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The National Red List of Sri Lanka: Assessment of the Threat Status of the Freshwater Fishes of Sri Lanka 2020
Abstract and Figures
A total of 61 endemic species were assessed. Of these, 12 point endemic species were listed as Critically Endangered (CR); 24 range-restricted species were Endangered (EN); and nine species were Vulnerable (VU). In addition, five species were Near Threatened (NT); two were listed as Data Deficient (DD); and the remaining were listed as Least Concern (LC). This means that 74% — nearly three quarters — of the freshwater fish endemic to Sri Lanka were found to be Threatened with extinction.
Thirty-six native species were also assessed and of these, only eight species were listed as Threatened.
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... Many of these studies have focused on the life histories, physiology, reproductive biology or ecophysiology of certain fish species of either commercial or ecological interest (Silva, 2005;Sivashanthini & Khan, 2004). Marine and freshwater fishes of Sri Lanka have also been documented (De bruin et al., 1995;Goonatilake et al., 2020). Although Sri Lanka has 45 estuaries and 40 lagoons (with a total extent of 1580.17 km 2 ) (Kularatne, 2020;Samarakoon & Samarawickrama, 2012), inventories on the brackish water ichthyofauna are sparse and data on fish diversity and assemblages are scant. ...
The Batticaloa Lagoon (Sri Lanka's third largest brackish waterbody) has suffered habitat degradation and water quality deterioration during the past 30 years due to various anthropogenic activities. Despite Sri Lanka having 40 lagoons, inventories on the lagoon ichthyofauna are rather meagre and data on fish diversity and assemblages are scarce. An assessment of fish diversity is essential to maintain the ecological stability and the lagoon fisheries. This study examined the fish fauna of Batticaloa lagoon considering the northern and southern regions of the lagoon and various depths through a three‐year survey (2017–2019) and documented the dominant and rare fish species. In addition to documenting biodiversity measures and species assemblages and the role of environmental parameters on the distribution of fishes. Various diversity indices (Margalef richness index, Shannon‐Weiner Diversity index, Pielou's Evenness, dominance index, taxonomic diversity index, average taxonomic distinctness index and the total taxonomic distinctness index) were calculated. Analysis of Similarities (ANOSIM) was used to examine the seasonal and regional differences in the fish assemblages. The survey showed the occurrence of 96 species belonging to 40 families and 11 orders. Ambassis gymnocephalus was the most abundant fish species (8.7% of the total number of fishes collected) followed by Etroplus suratensis (6.8%), Arius maculatus (6.1%), Gerres filamentosus (5.3%), Oreochromis niloticus (4.6%) and G. abbreviates (3.9%). Dasyatis uarnak (0.02%), Acanthurus gahhm (0.03%), Alectis ciliaris (0.04%), Crossorhombus valderostratus (0.08%) species were considered as rare species which constitute less than 0.1% abundance of the total while Dasyatis uarnak considered as doubletons species (represented twice in the whole sample‐16 stations). Two types of species assemblages, one in the northern and one in the southern regions were evident in a dendrogram (the samples collected from each region combined with samples of the same region and this part dendrogram joined with other part of the dendrogram having samples of the region finally) based on sample composition similarity estimated with a Bray‐Curtis matrix and non‐metric multidimensional scaling plots. The Bray–Curtis dissimilarity was 59.03% between the two regions indicating statistically significant differences in assemblages (ANOSIM R 0.801; P < 0.01). The northern region of the lagoon had a higher number of species, density, Margalef richness, Pielou's evenness, Shannon‐Wiener diversity, Taxonomic diversity, Taxonomic distinctness and Total taxonomic distinctness compared to the southern region. Northern region showed significantly higher levels of salinity and dissolved oxygen (DO) and the southern region higher temperature, turbidity, phosphates and nitrates. The BEST(BIO‐ENV) test showed a significant relationship between fish assemblage and environmental parameters. The DISTLM analysis showed the significant relationship between fish assemblage and the environmental parameters salinity, temperature, pH and DO. The sequential test of this analysis showed the environmental parameters to explain about 74.9% (R2) of the total variation. The bio‐environmental model developed was found to be quite appropriate. Thirteen species were found to be influential as they explained the overall fish distribution pattern with the Spearman rank correlation of 0.951. Ten groups of coherent species were also identified in the study area. In stations having anthropogenic activities the fish diversity was low. The fish fauna of Batticaloa lagoon has to be monitored periodically to protect the fishery resources here. An understanding of the role that environment plays in structuring the fish assemblage in Batticaloa Lagoon and the locations with critical habitats will be of great importance in the conservation and management of fishery resources in this lagoon. However as monitoring only the dominant species may fail to pick up on important impacts affecting the less common species, monitoring can be done using the diversity indices and rare fish species. Monitoring is imperative in view of the livelihood of fishers this lagoon supports and health of the local people as fish is a healthy food. The fishery resources of this lagoon must be protected for posterity with appropriate management measures.
