Zoology

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A comparative assessment of the fisheries in lacustrine inland waters in three Asian countries based on catch and effort data
(Fisheries Research, 1991) de Silva, S.S.; Moreau, J.; Amarasinghe, U.S.; Chookajorn, T.; Guerrero, R.D.
The catch and effort data of the artisanal fisheries of the natural lakes and reservoirs in the Philippines, and reservoirs in Sri Lanka and Thailand are evaluated. The yield (kg ha?1 year?1) to effort relationship of the Philippines lakes and Thai reservoirs conformed to a second-order curve, and that of Sri Lankan reservoirs was linear. Similarly, the catch per unit effort (CPUE) to effort per unit area relationships for the Philippines and Thai fisheries were similar and conformed to the Fox model. The relationship of the mean annual yield (kg ha?1) to mean effort in the Sri Lankan reservoirs when considered as a whole, on a yearly basis, conformed to the Schaefer model. On the basis of these relationships the effort which gave the maximum yield per annum was computed for each fishery. The yields were 515, 256 and 93 kg ha?1 for efforts of 20, 6.4 and 10 fishermen for the fisheries of the Philippines, Sri Lanka and Thailand, respectively. An attempt is made to explain the reasons for the apparent differences in these three artisanal fisheries, and the importance of the models in the management of the respective fisheries are discussed. 1 Present address: Deakin University, Warrnambool Faculty of Applied Science and Environmental Technology, P.O. Box 423, Warrnambool 3280, Australia.
A comparative study of the effects of benzene, toluene and xylenes on their in vitro metabolism and drug metabolizing enzymes in rat liver
(Toxicology and Applied Pharmacology, 1986) Pathiratne, A.; Puyear, R.L.; Brammer, J.D.
A comparative study of the food and feeding habits of Puntius Bimaculatus and P.Titteya (Pisces, Cyprinidae)
(brillonline.com, 1976) de Silva, S.S.; Kortmulder, K.; Wijeyaratne, M.J.S.
A comparison of proximate composition and water stability of three selected Shrimp feeds used in Sri Lanka
(Asian Fisheries Society, Manila Philippines, 2007) Epa, U.P.K.; Wijeyaratne, M.J.S.; de Silva, S.S.
A note on the occurrence of a Branchial parasite, Epipenaeon ingens Nobili in Penaeus semisulcatus De haan in Puttalam lagoon, Sri Lanka
(J. Nat. Res. Ag. Sri Lan., 1986) Rajapakse, T.A.; Amarasinghe, U.S.
A synthesis on the management of the capture fisheries of Sri Lankan reservoirs
(Vidyodaya Journal of Science, 1994) Amarasinghe, U.S.
Sri Lankan reservoir fishery is one of the best documented in the South East Asian region. It is very productive and the average fish yield in reservoirs of the country is about 300 kg ha-I, yr". Nevertheless the Sri Lankan reservoir fishery is not managed scientifically and in some reservoirs, fish stocks are over-exploited. Since recently, some studies have been carried out on the aspects of management of the capture fisheries in perennial reservoirs of the country. Empirical yield prediction models are found to be useful for setting limits to the size of the fishery. Also by employing surplus yield predictive models, maximum sustainable yield and optimal fishing intensity have been estimated to be 256 kg ha'" yr-I and 3.2 boats km? respectively. Dynamic pool models are also reliably applicable for the reservoir fisheries of Sri Lanka. Fish yields in reservoirs could further be increased by introducing a subsidiary gillnet fishery for minor cyprinids. Socioeconomics of fishing communities should be better understood for effective implementation of fisheries manage- ment strategies in Sri Lankan reservoirs.
Abundance and diversity of freshwater molluscs in some selected reservoirs of the Kala Oya river basin, Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Weerakoon, S.N.; Chandrasekera, L.W.H.U.; Amarasinghe, U.S.
