Sri Lanka Journal of Aquatic Sciences最新文献

{"title":"Critical better management practices and critical bio-security measures for prevention of entry and spread of white spot virus and pathogenic Vibrio in grow-out farms of cultured Penaeus monodon in Sri Lanka","authors":"K.R.P.S. Kumara, M. Hettiarachchi","doi":"10.4038/SLJAS.V23I2.7556","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7556","url":null,"abstract":"Since the first record of white spot disease (WSD) in 1996, PCR tested, white spot virus (WSV) free post larvae of Penaeus monodon (Fabricius 1798) are stocked in grow-out farms as the major bio-security measure. However, significantly high mortality in young shrimp and total rejection of harvest have been recorded in North Western Province, Sri Lanka due to WSD and/or vibriosis. Present study was planned to identify critical better management practices (CBMPs) and critical bio-security measures (CBSMs) that should be strictly adopted to prevent the entry and spread of WSV and pathogenic Vibrio in grow-out farms of P. monodon. A questionnaire survey, carried out at randomly selected 100 grow-out farms located in the North Western Province, revealed that there was a relationship between the occurrence of WSD and /or vibriosis and levels of practicing better management practices (BMPs) and/or bio-security measures (BSMs). Proper pre-stocking pond preparation, adoption of zero water exchange, monitoring and controlling water quality parameters including pathogenic Vibrio in culture water and use of a suitable bioaugmenter and a probiotic were identified as the CBMPs while proper disinfection of culture water, stocking of WSV and MBV free post larvae and prevention of WSV contamination through other routes over the rearing period were the identified CBSMs. Entry and spread of WSV and pathogenic Vibrio in P. monodon grow-out farms in the North Western Province, Sri Lanka could be prevented by strict adoption of CBMPs and CBSMs identified during the present study.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"121 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78115424","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":"Abundance-Biomass Comparison approach to assess the environmental stressors in Diyawannawa wetland in monsoonal and non-monsoonal seasons","authors":"W. Wijeyaratne, B. Bellanthudawa","doi":"10.4038/SLJAS.V23I2.7555","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7555","url":null,"abstract":"Abundance-Biomass Comparison (ABC) approach is a graphical approach that compares the abundance and biomass of organisms in order to predict the environmental stress level of an ecosystem. The present study was conducted in selected sites located at non-rehabilitated and rehabilitated areas of the Diyawannawa wetland in Sri Lanka in the monsoonal and non-monsoonal seasons. The ABC was performed on the macrobenthic mollusk species collected from the study sites. Eight species of macrobenthic mollusks, namely, Bithynia tentaculata, Melanoides turbeculata, Melanoides turriculus, Thiara scabra, Lamellidens marginalis, Pila globosa, Gyraulus saigonensis and Lymnaea stagnalis were recorded during the study period. Based on Principal Component Analysis, B. tentaculata, and, P. globosa were identified as characteristic gastropod species that could be used to classify study sites in the rehabilitated and non-rehabilitated areas of this tropical wetland system. In the monsoonal season, overlapping cumulative percentage dominance of abundance and cumulative percentage dominance of biomass curves in sites A, B, and F indicated partially disturbed environmental conditions. The site C of the non-rehabilitated area, showed a typical undisturbed condition and the sites D and E of the rehabilitated area the cumulative percentage dominance of biomass curve was located above the abundance curve, indicating disturbed environmental conditions in these sites during monsoonal season. During the non-monsoonal season in all the sites except site F of the rehabilitated area, the cumulative percentage dominance of abundance curve was located above the biomass curve, indicating undisturbed environmental conditions in these sites. In the site F, the cumulative percentage dominance of abundance and the cumulative percentage dominance of biomass curves were crossing each other, indicating partially disturbed environmental conditions at this site. The values of the W statistic, which ranged from 0.004 to 0.374 in the non-monsoonal season and ranged from 0.1 to 0.2 in the monsoonal season, and pollution and water quality categorization by modified biotic index (MBI) were in agreement with the results of the ABC approach.