Population dynamics of two cichlid species, Oreochromis mossambicus and 0. niloticus in two reservoirs in Sri Lanka were studied using length-based methods. Asymptotic total length (L.,.) and growth constant (K per year) of 0. mossambicus (L.,.. = 43.7 cm and K = 0.52 in Kaudulla; L_ = 45.0 cm and K = 0.45 in Minneriya) and 0. niloticus (L_ = 54.5 cm in both reservoirs; K = 0.35 and 0.48 in Kaudulla and Minneriya, respectively) were used to estimate mortality and exploitation rates (E). The growth performance of 0. mossambicus in both reservoirs was better than that of 0. mossambicus populations in various geographical areas. This may be due to introgressive hybridization between 0. mossambicus and 0. niloticus or a very favorable environment for 0. mossambicus in Sri Lank.an reservoirs which provide a variety of nutritious food sources. Length-structured Virtual Population Analysis indicates that fishing mortality rates are approximately constant throughout the recruited stocks, suggesting that the effects of gill-net selectivity on the catch samples are small. Relative yield-per-recruit analyses incorporating probabilities of capture indicate that 0. mossambicus and 0. niloticus yields in Minneriya could be increased by increasing size at first capture. In Kaudulla, any increase in E of 0. mossambicus stock would adversely affect the 0. niloticus stock. Also, increase in size at first capture of 0. niloticus to optimize yield would leave the 0. mossambicus stock underexploited.
Kelani River is the fourth longest river in the South-Asian island, Sri Lanka. It originates from the central hills and flows through a diverse array of landscapes, including some of the most urbanized regions and intensive land uses. Kelani River suffers a multitude of environmental issues: illegal water diversions and extractions, impoundment for hydroelectricity generation, and pollution, mostly from agrochemicals, urban runoff, industrial discharges, and domestic waste. Moreover, loss of riparian forest cover, sand-mining, and unplanned development in floodplains have accentuated the environmental damage. In this study, based on Kelani River basin, we reviewed the status of biodiversity, threats encountered, conservation challenges, and provided guidance for science-based conservation planning. Kelani River basin is high in biodiversity and endemism, which includes 60 freshwater fish species of which 30 are endemic. Urbanization related threats are more severe in the middle and lower reaches while agriculture and impoundments peril the river in upper reaches. Documentation of these threats can be dated back to 1980, yet, Sri Lankan government has failed to take substantial actions for sustainable management of Kelani River basin, despite the presence of nearly 50 legislations pertaining to water and land management. Given high biodiversity richness, human dependency, and evident ecological deterioration, Kelani River basin should be prioritized for biodiversity conservation and sustainable resource management. Conservation and wise use of freshwater resources is a global concern, particularly for developing nations in Asia. Therefore, our review and guidance for scientifically informed conservation would serve as a prototype for basin-wide river management for Sri Lanka as well as for other developing nations of tropical Asia.