Benthic macroinvertebrates such as molluscs are known to be possible bioindicators of aquatic ecosystems. We carried out a study to investigate how the abiotic factors affect the abundance and diversity of molluscan fauna at 10 irrigation reservoirs in the Kala Oya river basin during the dry season from August to November 2014. In each reservoir, three sampling sites were selected where at each site, a 50 m long perpendicular line transect was established running from its maximum water supply level towards the center of the reservoir. Three soil samples were collected at 10 m intervals each along each transect using a 0.5 dm3 soil corer. These samples were sieved in situ through a 1 mm sieve and the remains were preserved in 10% formalin solution containing Rose Bengal. Later the molluscs and other associated macrofauna were identified to the nearest possible taxonomic category using standard taxonomic keys and the fauna belonging to each taxon were enumerated separately. In addition, data related to vegetation cover, intensity of human disturbances, intensity of pollution, agrochemical inputs, soil texture and human settlements based on a modified scoring system were also collected. Altogether 4328 molluscs belonging to 11 genera were recorded. Molluscan genera such as Bellamya (45.9%), Melanoides (26.7 %) and Thiara (16.9 %) dominated the samples while the remainder (10.5%) belonged to less dominant genera consisting of Planorbis, Gyraulus, Indoplanorbis, Lamellidans, Planorbella, Lymnaea and Pila. The abundance of the molluscan genera varied significantly between the reservoirs (MANOVA; F (99, 899) = 4.300, P = 0.000; Wilk’s λ = 0.06515) and along the transect distances (MANOVA; F (44, 483) = 0.901, P = 0.654; Wilk’s λ = 0.73988). High diversity measures of molluscs were observed at Angamuwa wewa, Katiyawa wewa, Rajanganaya reservoir and Usgala-siyambalangamuwa wewa. Principal Component Analysis (PCA) for the mollusc abundance and the relationship between PC1 scores and Shannon–Wiener diversity index endorsed that Bellamya, Melanoides and Thiara were the highly contributing genera to the high diversity of the molluscs in the above reservoirs. Results of the PCA for abiotic factors revealed that both the abundance and species diversities were high at moderately sandy bottoms with high vegetation cover and agrochemical inputs. In contrast, the intensity of human disturbances, pollution, human settlement and shadiness showed a negative effect on the abundance and diversity of these molluscs. This study was carried out as part of a comprehensive study which investigates how the aspects related to biotic integrity and multiple uses of reservoirs could be used to develop effective management options for reservoir fisheries in Sri Lanka.
Accidental introduction of alien plankton into the Sri Lankan coastal zone through ballast water of cargo ships
(Sri Lanka Association for Fisheries and Aquatic Resources, 2009) Chandrasekera, L.W.H.U.; Fernando, M.A.S.T.
Accidental introduction of alien plankton through ballast water is a major ecological issue in many countries in the world. As there are no local studies addressing this problem, the present study was carried out to see whether alien plankton are introduced into Sri Lankan coastal zone through ballast water. Marine plankton occurring within ballast water holds of five cargo ships arrived at Colombo harbour and three local sites including Colombo inner harbour and two neighboring coastal sites were sampled. The physico-chemical parameters of water samples were also measured. Data on species abundance and physico-chemical parameters were analyzed using multivariate and univariate statistical tests as appropriate. Altogether 159 taxa of plankton were found in the samples. In the ballast water samples alone, there were 56 different taxa of which 50% of them were totally alien to the local coastal zone. The physico-chemical parameters of water samples between the four sites were not significantly different. However, multivariate statistical tests confirmed that the plankton community of the ballast water samples was significantly different from that of the three local sites. Considering the large number of ships calling annually at Colombo harbour, the great potential of accidental introduction of alien plankton into the Sri Lankan coastal zone should never be underestimated.
Accounting for Diel Feeding Periodicity in Quantifying Food Resource Partitioning in Fish Assemblages in Three Reservoirs of Sri Lanka
(Asian Fisheries Society, 2003) Weliange, W.S.; Amarasinghe, U.S.