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"54 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88402664","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":"Morphometric analysis of Squalius namak Khaefi et al. 2016 in Khaznagh and Ghare-Chai rivers","authors":"A. Mouludi-Saleh, Y. Keivany","doi":"10.4038/SLJAS.V23I2.7558","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7558","url":null,"abstract":"The Namak Chub, Squalius namak, is a newly described cyprinid from Namak basin of Iran, but there is little information on its body variations. To investigate the population differences, fifty-two specimens (37 from Khaznagh and 15 from Ghare-Chai) of Squalius namak (Teleostei: Cyprinidae) were captured by seine net during the summer of 2010. After anesthetizing, specimens were transferred to Ichthyology Museum (IUT-IM) for further studies. The specimens were photographed from their left side and 13 landmarks were defined on the photos in Tpsdig2 software. Procrustes analysis (GPA) was performed to eliminate non-shaped effects, the size, direction and position of the specimens. Principal Component Analysis (PCA), Discriminant Function Analysis (DFA) and wireframe graph were used to analyze these populations. The results of this study showed a significant difference between the two populations. The major differences observed were the depth of the body, head size and the position of the mouth. The Ghare-Chai River population has a greater body depth and smaller head length. Further, the position of the mouth in the Khaznagh river population was more inferior compared to the Ghare-Chai River population.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"186 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77057595","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":"Capacity Utilization in Small-Scale Fisheries: A Case of the Sultanate of Oman","authors":"M. A. Siyabi, S. Bose","doi":"10.4038/SLJAS.V23I2.7557","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7557","url":null,"abstract":"The interrelated issues of capacity utilization (CU) and technical efficiency (TE) have received global importance as they relate to the problem of overcapitalization and overfishing. Given the limited research on these issues in the context of small-scale fisheries, this paper attempts to provide empirical estimates of TE and CU with particular focus on small-scale fisheries in Oman using Data Envelopment Analysis (DEA). The output variables included aggregated catch of three fish categories namely large pelagic, demersal, and other, while the boat length, engine power and number of crews were used as input variables in the empirical analysis. The data for the year 2010 were used and 97 active fishing boats were selected for the analysis. The TE and CU estimates were generated under the assumption of constant returns to scale (CRS) and variable returns to scale (VRS). The TE estimates under both CRS and VRS assumptions indicate that about 84.5% and 79.4% of the representative boats are operating in a technically inefficient manner. In addition, the unbiased CU estimates under the same assumptions show that about 77.3 % and 82.5% of the boats are not operating at full capacity. Furthermore, the average score of unbiased CU measure suggests that the representative boats may not be using variable inputs efficiently. To gain a better understanding of harvesting operations in small-scale fisheries sector in the country, it is prescribed that the management authority should extend this study for other coastal governorates and investigate the potential causes of inefficiency to design effective management strategies.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"38 4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82823445","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":"Hair mercury levels and dietary exposure of mercury in relation to fish consumption among coastal population in Negombo, Sri Lanka","authors":"M. Rathnasuriya, B. Jinadasa, T. Madhujith","doi":"10.4038/SLJAS.V23I2.7559","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7559","url":null,"abstract":"Consumption of contaminated fish is the major source of the human exposure to total mercury (T-Hg) and methyl mercury. This study reports the fish consumption habits of three groups based on the age category and their occupation; “Children” (age 9-20 years) and two groups of “Adults” (age above 21 years) based on their occupation; “Adults-Fishermen” (fishermen) and “Adults-Other”. Hair T-Hg levels were measured from 30 individuals (age 9-48 years) from Negombo area in Sri Lanka. All individuals in this survey consumed fish at least six servings per week, which belongs to