Polycyclic aromatic hydrocarbons PAHs are a group of organic compounds with more than one benzene ring formed due to natural processes such as forest fires and anthropogenic activities These ubiquitous contaminants have gathered an interest due to their toxicity and carcinogenic activity Exposure to PAHs has also been linked with cancer, cardiovascular disease and poor fetal development PAHs are considered as persistent organic pollutants because of their stable chemical structure and inherent resistance to decomposition. In this study, the water bodies near two diesel fueled power plants in Sri Lanka i e , Kerawalapitiya and Kelanitissa were selected to determine the presence of PAHs in surface water and its sediment In the preliminary sampling rounds, the presence of PAHs were identified With increased sample size, three sampling rounds were carried out in addition to water and sediment from Hamilton canal and Sebastian canal, water samples from wells near both power plants were analyzed PAHs in water samples were extracted to dichloromethane and analyzed by HPLC with UV DAD 254 nm and HPLC FLD excitation at 250 nm, emission at 410 nm Sediment samples were pretreated before the analysis and then, PAHs were extracted to methanol by ultra sonication. The presence of low, medium and high molecular weight PAHs in water and sediment samples obtained from both sites were detected Total concentration of PAHs in surface water samples obtained from Sebastian canal during rainy season April 2015 , dry season July 2015 and rainy season June 2016 were 0 11 1 71 μg L, 2 36 14 68 μg L and 6 88 μg L 10 05 μg L, respectively Furthermore, PAH content in water samples obtained from Hamilton canal during rainy season April 2015 , dry season July 2015 and rainy season April 2016 were 0 16 2 74 μg L, 11 06 54 89 μg L and 5 35 7 79 μg L, respectively Well water samples obtained from Kelanitissa W1 and Kerawalapitiya W3 showed the presence of high amounts of BaP 0 025 μg L and BkF 0 339 μg L respectively which are higher than the guideline values for BaP 0 01 μg L and BkF 0 1 μg L according to European Unions drinking water standards. The total PAH amount in surface water in both sites were higher in dry season than that of in rainy season This may due to accumulation of PAHs over the time in water bodies around diesel fueled power stations during dry seasons due to lack of water flow By investigating more dry and rainy seasons, an accumulation trend can be identified to address the seasonal variation of PAHS in water bodies.
River Mahaweli in Sri Lanka was greatly altered by dams under the Mahaweli diversion Scheme. Fish assemblages in segments of five tributaries of Mahaweli; Badulu Oya, upstream of Ulhitiya Oya and Loggal Oya (unregulated streams) and, Minipe and downstream of Ulhitiya Oya (regulated streams) were compared. Sampling was carried out in three selected 100 m segments from each study stream using hand nets, drag nets and cast nets. 40 fish species in 10 families were recorded. Ulihitiya downstream recorded the lowest abundance and species richness. Unregulated streams demonstrated a higher proportion of endemics (Dry: 41-54% and Wet: 50-60%) while regulated streams had highest proportions of exotics in both seasons (Dry; 26 and 72 %; Wet: 34 and 66 % in Minipe and Ulhitiya downstream, respectively). The results suggest that native and endemic fishes are more sensitive to altered habitat conditions highlighting the importance of protecting the remaining natural habitats.
The endemic Sri Lankan synbranchid 'Monopterus' desilvai is redescribed based on additional material. In life, individuals have a maroon background colour with numerous dark brown blotches. They breathe air, which is stored in paired suprabranchial pouches. The head skeleton of M. desilvai is described in detail. This species shares with M. cuchia, M. indicus, M. fossorius, M. ichthyophoides, M. rongsaw, M. luticolus, and M. boueti derived and unique modifications of the gill arch skeleton: ceratobranchial 1 is spatially removed from hypobranchial 1 and aligned with hypo-and ceratobranchial 2, leading to a separation of the anterior from the posterior gill arch skeleton. It shares with M. cuchia, M. indicus, M. fossorius, and M. ichthyophoides an even further derived gill arch skeleton, in which epibranchial 1, the interarcual bone and pharyngobranchial 2 are absent, modifications puta-tively related to the evolution of paired suprabranchial pouches in these species. Based on these shared derived characters the group comprising M. cuchia, M. indicus, M. fossorius, M. ichthyophoides and M. desilvai, is recognized as a monophyletic unit for which the oldest available generic name is Ophichthys Swainson.