Most investigations on food resource partitioning in fish along the temporal dimension are based on the diet composition of constituent species in fish assemblages, pooled over a longer time lapse, but variation within 24-hour cycle is not considered. In the present study, an attempt was made to account for diel feeding periodicity in fish species in quantifying dietary overlaps among constituent species in fish assemblages in three reservoirs of Sri Lanka. The dietary overlap of fish species estimated as a mean for short time intervals in three reservoirs is significantly lower than that is based on the sum of all time intervals, especially for pairs with moderate and high overlaps. Furthermore, the dietary overlaps estimated for short time intervals, which indicate moderate and high dietary overlaps between pairs, exhibit negligible overlaps of peak feeding period indicating the necessity to account for diel feeding periodicity in quantification of food resource partitioning.
Accumulation of lead, cadmium and copper in brackishwater clam, Meretrix casta from selected estuaries in Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2009) Amarasekara, E.A.K.K.; Pathiratne, A.; Wanninayake, W.M.T.B.
Accumulation of Lead, Cadmium and Copper in food fish, Oreochromis mossambicus in Beira Lake, Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2002) Anil, K.A.; Pathiratne, A.
Acetylcholinesterase inhibition and gill lesions in Rasbora caverii, an indigenous fish inhabiting rice field associated waterbodies in Sri Lanka
(Kluwer Academic Publishers-Plenum Publishers., 2006) Wijeyaratne, W.M.D.N.; Pathiratne, A.
The present study was aimed at applying condition factor (CF), brain acetylcholinesterase (AChE) and gill histology as biomarkers for detecting possible exposure/effect induced by pesticides in fish residing rice field associated waterbodies in Sri Lanka. Biomarkers of an indigenous fish, Rasbora caverii collected from five sampling sites including canals near rice fields, a river and a reservoir (the reference site) were evaluated at four sampling stages covering pesticide application periods during rice cultivation season in 2004. Results indicated that CF of the fish did not show significant alterations regardless of the sampling sites or sampling stages. Site specific differences in AChE activities of the fish were not evident either prior to application of pesticides or at 7 days after Paraquat application to the rice fields. Two days after the application of a mixture of Fenthion and Phenthoate to the rice fields, AChE activity of the fish collected from canals near rice fields was significantly depressed (65–75%) compared to the fish in the reference site. The activities remain depressed to 50–56% even at 65 days after the insecticides application. Laboratory studies showed that prior exposure of R. caverii to Paraquat (2 μg l−1, 7 days) enhanced the extent of inhibition of brain AChE activity induced by Fenthion (3 μg l−1) or a mixture of Fenthion (3 μg l−1) and Phenthoate (5 μg l−1). Gills of fish collected from canals near rice fields exhibited abnormal multiple divisions at the tips of some secondary lamellae in addition to hyperplasia, hypertrophy and club shaped deformities. Results indicate that application of pesticides in rice culture could manifest a threat to native fish populations residing rice field associated waterbodies. The response of brain AChE and histological changes in the gills of R. caverii allowed differentiating sampling sites after insecticide applications to the rice fields. Hence, R. caverii may be considered as a surrogate species in ecotoxicological risk evaluation of agrochemicals in the region.
Acetylcholinesterase inhibition in Nile tilapia, Oreochromis niloticus following exposure to low concentrations of Chlorpyrifos and Carbosulfan: exposure– response relationships in fry, fingerlings and sub-adults
(Sri Lanka Association for Fisheries and Aquatic Resources, 2004) Chandrasekera, L.W.H.U.; Pathiratne, A.
