. In addition, restorative methods such as in-situ bioremediation and carbon farming, cultural or reconciliatory practices such as mulching seaweeds as organic fertilizer and using organic Neem-based pesticides, and regenerative solutions such as agroforestry or permaculture (includes intercropping with symbiotic nitrogen fixing crops) and holistic farming are less expensive and highly resilient or systemically vital methods suggested by this review.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135153774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of sub-lethal concentration (LC&lt;sub&gt;50&lt;/sub&gt;) of &lt;em&gt;Aeromonas hydrophila &lt;/em&gt;Against Hybrid Lemon Fin Barb (&lt;em&gt;Hypsibarbus wetmorei &lt;/em&gt;♂ &amp;times; &lt;em&gt;Barbonymus gonionotus &lt;/em&gt;♀) Early Fry","authors":"Rochana Weerasingha, Mohd Salleh Kamarudin, Murni Marlina Abd Karim, Mohammad Fadhil Syukri Ismail","doi":"10.4038/sljas.v28i2.7609","DOIUrl":"https://doi.org/10.4038/sljas.v28i2.7609","url":null,"abstract":"The common bacterial pathogens of cultured freshwater fish are mostly aeromonads, especially the pathogenic strains of Aeromonas hydrophyla. Early fry stages of fish reared in hatcheries face severe disease outbreaks caused by aeromonads. Disease challenge studies with pathogenic bacteria including Aeromonas sp. have become a more common tool used in the investigation of the effects of micronutrients and other immunomodulatory additives in fish diets. This study examined the sub-lethal concentration (LC50) of A. hydrophila against hybrid lemon fin barb (Barbonymus gonionotus ♀ × Hypsibarbus wetmorei ♂) early fry for 14 days. Three hundred and seventy-five fry (24 days after hatching) averaging 1.8±0.24 mg were randomly distributed in fifteen 2L plastic tanks. Fish fry were submerged in varying concentrations of A. hydrophila (2.5×105, 2.5×106, 2.5×107, 2.5×108 and 1×109 CFU ml-1). During the trial period, early fry was fed with a formulated diet containing the optimum crude protein and lipid contents. The mortality of fry in each tank was recorded daily. The LC50 of A. hydrophila for early fry of hybrid lemon fin barb by immersion was found at 6.06×108 CFU ml-1.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"171 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135154819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Present Status and Future Developmental Perspectives of Pole and Line Fishery in Sri Lanka","authors":"K. H. K. Bandaranayake, S. S. Gunasekera, R. P. Prabath K. Jayasinghe, Rekha Maldeniya","doi":"10.4038/sljas.v28i2.7607","DOIUrl":"https://doi.org/10.4038/sljas.v28i2.7607","url":null,"abstract":"Pole and line fishery is one of the oldest traditional techniques employed in tuna fishing in the Indian Ocean including Sri Lanka, which is mainly targeted to exploit skipjack tuna. This fishery has fallen to a relatively low level of significance during the past three decades. The potentialities for the expansion of pole and line fishery in Sri Lanka are regained with the possible negative consequences allied with the drift gill net in the region. The present study attempts to understand the factors that hinder the practice of gear progressively in past decades while providing necessary recommendations for the future expansion of the fishery. Scarcity of Dipterygonotus balteatus (Redbait), the main live bait species used in the fishery is one of the main reasons documented in the literature. The present findings based on Dr Fridtjof Nansen survey in 2018 revealed that the resource is abundant in the waters but requires an efficient harvesting technique. The impediment factor which hindered the popularization of the fishery is the deficiency of free schools of skipjack tuna where more than 99% of the surface tuna were found to be concentrated beyond the fishing range of existing practices. The commercialization of pole and line fishery in Sri Lanka will be feasible primarily with the modernization of the fishery which includes vessel upgrades, introduction of Fish Aggregating Devices (FADs), forecasting of free tuna schools, and efficient methods to harvest live bait and secondarily through proper awareness and skill development.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135154809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Population dynamics of two squid species, Uroteuthis duvaucelii (D'Orbigny, 1835) and U. singhalensis (Ortmann, 1891) (Family: Loliginidae) in the Trincomalee bay, Sri Lanka","authors":"N. Punyadewa, K. Wijayasinghe, Upali Sarath Amarasinghe","doi":"10.4038/sljas.v28i1.7605","DOIUrl":"https://doi.org/10.4038/sljas.v28i1.7605","url":null,"abstract":"","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89425275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Potential solutions to environmental conflict on exploitation of fish stocks in palk strait among fishermen of India and Sri Lanka","authors":"S. Sivaramanan","doi":"10.4038/sljas.v28i1.7606","DOIUrl":"https://doi.org/10.4038/sljas.v28i1.7606","url":null,"abstract":"","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73384547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}