Molecular and morphological analyses show that Esomus thermoicos is the only species of Esomus in Sri Lanka. Esomus thermoicos is distinguished from its congeners by the combination of having a complete lateral line, a dark mediolateral stripe, a short pectoral fin that does not reach the anal-fin origin when adpressed, and by lacking conspicuous spots or blotches on the body. A limited series of specimens from southern peninsular India are also identified as E. thermoicos. Esomus brevibarbartus is a junior subjective synonym of E. thermoicos.
The Sri Lankan population of the spiny eel previously assigned to Macrognathus aral Schneider (Teleostei: Mastacembelidae) is shown to be a distinct species, for which the name M. pentophthalmos Gronow is available. Macrognathus pentophthalmos is distinguished from its closest congener, M. aral, by having 14–16 dorsal spines and a pre-dorsal length of 43.3–46.8% of standard length (SL) (vs. dorsal spines 18–22 and pre-dorsal length 35.5–40.8% SL in M. aral). Macrognathus pentophthalmos differs from its only other Indian congener, M. guentheri Day, among other characters, by having 24 pairs of rostral tooth plates (vs. rostral tooth plates absent). With the present designation of a neotype, Rhynchobdella orientalis Bloch & Schneider (type locality East Indies to Sri Lanka) becomes an objective junior synonym of M. aculeatus Bloch. Although assessed as ‘common’ in 1980, the population of M. pentophthalmos suffered a precipitous decline in the following decade, the causes of which are unknown. The species may now be extinct.
Since its first record from the island in 1912, the barb Puntius amphibius Valenciennes has regularly featured in Sri Lanka’s ichthyofaunal inventories. Recent work has shown, however, that the name P. amphibius should be reserved for a species originally collected from Bombay, India, and described by Achille Valenciennes in 1842, now known only from its lectotype. The Sri Lankan fish hitherto known by this name is an undescribed species. Puntius kamalika, new species, is distinguished from all Sri Lankan and peninsular-Indian congeners by having (in addition to a suite of mensural characters) ½4/1/2½ scales in transverse line between mid-dorsal scale row and pelvic-fin origin and lacking any prominent markings on fins and body in both living and preserved examples. The new species is widely distributed in the island’s wet-zone lowlands (rainfall > 2,500 mm yr -1 ), where it occurs in streams, rivers and marshes between the Kelani-River basin draining to the island’s west, and the Gin River basin to the south. It is locally common.
We address several problems arising from 'A review of the genus Devario in Sri Lanka (Teleostei: Cyprinidae), with description of two new species', a paper authored by S. Batuwita, M. de Silva and S. Udugampola and published in 2017 in the journal FishTaxa (2(3): 156-179). The neotypes they designate for Perilampus malabaricus Jerdon and Perilampus mysoricus Jerdon are inconsistent with article 75.3 of the International Code of Zoological Nomenclature ('the Code') and are hence invalid. Devario udenii, which they describe as a new species, is shown to be indistinguishable from D. microne-ma sensu Batuwita et al. The characters by which they distinguish another new species, D. annnataliae, are shown to be self-contradictory, making it impossible to distinguish from its congeners; it is treated as a species inquirendum. The diagnoses provided for D. malabaricus, D. micronema and D. monticola are ambiguous and self-contradictory, rendering them unusable. Much of the material examined, stated to be in the collection of the National Museum of Sri Lanka, is not deposited in that institution: such material as is deposited is inconsistent with the specimen data published by Batuwita et al.