Acetylcholinesterase (AChE) inhibition is considered as a specific biomarker of exposure and effect for organophosphorous and carbamate pesticides. Oreochromis niloticus, which is an abundant food fish in inland water bodies is a potential sentinel species in monitoring biological effects of pollutants in aquatic environments in Sri Lanka. In the present study, pesticide exposure and AChE inhibition relationships in different size groups of O. niloticus were assessed under laboratory conditions following exposure to an organophosphate, Chlorpyrifos and a carbamate, Carbosulfan, to evaluate the influence of body size on exposure-response relationships. Fry (0.9-2.0 g, 3.2-4.8 cm), fingerlings (3.0-9.7 g, 5.9-8.5 cm) and sub-adults (11-40 g, 9.2-15.0 cm) of fish were continuously exposed to a series of environmentally relevant concentrations of Chlorpyrifos (0.5 –12 g l-1) or Carbosulfan (1 –10 g l-1) for 14 days in a static system and brain AChE activities on 2, 6, 10, 14 days post exposure were determined using the standard spectrophotometeric method. Comparable size groups of fish maintained in aged tap water under similar laboratory conditions served as controls. Results showed that AChE activities in all groups of fish were inhibited following exposure to the insecticides tested in a concentration dependent manner. Exposure-response relationships indicated that fry stages were more sensitive to the pesticide exposure in comparison to the fingerlings and sub-adults. AChE activity of fingerlings and sub-adults exposed to 1 g l-1 Chlorpyrifos or Carbosulfan restored to near normal levels in 14 days post exposure whereas the activities of the fish exposed to other concentrations remained significantly inhibited even after 14 days. The results suggest that brain AChE activity in O. niloticus could be used as a sensitive molecular biomarker in monitoring organophosphorus and carbamate pollution in aquatic environments. However, the size groups of the fish should be taken into consideration when this fish is used in environmental monitoring
Acetylcholinesterse inhibition and gill lesions in Rasboracaverii, an indegeneous fish inhabiting rice field associated waterbodies in Sri Lanka
(Ecotoxicology, 2006) Wijeyaratne, W.M.D.N.; Pathiratne, A.
Activation of C14 toluene to covalently binding metabolites by rat liver microsomes
(Drug Metabolism and Disposition, 1986) Pathiratne, A.; Puyear, R.L.; Brammer, J.D.
Activity Pattern and Environmental Variation of Micro Habitats of Six-Toed Green Frog Euphlyctis hexadactylus Lesson 1834(Anura:Ranidae)in Sri Lanka
(The Herpetology of Sri Lanka, 2004) Weerawardhena, S.R.; Amarasinghe, U.S.; Kotagama, S.W.
Acute toxicity test of aqueous extract of white hoary pea, Tephrosia candida (Papilionoideae) on Nile tilapia, Oreochromis niloticus (Cichlidae) fingerlings
(Sri Lanka Association for Fisheries and Aquatic Resources, 2015) Epa, U.P.K.; Mohotti, C.R.W.C.
Tephrosia candida was introduced to Sri Lanka as a legume live mulch for weed control and to protect soil surface. It is a source of flavonoids and rotenoids a including rotenone, tephrosin, and deguelin. Fishermen add large amount of grounded plant matter to the water that kills almost all the fish in the stream within a short period of time. This method of unregulated fishing may have a long term negative effect on fish diversity and abundance in the country. A 96hr static renewal toxicity bioassay was carried out in the laboratory to determine the median lethal concentration (LC50) of aqueous extract of T. candida leaves on Nile Tilapia (Oreochromis niloticus) fingerlings. Experimental fish were exposed to test water in 20L glass aquaria with concentrations of aqueous extract of 5, 7.5, 10, 15 and 20 mgL-1. All five treatments and the control aquaria were triplicated. Temperature, pH, total dissolved solids, conductivity and dissolved oxygen (DO) in water in all the aquaria were monitored using multi parameter water quality checker before and after the addition of toxicant, 24, 72 and 96hr of fish stocking thereafter. The median lethal concentration (LC50) values and its corresponding 95% confidence limits were calculated by Probit analysis. The LC50 values at various exposure periods were 10.83mgL-1 for 24h; 8.61mgL-1 for 48h; 7.26mgL-1 for 72h and 6.43mgL-1 for 96h. Symptoms of toxicity observed included, initial inactivation, agitated swimming, turning movement, air gulping, increased opercular beat, then erratic swimming, loss of reflex, slow opercular movement, setting at the bottom motionless and knockdown before death. The gills of the dead fishes were damaged, swollen and external bleedings were observed. Lower concentrations of the extracts had sub lethal effects which manifested as zigzag movement, air gulping, increased opercular movement and some fish gathered near the air stones. It could be concluded that the application of T. candida extract causes lethal toxic effects on fish at even very low concentrations.
Adaptive learning: Some experiences from implementing adaptive fisheries co-management in Lao PDR and India
(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Arthur, R.; Garaway, C.