the high fish consumer category (> 3 servings/week) according to World Health Organization (WHO) guidelines. The main fish groups consumed by the respondents were mainly yellow-fin tuna (YFT), skipjack tuna (SKT), kawakawa and frigate tuna and small fish such as sardines (spotted sardines, goldstripe sardine, other sardines, scads and trevallies). The majority consumed an equal amount of big fish and small fish. The average weekly fish consumption per individual varied depending on the test group (Children; 1270 g/week per person, Adults-other; 1078 g/week per person and Adults-fishermen 1852 g/week per person) which exceeded United States Food & Drug Administration (USFDA) recommended level of 340 g/ week of seafood containing low concentration of Hg. The mean hair T-Hg of respondents of Negombo population was 4.89±3.23 µg/g (range 1.60-13.38 µg/g), which exceeded the United States Environmental Protection Agency (USEPA) reference dose (1 µg/g) for T-Hg level of hair. The total hair mercury in three respondent groups (Children 3.33±1.36 µg/g, Adults-other 2.89±1.26 µg/g and Adults-Fishermen 6.08±3.62 µg/g), were not significantly different (p>0.05) from each other. Real exposure value of three respondent groups were not significantly different (p>0.05). There was a low strength positive correlation (r=0.353, p>0.05) between hair T-Hg levels with the weekly large fish consumption.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83622151","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":"Professor C.H. Fernando (1929-2018)","authors":"A. Hettiarachchi","doi":"10.4038/SLJAS.V23I2.7554","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7554","url":null,"abstract":"","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84885655","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":"Empirical yield predictive models for the fisheries of irrigation reservoirs in Sri Lanka","authors":"S. Nadarajah, W. Wijenayake, Upali Sarath Amarasinghe","doi":"10.4038/SLJAS.V23I2.7561","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7561","url":null,"abstract":"As fisheries production in reservoirs of most countries is a secondary use, challenges for improved management of fisheries should be addressed by building partnership between fisheries and other interested groups such as agriculture concerned with water management. Attempts were therefore made to develop empirical fish yield predictive models in ten irrigation reservoirs of Sri Lanka incorporating morphological, edaphic and hydrological parameters together with fishing intensity, with a view to investigating their influence on fish yields. Reservoir fish yield was found to be significantly correlated with two formulations of morpho-edaphic index (i.e., conductivity in μS cm-1/mean depth in m [MEIc] and alkalinity in m. equiv. l-1)/mean depth in m [MEIa]), and a relative reservoir level fluctuation index (RRLF), defined as the mean amplitude of the annual reservoir level fluctuations divided by the mean depth of the reservoir. Both MEIc and MEIa also had significant positive ln-ln relationships with RRWL, indicating that RRWL can be used as an independent variable in reservoir fish yield prediction. Reservoir fish yield was also related to fishing intensity (FI in boat-days ha-1, yr-1) conforming to a ln-linear regression model (p Ln FY = 3.245 + 0.327 Ln MEIa + 0.023 FI (R2 = 0.355; p Ln FY = 3.403 + 0.249 Ln MEIc + 0.019 FI (R2 = 0.369; p Ln FY = 1.330 + 0.650 Ln RRWL + 0.016 FI (R2 = 0.593; p The empirical yield predictive model based on RRWL and FI as independent variables was more robust than those based on MEIa and MEIc, and the former has significant management implications because RRWL can be manipulated by irrigation authorities whereas control of FI is under the jurisdiction of fisheries authorities. Hence, through an effective dialogue between irrigation and fisheries authorities, there is a considerable potential to optimize fish yields in irrigation reservoirs of Sri Lanka.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"72 2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85507486","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":"Influence of hydraulic retention time and amplitude of water level fluctuations on water quality in irrigation reservoirs of the Kala Oya river basin, Sri Lanka","authors":"S. Nadarajah, W. Wijenayake, N.D.P. Gunawardane, Upali Sarath Amarasinghe","doi":"10.4038/SLJAS.V23I2.7560","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I2.7560","url":null,"abstract":"Management of reservoir water quality is a global challenge due to the natural process of eutrophication and anthropogenic aggravation. In Sri Lanka, irrigation reservoirs