The National Red List: Assessment of the Threat Status of the Freshwater Fishes of Sri Lanka 2020

Introduction:

The Red List is one of the best indicators of the health of a species as it is an assessment that takes into consideration most of the internal and external factors that influence the long-term survival of the species being assessed. It is a very useful tool that provides the basis for planning conservation action as well as policy and research directions. The Red List can be used by government agencies involved in natural resource management to set conservation goals as well as an indicator to monitor the effectiveness of their management. The Red List is also useful to a number of other actors that have a stake in conservation such as non-governmental organizations, natural resource planners, educational organizations, students, and the private sector organizations.

The preparation of the Red List is done at both Global and Local levels as some species occur in more than one country and as such their long-term survival depends on the status of the species in each of the range states. Whereas, for the endemic species the national and global status should be the same. However, Sri Lankan freshwater fish, especially endemic species are underrepresented in the global Red List. For instance, up to 2019, the global IUCN Red List carried the threat status of 54 species present in Sri Lanka, including only 18 out of the 62 endemic species listed for Sri Lanka in 2019. Out of the 18 endemic species only eight have been listed as threatened species. Further, more than 20 species of endemic species of fish were not even recognized as valid species in the global Red List database. Therefore, one of the objectives of this assessment was to update the global Red List with respect to endemic freshwater fish of Sri Lanka. As a result of the present assessment, the threat status of 59 out of the 61 species were updated in the global Red List. The remaining two species were not updated due to taxonomic uncertainties.

The last national assessment of the freshwater fish was carried out in 2012, by the Biodiversity Secretariat of the then Ministry of Environment — with inputs from a freshwater expert panel — using Red List™ criteria version 3.1. Ninety-one species, including 50 endemic species were assessed. Of the 50 endemics considered, 45 were listed as Nationally Threatened. However, the Red List is a living document that must be updated regularly as the drivers and pressures on species as well as taxonomic status, distribution status as well as the available information are subject to change with time. For instance, since the last national assessment in 2012, 14 new species including 11 endemics have been added to the freshwater fish list while four species have been removed. Therefore, this assessment was undertaken, using the IUCN Global Red List™ criteria (version 3.1), to determine the current threat status of freshwater fish species both endemic and indigenous to Sri Lanka. The completed data from this assessment were used to update the global Red List™ website (www:redlist.org) as well as finalise the National Red List threat status of the freshwater fishes in Sri Lanka.

Methodology:

The freshwater fish checklist published in the National Red List (2012) was updated using all published information since 2012 on newly described species, changes in genus or species name based on taxonomic reviews, species that have been removed from list of freshwater species list or synonymized based on published taxonomic reviews. This new list was reviewed and adopted at a meeting of the

National Freshwater Fish Expert Panel held at the Biodiversity Secretariat. Ninety-seven freshwater fish species, including 61 species, endemic to Sri Lanka were assessed using the IUCN Red List categories and criteria version 3.1 (IUCN, 2012), and the most appropriate threat status was assigned to each species. Thirty exotic species were not considered in this assessment. This assessment was coordinated by the Sri Lanka Country Office of IUCN, in collaboration with the IUCN Freshwater Biodiversity Unit, IUCN Global Species Programme, and the National Freshwater Fish Expert Panel, appointed by the Biodiversity Secretariat of the Ministry of Mahaweli Development and Environment. All available published and unpublished data on the distribution of freshwater fishes of Sri Lanka (369 documents) were compiled and locations mapped and verified, in consultation with the National Freshwater Fish Expert Panel and individual fish experts, to fulfill the requirements of the IUCN Species Information Service (SIS) database.

Results:

Fifty-three out of 97 assessed species were determined to be threatened during this assessment. Further, 74% - nearly three quarters - of the freshwater fish endemic to Sri Lanka were found to be threatened. Out of the 60-endemic species, 12-point endemic species were listed as Critically Endangered (CR); 24 range-restricted species were listed as Endangered (EN) while further nine species were listed as Vulnerable (VU). In addition, five species were listed as Near Threatened (NT); two species as Data Deficient (DD); and the remaining species were listed as Least Concern (LC). All the accessed endemic species were used to update the global Red List (except for two species hose taxonomic status is yet to be resolved) and can be access now from www.redlsit.org. Among the native species (36) were also assessed and out of these, eight species were listed as Threatened.

Drivers of change:

Most of Sri Lanka’s freshwater fish are found outside protected areas and are thus affected directly by all the major drivers of biodiversity loss (habitat loss and degradation, habitat fragmentation, habitat conversion, overexploitation, pollution, invasive alien species and climate change). The results of the assessment call for urgent and planned conservation actions, at least for the critically endangered endemic species all of which show a highly restricted distribution and inhabits unprotected streams.

Other than the main drivers mentioned above, many rivers and minor streams habitats are directly affected by gem mining. Further, water pollution due to release of urban and industrial waste into surface water bodies has resulted in local extinctions or drastic reduction in the populations of certain species freshwater fish species, especially species that inhabit urban wetlands. Excessive use of agrochemicals in vegetable cultivated areas in the upper catchments of the major rivers in the wet zone such as Kelani, Kalu, Gin and Nilwala also have direct and indirect effects on the freshwater fish species. Finally, climate change driven changes such as changes in rainfall patterns and establishment of salinity barriers in major rivers can also have a significant influence on the survival of freshwater fish species.

Recommendations:

• The data compiled in this assessment indicate that many parts of the dry zone, especially the northern region are not adequately surveyed. Further, during the last three decades many new endemic species have been described from Sri Lanka which indicates that more new species are awaiting to be discovered. Therefore, an island-wide systematic survey of the freshwater habitats of Sri Lanka are needed urgently in order to ensure that freshwater fauna of Sri Lanka is fully inventoried.

• The ideal indicator of long-term survival rates of species is its population> However, population trends are known only for few species of freshwater fish in Sri Lanka. Therefore, population studies should be conducted at least for the 12 Critically Endangered Species.

• Red List assessment will help identify species that require conservation action in a country. However long-term conservation of a species will depend on formulation and implementation of recovery plans for those species that are identified as threatened with extinction. Therefore, conservation plans should be prepared and implemented for at least the 12 species of freshwater fish that are listed as Critically Endangered. There are several approaches to achieve this goal. These include
  • Site-directed action plans (SDAP): suitable for species inhabiting a defined area and subject to multiple, localised threats linked to the specific area.
  • Individual species recovery plans (ISRP): suitable for species whose conservation needs do not overlap significantly with those of other species.
  • Ex-situ conservation feasibility assessments (ECFA): suitable for species where in-situ conservation alone is unlikely to prevent extinction and requires boosting of a dwindling wild population.
  • Habitat-directed action plans (HDAP): suitable for species which are dependent on the same habitat type that is subject to a common threat or threats.
  • Threat-directed action plans (TDAP): suitable address drivers that affect a group of species such as gem mining, excessive pesticide use etc.,

• The awareness among students and local communities. As most freshwater fish species occur in human-dominated landscapes, conservation approaches involving local communities in conservation action of freshwater fish should be developed, at least for the restricted-range species.