Experiences with inland fisheries systems have shown that they are often both complex and dynamic in terms of their biophysical, technical and institutional aspects and that the outcomes of management actions cannot always be assumed. Adaptive co-management has emerged as a potential management approach that seeks to reduce uncertainties by using management actions as a way to generate information about the system and its dynamics at the same time as providing benefits to resource users. Adaptive learning provides a tested framework for implementing this approach where management is treated explicitly as a learning process based on the generation, sharing and utilisation of information. The principles on which adaptive learning is based are described along with experiences of implementing the process in small water body fisheries in southern Lao PDR. Some additional experiences from implementing the process in India are also included.
Adopting a STREAM approach for inland fisheries management
(Sri Lanka Association for Fisheries and Aquatic Resources, 2008) Haylor, G.
This paper advocates strategies, processes and practices that enable livelihoods approaches rather than resource-based approaches, ‘direct’ institutional and policy development rather than ‘project demonstrations’, and support for regional, national and local communications. A resource-focused approach, can over simplify how (poor) people interact with (aquatic) resources (such as reservoirs). With a resource-focused approach, if people don’t take up a technology, or a policy doesn’t work, the approach will not tell us why and how to make changes. A livelihoods approach can identify people’s access to resources, their objectives for the resources to which they have access, the desirable and undesirable properties of resources for particular activities, skills and knowledge levels, support networks, infrastructure and services, interests, motivations, circumstances and what people can achieve, and the effect of policies and other factors which influence all of these. This can provide the details that are needed to develop with stakeholders, appropriate supporting institutions and policies. Instead of projects, which aim to demonstrate new ways of working, governments sometimes seek support to change institutions and policies directly. The ‘direct strategies’ that are emerging bring together expertise, and relevant knowledge from farmers, fishers, people’s organizations, local government and NGO service providers, state-level and national policy shapers and policy makers to identify and share better practices, and learning from elsewhere. Negotiating a direct role in change processes may have more impact than demonstrating an approach in a project context. Finally, to facilitate participation in resource management, five communication elements are highlighted. The strategy here is to facilitate ‘links’: to information sources and media, to learning (research, development, networks, and other sectors), to service providers (Governments, non-government organizations), to policy makers (closing discourse gaps, e.g. between fishers and policy makers) and to pay attention to sharing meaning across languages and cultures and with fishers and farmers who are poor (via networks of dedicated Communication Hubs). The three main components of the STREAM approach discussed in this paper are not pursued separately, for they are closely interlinked. Understanding people’s livelihoods helps to identify the important characteristics and requirements of supporting institutions and policies and where communications links must be built so that people can participate in shaping policies and institutions that support their objectives.
Advancing tourism demand forecasting in Sri Lanka: evaluating the performance of machine learning models and the impact of social media data integration
(Emerald Publishing Limited, 2023) Hewapathirana, Isuru Udayangani
Purpose – This study explores the pioneering approach of utilising machine learning (ML) models and integrating social media data for predicting tourist arrivals in Sri Lanka. Design/methodology/approach – Two sets of experiments are performed in this research. First, the predictive accuracy of three ML models, support vector regression (SVR), random forest (RF) and artificial neural network (ANN), is compared against the seasonal autoregressive integrated moving average (SARIMA) model using historical tourist arrivals as features. Subsequently, the impact of incorporating social media data from TripAdvisor and Google Trends as additional features is investigated. Findings – The findings reveal that the ML models generally outperform the SARIMA model, particularly from 2019 to 2021, when several unexpected events occurred in Sri Lanka. When integrating social media data, the RF model performs significantly better during most years, whereas the SVR model does not exhibit significant improvement. Although adding social media data to the ANNmodel does not yield superior forecasts, it exhibits proficiency in capturing data trends. Practical implications – The findings offer substantial implications for the industry’s growth and resilience, allowing stakeholders to make accurate data-driven decisions to navigate the unpredictable dynamics of Sri Lanka’s tourism sector. Originality/value – This study presents the first exploration of ML models and the integration of social media data for forecasting Sri Lankan tourist arrivals, contributing to the advancement of research in this domain.