support several secondary uses such as fish production, livestock farming, and many communal uses including drinking water supply. In the present study, basic limnological parameters of ten irrigation reservoirs of Sri Lanka were investigated from June 2013 to February 2016, with a view to identifying influence of hydrological regimes on reservoir water quality. Spatio-temporal similarities of water quality parameters were studied employing the self-organizing map (SOM) routine of the artificial neural network application. The sample vectors, classified on the SOM lattice, indicated 6 clusters at 50% similarity level. When reservoir that were categorized according to hydraulic retention time (HRT) and relative reservoir level fluctuation (RRWL; defined as the ratio of the mean reservoir level amplitude to mean depth), were compared with dominant water quality parameters in SOM lattice, it was evident that some productivity-related water quality parameters were influenced HRT and RRWL. The results of the study revealed that HRT and RRWL can essentially be controlled through management of hydrological regimes in irrigation reservoirs, thus, close dialogue between irrigation authorities and other users of reservoir water resources are needed to ensure desired water quality of the reservoirs.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86687044","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":"Fisheries enhancements in inland waters in Sri Lanka with special reference to culture based fisheries: current status and impacts","authors":"J. Chandrasoma, K. Pushpalatha","doi":"10.4038/SLJAS.V23I1.7546","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I1.7546","url":null,"abstract":"Sri Lanka is endowed with more than 12,000 reservoirs. Depending on their hydrological regimes, they are broadly categorized into perennial and seasonal reservoirs and are secondarily used for the development of inland fisheries. This paper discusses the importance and status of culture-based fisheries (CBF) in reservoirs of Sri Lanka and assess the impacts of introduction of CBF. The CBF in seasonal reservoirs was initiated in the 1980s and it is well documented. There are around 200,000 ha of perennial reservoirs in Sri Lanka and CBF in perennial reservoirs is a recent development. Introduction of CBF into perennial reservoirs has resulted in significant increases in fish production, increased availability of fresh fish to rural communities, enhanced livelihood opportunities and income for fishers and strengthening the rural economy. Progress achieved so far in respect of seasonal reservoirs has not reached the envisaged levels. Nile tilapia, catla, rohu and mrigal are the main contributory species for fish production through CBF in perennial reservoirs. Although the contribution to fish catches is low, stocking of freshwater prawn ( Macrobrachium rosenbergii ) is financially feasible. Adequate stocking with suitable species, the existence of active Community Based Organizations (CBOs) and their involvement in planning and implementation of CBF, and the existence of a legal framework which facilitate implementation of activities pertaining to CBF are the key factors for successful implementation and sustainability of CBF in perennial reservoirs.","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"57 1","pages":"49"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82176557","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":"Life history patterns of some selected endemic freshwater fish species inhabiting two major river basins of Sri Lanka","authors":"R.R.A.R. Shirantha, M. Wijeyaratne, Upali Sarath Amarasinghe","doi":"10.4038/SLJAS.V23I1.7548","DOIUrl":"https://doi.org/10.4038/SLJAS.V23I1.7548","url":null,"abstract":"Life history information on six endemic fish species namely Belontia signata, Pethiya cumingii, P. nigrofasciata, Puntius titteya, Rasboroides vaterifloris and Garra ceylonensis inhabiting the Kalu Ganga and Kelani Ganga river basins in Sri Lanka was evaluated. The growth constant of the fish species showed a positive relationship with the river order where they inhabited. The length at 50% maturity (Lm) significantly correlated with the asymptotic length and growth constant indicating that fishes with slow growth become sexually mature late in their life cycles. The optimal lengths for sustainable exploitation of the fish species studied were significantly (p","PeriodicalId":21784,"journal":{"name":"Sri Lanka Journal of Aquatic Sciences","volume":"4 1","pages":"77"},"PeriodicalIF":0.0,"publicationDate":"2018-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87446118","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}